SOURCES OF AIR POLLUTION
Two main categories
Stationary sources such as power stations, oil refineries
Mobile sources such as motor vehicles
STRATEGIES TO CONTROL AIR
POLLUTION
Stationary sources
Siting of industries
Should be sited far away from residential areas
Install pollution control equipment and have tall stacks for dispersion of air pollutants
Fuel quality
Control type and quality of fuel
E.g. Use fuel with sulphur content not exceeding 2% by weight
Pollution control equipment
Equipment/processes which give rise to emissions are designed to be able to comply with emission standards
Industries encouraged to adopt cleaner technologies
Wet & Dry collectors (scrubbers)
Cyclones
Fabric filters
Electrostatic Precipitators
Tax incentives
Enforcement
Regular inspections to ensure that pollution control equipment and facilities are properly maintained
Mobile sources
Fuel quality
Use of unleaded petrol
Sulphur content of diesel is 0.05% by weight
Fitted with catalytic converters
Emission standards
Inspection and enforcement
Mandatory periodic inspections
Air pollution
Air Pollution
is the presence of any chemical, physical (e.g. particulate matter), or biological agent that modifies the natural characteristics of the atmosphere.
The atmosphere is a complex, dynamic natural gaseous system that is essential to support life on planet earth.
Worldwide air pollution is responsible for large numbers of deaths and cases of respiratory diseases
Types of air pollutants
Main gaseous pollutants
Sulphur dioxide (SO2)
Oxides of nitrogen (NO and NO2)
Carbon monoxide (CO)
Hydrocarbons (HC)
Ozone (O3)
Main non-gaseous pollutants
Suspended particulate matter
Lead
Sources of air pollution
Stationary sources
any fixed emitter of air pollutants
Fossil fuel burning power stations
Petroleum/Oil refineries
Petrochemical plants
Food processing plants
Heavy Industrial sources
Mobile sources
non-stationary source of air pollutants
automobiles, buses, trucks, ships, trains, aircraft and various other vehicles
tobacco smokers
Sources of air pollution
Sulphur dioxide
Largest single source of SO2 is the combustion of sulphur – containing fossil fuel both for electric power generation and for process heat
Some important industrial emitters
Nonferrous smelters
Except iron and aluminum, metal ores are suphur compounds
When ore is reduced to pure metal, sulphur in the ore is oxidized to SO2
Oil refining
Sulphur and hydrogen are constituents of crude oil
Hydrogen sulphide is released as gas during catalytic cracking
Hydrogen sulphide is more toxic then sulphur dioxide
It is flared to sulphur dioxide before release into air
Pulp and paper manufacture
Sulphite process for wood pulping use hot sulphiric acid
Thus emits sulphur dioxide into air
Kraft pulping process produces hydrogen sulphide, that is flared to sulphur dioxide
Natural sources
Volcanic eruptions
Sulphur containing geothermal sources – hot springs
Oxides of nitrogen
formed by the combustion of nitrogen - containing compounds
and thermal fixation by atmospheric nitrogen
NOx is created when nitrogen and oxygen in combustion air are heated to high temperature
The equilibrium constant for the reaction: N2 + O2 2NO
All high temp processes produce NO, that is oxidized to NO2 in the ambient air
Carbon monoxide
Product of incomplete combustion of carbon-containing compounds
Most of the CO in ambient air comes from vehicle exhaust
Internal combustion engines do not burn fuel completely to CO2 and water
Some unburned fuel will always be exhausted, with CO as a component
Tobacco smoke
Hydrocarbons
Major source
vehicles
Stationary sources
Petrochemical manufacture
Oil refining
Incomplete incineration
Paint manufacture and use
Dry cleaning
Particulate matter
Every industrial process is a potential source of dust, smoke 0r aerosol emissions
Waste incineration
Coal combustion
Petrochemical industry
Smelting
Agricultural operations
major source of dust – dry farming
Demolition and construction
Great quantities of dust
Fires
Major sources of airborne particulate matter, HC, CO
Tobacco smoke
CO, organic tars, metal oxides particles
Wood – burning stoves and fireplaces
Produce smoke that contains partly burned HC, tars, dioxins
Airborne lead
Vehicle exhaust
Leaded paint
Wednesday, November 11, 2009
ENV 382 cont...
Spectroscopic Methods
Spectroscopy
is the study of matter by investigating light, sound, or particles that are emitted, absorbed or scattered by the matter under investigation
Spectroscopy may also be defined as the study of the interaction between light and matter
Physical quantity measured
The type of spectroscopy depends on the physical quantity measured.
Normally, the quantity that is measured is an amount or intensity of something
Three main types of spectroscopy
Absorption spectroscopy uses the range
of electromagnetic spectra in which a
substance absorbs.
commonly used in atomic absorption spectroscopy, the sample is atomized and then light of a particular frequency is passed through the vapour
the amount of absorption can be related to the concentrations of various metal ions through the Beer-Lambert law
widely used to measure concentrations of ions such as sodium and calcium
Other types of spectroscopy may not require sample atomization
For example, ultraviolet/visible (UV/ Vis) absorption spectroscopy is most often performed on liquid samples to detect molecular content
Emission spectroscopy uses the range of
electromagnetic spectra in which a
substance radiates
The substance first absorbs energy and then radiates this energy as light
This energy can be from a variety of sources, including chemical reactions
Scattering spectroscopy
measures certain physical properties by measuring the amount of light that a substance scatters at certain wavelengths
Common types of spectroscopy
Flame Spectroscopy
Liquid solution samples are aspirated into a burner or nebulizer/burner combination, desolated, atomized, and sometimes excited to a higher energy electronic state
The use of a flame during analysis requires fuel and oxidant, typically in the form of gases
Common fuel gases used are acetylene or hydrogen
Common oxidant gases used are oxygen, air, or nitrous oxide
methods are often capable of analyzing metallic element analytes in the part per million, billion, or possibly lower concentration ranges
Atomic Emission Spectroscopy
uses flame excitation; atoms are excited from the heat of the flame to emit light
commonly uses a total consumption burner with a round burning outlet
A higher temperature flame than atomic absorption spectroscopy (AA) is typically used to produce excitation of analyze atoms
Since analyte atoms are excited by the heat of the flame, no special elemental lamps to shine into the flame are needed
Atomic Fluorescence Spectroscopy
This method commonly uses a burner with a round burning outlet
The flame is used to solvate and atomize the sample, but a lamp shines light at a specific wavelength into the flame to excite the analyte atoms in the flame
The atoms of certain elements can then fluoresce emitting light in a different direction. The intensity of this fluorescing light is used for quantifying the amount of analyte element in the sample.
A graphite furnace can also be used for atomic fluorescence spectroscopy. This method is not as commonly used as atomic absorption or plasma emission spectroscopy.
Alternatively, a monochromator can be set at one wavelength to concentrate on analysis of a single element at a certain emission line
Plasma emission spectroscopy is a more modern version of this method.
Atomic Absorption Spectroscopy (often called AAS)
commonly uses a pre-burner nebulizer (or nebulizing chamber) to create a sample mist and a slot-shaped burner which gives a longer path-length flame
The temperature of the flame is low enough that the flame itself does not excite sample atoms from their ground state
The nebulizer and flame are used to desolvate and atomize the sample, but the excitation of the analyte atoms is done by the use of lamps shining through the flame at various wavelengths for each type of analyte
In AA, the amount of light absorbed after going through the flame determines the amount of analyte in the sample
A graphite furnace for heating the sample to desolvate and atomize is commonly used for greater sensitivity
The graphite furnace method can also analyze some solid or slurry samples.
Because of its good sensitivity and selectivity, it is still a commonly used method of analysis for certain trace elements in aqueous (and other liquid) samples.
Spark or arc (emission) spectroscopy
can be used for the analysis of metallic elements in solid samples
An electric arc or spark is passed through the sample, heating the sample to a high temperature to excite the atoms in it
The excited analyte atoms glow emitting light at various wavelengths which could be detected by common spectroscopic methods
Since the conditions producing the arc emission typically are not controlled quantitatively, the analysis for the elements is qualitative.
Visible spectroscopy
Many atoms emit or absorb visible light. In order to obtain a fine line spectrum, the atoms must be in a gas phase. This means that the substance has to be vaporized.
Spectrum is studied in absorption or emission.
UV spectroscopy
All atoms absorb in the UV region because photons are energetic enough to excite outer electrons. If the frequency is high enough, photoionisation takes place.
Infra-red spectroscopy
In organic chemistry different types of interatomic bond vibrate at different frequencies in the infra-red part of the spectrum.
The analysis of IR absorption spectra shows what type of bonds are present in the sample.
Nuclear Magnetic Resonance (NMR)
spectroscopy
NMR spectroscopy analyzes certain atomic nuclei to determine different local environments of hydrogen, carbon, or other atoms in the molecule of an organic compound or other compound. This is used to help determine the structure of the compound.
Use of Atomic Absorption (AA) Spectroscopic methods
Metals
Significance
Effects of metals in water and wastewater range from beneficial to dangerously toxic
Some metals are essential
Fe – blood
Cu, Zn – physical performance
Others may adversely affect water consumers, wastewater treatment systems, and receiving waters
Arsenic- cancer, toxic to aquatic spp
Asbestos – asbestosis ( ‘black' lung cancer)
Cadmium, chromium, copper – liver and kidney damage
Methods
Atomic absorption (AA)
Colorimetric methods
Sampling and sample preservation
What fraction to be analyzed
Dissolved
Suspended
Total
Acid-extractable
Preservation
Acidify with 1.5 ml (5ml for alkaline samples) HNO3 /L sample to pH < 2
Filter samples for dissolved metals before preserving
Store in fridge at 4oC
Stable for 6 months
Pre-treatment of samples
Total metals – all metals inorganically and organically bound, both dissolved and particulate
Colorless, odorless water - < I NTU – acidify with HNO3 to pH <2 and analyze directly
Dissolved metals
filter sample (0.45 micrometer membrane filter)
acidify filtrate with HNO3 to pH < 2
And analyze directly
Suspended metals
Filter sample (0.45 micrometer membrane filter)
Digest filter
And analyze
Acid-extractable metals
Extract metals
And analyze extract
Pre-treatment for Acid-extractable metals
extractable metals – lightly absorbed on particulate matter
At collection acidify sample with 5 ml HNO3/L sample
To prepare sample
Mix well
Transfer 100 ml to flask
Add 5 ml HCl
Heat 15 min on a steam bath
Filter thorough 0.45 micrometer membrane filter)
Adjust filtrate volume to 100 ml with water and analyze
Pre-digestion of metals
Reduce interference by organic matter and to convert metal associated with particulates to a form that can be determined by AA
HNO3 – digestion is adequate for clean samples or easily oxidized materials
HNO3-H2SO4 or HNO3-HCl – digestion is adequate for readily oxidizable organic matter
HNO3-HClO4 or HNO3-HClO4-HF – is for the difficult to oxidize organic matter or minerals
Nitric Acid Digestion
Mix sample
Transfer 50 to 100ml to 125 ml conical flask
Add 5 ml conc. HNO3 and few boiling chips
Boil and evaporate on hot plate to lowest volume (10 to 20 ml) before precipitation occurs
Continue heating and adding HNO3 until digestion is complete (light-coloured, clear solution)
Wash down flask walls with water and then filter
Transfer filtrate to 100 ml flask , cool, dilute to mark, mix and analyze.
Direct Air-Acetylene Flame Method
Applicable for Ca, Cd, Cr, Co, Cu, Fe, Mg, Mn, Ni, Zn, etc
Principle
The technique of flame atomic absorption spectroscopy (AA) requires a liquid sample to be aspirated, aerosolized, and mixed with combustible gases, such as acetylene and air or acetylene and nitrous oxide
The mixture is ignited in a flame whose temperature ranges from 2100 to 2800 oC
During combustion, atoms of the element of interest in the sample are reduced to free, unexcited ground state atoms, which absorb light at characteristic wavelengths
RISK ASSESSMENT
Environmental Engineer
objective
Reduce risk from hazards to the environment and public health
Estimate future risks, then use science to prevent or mitigate them
To determine the comparative risks from various environmental pollutants and which risks it is most important to decrease or eliminate
risk analysis
Risks associated with various hazards must evaluated and quantified
Risk
1970s – environmental laws were enacted to protect public heath
E.g. US Clean Air Act
No mention of risk in US Clean Air and Clean Water Acts
Acts required that pollution standards be set that would allow adequate margins of safety to protect public health
Assumption was that pollutants have thresholds and exposure to concentrations below these thresholds would produce no harm
Problems of toxic waste were finally recognized
Toxic substances are suspected carcinogens
Even smallest exposures creates a risk
If any exposure to a substance causes some risk, how can air quality and water quality standards be set
Emergence of the field of environmental risk assessment
1980s - environmental policy - was acceptance of the role of risk assessment and risk management in environmental decision making
Risk assessment
Is a system of analysis that includes four tasks
Identification of substance (toxicant) that may have adverse health effects
Scenarios for exposure to toxicant
Characterization of health effects
As estimate of the probability (risk) of occurrence of these health effects
Is the gathering of data that are used to relate response to dose
Such dose-response data can then be combined with estimates of the likely human exposure to produce overall assessment of risk
Risk management
is the process of deciding what to do
It is the decision making, about how to allocate national resources to protect public health and the environment
Is a one-in-a-million lifetime risk of getting cancer acceptable and, if it is, how do we go about trying to achieve it?
