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
Monday, October 26, 2009
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
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