Hazardous substances
Hazardous and toxic substances are
defined as those chemicals present in the
environment which are capable of causing harm
Risk
is the possibility of loss or
injury to people and property
Hazard
a chemical, physical, or biological agent or a set of conditions that has the potential to cause harm
Risk Assessment
Hazard identification
Is the process of determine whether or not a particular chemical is causally linked to a particular health effects, such as cancer on birth effects
Dose-response assessment
Is the process of characterizing the relationship between the dose of an agent administered or received and the incidence of an adverse effect
Dose-Response Assessment
Characteristic features of the Dose- Response
relationship:
Threshold
Is the lowest dose at which there is an observable effect
Curve A – illustrate threshold response i.e. there is no observed effect until a particular concentration is reached
Curve B - linear response with no threshold i.e. the intensity of the effect is directly proportionally to the pollutant dose, and the effect is observed for any detectable concentration of the pollutant in question
Curve C –sublinear dose-response curve and is characteristic of many pollutant dose-response relationships.
It has no clearly defined threshold, the lowest dose at which a response can be detected is called threshold limit value (TLV)
Curve D – supralinear relationship, which is found when low doses of a pollutant appear to provoke a disproportionately large response
Total body burden
An organism or a person can be exposed to simultaneously to several sources of a given pollutant
Example
inhale about 50g/day lead from ambient air and
ingest 300g/day in food and water
The concentration of lead in the body is sum of what is inhaled and ingested and what remains in the body fro prior exposure, less what has been eliminated from the body
Physiological half-life
Is the time needed for the organism to eliminate half of the internal concentration of the pollutant, through metabolism or other normal physiological functions
Bioaccumulation and bioconcentation
Bioaccumulation occurs when a substance is concentrated in one organ or the of tissue of an organism
E.g. Iodine - bioaccumulates in the thyroid gland
The organ dose of a pollutant can thus be considerably greater than what the total body burden would predict
Bioconcentation occurs with a movement up the food chain
E.g. A study of Lake Michigan ecosystem (Hickey et al. 1966) found bioconcentation of DDT as follows:
0.014 ppm (wet weight) in bottom sediments
0.41 ppm in bottom-feeding crustacea
3-6 ppm in fish
2 400 ppm in fish –eating birds
Exposure time and time vs. dosage
Most pollutant need time to react; the exposure time is thus as important as the level of exposure
Synergism
Occurs when two or more substances enhance each other’s effects, and when the resulting effect of the combination on the organism is greater than the additive effects of the substances separately
E.g. black lung disease in miners – occurs more often in miners who smoke than in those who do not
LC50 and LD50
LD50 is the dose that is lethal for 50% of the experimental animals
LC50 refers to lethal concentration rather than lethal dose
LD50 values are most useful in comparing toxicities for pesticides and agricultural chemicals
Population responses
Differ from one individual to another
Depends on age, sex, and general state of physical and emotional health
Exposure and Latency
Characterization of some health risks can take a very time
E.g.. Cancers are noticed many years or decades after exposure to potentially responsible carcinogen
Cancer in adults have a latency period between 10 – 40 years
Latency period – length of time between exposure to a risk factor and expression of adverse effect
Relative risk
Is the ratio of the probabilities that an adverse effect will occur in two different populations
E.g. relative risk of lung cancer in smokers
Ps/Pn = (Xs/Ns)/(Xn/Nn)
where
Ps = probability of fatal lung cancer in smoker
Pn = probability of fatal lung cancer in non-smokers
Xs = number of fatal lung cancer among smokers
Xn = number of fatal lung cancer among non- smokers
Ns = total number of smokers
Nn= total number on non-smoker
Relative risk of death is also called standard mortality ratio (SMR)
SMR = Ds/Dn= Ps/Pn
where
Ds = observed lung cancer deaths in a population of habitual smokers
Dn = expected lung cancer deaths in a non-smoking population of the same size
Exposure assessment
Involves determining the size and nature of the population that has been exposed to the toxicant under consideration, and the length of time and toxicant concentration to which they have been exposed
Risk characterization
Is the integration of the foregoing three steps, which results in an estimate of the magnitude of the public-health problem
Spectroscopy
is the study of matter by investigating light, sound, or particles that are emitted, absorbed or scattered by the matter under investigation
Spectroscopy may also be defined as the study of the interaction between light and matter
Physical quantity measured
The type of spectroscopy depends on the physical quantity measured.
Normally, the quantity that is measured is an amount or intensity of something
Three main types of spectroscopy
Absorption spectroscopy uses the range
of electromagnetic spectra in which a
substance absorbs.
commonly used in atomic absorption spectroscopy, the sample is atomized and then light of a particular frequency is passed through the vapour
the amount of absorption can be related to the concentrations of various metal ions through the Beer-Lambert law
widely used to measure concentrations of ions such as sodium and calcium
Other types of spectroscopy may not require sample atomization
For example, ultraviolet/visible (UV/ Vis) absorption spectroscopy is most often performed on liquid samples to detect molecular content
Emission spectroscopy uses the range of
electromagnetic spectra in which a
substance radiates
The substance first absorbs energy and then radiates this energy as light
This energy can be from a variety of sources, including chemical reactions
Scattering spectroscopy
measures certain physical properties by measuring the amount of light that a substance scatters at certain wavelengths
Common types of spectroscopy
Flame Spectroscopy
Liquid solution samples are aspirated into a burner or nebulizer/burner combination, desolated, atomized, and sometimes excited to a higher energy electronic state
The use of a flame during analysis requires fuel and oxidant, typically in the form of gases
Common fuel gases used are acetylene or hydrogen
Common oxidant gases used are oxygen, air, or nitrous oxide
methods are often capable of analyzing metallic element analytes in the part per million, billion, or possibly lower concentration ranges
Atomic Emission Spectroscopy
uses flame excitation; atoms are excited from the heat of the flame to emit light
commonly uses a total consumption burner with a round burning outlet
A higher temperature flame than atomic absorption spectroscopy (AA) is typically used to produce excitation of analyze atoms
Since analyte atoms are excited by the heat of the flame, no special elemental lamps to shine into the flame are needed
Atomic Fluorescence Spectroscopy
This method commonly uses a burner with a round burning outlet
The flame is used to solvate and atomize the sample, but a lamp shines light at a specific wavelength into the flame to excite the analyte atoms in the flame
The atoms of certain elements can then fluoresce emitting light in a different direction. The intensity of this fluorescing light is used for quantifying the amount of analyte element in the sample.
A graphite furnace can also be used for atomic fluorescence spectroscopy. This method is not as commonly used as atomic absorption or plasma emission spectroscopy.
Alternatively, a monochromator can be set at one wavelength to concentrate on analysis of a single element at a certain emission line
Plasma emission spectroscopy is a more modern version of this method.
Atomic Absorption Spectroscopy (often called AAS)
commonly uses a pre-burner nebulizer (or nebulizing chamber) to create a sample mist and a slot-shaped burner which gives a longer path-length flame
The temperature of the flame is low enough that the flame itself does not excite sample atoms from their ground state
The nebulizer and flame are used to desolvate and atomize the sample, but the excitation of the analyte atoms is done by the use of lamps shining through the flame at various wavelengths for each type of analyte
In AA, the amount of light absorbed after going through the flame determines the amount of analyte in the sample
A graphite furnace for heating the sample to desolvate and atomize is commonly used for greater sensitivity
The graphite furnace method can also analyze some solid or slurry samples.
Because of its good sensitivity and selectivity, it is still a commonly used method of analysis for certain trace elements in aqueous (and other liquid) samples.
Spark or arc (emission) spectroscopy
can be used for the analysis of metallic elements in solid samples
An electric arc or spark is passed through the sample, heating the sample to a high temperature to excite the atoms in it
The excited analyte atoms glow emitting light at various wavelengths which could be detected by common spectroscopic methods
Since the conditions producing the arc emission typically are not controlled quantitatively, the analysis for the elements is qualitative.
Visible spectroscopy
Many atoms emit or absorb visible light. In order to obtain a fine line spectrum, the atoms must be in a gas phase. This means that the substance has to be vaporized.
Spectrum is studied in absorption or emission.
UV spectroscopy
All atoms absorb in the UV region because photons are energetic enough to excite outer electrons. If the frequency is high enough, photoionisation takes place.
Infra-red spectroscopy
In organic chemistry different types of interatomic bond vibrate at different frequencies in the infra-red part of the spectrum.
The analysis of IR absorption spectra shows what type of bonds are present in the sample.
Nuclear Magnetic Resonance (NMR)
spectroscopy
NMR spectroscopy analyzes certain atomic nuclei to determine different local environments of hydrogen, carbon, or other atoms in the molecule of an organic compound or other compound. This is used to help determine the structure of the compound.
Use of Atomic Absorption (AA) Spectroscopic methods
Metals
Significance
Effects of metals in water and wastewater range from beneficial to dangerously toxic
Some metals are essential
Fe – blood
Cu, Zn – physical performance
Others may adversely affect water consumers, wastewater treatment systems, and receiving waters
Arsenic- cancer, toxic to aquatic spp
Asbestos – asbestosis ( ‘black' lung cancer)
Cadmium, chromium, copper – liver and kidney damage
Methods
Atomic absorption (AA)
Colorimetric methods
Sampling and sample preservation
What fraction to be analyzed
Dissolved
Suspended
Total
Acid-extractable
Preservation
Acidify with 1.5 ml (5ml for alkaline samples) HNO3 /L sample to pH < 2
Filter samples for dissolved metals before preserving
Store in fridge at 4oC
Stable for 6 months
Pre-treatment of samples
Total metals – all metals inorganically and organically bound, both dissolved and particulate
Colorless, odorless water - < I NTU – acidify with HNO3 to pH <2 and analyze directly
Dissolved metals
filter sample (0.45 micrometer membrane filter)
acidify filtrate with HNO3 to pH < 2
And analyze directly
Suspended metals
Filter sample (0.45 micrometer membrane filter)
Digest filter
And analyze
Acid-extractable metals
Extract metals
And analyze extract
Pre-treatment for Acid-extractable metals
extractable metals – lightly absorbed on particulate matter
At collection acidify sample with 5 ml HNO3/L sample
To prepare sample
Mix well
Transfer 100 ml to flask
Add 5 ml HCl
Heat 15 min on a steam bath
Filter thorough 0.45 micrometer membrane filter)
Adjust filtrate volume to 100 ml with water and analyze
Pre-digestion of metals
Reduce interference by organic matter and to convert metal associated with particulates to a form that can be determined by AA
HNO3 – digestion is adequate for clean samples or easily oxidized materials
HNO3-H2SO4 or HNO3-HCl – digestion is adequate for readily oxidizable organic matter
HNO3-HClO4 or HNO3-HClO4-HF – is for the difficult to oxidize organic matter or minerals
Nitric Acid Digestion
Mix sample
Transfer 50 to 100ml to 125 ml conical flask
Add 5 ml conc. HNO3 and few boiling chips
Boil and evaporate on hot plate to lowest volume (10 to 20 ml) before precipitation occurs
Continue heating and adding HNO3 until digestion is complete (light-coloured, clear solution)
Wash down flask walls with water and then filter
Transfer filtrate to 100 ml flask , cool, dilute to mark, mix and analyze.
Direct Air-Acetylene Flame Method
Applicable for Ca, Cd, Cr, Co, Cu, Fe, Mg, Mn, Ni, Zn, etc
Principle
The technique of flame atomic absorption spectroscopy (AA) requires a liquid sample to be aspirated, aerosolized, and mixed with combustible gases, such as acetylene and air or acetylene and nitrous oxide
The mixture is ignited in a flame whose temperature ranges from 2100 to 2800 oC
During combustion, atoms of the element of interest in the sample are reduced to free, unexcited ground state atoms, which absorb light at characteristic wavelengths
RISK ASSESSMENT
Environmental Engineer
objective
Reduce risk from hazards to the environment and public health
Estimate future risks, then use science to prevent or mitigate them
To determine the comparative risks from various environmental pollutants and which risks it is most important to decrease or eliminate
risk analysis
Risks associated with various hazards must evaluated and quantified
Risk
1970s – environmental laws were enacted to protect public heath
E.g. US Clean Air Act
No mention of risk in US Clean Air and Clean Water Acts
Acts required that pollution standards be set that would allow adequate margins of safety to protect public health
Assumption was that pollutants have thresholds and exposure to concentrations below these thresholds would produce no harm
Problems of toxic waste were finally recognized
Toxic substances are suspected carcinogens
Even smallest exposures creates a risk
If any exposure to a substance causes some risk, how can air quality and water quality standards be set
Emergence of the field of environmental risk assessment
1980s - environmental policy - was acceptance of the role of risk assessment and risk management in environmental decision making
Risk assessment
Is a system of analysis that includes four tasks
Identification of substance (toxicant) that may have adverse health effects
Scenarios for exposure to toxicant
Characterization of health effects
As estimate of the probability (risk) of occurrence of these health effects
Is the gathering of data that are used to relate response to dose
Such dose-response data can then be combined with estimates of the likely human exposure to produce overall assessment of risk
Risk management
is the process of deciding what to do
It is the decision making, about how to allocate national resources to protect public health and the environment
Is a one-in-a-million lifetime risk of getting cancer acceptable and, if it is, how do we go about trying to achieve it?
Hazardous substances
Hazardous and toxic substances are
defined as those chemicals present in the
environment which are capable of causing harm
Risk
is the possibility of loss or
injury to people and property
Hazard
a chemical, physical, or biological agent or a set of conditions that has the potential to cause harm
Risk Assessment
Hazard identification
Is the process of determine whether or not a particular chemical is causally linked to a particular health effects, such as cancer on birth effects
Dose-response assessment
Is the process of characterizing the relationship between the dose of an agent administered or received and the incidence of an adverse effect
Dose-Response Assessment
Characteristic features of the Dose- Response
relationship:
Threshold
Is the lowest dose at which there is an observable effect
Curve A – illustrate threshold response i.e. there is no observed effect until a particular concentration is reached
Curve B - linear response with no threshold i.e. the intensity of the effect is directly proportionally to the pollutant dose, and the effect is observed for any detectable concentration of the pollutant in question
Curve C –sublinear dose-response curve and is characteristic of many pollutant dose-response relationships.
It has no clearly defined threshold, the lowest dose at which a response can be detected is called threshold limit value (TLV)
Curve D – supralinear relationship, which is found when low doses of a pollutant appear to provoke a disproportionately large response
Total body burden
An organism or a person can be exposed to simultaneously to several sources of a given pollutant
Example
inhale about 50g/day lead from ambient air and
ingest 300g/day in food and water
The concentration of lead in the body is sum of what is inhaled and ingested and what remains in the body fro prior exposure, less what has been eliminated from the body
Physiological half-life
Is the time needed for the organism to eliminate half of the internal concentration of the pollutant, through metabolism or other normal physiological functions
Bioaccumulation and bioconcentation
Bioaccumulation occurs when a substance is concentrated in one organ or the of tissue of an organism
E.g. Iodine - bioaccumulates in the thyroid gland
The organ dose of a pollutant can thus be considerably greater than what the total body burden would predict
Bioconcentation occurs with a movement up the food chain
E.g. A study of Lake Michigan ecosystem (Hickey et al. 1966) found bioconcentation of DDT as follows:
0.014 ppm (wet weight) in bottom sediments
0.41 ppm in bottom-feeding crustacea
3-6 ppm in fish
2 400 ppm in fish –eating birds
Exposure time and time vs. dosage
Most pollutant need time to react; the exposure time is thus as important as the level of exposure
Synergism
Occurs when two or more substances enhance each other’s effects, and when the resulting effect of the combination on the organism is greater than the additive effects of the substances separately
E.g. black lung disease in miners – occurs more often in miners who smoke than in those who do not
LC50 and LD50
LD50 is the dose that is lethal for 50% of the experimental animals
LC50 refers to lethal concentration rather than lethal dose
LD50 values are most useful in comparing toxicities for pesticides and agricultural chemicals
Population responses
Differ from one individual to another
Depends on age, sex, and general state of physical and emotional health
Exposure and Latency
Characterization of some health risks can take a very time
E.g.. Cancers are noticed many years or decades after exposure to potentially responsible carcinogen
Cancer in adults have a latency period between 10 – 40 years
Latency period – length of time between exposure to a risk factor and expression of adverse effect
Relative risk
Is the ratio of the probabilities that an adverse effect will occur in two different populations
E.g. relative risk of lung cancer in smokers
Ps/Pn = (Xs/Ns)/(Xn/Nn)
where
Ps = probability of fatal lung cancer in smoker
Pn = probability of fatal lung cancer in non-smokers
Xs = number of fatal lung cancer among smokers
Xn = number of fatal lung cancer among non- smokers
Ns = total number of smokers
Nn= total number on non-smoker
Relative risk of death is also called standard mortality ratio (SMR)
SMR = Ds/Dn= Ps/Pn
where
Ds = observed lung cancer deaths in a population of habitual smokers
Dn = expected lung cancer deaths in a non-smoking population of the same size
Exposure assessment
Involves determining the size and nature of the population that has been exposed to the toxicant under consideration, and the length of time and toxicant concentration to which they have been exposed
Risk characterization
Is the integration of the foregoing three steps, which results in an estimate of the magnitude of the public-health problem
Monday, October 26, 2009
Spectroscopic Methods
Modern Electrochemistry - by J O'M Bockris, Amulya K N Reddy
Polymer Chemistry - by Malcolm P Stevens
Continuous Emission Monitoring - by James A. Jahnke
Spectroscopy
is the study of matter by investigating light, sound, or particles that are emitted, absorbed or scattered by the matter under investigation
Spectroscopy may also be defined as the study of the interaction between light and matter
Physical quantity measured
The type of spectroscopy depends on the physical quantity measured.
Normally, the quantity that is measured is an amount or intensity of something
Three main types of spectroscopy
Absorption spectroscopy uses the range
of electromagnetic spectra in which a
substance absorbs.
commonly used in atomic absorption spectroscopy, the sample is atomized and then light of a particular frequency is passed through the vapour
the amount of absorption can be related to the concentrations of various metal ions through the Beer-Lambert law
widely used to measure concentrations of ions such as sodium and calcium
Other types of spectroscopy may not require sample atomization
For example, ultraviolet/visible (UV/ Vis) absorption spectroscopy is most often performed on liquid samples to detect molecular content
Emission spectroscopy uses the range of
electromagnetic spectra in which a
substance radiates
The substance first absorbs energy and then radiates this energy as light
This energy can be from a variety of sources, including chemical reactions
Scattering spectroscopy
measures certain physical properties by measuring the amount of light that a substance scatters at certain wavelengths
Common types of spectroscopy
Flame Spectroscopy
Liquid solution samples are aspirated into a burner or nebulizer/burner combination, desolvated, atomized, and sometimes excited to a higher energy electronic state
The use of a flame during analysis requires fuel and oxidant, typically in the form of gases
Common fuel gases used are acetylene or hydrogen
Common oxidant gases used are oxygen, air, or nitrous oxide
methods are often capable of analyzing metallic element analytes in the part per million, billion, or possibly lower concentration ranges
Atomic Emission Spectroscopy
uses flame excitation; atoms are excited from the heat of the flame to emit light
commonly uses a total consumption burner with a round burning outlet
A higher temperature flame than atomic absorption spectroscopy (AA) is typically used to produce excitation of analyze atoms
Since analyte atoms are excited by the heat of the flame, no special elemental lamps to shine into the flame are needed
Atomic Fluorescence Spectroscopy
This method commonly uses a burner with a round burning outlet
The flame is used to solvate and atomize the sample, but a lamp shines light at a specific wavelength into the flame to excite the analyte atoms in the flame
The atoms of certain elements can then fluoresce emitting light in a different direction. The intensity of this fluorescing light is used for quantifying the amount of analyte element in the sample.
A graphite furnace can also be used for atomic fluorescence spectroscopy. This method is not as commonly used as atomic absorption or plasma emission spectroscopy.
Alternatively, a monochromator can be set at one wavelength to concentrate on analysis of a single element at a certain emission line
Plasma emission spectroscopy is a more modern version of this method.
Atomic Absorption Spectroscopy (often called AA)
commonly uses a pre-burner nebulizer (or nebulizing chamber) to create a sample mist and a slot-shaped burner which gives a longer pathlength flame
The temperature of the flame is low enough that the flame itself does not excite sample atoms from their ground state
The nebulizer and flame are used to desolvate and atomize the sample, but the excitation of the analyte atoms is done by the use of lamps shining through the flame at various wavelengths for each type of analyte
In AA, the amount of light absorbed after going through the flame determines the amount of analyte in the sample
A graphite furnace for heating the sample to desolvate and atomize is commonly used for greater sensitivity
The graphite furnace method can also analyze some solid or slurry samples.
Because of its good sensitivity and selectivity, it is still a commonly used method of analysis for certain trace elements in aqueous (and other liquid) samples.
Atomic Fluorescence Spectroscopy
This method commonly uses a burner with a round burning outlet
The flame is used to solvate and atomize the sample, but a lamp shines light at a specific wavelength into the flame to excite the analyte atoms in the flame
The atoms of certain elements can then fluoresce emitting light in a different direction. The intensity of this fluorescing light is used for quantifying the amount of analyte element in the sample.
A graphite furnace can also be used for atomic fluorescence spectroscopy. This method is not as commonly used as atomic absorption or plasma emission spectroscopy.
Spark or arc (emission) spectroscopy
can be used for the analysis of metallic elements in solid samples
An electric arc or spark is passed through the sample, heating the sample to a high temperature to excite the atoms in it
The excited analyte atoms glow emitting light at various wavelengths which could be detected by common spectroscopic methods
Since the conditions producing the arc emission typically are not controlled quantitatively, the analysis for the elements is qualitative.
Visible spectroscopy
Many atoms emit or absorb visible light. In order to obtain a fine line spectrum, the atoms must be in a gas phase. This means that the substance has to be vaporised.
Spectrum is studied in absorption or emission.
UV spectroscopy
All atoms absorb in the UV region because photons are energetic enough to excite outer electrons. If the frequency is high enough, photoionisation takes place.
Infra-red spectroscopy
In organic chemistry different types of interatomic bond vibrate at different frequencies in the infra-red part of the spectrum.
The analysis of IR absorption spectra shows what type of bonds are present in the sample.
Nuclear Magnetic Resonance (NMR) spectroscopy
NMR spectroscopy analyzes certain atomic nuclei to determine different local environments of hydrogen, carbon, or other atoms in the molecule of an organic compound or other compound. This is used to help determine the structure of the compound.
Use of Atomic Absorption (AA) Spectroscopic methods
Metals
Significance
Effects of metals in water and wastewater range from beneficial to dangerously toxic
Some metals are essential
Fe – blood
Cu, Zn – physical performance
Others may adversely affect water consumers, wastewater treatment systems, and receiving waters
Arsenic- cancer, toxic to aquatic spp
Asbestos – asbestosis ( ‘black' lung cancer)
Cadmium, chromium, copper – liver and kidney damage
Methods
Atomic absorption (AA)
Colorimetric methods
Sampling and sample preservation
What fraction to be analyzed
Dissolved
Suspended
Total
Acid-extractable
Preservation
Acidify with 1.5 ml (5ml for alkaline samples) HNO3 /L sample to pH < 2
Filter samples for dissolved metals before preserving
Store in fridge at 4oC
Stable for 6 months
Pre-treatment of samples
Total metals – all metals inorganically and organically bound, both dissolved and particulate
Colorless, odorless water - < I NTU – acidify with HNO3 to pH <2 and analyze directly
Dissolved metals
filter sample (0.45 micrometer membrane filter)
acidify filtrate with HNO3 to pH < 2
And analyze directly
Suspended metals
Filter sample (0.45 micrometer membrane filter)
Digest filter
And analyze
Acid-extractable metals
Extract metals
And analyze extract
Pre-treatment for Acid-extractable metals
extractable metals – lightly absorbed on particulate matter
At collection acidify sample with 5 ml HNO3/L sample
To prepare sample
Mix well
Transfer 100 ml to flask
Add 5 ml HCl
Heat 15 min on a steam bath
Filter thorough 0.45 micrometer membrane filter)
Adjust filtrate volume to 100 ml with water and analyze
Pre-digestion of metals
Reduce interference by organic matter and to convert metal associated with particulates to a form that can be determined by AA
HNO3 – digestion is adequate for clean samples or easily oxidized materials
HNO3-H2SO4 or HNO3-HCl – digestion is adequate for readily oxidizable organic matter
HNO3-HClO4 or HNO3-HClO4-HF – is for the difficult to oxidize organic matter or minerals
Nitric Acid Digestion
Mix sample
Transfer 50 to 100ml to 125 ml conical flask
Add 5 ml conc. HNO3 and few boiling chips
Boil and evaporate on hot plate to lowest volume (10 to 20 ml) before precipitation occurs
Continue heating and adding HNO3 until digestion is complete (light-coloured, clear solution)
Wash down flask walls with water and then filter
Transfer filtrate to 100 ml flask , cool, dilute to mark, mix and analyze.
Direct Air-Acetylene Flame Method
Applicable for Ca, Cd, Cr, Co, Cu, Fe, Mg, Mn, Ni, Zn, etc
Principle
The technique of flame atomic absorption spectroscopy (AA) requires a liquid sample to be aspirated, aerosolized, and mixed with combustible gases, such as acetylene and air or acetylene and nitrous oxide
The mixture is ignited in a flame whose temperature ranges from 2100 to 2800 oC
During combustion, atoms of the element of interest in the sample are reduced to free, unexcited ground state atoms, which absorb light at characteristic wavelengths
Polymer Chemistry - by Malcolm P Stevens
Continuous Emission Monitoring - by James A. Jahnke
Spectroscopy
is the study of matter by investigating light, sound, or particles that are emitted, absorbed or scattered by the matter under investigation
Spectroscopy may also be defined as the study of the interaction between light and matter
Physical quantity measured
The type of spectroscopy depends on the physical quantity measured.
Normally, the quantity that is measured is an amount or intensity of something
Three main types of spectroscopy
Absorption spectroscopy uses the range
of electromagnetic spectra in which a
substance absorbs.
commonly used in atomic absorption spectroscopy, the sample is atomized and then light of a particular frequency is passed through the vapour
the amount of absorption can be related to the concentrations of various metal ions through the Beer-Lambert law
widely used to measure concentrations of ions such as sodium and calcium
Other types of spectroscopy may not require sample atomization
For example, ultraviolet/visible (UV/ Vis) absorption spectroscopy is most often performed on liquid samples to detect molecular content
Emission spectroscopy uses the range of
electromagnetic spectra in which a
substance radiates
The substance first absorbs energy and then radiates this energy as light
This energy can be from a variety of sources, including chemical reactions
Scattering spectroscopy
measures certain physical properties by measuring the amount of light that a substance scatters at certain wavelengths
Common types of spectroscopy
Flame Spectroscopy
Liquid solution samples are aspirated into a burner or nebulizer/burner combination, desolvated, atomized, and sometimes excited to a higher energy electronic state
The use of a flame during analysis requires fuel and oxidant, typically in the form of gases
Common fuel gases used are acetylene or hydrogen
Common oxidant gases used are oxygen, air, or nitrous oxide
methods are often capable of analyzing metallic element analytes in the part per million, billion, or possibly lower concentration ranges
Atomic Emission Spectroscopy
uses flame excitation; atoms are excited from the heat of the flame to emit light
commonly uses a total consumption burner with a round burning outlet
A higher temperature flame than atomic absorption spectroscopy (AA) is typically used to produce excitation of analyze atoms
Since analyte atoms are excited by the heat of the flame, no special elemental lamps to shine into the flame are needed
Atomic Fluorescence Spectroscopy
This method commonly uses a burner with a round burning outlet
The flame is used to solvate and atomize the sample, but a lamp shines light at a specific wavelength into the flame to excite the analyte atoms in the flame
The atoms of certain elements can then fluoresce emitting light in a different direction. The intensity of this fluorescing light is used for quantifying the amount of analyte element in the sample.
A graphite furnace can also be used for atomic fluorescence spectroscopy. This method is not as commonly used as atomic absorption or plasma emission spectroscopy.
Alternatively, a monochromator can be set at one wavelength to concentrate on analysis of a single element at a certain emission line
Plasma emission spectroscopy is a more modern version of this method.
Atomic Absorption Spectroscopy (often called AA)
commonly uses a pre-burner nebulizer (or nebulizing chamber) to create a sample mist and a slot-shaped burner which gives a longer pathlength flame
The temperature of the flame is low enough that the flame itself does not excite sample atoms from their ground state
The nebulizer and flame are used to desolvate and atomize the sample, but the excitation of the analyte atoms is done by the use of lamps shining through the flame at various wavelengths for each type of analyte
In AA, the amount of light absorbed after going through the flame determines the amount of analyte in the sample
A graphite furnace for heating the sample to desolvate and atomize is commonly used for greater sensitivity
The graphite furnace method can also analyze some solid or slurry samples.
Because of its good sensitivity and selectivity, it is still a commonly used method of analysis for certain trace elements in aqueous (and other liquid) samples.
Atomic Fluorescence Spectroscopy
This method commonly uses a burner with a round burning outlet
The flame is used to solvate and atomize the sample, but a lamp shines light at a specific wavelength into the flame to excite the analyte atoms in the flame
The atoms of certain elements can then fluoresce emitting light in a different direction. The intensity of this fluorescing light is used for quantifying the amount of analyte element in the sample.
A graphite furnace can also be used for atomic fluorescence spectroscopy. This method is not as commonly used as atomic absorption or plasma emission spectroscopy.
Spark or arc (emission) spectroscopy
can be used for the analysis of metallic elements in solid samples
An electric arc or spark is passed through the sample, heating the sample to a high temperature to excite the atoms in it
The excited analyte atoms glow emitting light at various wavelengths which could be detected by common spectroscopic methods
Since the conditions producing the arc emission typically are not controlled quantitatively, the analysis for the elements is qualitative.
Visible spectroscopy
Many atoms emit or absorb visible light. In order to obtain a fine line spectrum, the atoms must be in a gas phase. This means that the substance has to be vaporised.
Spectrum is studied in absorption or emission.
UV spectroscopy
All atoms absorb in the UV region because photons are energetic enough to excite outer electrons. If the frequency is high enough, photoionisation takes place.
Infra-red spectroscopy
In organic chemistry different types of interatomic bond vibrate at different frequencies in the infra-red part of the spectrum.
The analysis of IR absorption spectra shows what type of bonds are present in the sample.
Nuclear Magnetic Resonance (NMR) spectroscopy
NMR spectroscopy analyzes certain atomic nuclei to determine different local environments of hydrogen, carbon, or other atoms in the molecule of an organic compound or other compound. This is used to help determine the structure of the compound.
Use of Atomic Absorption (AA) Spectroscopic methods
Metals
Significance
Effects of metals in water and wastewater range from beneficial to dangerously toxic
Some metals are essential
Fe – blood
Cu, Zn – physical performance
Others may adversely affect water consumers, wastewater treatment systems, and receiving waters
Arsenic- cancer, toxic to aquatic spp
Asbestos – asbestosis ( ‘black' lung cancer)
Cadmium, chromium, copper – liver and kidney damage
Methods
Atomic absorption (AA)
Colorimetric methods
Sampling and sample preservation
What fraction to be analyzed
Dissolved
Suspended
Total
Acid-extractable
Preservation
Acidify with 1.5 ml (5ml for alkaline samples) HNO3 /L sample to pH < 2
Filter samples for dissolved metals before preserving
Store in fridge at 4oC
Stable for 6 months
Pre-treatment of samples
Total metals – all metals inorganically and organically bound, both dissolved and particulate
Colorless, odorless water - < I NTU – acidify with HNO3 to pH <2 and analyze directly
Dissolved metals
filter sample (0.45 micrometer membrane filter)
acidify filtrate with HNO3 to pH < 2
And analyze directly
Suspended metals
Filter sample (0.45 micrometer membrane filter)
Digest filter
And analyze
Acid-extractable metals
Extract metals
And analyze extract
Pre-treatment for Acid-extractable metals
extractable metals – lightly absorbed on particulate matter
At collection acidify sample with 5 ml HNO3/L sample
To prepare sample
Mix well
Transfer 100 ml to flask
Add 5 ml HCl
Heat 15 min on a steam bath
Filter thorough 0.45 micrometer membrane filter)
Adjust filtrate volume to 100 ml with water and analyze
Pre-digestion of metals
Reduce interference by organic matter and to convert metal associated with particulates to a form that can be determined by AA
HNO3 – digestion is adequate for clean samples or easily oxidized materials
HNO3-H2SO4 or HNO3-HCl – digestion is adequate for readily oxidizable organic matter
HNO3-HClO4 or HNO3-HClO4-HF – is for the difficult to oxidize organic matter or minerals
Nitric Acid Digestion
Mix sample
Transfer 50 to 100ml to 125 ml conical flask
Add 5 ml conc. HNO3 and few boiling chips
Boil and evaporate on hot plate to lowest volume (10 to 20 ml) before precipitation occurs
Continue heating and adding HNO3 until digestion is complete (light-coloured, clear solution)
Wash down flask walls with water and then filter
Transfer filtrate to 100 ml flask , cool, dilute to mark, mix and analyze.
Direct Air-Acetylene Flame Method
Applicable for Ca, Cd, Cr, Co, Cu, Fe, Mg, Mn, Ni, Zn, etc
Principle
The technique of flame atomic absorption spectroscopy (AA) requires a liquid sample to be aspirated, aerosolized, and mixed with combustible gases, such as acetylene and air or acetylene and nitrous oxide
The mixture is ignited in a flame whose temperature ranges from 2100 to 2800 oC
During combustion, atoms of the element of interest in the sample are reduced to free, unexcited ground state atoms, which absorb light at characteristic wavelengths
OXYGEN DEMAND
OD
Concept derives from river support aquatic life at 20oC
Pollution of rivers with sewage
Incapable of supporting aquatic species such as fish
Rivers devoid oxygen
Pollution potential expressed in terms of oxygen demand
Options of measuring OD
Biochemical Oxygen Demand (BOD)
Chemical Oxygen Demand (COD
BIOCHEMICAL OXYGEN DEMAND
Biochemical oxygen demand (BOD) is a measure of the quantity of oxygen used by microorganisms (e.g., aerobic bacteria) in the oxidation of organic matter
Natural sources of organic matter include plant decay and leaf fall
Urban runoff carries pet wastes from streets and sidewalks; nutrients from lawn fertilizers; leaves, grass clippings, and paper from residential areas, which increase oxygen demand.
Oxygen consumed in the decomposition process robs other aquatic organisms of the oxygen they need to live
Organisms that are more tolerant of lower dissolved oxygen levels may replace a diversity of more sensitive organisms.
BIOCHEMICAL OXYGEN DEMAND (BOD)
Principle:
The method consists of filling with sample, to overflowing, an airtight bottle of the specified size and incubating it at the specified temperature for 5 days
Dissolved oxygen is measured initially and after incubation, and the BOD is computed from the difference between initial and final DO
Because the initial DO is determined shortly after the dilution is made, all oxygen uptake occurring after this measurement is included in the BOD measurement
In the presence of free oxygen, aerobic bacteria use the organic matter found in wastewater as “food”
The BOD test is an estimate of the “food” available in the sample.
The more “food” present in the waste, the more Dissolved Oxygen (DO) will be required
The BOD test measures the strength of the wastewater by measuring the amount of oxygen used by the bacteria as they stabilize the organic matter under controlled conditions of time and temperature.
Significance of BOD test
The BOD test is used to determine the relative oxygen requirements of wastewaters, effluents, and polluted waters
The test measures the oxygen utilized during a specified incubation period for the biochemical degradation of organic material.
It is also used to determine treatment plant efficiency in terms of BOD removal
measure waste loads to treatment plants
determine the effects of discharges on receiving waters
A major disadvantage of the BOD test is the amount of time (5 days) required to obtain the results.
When a measurement is made of all oxygen consuming materials in a sample, the result is termed “Total Biochemical Oxygen Demand” (TBOD), or often just simply “Biochemical Oxygen Demand” (BOD)
test is performed over a five day period, it is often referred to as a “Five Day BOD”, or a BOD5.
effluent contains large numbers of nitrifying organisms
organisms can exert an oxygen demand as they convert nitrogenous compounds (ammonia and organic nitrogen) to more stable forms (nitrites and nitrates)
measure just the oxygen demand exerted by organic (carbonaceous) compounds, excluding the oxygen demand exerted by the nitrogenous compounds
termed “Carbonaceous Biochemical Oxygen Demand”, or CBOD
the nitrifying organisms can be inhibited from using oxygen by the addition of a nitrification inhibitor to the samples
Sample Preservation
Samples may change greatly during handling and storage
Testing should be started as quickly as possible
To reduce the changes in those samples which must be held, keep the samples at or below 4°C
Do not allow samples to freeze
Samples may be kept for no more than 48 hours before beginning the BOD test.
Winkler Method
sample is pipetted into a 300ml BOD bottle containing aerated dilution water.
The DO content is determined and recorded and the bottle is incubated in the dark for five days at 20°C
At the end of five days, the final DO content is determined
the difference between the final DO reading and the initial DO reading is calculated
The decrease in DO is corrected for sample dilution, and represents the biochemical oxygen demand of the sample.
5 day period oxidation is 60-80%
20 day period - oxidation of carbonaceous matter is 95-99%
When dilution is not seeded,
BOD5 mg/l = (D1-D2)/P
When dilution is seeded,
BOD5 mg/l = (D1 - D2) - (B1 – B2)f/P
Where
D1 =Initial DO before incubation
D2 = Final DO after incubation
B1 = initial DO seed blank before incubation
B2 = final DO seeded blank after incubation
P = decimal volumetric fraction of sample used
f = ratio of seed diluted sample to seeded blank
Interferences
BOD test is dependent on biological activity
major interferences will be those substances which inhibit the growth of the microorganisms
chlorine, caustic alkalinity or acidity, mineral acids, and heavy metals (such as copper, zinc, chromium, and lead)
Excessive nitrites can interfere with the BOD determination
Growth of algae in the presence of light can cause problems
increasing the DO of the sample before testing
must be removed by deaeration
Nitrification
Noncarbonaceous matter – ammonia
two bacteria – capable of oxidizing ammonia to nitrite and subsequently to nitrate
Ammonia > Nitrite (Nitrosomonas)
Nitrite > Nitrate (Nitrobacter)
NH3 + O2 → NO2− + 3H
NO2− + H2O → NO3− + 2H
Oxygen demand - oxidation of ammonia to nitrate is called nitrogemous biochemical oxygen demand (NBOD)
Nitrification occurs – measured value will be higher than the true value
Pretreating Samples
Nitrification
Add 1 ml of nitrification inhibitors allylthiourea (ATU to each liter of dilution water
alkalinity or acidity
prevent bacteria from growing during the course of the BOD test
to prevent this, samples which have pH values higher than pH 8.0 or lower than pH 6.0 must be neutralized to pH 7.0 before the test is performed.
Chlorine
is such a strong oxidizing agent, it will inhibit the growth of living bacteria in the BOD test
samples containing residual chlorine must be pretreated to remove chlorine before the test is run by adding sodium sulfite to the sample
Seeding
BOD test relies on the presence of healthy organisms
If the samples tested contain materials which could kill or injure the microorganisms (such as chlorine, high or low pH, toxic materials)
then the condition must be corrected and healthy active organisms added
this process is known as seeding
preferred seed is effluent or mixed liquor from a biological treatment system processing the waste
Chemical oxygen demand
(COD)
Measure the oxygen equivalent of the organic matter in wastewater that can be oxidized chemically using dichromate in an acid solution
used in biological and non-biological oxidation of materials in water
COD = 2 X BOD
Advantages of COD test
Organic substances which are difficult to oxidize biologically – lignin – can be oxidized chemically
Certain organic substances may be toxic to microorganisms used in BOD test
COD test – can be completed in 2.5 hours
Concept derives from river support aquatic life at 20oC
Pollution of rivers with sewage
Incapable of supporting aquatic species such as fish
Rivers devoid oxygen
Pollution potential expressed in terms of oxygen demand
Options of measuring OD
Biochemical Oxygen Demand (BOD)
Chemical Oxygen Demand (COD
BIOCHEMICAL OXYGEN DEMAND
Biochemical oxygen demand (BOD) is a measure of the quantity of oxygen used by microorganisms (e.g., aerobic bacteria) in the oxidation of organic matter
Natural sources of organic matter include plant decay and leaf fall
Urban runoff carries pet wastes from streets and sidewalks; nutrients from lawn fertilizers; leaves, grass clippings, and paper from residential areas, which increase oxygen demand.
Oxygen consumed in the decomposition process robs other aquatic organisms of the oxygen they need to live
Organisms that are more tolerant of lower dissolved oxygen levels may replace a diversity of more sensitive organisms.
BIOCHEMICAL OXYGEN DEMAND (BOD)
Principle:
The method consists of filling with sample, to overflowing, an airtight bottle of the specified size and incubating it at the specified temperature for 5 days
Dissolved oxygen is measured initially and after incubation, and the BOD is computed from the difference between initial and final DO
Because the initial DO is determined shortly after the dilution is made, all oxygen uptake occurring after this measurement is included in the BOD measurement
In the presence of free oxygen, aerobic bacteria use the organic matter found in wastewater as “food”
The BOD test is an estimate of the “food” available in the sample.
The more “food” present in the waste, the more Dissolved Oxygen (DO) will be required
The BOD test measures the strength of the wastewater by measuring the amount of oxygen used by the bacteria as they stabilize the organic matter under controlled conditions of time and temperature.
Significance of BOD test
The BOD test is used to determine the relative oxygen requirements of wastewaters, effluents, and polluted waters
The test measures the oxygen utilized during a specified incubation period for the biochemical degradation of organic material.
It is also used to determine treatment plant efficiency in terms of BOD removal
measure waste loads to treatment plants
determine the effects of discharges on receiving waters
A major disadvantage of the BOD test is the amount of time (5 days) required to obtain the results.
When a measurement is made of all oxygen consuming materials in a sample, the result is termed “Total Biochemical Oxygen Demand” (TBOD), or often just simply “Biochemical Oxygen Demand” (BOD)
test is performed over a five day period, it is often referred to as a “Five Day BOD”, or a BOD5.
effluent contains large numbers of nitrifying organisms
organisms can exert an oxygen demand as they convert nitrogenous compounds (ammonia and organic nitrogen) to more stable forms (nitrites and nitrates)
measure just the oxygen demand exerted by organic (carbonaceous) compounds, excluding the oxygen demand exerted by the nitrogenous compounds
termed “Carbonaceous Biochemical Oxygen Demand”, or CBOD
the nitrifying organisms can be inhibited from using oxygen by the addition of a nitrification inhibitor to the samples
Sample Preservation
Samples may change greatly during handling and storage
Testing should be started as quickly as possible
To reduce the changes in those samples which must be held, keep the samples at or below 4°C
Do not allow samples to freeze
Samples may be kept for no more than 48 hours before beginning the BOD test.
Winkler Method
sample is pipetted into a 300ml BOD bottle containing aerated dilution water.
The DO content is determined and recorded and the bottle is incubated in the dark for five days at 20°C
At the end of five days, the final DO content is determined
the difference between the final DO reading and the initial DO reading is calculated
The decrease in DO is corrected for sample dilution, and represents the biochemical oxygen demand of the sample.
5 day period oxidation is 60-80%
20 day period - oxidation of carbonaceous matter is 95-99%
When dilution is not seeded,
BOD5 mg/l = (D1-D2)/P
When dilution is seeded,
BOD5 mg/l = (D1 - D2) - (B1 – B2)f/P
Where
D1 =Initial DO before incubation
D2 = Final DO after incubation
B1 = initial DO seed blank before incubation
B2 = final DO seeded blank after incubation
P = decimal volumetric fraction of sample used
f = ratio of seed diluted sample to seeded blank
Interferences
BOD test is dependent on biological activity
major interferences will be those substances which inhibit the growth of the microorganisms
chlorine, caustic alkalinity or acidity, mineral acids, and heavy metals (such as copper, zinc, chromium, and lead)
Excessive nitrites can interfere with the BOD determination
Growth of algae in the presence of light can cause problems
increasing the DO of the sample before testing
must be removed by deaeration
Nitrification
Noncarbonaceous matter – ammonia
two bacteria – capable of oxidizing ammonia to nitrite and subsequently to nitrate
Ammonia > Nitrite (Nitrosomonas)
Nitrite > Nitrate (Nitrobacter)
NH3 + O2 → NO2− + 3H
NO2− + H2O → NO3− + 2H
Oxygen demand - oxidation of ammonia to nitrate is called nitrogemous biochemical oxygen demand (NBOD)
Nitrification occurs – measured value will be higher than the true value
Pretreating Samples
Nitrification
Add 1 ml of nitrification inhibitors allylthiourea (ATU to each liter of dilution water
alkalinity or acidity
prevent bacteria from growing during the course of the BOD test
to prevent this, samples which have pH values higher than pH 8.0 or lower than pH 6.0 must be neutralized to pH 7.0 before the test is performed.
Chlorine
is such a strong oxidizing agent, it will inhibit the growth of living bacteria in the BOD test
samples containing residual chlorine must be pretreated to remove chlorine before the test is run by adding sodium sulfite to the sample
Seeding
BOD test relies on the presence of healthy organisms
If the samples tested contain materials which could kill or injure the microorganisms (such as chlorine, high or low pH, toxic materials)
then the condition must be corrected and healthy active organisms added
this process is known as seeding
preferred seed is effluent or mixed liquor from a biological treatment system processing the waste
Chemical oxygen demand
(COD)
Measure the oxygen equivalent of the organic matter in wastewater that can be oxidized chemically using dichromate in an acid solution
used in biological and non-biological oxidation of materials in water
COD = 2 X BOD
Advantages of COD test
Organic substances which are difficult to oxidize biologically – lignin – can be oxidized chemically
Certain organic substances may be toxic to microorganisms used in BOD test
COD test – can be completed in 2.5 hours
Landfill
Landfill
An engineered method for disposing refuse/waste by spreading the waste in thin layers, reducing each layer to the smallest practicable volume and periodically applying and compacting a layer of soil to cover the waste
Landfilling process
Deposition of solid waste in a prepared section of the site
Spreading and compaction of waste in layers (30-60 cm)
Covering waste with a layer of cover soil at the end of each day’s work (minimum 15 cm)
Finally cover the entire construction with a compacted earth layer (minimum 60 cm)
Landfill techniques
Trench method
Narrow excavation
Soil removed and stockpiled
Waste deposited at one slopped end
waste spread on an inclination of 3 horizontal : 1 vertical spread and compacted
Covered with soil at the end of each day
When entire trench filled, final earth cover is placed
Suitability
Flat areas
Groundwater is at significant depth
Cover soil is available
Area method
Waste is placed on undisturbed existing ground surface
Only top soil is removed for final cover
Suitability
Rough and irregular areas
Groundwater water table is near the surface
Ramp method
Combines both trench and area methods
Before deposition, small excavation in front of the proposed face of an existing slope
Soil removed and stockpiled
Waste deposited onto slope
Suitability
Irregular terrain of moderate sloping
Landfill site selection
Siting criteria
Economic
Relate to the cost of obtaining, developing and operating a site to an acceptable standard
Cost of land – land area 10-20 years
Development cost – surface drainage
Cover material availability
Access roads
Hauling distance
Value of land
Regional waste disposal links
Environmental
Relate to the potential threat to the physical environment, specifically to water resources
Groundwater vulnerability
Permeability of soils
Landuse
Topography - Slope (gentle is best)
Geology
Social
Relate to the possible adverse impact of a landfill on quality of life and to potential public resistance
Distance form settlement
Prevailing wind direction
Public acceptability
Sites of cultural value
Visibility
Proximity to airports
Advantages
Cheap initial costs
Cheap operational costs
Flexible
Easy putting into operation
Reclamation of land
Disadvantages
Cover soil
Pollution problem
Public acceptance
Environmental pollution
Leachate
In a landfill that is deprived of oxygen, waste materials may liquefy into an acid water solution called leachate
This leachate dissolve toxic components in landfill solids as it flows down through the landfill and out the bottom
Groundwater pollution
Gases
50% CH4 and 45% CO2
Peak production – 2 years
Gases vented into atmosphere
Greenhouse effect – global warming
CO2 is heavier – settle at the ground making water acidic
Prevention/minimization of environmental
pollution
Prevention of leachate
Prevent surface runoff over the landfill
Use good cover material – impermeable
Raise landfill above surrounding ground
Lining bottom of landfill with synthetic (impermeable) plastic or clay material
Gases
Install gas collection
Convert methane into electricity
Odors, flies and rodents
Use good cover material
Dust
Sprinkle water on access road and within landfill
Paper and plastics
Planting trees around landfill
Classification of Landfill Sites
Landfill are classified according to
Waste types
Inert waste
Less than 5% of biodegradable organic components
General waste
All waste that is not inert, wet or hazardous
Wet waste
Waste with a high moisture content
Hazardous waste
Waste that has the potential to have a significant adverse impact on the public or environment
Landfill size
Rural
< 500 tons p.a (up to
2,000 people)
Small
500 – 6,500 tons p.a (up to 26,500 people)
Medium
6,500 – 65,000 tons p.a
Large
>65,000 tons p.a
Classification of
Inert waste landfill
General waste landfills
Wet/Hazardous waste landfills
An engineered method for disposing refuse/waste by spreading the waste in thin layers, reducing each layer to the smallest practicable volume and periodically applying and compacting a layer of soil to cover the waste
Landfilling process
Deposition of solid waste in a prepared section of the site
Spreading and compaction of waste in layers (30-60 cm)
Covering waste with a layer of cover soil at the end of each day’s work (minimum 15 cm)
Finally cover the entire construction with a compacted earth layer (minimum 60 cm)
Landfill techniques
Trench method
Narrow excavation
Soil removed and stockpiled
Waste deposited at one slopped end
waste spread on an inclination of 3 horizontal : 1 vertical spread and compacted
Covered with soil at the end of each day
When entire trench filled, final earth cover is placed
Suitability
Flat areas
Groundwater is at significant depth
Cover soil is available
Area method
Waste is placed on undisturbed existing ground surface
Only top soil is removed for final cover
Suitability
Rough and irregular areas
Groundwater water table is near the surface
Ramp method
Combines both trench and area methods
Before deposition, small excavation in front of the proposed face of an existing slope
Soil removed and stockpiled
Waste deposited onto slope
Suitability
Irregular terrain of moderate sloping
Landfill site selection
Siting criteria
Economic
Relate to the cost of obtaining, developing and operating a site to an acceptable standard
Cost of land – land area 10-20 years
Development cost – surface drainage
Cover material availability
Access roads
Hauling distance
Value of land
Regional waste disposal links
Environmental
Relate to the potential threat to the physical environment, specifically to water resources
Groundwater vulnerability
Permeability of soils
Landuse
Topography - Slope (gentle is best)
Geology
Social
Relate to the possible adverse impact of a landfill on quality of life and to potential public resistance
Distance form settlement
Prevailing wind direction
Public acceptability
Sites of cultural value
Visibility
Proximity to airports
Advantages
Cheap initial costs
Cheap operational costs
Flexible
Easy putting into operation
Reclamation of land
Disadvantages
Cover soil
Pollution problem
Public acceptance
Environmental pollution
Leachate
In a landfill that is deprived of oxygen, waste materials may liquefy into an acid water solution called leachate
This leachate dissolve toxic components in landfill solids as it flows down through the landfill and out the bottom
Groundwater pollution
Gases
50% CH4 and 45% CO2
Peak production – 2 years
Gases vented into atmosphere
Greenhouse effect – global warming
CO2 is heavier – settle at the ground making water acidic
Prevention/minimization of environmental
pollution
Prevention of leachate
Prevent surface runoff over the landfill
Use good cover material – impermeable
Raise landfill above surrounding ground
Lining bottom of landfill with synthetic (impermeable) plastic or clay material
Gases
Install gas collection
Convert methane into electricity
Odors, flies and rodents
Use good cover material
Dust
Sprinkle water on access road and within landfill
Paper and plastics
Planting trees around landfill
Classification of Landfill Sites
Landfill are classified according to
Waste types
Inert waste
Less than 5% of biodegradable organic components
General waste
All waste that is not inert, wet or hazardous
Wet waste
Waste with a high moisture content
Hazardous waste
Waste that has the potential to have a significant adverse impact on the public or environment
Landfill size
Rural
< 500 tons p.a (up to
2,000 people)
Small
500 – 6,500 tons p.a (up to 26,500 people)
Medium
6,500 – 65,000 tons p.a
Large
>65,000 tons p.a
Classification of
Inert waste landfill
General waste landfills
Wet/Hazardous waste landfills
Treatment of Wastes
Treatment of Wastes
Chemically, physically or biologically
Disposed or discharged without harm to the environment
Range of processes – depend on nature of the particular waste
INCINERATION
Is a solid waste treatment technology involving burning waste at high temperature
Thermal treatment
Is a controlled process that uses combustion to converts a waste to a less bulky, less toxic, or less noxious material -Co2, water, ash
i.e. converts the waste into heat (that can be used to generate electricity), gaseous emissions (CO2)to the atmosphere and residual ash.
Pollution
ash
emission to the atmosphere of combustion product gases and particulate matter
Gaseous emissions
The combustiont gases exhausted to the atmosphere by incineration are a source of concern
Main pollutamts in the exhaust gases include acid gases – hydrogen chloride, sulphur dioxide, nitrogen oxides and carbon dioxide
The most serious environmental concerns
wastes that it produces significant amounts of dioxin and furan emissions to the atmosphere.
Dioxins and furans are health hazards
Emission control designs
The quantity of pollutants in the emissions from lincinerators
reduced by a process known as scrubbing - lower concentrations to acceptable levels before atmospheric release
Solid outputs
produces fly ash and bottom ash
amount of ash produced -ranges from 15% to 25% by weight of the original quantity of waste
fly ash amounts to about 10% to 20% of the total ash
The fly ash, by far, constitutes more of a potential health hazard than bottom ash
fly ash contains toxic metals such as lead, cadimium, copper and zinc as well as small amounts of dioxins and furans
Advantages of incineration
burning wastes in a controlled manner
best known method for treatment of clinical wastes and certain hazardous waste where pathogens and toxins must be destroyed by high temperatures.
large expensive land areas are not required
Disadvantages of incineration
equipment is costly to operate
not always a means of ultimate disposal
gaseous and particulate products - hazardous to health
COMPOSTING
Composting is the process of producing compost through aerobic decomposition of biodegradable organic matter
The decomposition is performed primarily by aerobes
This decomposition occurs naturally in all but the most hostile environments, such as within landfills or in extremely arid deserts, which prevent the microbes and other decomposers from thriving
Composting can be divided into the two
areas
Home compositing
Industrial compositing
Composting is the controlled decomposition of organic matter.
composer provides an optimal environment in which decomposers can thrive
a compost pile needs the correct mix of the following ingredients:
Carbon
Nitrogen
Oxygen (from air)
Water
Decomposition happens even in the absence of some of these ingredients, but not as quickly or as pleasantly.
For example, vegetables in a plastic bag will decompose, but the absence of air encourages the growth of anaerobic microbes that produce disagreeable odors, degradation under anaerobic conditions is called anaerobic digestion)
The goal in a composting system
is to provide a healthy environment and nutrition for the rapid decomposers, the bacteria
most rapid composting occurs with the ideal conditions
moisture content - 50 - 60 %
C/N ratio – 25-30:1
temperature – 20-40 oC
pH - 6 - 7.5
oxygen
Materials for composting
all biodegradable material will compost
substances such as non-vegetarian animal manures and bedding, by-products of food production and processing, restaurant grease and cooking oils, and residuals from the treatment of wastewater and drinking water.
Composting will also break down petroleum hydrocarbons and some toxic compounds for recycling and beneficial reuse
most commonly referred to as a form of bioremediation
High-carbon sources provide the cellulose needed by the composting bacteria for conversion to sugars and heat
High-nitrogen sources provide the most concentrated protein, which allow the compost bacteria to thrive
Composting techniques
Different techniques for composting all
employ the two primary methods of
aerobic composting:
Active composting
allows the most effective decomposing bacteria to thrive
kills most pathogens and seeds, and rapidly produces usable compost
Passive composting
lets nature take its course in a more leisurely manner and leaves many pathogens and seeds dormant in the pile
Composting systems
enclosed
home container compositing
industrial in-vessel compositing
in piles
industrial windrow compositing
Home composting
passive composting
throw everything in a pile in a corner and leave it alone for a year or two
active composting
monitoring the temperature, turning the pile regularly, and adjusting the ingredients over time
Microbes and heating the pile
compost pile - kept about as damp as a well wrung-out sponge
provides the moisture that all life needs to survive
Mesophilic bacteria enjoy midrange temperatures, from about 20 to 40 °C
As they decompose the organic matter, they generate heat, and the inner part of a compost pile heats up the most.
The heap should be about 1m wide, 1 m tall
Provide suitable insulating mass to allow a good heat build-up as the material decays
ideal temperature is around 60 °C
kills most pathogens and weed seeds
provide a suitable environment for thermophiic (heat-loving) bacteria, which are the fastest acting decomposers
The centre of the heap can get too hot
Industrial composting
as an alternative form of waste management to landfill
industrial composting or anaerobic digestion can be combined with mechanical sorting of mixed waste streams
Industrial composting helps prevent global warming by treatment of bidegradable waste before it enters landfill
Once this waste is landfilled it breaks down anaerobically producing landfill gas that contains CH4, a potent greenhouse gas
active composting techniques
achieved by composting inside an enclosed vessel which is monitored and adjusted continuously for optimal temperature, air flow, moisture, and other parameters
Compost windrow turners
In-vessel
industrial composting systems
used by a few urban centers around the world
The world's largest composter is in Edmonton, Alberta, Canada
which turns 220,000 tonnes of residential solid waste and 22,500 dry tonnes of biosolids per year
into 80,000 tonnes of compost using a facility 38,690 square metres in size
Chemically, physically or biologically
Disposed or discharged without harm to the environment
Range of processes – depend on nature of the particular waste
INCINERATION
Is a solid waste treatment technology involving burning waste at high temperature
Thermal treatment
Is a controlled process that uses combustion to converts a waste to a less bulky, less toxic, or less noxious material -Co2, water, ash
i.e. converts the waste into heat (that can be used to generate electricity), gaseous emissions (CO2)to the atmosphere and residual ash.
Pollution
ash
emission to the atmosphere of combustion product gases and particulate matter
Gaseous emissions
The combustiont gases exhausted to the atmosphere by incineration are a source of concern
Main pollutamts in the exhaust gases include acid gases – hydrogen chloride, sulphur dioxide, nitrogen oxides and carbon dioxide
The most serious environmental concerns
wastes that it produces significant amounts of dioxin and furan emissions to the atmosphere.
Dioxins and furans are health hazards
Emission control designs
The quantity of pollutants in the emissions from lincinerators
reduced by a process known as scrubbing - lower concentrations to acceptable levels before atmospheric release
Solid outputs
produces fly ash and bottom ash
amount of ash produced -ranges from 15% to 25% by weight of the original quantity of waste
fly ash amounts to about 10% to 20% of the total ash
The fly ash, by far, constitutes more of a potential health hazard than bottom ash
fly ash contains toxic metals such as lead, cadimium, copper and zinc as well as small amounts of dioxins and furans
Advantages of incineration
burning wastes in a controlled manner
best known method for treatment of clinical wastes and certain hazardous waste where pathogens and toxins must be destroyed by high temperatures.
large expensive land areas are not required
Disadvantages of incineration
equipment is costly to operate
not always a means of ultimate disposal
gaseous and particulate products - hazardous to health
COMPOSTING
Composting is the process of producing compost through aerobic decomposition of biodegradable organic matter
The decomposition is performed primarily by aerobes
This decomposition occurs naturally in all but the most hostile environments, such as within landfills or in extremely arid deserts, which prevent the microbes and other decomposers from thriving
Composting can be divided into the two
areas
Home compositing
Industrial compositing
Composting is the controlled decomposition of organic matter.
composer provides an optimal environment in which decomposers can thrive
a compost pile needs the correct mix of the following ingredients:
Carbon
Nitrogen
Oxygen (from air)
Water
Decomposition happens even in the absence of some of these ingredients, but not as quickly or as pleasantly.
For example, vegetables in a plastic bag will decompose, but the absence of air encourages the growth of anaerobic microbes that produce disagreeable odors, degradation under anaerobic conditions is called anaerobic digestion)
The goal in a composting system
is to provide a healthy environment and nutrition for the rapid decomposers, the bacteria
most rapid composting occurs with the ideal conditions
moisture content - 50 - 60 %
C/N ratio – 25-30:1
temperature – 20-40 oC
pH - 6 - 7.5
oxygen
Materials for composting
all biodegradable material will compost
substances such as non-vegetarian animal manures and bedding, by-products of food production and processing, restaurant grease and cooking oils, and residuals from the treatment of wastewater and drinking water.
Composting will also break down petroleum hydrocarbons and some toxic compounds for recycling and beneficial reuse
most commonly referred to as a form of bioremediation
High-carbon sources provide the cellulose needed by the composting bacteria for conversion to sugars and heat
High-nitrogen sources provide the most concentrated protein, which allow the compost bacteria to thrive
Composting techniques
Different techniques for composting all
employ the two primary methods of
aerobic composting:
Active composting
allows the most effective decomposing bacteria to thrive
kills most pathogens and seeds, and rapidly produces usable compost
Passive composting
lets nature take its course in a more leisurely manner and leaves many pathogens and seeds dormant in the pile
Composting systems
enclosed
home container compositing
industrial in-vessel compositing
in piles
industrial windrow compositing
Home composting
passive composting
throw everything in a pile in a corner and leave it alone for a year or two
active composting
monitoring the temperature, turning the pile regularly, and adjusting the ingredients over time
Microbes and heating the pile
compost pile - kept about as damp as a well wrung-out sponge
provides the moisture that all life needs to survive
Mesophilic bacteria enjoy midrange temperatures, from about 20 to 40 °C
As they decompose the organic matter, they generate heat, and the inner part of a compost pile heats up the most.
The heap should be about 1m wide, 1 m tall
Provide suitable insulating mass to allow a good heat build-up as the material decays
ideal temperature is around 60 °C
kills most pathogens and weed seeds
provide a suitable environment for thermophiic (heat-loving) bacteria, which are the fastest acting decomposers
The centre of the heap can get too hot
Industrial composting
as an alternative form of waste management to landfill
industrial composting or anaerobic digestion can be combined with mechanical sorting of mixed waste streams
Industrial composting helps prevent global warming by treatment of bidegradable waste before it enters landfill
Once this waste is landfilled it breaks down anaerobically producing landfill gas that contains CH4, a potent greenhouse gas
active composting techniques
achieved by composting inside an enclosed vessel which is monitored and adjusted continuously for optimal temperature, air flow, moisture, and other parameters
Compost windrow turners
In-vessel
industrial composting systems
used by a few urban centers around the world
The world's largest composter is in Edmonton, Alberta, Canada
which turns 220,000 tonnes of residential solid waste and 22,500 dry tonnes of biosolids per year
into 80,000 tonnes of compost using a facility 38,690 square metres in size
Monday, September 14, 2009
ENV 462 NOTES
SUSTAINABLE WASTE MANAGEMENT
Waste – is anything which is no longer useful and needs to be got rid of
Waste Management
Effective management of wastes is a fundamental requirement of ecologically sustainable development
Objectives of WM
Protection of human health
Promotion of hygiene
Protection of environment
Recycling of materials
Avoidance of waste
Reduction of waste quantities
Reduction of emissions and residuals
Protection of natural resources
Waste Management Strategy (WMS)
Waste management strategy (WMS) sets out to deal comprehensively with waste issues
identifies the most effective options for dealing with specific needs and problems
WMS enable a country to achieve a state of sustainable waste management
Waste Management Strategy (WMS)
Primary Objective
Provide a framework within which waste can be managed effectively to minimize or avoid adverse impacts on the environment, while at the same time allowing economic development and improvement in the quality of life
Secondary Objectives
Promote more efficient use and conservation of resources
Reduce the need for waste treatment facilities
Reduce inspection and enforcement costs
Greater cost efficiency within industry by reducing the volume of raw materials and lowering disposal costs
Compatible with international strategies and regulations
Principles of WMS
Integrated waste management
waste management from the point of generation to final disposal
The principles of ‘polluter pays’ and ‘user pAays’
The EU End-of-Life Vehicles Directive (2000/53/EC)
Waste generators and product designers
responsibility for the fate of their wastes and products
Waste management hierarchy
Waste management should be based on a waste management ‘hierarchy’ of
Waste Prevention/Source reduction
avoidance and reduction of waste creation
Recycling & Reuse
reuse and recycling of waste
Treatment
destroying, detoxifying or neutralising wastes
Disposal
discharging wastes
The internationally accepted approach to
waste management
Based on zero waste philosophy
Waste management hierarchy Example 1
ASK FOR THE DIAGRAM... IN CLASS
Waste management hierarchy Example 2
ASK FOR THE DIAGRAM... IN CLASS
Waste prevention/Minimisation
involves altering the design, manufacture, purchase, or use of products and materials to reduce the amount and toxicity of what gets thrown away
Waste prevention is sometimes called source reduction because it reduces or eliminates pollution at the source
donating an unwanted computer to a charity
photocopying on both sides of a sheet of paper
Altering material specifications so that fewer hazardous constituents are used in a manufacturing process
WASTE MANAGEMENT AND POLLUTION CONTROL
Basic consideration and concepts in
Environmental Quality
Development
An evolutionary process which uses the resource endowment of the planet to improve the welfare of the beneficiary community
Traditionally evaluated by economic and technological growth (measured in terms of GND and GDP)
Human Development Index (HDI) embraces
Health and nutrional status
Education achievement
Assess to resources and information
Equitable distribution of income
Well-paid employment opportunities
Basic freedom
All development activities inevitably lead to
some environmental changes (degradation)
Environment
Where we live, or our surroundings of air, water and land
Health
A state of complete physical, mental and social well being
Determined by population, environment, behavior and level of health services
Pollution
Contamination of the environment by biological, chemical, and/or physical agents and may arise through material events, volcanic eruptions, flooding, drought or human activity
Major driving forces of pollution (environmental decline)
Poverty
Resource-consumption
Economic growth
Rapid population growth
Sustainable Development
A development that meets the needs of the present without compromising the ability of future generations to meet their needs
Environmental Health
The control of all those factors in man’s physical environment which exercise or may exercise a deleterious effect on his physical environment, health and survival
Major components
Water resources management
Air quality management
Sanitation and waste management
Housing
Food safety
Occupational health and safety (incl. chemical safety and safe use of chemical
Control of environmental health
Public Health
The science and art of preventing disease, prolonging life and promoting health through organized efforts of society
Definitions of Waste
Several definitions used by different countries and organizations (e.g. UK EPA, EEC, US EPA, Botswana WMA 98, etc
Four major classes of waste are recognized
General waste
Controlled waste
Special waste
Hazardous waste
General waste
World Bank definition
A waste is a mixable object which has no direct use and is discarded permanently
UK EPA 1990 definition
Any substance which constitutes a scrap metal or an effluent or other unwanted surplus substance arising from the application of a process
Any substance or article which requires to be disposed of as being broken, worn out, contaminated or otherwise spoiled but excluding Explosives Act 1875
Botswana Waste Management Act 1998
Waste includes the following substances and any combination thereof which are discarded by any person or are accumulated or stored by any person for the purpose of recycling
Undesirable or superfluous by-products;
Residue or remainder of any process or activity;
Any gaseous, liquid or solid matter
Controlled waste
Households
Commercial
Industrial
Or any such waste
Special waste
These are waste “dangerous to life" as a result of their toxicity, corrosivity, volatility and inflammability and restrictive nature
Hazardous waste
Hazardous waste mean waste (solids, sludges, liquids and containerized infectious) which by reason of their chemical activity or toxic, explosive, corrosive and other characteristics, cause danger to health or the environment, whether alone or when coming into contact with other wastes
ENVIRONMENTAL LEGISLATION
Legislation
Is a law or set of laws passed by a parliament
Empower the environmental department or agency act on behalf of the environment and the community
Purpose
All waste disposal sites should be subject to legislative control
3 areas of concern
Planning for landuse
Pollution control
Waste management licenses
Environmental protection
Regulations and controls for health and safety
Botswana
Environmental legislation
Doesn’t exist
Fragmented both in substance and in terms of implementation mechanisms
Waste Management Act, 1998
Makes provision for efficient waste management in the country to prevent harm to human, animal and plant life and to minimize the pollution of the environment and cause provisions of the Basel Convention to prevail
Aim to control and regulate waste management in Botswana
Public Health Act, 1981
Designed to maintain a good environment for the protection of human health
It forbids the pollution of water resources by indiscriminate dumping of chemicals in the water
Local Authorities Bye-Laws
Provision for disposal of wastes
Enforcement by police officials
The Water Act, 1968
Provision on water pollution
Atmospheric Pollution (Prevention) Act, 1997
Aims to prevent atmospheric pollution by an industrial processes in any trade
Agricultural Resources (Conservation) Act, 1974
Aims at proper use and conservation of resources which are of agricultural importance
Agricultural Resources Board can issue regulations or conservation orders at controlling or preventing soil pollution
Environmental Impact Assessment Act, 2005
Mines and Minerals Act, (CAP.66:01 of 1977)
Mines, Quarries and Machinery Act (CAP.44:02 of 1978)
Explosives Act and Explosive Regulation Act (Cap 24:02)
Herbage Preservation (Preservation of fires) (CAP.38:02 of 1978)
United Nations Convention on Biodiversity (1992)
Wildlife Conservation Policy, 1986
National Conservation Strategy, 1990
National Policy on Natural Resources, Conservation and Development
Forestry Act (CAP.38:04 of 1976)
The Roads Act
Monuments and Relics Act (Cap 59:03)
Town and Country Planning Act (Cap.32:09 of 1980)
Basel Convention on the Control of
Transboundary Movements of
Hazardous Wastes and their Disposal,
1989
Botswana ratified convention in 2000
Aim to regulate movement and disposal of hazardous wastes from one country to another
Stockholm Convention on persistent
Organic pollutants (POPS), 2001
Botswana ratified convention in 2002
Aim to protect human health and the environment from persistent organic pollutants (POPs).
Bamako Convention on the ban of the
import into Africa and the Control of
Transboundary Movement of
Hazardous Wastes within Africa, 1991
Botswana ratified this convention in 2004
Aim to protect human health and the environment from dangers posed by hazardous wastes by reducing their generation to a minimum in terms of quantity and/or hazard potential
The Climate Change Convention,
1992
Botswana acceded to this convention in 1992
To regulate levels of greenhouse gas concentration in atmosphere in order to minimize the occurrence of climate change on a level that would impede sustainable development, or compromise food production.
Vienna Convention on the Protection
of the Ozone layer, 1985
Botswana ratified this convention in 1991
Its objective is to protect human health and the environment against adverse effects resulting from modifications of ozone layer
The Convention encourages and where necessary facilitates cooperation in research and the sharing of information relating to the depletion of ozone layer.
Montreal Protocol on Substances that
Deplete the Ozone layer, 1987
Botswana ratified this convention in 1991
Its objective is to encourage participants to take precautionary measures to control global emissions of the ozone layer depleting substances
It is responsible for the control and use of chlorofluorocarbons (CFCs) and other chlorine containing substances, with the ultimate objective of their elimination
Waste Management
3 (4) Rs of WM
The three (four) R’s of reduce, reuse and recycle (& refuse) should be looked as partial solutions
All three of these activities serve to lessen the impact that human activities have on the environment
Promote prevention and minimization
Waste prevention – 1st goal
Waste minimization
attitude of mind
Technique for industry
Input materials
Product design
Process change
Recycling
Recycling can be defined as making something new/useful from waste materials that could otherwise be thrown away
Benefits of recycling
Saves Landfill Space
Recycling is one way to reduce the amount of waste that is landfilled
Recycling Can Reduce the Cost of Waste Disposal
Getting rid of waste isn’t a free proposition
Garbage trucks must pay to dump their waste at a landfill
The payment is called a tipping fee, and it is based on the weight or volume of the garbage.
2008 Gaborone Landfill rates
General waste – P40 a ton
Garden waste – P60 a ton
Rubble/soil – P50 for 2tons
Medical waste – P50 a kg
In Vermont, one landfill charges about $65 a ton for the waste it receives
In 2003, recycling and composting diverted 72 million tons of material from landfill
Recycling Can Save Energy
It almost always takes less energy to make a product from recycled materials than it does to make it from new materials
Using recycled aluminum scrap to make new aluminum cans, for example, uses 95 percent less energy than making aluminum cans from bauxite ore, the raw material used to make aluminum
Recycling Saves Natural Resources
Natural resources are riches provided courtesy of Mother Nature
Natural resources include land, plants, minerals, and water
By using materials more than once, we conserve natural resources
In the case of paper, recycling saves trees and water. Making a ton of paper from recycled stock saves up to 17 trees and uses 50 percent less water.
Recycling Can Reduce Air and Water Pollution
Using aluminum scrap instead of bauxite ore to make new aluminum products cuts air and water pollution by 95 percent
Recycling Creates Jobs
Recycling is estimated to create almost five times as many jobs as waste disposal
Recycling requires businesses that collect, haul, and process recyclables, as well as businesses that manufacture products from recycled materials
People employed in the recycling industry may be material sorters, truck drivers, sales representatives, process, engineers, or chemists. The National Recycling Coalition reports that recycling supports 1.1 million jobs in the U.S.
Why Recycling is needed?
Many residents, as well as shops and commercial establishments, dump indiscriminately at unofficial dumping sites, often old sand quarries
These unofficial sites present a direct hazard to people and livestock
They are unfenced, and contain anything from construction debris to plastic bags, tins, paint cans and possibly medical or other infectious wastes
Cows and goats routinely rummage through the sites, sometimes ingesting plastic bags or cutting themselves on glass.
People are also found at these sites, often barefooted, scavenging what reusable material they can find.
Materials that can be recycled include, but
not limited to:
Paper
Steel cans
Aluminum cans
Scrap metal
Plastics
Glass
Tires
Organic/ Garden Waste
Car batteries
Used Oil
Paper
Uncontaminated waste paper such as general office paper, news papers, magazines, food packaging, cement packets, cardboard boxes, corrugated brown and white cartons and craft paper of all kinds can be collected and taken for recycling
Some papers such as plastic-coated, tarred, carbon-paper and contaminated paper are not collected for recycling
In Botswana, the recycling companies collect various kinds of paper from different areas such as shopping malls, schools and institutions
The collected paper is then baled/ compacted into bundles and then loaded into trucks/ train wagons and sent to recycling plants either in Zimbabwe or South Africa.
Steel cans
Hard metal-cans which are often used for food packaging (tin-stuff)
Steel cans can be collected and thereby sent to recycling companies such as Collect-a-Can
Cans are then crushed into ingots and then taken to South African plants for recycling
The crushed cans can be used to make industrial steel products such as reinforcing wire and fencing wire
It takes 75% less energy to make steel from recovered metal than from raw materials
More cans can be made from fewer raw materials, and today every steel can contains 25% of recycled steel.
Aluminium Cans
Relatively soft metal-cans, which are often used to store beverages.
Aluminium drink cans can be recycled time and time again without loss of quality to enable them to be manufactured again and again into new drink cans of high quality
The recycling process of these cans happens in much the same way as steel cans
Recycling aluminium cans is economical and sustainable, i.e. 95 percent of the energy used in producing aluminium from its natural state (Bauxhite) is saved
Scrap Metal
Include old car bodies, engine blocks, gearboxes and any other metal component that is found in used motor-vehicles.
A number of companies around Gaborone collect scrap metal from various sources and send it to South Africa for recycling
Motor vehicle batteries
Old car batteries, which are potentially very polluting can be recycled
Lead acid batteries should be taken back to the supplier after their end of life use
Prevents the harmful substances that are contained in batteries from posing a health hazard to humans and other life forms.
Plastics
Plastics are used world-wide as a packaging material and are routinely classified into seven types according to the following number system:
PET (Polyethylene Terephthalate)
PE-HD (High Density Polyethylene)
PVC (Polyvinyl Chloride)
PE-LD (Low Density Polyethylene)
PP (Polypropylene)
PS (Polystyrene)
Other
The most common type of plastics found in the domestic waste stream in Botswana are polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC) Each type of plastic is technically recyclable, however, in practice types 1, 2 and 4 are the easiest to recycle into new products
All plastics for recycling must be clean and label free
Plastic shopping bags are the least desirable for recycling but can be re-used for making bags, mats, and hats
Glass
Used glass bottles can be re-used again to store various liquid materials in the household
Some beverage bottles can be returned to retail stores or Kgalagadi Beverages for cash-deposit. Somarelang Tikologo currently collects glass bottles from schools, bars, hotels and shopping malls in and around Gaborone and take them to South Africa for recycling
Local entrepreneurs are encouraged to get into recycling of glass bottles as some financial benefits can be accrued with the environment being kept clean at the same time
Tyres
It takes over 800 years to decompose old tires
This makes them to be persistent in the environment and thereby posing health hazards to humans and other organisms
To remedy this problem, they can be recycled into road asphalt, shoes, and furniture
Some local entrepreneurs re-use tires to produce flowerpots, drinking/ watering troughs and other useful items
Organic Waste:
The non-animal kitchen waste can be easily composted to improve garden soil, for instance: vegetable waste, bread, fruit peels, and grains
These can be mixed with garden waste to enhance the formation of compost
This means that composting could save a large part of the land, which would otherwise be used for disposal of municipal and garden waste
Waste – is anything which is no longer useful and needs to be got rid of
Waste Management
Effective management of wastes is a fundamental requirement of ecologically sustainable development
Objectives of WM
Protection of human health
Promotion of hygiene
Protection of environment
Recycling of materials
Avoidance of waste
Reduction of waste quantities
Reduction of emissions and residuals
Protection of natural resources
Waste Management Strategy (WMS)
Waste management strategy (WMS) sets out to deal comprehensively with waste issues
identifies the most effective options for dealing with specific needs and problems
WMS enable a country to achieve a state of sustainable waste management
Waste Management Strategy (WMS)
Primary Objective
Provide a framework within which waste can be managed effectively to minimize or avoid adverse impacts on the environment, while at the same time allowing economic development and improvement in the quality of life
Secondary Objectives
Promote more efficient use and conservation of resources
Reduce the need for waste treatment facilities
Reduce inspection and enforcement costs
Greater cost efficiency within industry by reducing the volume of raw materials and lowering disposal costs
Compatible with international strategies and regulations
Principles of WMS
Integrated waste management
waste management from the point of generation to final disposal
The principles of ‘polluter pays’ and ‘user pAays’
The EU End-of-Life Vehicles Directive (2000/53/EC)
Waste generators and product designers
responsibility for the fate of their wastes and products
Waste management hierarchy
Waste management should be based on a waste management ‘hierarchy’ of
Waste Prevention/Source reduction
avoidance and reduction of waste creation
Recycling & Reuse
reuse and recycling of waste
Treatment
destroying, detoxifying or neutralising wastes
Disposal
discharging wastes
The internationally accepted approach to
waste management
Based on zero waste philosophy
Waste management hierarchy Example 1
ASK FOR THE DIAGRAM... IN CLASS
Waste management hierarchy Example 2
ASK FOR THE DIAGRAM... IN CLASS
Waste prevention/Minimisation
involves altering the design, manufacture, purchase, or use of products and materials to reduce the amount and toxicity of what gets thrown away
Waste prevention is sometimes called source reduction because it reduces or eliminates pollution at the source
donating an unwanted computer to a charity
photocopying on both sides of a sheet of paper
Altering material specifications so that fewer hazardous constituents are used in a manufacturing process
WASTE MANAGEMENT AND POLLUTION CONTROL
Basic consideration and concepts in
Environmental Quality
Development
An evolutionary process which uses the resource endowment of the planet to improve the welfare of the beneficiary community
Traditionally evaluated by economic and technological growth (measured in terms of GND and GDP)
Human Development Index (HDI) embraces
Health and nutrional status
Education achievement
Assess to resources and information
Equitable distribution of income
Well-paid employment opportunities
Basic freedom
All development activities inevitably lead to
some environmental changes (degradation)
Environment
Where we live, or our surroundings of air, water and land
Health
A state of complete physical, mental and social well being
Determined by population, environment, behavior and level of health services
Pollution
Contamination of the environment by biological, chemical, and/or physical agents and may arise through material events, volcanic eruptions, flooding, drought or human activity
Major driving forces of pollution (environmental decline)
Poverty
Resource-consumption
Economic growth
Rapid population growth
Sustainable Development
A development that meets the needs of the present without compromising the ability of future generations to meet their needs
Environmental Health
The control of all those factors in man’s physical environment which exercise or may exercise a deleterious effect on his physical environment, health and survival
Major components
Water resources management
Air quality management
Sanitation and waste management
Housing
Food safety
Occupational health and safety (incl. chemical safety and safe use of chemical
Control of environmental health
Public Health
The science and art of preventing disease, prolonging life and promoting health through organized efforts of society
Definitions of Waste
Several definitions used by different countries and organizations (e.g. UK EPA, EEC, US EPA, Botswana WMA 98, etc
Four major classes of waste are recognized
General waste
Controlled waste
Special waste
Hazardous waste
General waste
World Bank definition
A waste is a mixable object which has no direct use and is discarded permanently
UK EPA 1990 definition
Any substance which constitutes a scrap metal or an effluent or other unwanted surplus substance arising from the application of a process
Any substance or article which requires to be disposed of as being broken, worn out, contaminated or otherwise spoiled but excluding Explosives Act 1875
Botswana Waste Management Act 1998
Waste includes the following substances and any combination thereof which are discarded by any person or are accumulated or stored by any person for the purpose of recycling
Undesirable or superfluous by-products;
Residue or remainder of any process or activity;
Any gaseous, liquid or solid matter
Controlled waste
Households
Commercial
Industrial
Or any such waste
Special waste
These are waste “dangerous to life" as a result of their toxicity, corrosivity, volatility and inflammability and restrictive nature
Hazardous waste
Hazardous waste mean waste (solids, sludges, liquids and containerized infectious) which by reason of their chemical activity or toxic, explosive, corrosive and other characteristics, cause danger to health or the environment, whether alone or when coming into contact with other wastes
ENVIRONMENTAL LEGISLATION
Legislation
Is a law or set of laws passed by a parliament
Empower the environmental department or agency act on behalf of the environment and the community
Purpose
All waste disposal sites should be subject to legislative control
3 areas of concern
Planning for landuse
Pollution control
Waste management licenses
Environmental protection
Regulations and controls for health and safety
Botswana
Environmental legislation
Doesn’t exist
Fragmented both in substance and in terms of implementation mechanisms
Waste Management Act, 1998
Makes provision for efficient waste management in the country to prevent harm to human, animal and plant life and to minimize the pollution of the environment and cause provisions of the Basel Convention to prevail
Aim to control and regulate waste management in Botswana
Public Health Act, 1981
Designed to maintain a good environment for the protection of human health
It forbids the pollution of water resources by indiscriminate dumping of chemicals in the water
Local Authorities Bye-Laws
Provision for disposal of wastes
Enforcement by police officials
The Water Act, 1968
Provision on water pollution
Atmospheric Pollution (Prevention) Act, 1997
Aims to prevent atmospheric pollution by an industrial processes in any trade
Agricultural Resources (Conservation) Act, 1974
Aims at proper use and conservation of resources which are of agricultural importance
Agricultural Resources Board can issue regulations or conservation orders at controlling or preventing soil pollution
Environmental Impact Assessment Act, 2005
Mines and Minerals Act, (CAP.66:01 of 1977)
Mines, Quarries and Machinery Act (CAP.44:02 of 1978)
Explosives Act and Explosive Regulation Act (Cap 24:02)
Herbage Preservation (Preservation of fires) (CAP.38:02 of 1978)
United Nations Convention on Biodiversity (1992)
Wildlife Conservation Policy, 1986
National Conservation Strategy, 1990
National Policy on Natural Resources, Conservation and Development
Forestry Act (CAP.38:04 of 1976)
The Roads Act
Monuments and Relics Act (Cap 59:03)
Town and Country Planning Act (Cap.32:09 of 1980)
Basel Convention on the Control of
Transboundary Movements of
Hazardous Wastes and their Disposal,
1989
Botswana ratified convention in 2000
Aim to regulate movement and disposal of hazardous wastes from one country to another
Stockholm Convention on persistent
Organic pollutants (POPS), 2001
Botswana ratified convention in 2002
Aim to protect human health and the environment from persistent organic pollutants (POPs).
Bamako Convention on the ban of the
import into Africa and the Control of
Transboundary Movement of
Hazardous Wastes within Africa, 1991
Botswana ratified this convention in 2004
Aim to protect human health and the environment from dangers posed by hazardous wastes by reducing their generation to a minimum in terms of quantity and/or hazard potential
The Climate Change Convention,
1992
Botswana acceded to this convention in 1992
To regulate levels of greenhouse gas concentration in atmosphere in order to minimize the occurrence of climate change on a level that would impede sustainable development, or compromise food production.
Vienna Convention on the Protection
of the Ozone layer, 1985
Botswana ratified this convention in 1991
Its objective is to protect human health and the environment against adverse effects resulting from modifications of ozone layer
The Convention encourages and where necessary facilitates cooperation in research and the sharing of information relating to the depletion of ozone layer.
Montreal Protocol on Substances that
Deplete the Ozone layer, 1987
Botswana ratified this convention in 1991
Its objective is to encourage participants to take precautionary measures to control global emissions of the ozone layer depleting substances
It is responsible for the control and use of chlorofluorocarbons (CFCs) and other chlorine containing substances, with the ultimate objective of their elimination
Waste Management
3 (4) Rs of WM
The three (four) R’s of reduce, reuse and recycle (& refuse) should be looked as partial solutions
All three of these activities serve to lessen the impact that human activities have on the environment
Promote prevention and minimization
Waste prevention – 1st goal
Waste minimization
attitude of mind
Technique for industry
Input materials
Product design
Process change
Recycling
Recycling can be defined as making something new/useful from waste materials that could otherwise be thrown away
Benefits of recycling
Saves Landfill Space
Recycling is one way to reduce the amount of waste that is landfilled
Recycling Can Reduce the Cost of Waste Disposal
Getting rid of waste isn’t a free proposition
Garbage trucks must pay to dump their waste at a landfill
The payment is called a tipping fee, and it is based on the weight or volume of the garbage.
2008 Gaborone Landfill rates
General waste – P40 a ton
Garden waste – P60 a ton
Rubble/soil – P50 for 2tons
Medical waste – P50 a kg
In Vermont, one landfill charges about $65 a ton for the waste it receives
In 2003, recycling and composting diverted 72 million tons of material from landfill
Recycling Can Save Energy
It almost always takes less energy to make a product from recycled materials than it does to make it from new materials
Using recycled aluminum scrap to make new aluminum cans, for example, uses 95 percent less energy than making aluminum cans from bauxite ore, the raw material used to make aluminum
Recycling Saves Natural Resources
Natural resources are riches provided courtesy of Mother Nature
Natural resources include land, plants, minerals, and water
By using materials more than once, we conserve natural resources
In the case of paper, recycling saves trees and water. Making a ton of paper from recycled stock saves up to 17 trees and uses 50 percent less water.
Recycling Can Reduce Air and Water Pollution
Using aluminum scrap instead of bauxite ore to make new aluminum products cuts air and water pollution by 95 percent
Recycling Creates Jobs
Recycling is estimated to create almost five times as many jobs as waste disposal
Recycling requires businesses that collect, haul, and process recyclables, as well as businesses that manufacture products from recycled materials
People employed in the recycling industry may be material sorters, truck drivers, sales representatives, process, engineers, or chemists. The National Recycling Coalition reports that recycling supports 1.1 million jobs in the U.S.
Why Recycling is needed?
Many residents, as well as shops and commercial establishments, dump indiscriminately at unofficial dumping sites, often old sand quarries
These unofficial sites present a direct hazard to people and livestock
They are unfenced, and contain anything from construction debris to plastic bags, tins, paint cans and possibly medical or other infectious wastes
Cows and goats routinely rummage through the sites, sometimes ingesting plastic bags or cutting themselves on glass.
People are also found at these sites, often barefooted, scavenging what reusable material they can find.
Materials that can be recycled include, but
not limited to:
Paper
Steel cans
Aluminum cans
Scrap metal
Plastics
Glass
Tires
Organic/ Garden Waste
Car batteries
Used Oil
Paper
Uncontaminated waste paper such as general office paper, news papers, magazines, food packaging, cement packets, cardboard boxes, corrugated brown and white cartons and craft paper of all kinds can be collected and taken for recycling
Some papers such as plastic-coated, tarred, carbon-paper and contaminated paper are not collected for recycling
In Botswana, the recycling companies collect various kinds of paper from different areas such as shopping malls, schools and institutions
The collected paper is then baled/ compacted into bundles and then loaded into trucks/ train wagons and sent to recycling plants either in Zimbabwe or South Africa.
Steel cans
Hard metal-cans which are often used for food packaging (tin-stuff)
Steel cans can be collected and thereby sent to recycling companies such as Collect-a-Can
Cans are then crushed into ingots and then taken to South African plants for recycling
The crushed cans can be used to make industrial steel products such as reinforcing wire and fencing wire
It takes 75% less energy to make steel from recovered metal than from raw materials
More cans can be made from fewer raw materials, and today every steel can contains 25% of recycled steel.
Aluminium Cans
Relatively soft metal-cans, which are often used to store beverages.
Aluminium drink cans can be recycled time and time again without loss of quality to enable them to be manufactured again and again into new drink cans of high quality
The recycling process of these cans happens in much the same way as steel cans
Recycling aluminium cans is economical and sustainable, i.e. 95 percent of the energy used in producing aluminium from its natural state (Bauxhite) is saved
Scrap Metal
Include old car bodies, engine blocks, gearboxes and any other metal component that is found in used motor-vehicles.
A number of companies around Gaborone collect scrap metal from various sources and send it to South Africa for recycling
Motor vehicle batteries
Old car batteries, which are potentially very polluting can be recycled
Lead acid batteries should be taken back to the supplier after their end of life use
Prevents the harmful substances that are contained in batteries from posing a health hazard to humans and other life forms.
Plastics
Plastics are used world-wide as a packaging material and are routinely classified into seven types according to the following number system:
PET (Polyethylene Terephthalate)
PE-HD (High Density Polyethylene)
PVC (Polyvinyl Chloride)
PE-LD (Low Density Polyethylene)
PP (Polypropylene)
PS (Polystyrene)
Other
The most common type of plastics found in the domestic waste stream in Botswana are polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC) Each type of plastic is technically recyclable, however, in practice types 1, 2 and 4 are the easiest to recycle into new products
All plastics for recycling must be clean and label free
Plastic shopping bags are the least desirable for recycling but can be re-used for making bags, mats, and hats
Glass
Used glass bottles can be re-used again to store various liquid materials in the household
Some beverage bottles can be returned to retail stores or Kgalagadi Beverages for cash-deposit. Somarelang Tikologo currently collects glass bottles from schools, bars, hotels and shopping malls in and around Gaborone and take them to South Africa for recycling
Local entrepreneurs are encouraged to get into recycling of glass bottles as some financial benefits can be accrued with the environment being kept clean at the same time
Tyres
It takes over 800 years to decompose old tires
This makes them to be persistent in the environment and thereby posing health hazards to humans and other organisms
To remedy this problem, they can be recycled into road asphalt, shoes, and furniture
Some local entrepreneurs re-use tires to produce flowerpots, drinking/ watering troughs and other useful items
Organic Waste:
The non-animal kitchen waste can be easily composted to improve garden soil, for instance: vegetable waste, bread, fruit peels, and grains
These can be mixed with garden waste to enhance the formation of compost
This means that composting could save a large part of the land, which would otherwise be used for disposal of municipal and garden waste
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