4. Solid waste
• Solid waste is defined as discarded solid fraction produced
from domestic, commercial, trade, industrial, agricultural,
institutional, mining activities and public services.
• Handling the problem of solid waste in an efficient manner is
known as the solid waste management.
• The organic matter (night soil, excreta, food, vegetable, paper)
can be converted into useful biogas and compost.
• The problem is of separating it from the inorganic waste like
ashes, rubbish, non bio-degradable waste.
• Segregation – Producer end – Punishment.
5. Continued. .
• Efficient collection and transportation are essential parts of
solid waste management.
• There is no effective door to door collection system or a self
motivated culture of putting the waste in the bins.
• As a result most of the budget (60-70%) available with
municipalities is used for street sweeping and 20-30% for
transportation.
• So very less amount (5%) for scientific treatment of collected
waste.
• Open dumping – Leachates, burning – Harmful gases.
6. Sources
Domestic/Residential
waste
Cooking , cleaning etc
Municipal waste
Street sweepings,
dead animals
Commercial waste
Offices, restaurants
Institutional waste
Colleges, universities
Garbage
Animal vegetable
wastes from food
preparation
Ashes
7. Bulky waste
Burning of wood, coal.
Street sweepings
Paper, plastic
Dead animals
Construction and
demolition waste
Industrial wastes
Manufacturing process
wastes
Hazardous waste
Waste from hospitals,
radio active waste.
Sewage waste
Solid by-products of sewage treatment
8.
9. Composition & Characteristics of solid
waste
• The composition and characteristics of municipal
solid waste is not same throughout the world and
even in the same country it changes from place to
place and time to time.
• It depends upon the living standard, social customs,
location of a place, climate and weather conditions.
• Quantity and Composition of waste changes among
different income groups.
10. Physical characteristics
• Density
Important for the design of all the elements of the SWM.
Varies significantly from source to disposal site(Handling)
• Moisture content
Weight of moisture to unit weight of wet material.
20-45 % , increase in moisture causes high density and
transportation costs
11. Chemical characteristics
• Chemical : pH, N-P-K, C/N, total carbon etc.
Calorific value
– Amount of heat generated by combustion of unit weight of
solid waste (kcal / kg).
– Bomb calorimeter.
• Bio chemical
– Biodegradable factor, carbohydrates, proteins etc.
• Toxic characteristics
– Heavy metals, pesticides, insecticides.
12. These characteristics are required to
• Design
• Conceive and assess the most appropriate
ways of
• Transportation
• The requirements of treatment
• Extraction of energy
• Safe, sanitary way of disposal for the
protection of Environment.
13. Solid Waste Management(SWM)
The solid waste management has the following
components:
Identification of waste and its minimization at the
source
Collection, segregation and storage at the site of
collection
Transportation
Treatment
Energy recovery and Disposal
13
14. 1.Identification of waste and its
minimization at the source
• Identification helps in further process of
transportation, treatment and disposal.
• Ex: Hazardous waste should be treated in
different manner than ordinary SW.
14
15. Contd..
• Minimization of waste production is the best
strategy.
• Examples
1. Footwear making Industry-->Waste Rubber can
be reused to make Toys
2. Thermal Power plants --> fly ash can be used in
fly ash bricks, cement as binder.
3. Food Waste in Hotels/Hostels --> Making Bio-gas
by anaerobic digestion
4. Kitchen Waste in a household --> as Composts
15
16. Contd…
• The mentioned methods/examples can also
be adopted on large scale
• But, firstly waste is collected, transported and
then utilized which incurs a large cost.
• So, it is always preferable to minimize waste
production by reusing, recycling of waste at
the source itself.
16
17. 2.Collection, segregation and storage
at the site of collection
• Main problem of SWM is Collection.
• Household waste consists of all types of general
waste.
• No scientific , clean , hygienic, efficient practice of
waste collection
• No penalty on throwing wastes
• spitting on streets, defecating, throwing wastes
here and there even if collection bins are
provided. Hence waste collection is a big problem
17
18. Contd…
• In our country, Waste is handled manually
• Sweeps with poor design broom sticks
• Discharging of harmful chemicals, dyes,
metals, heavy metals, organic matter in the
open drains to pollute land and river water
18
19. Contd…
• Best way is Segregation of waste at the generation point.
• Segregation: Collecting it in different bins or plastic bags.
• Domestic waste: Reusable (paper, plastic, metal etc) Non
reusable (Organic-kitchen waste, Inorganic-dust, dirt etc)
• Fixing two separate containers bins or bags for
separatingorganics and Inorganic
• Organics: for energy recovery, Composts.
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20. 3. Transportation of SW
• Transportation must be done in closed
containers.
• Transportation of solid waste should be done
through the technically competent and well
reputed contractors under the supervision of
experienced and honest municipal authorities
and watchful citizens.
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21. 4. Treatment of SW
• The waste has to be treated before disposal
for the protection of environment.
• Biodegradable waste can be processed by
composting, vermi-composting, anaerobic
digestion.
• Anaerobic Digestion: foul gases are evolved,
dirty offensive dark colored fluid is also
generated: called Leachate.
21
22. Contd…
• Solid waste contains both Municipal waste
and Industrial Waste
• Small Scale Industries: Generates huge solid
waste, No Individual treatment plants.
• So, Combined effluent treatment plants are to
be operated by local bodies & funded by
industries in proportion.
• Economical treatment.
22
23. 5.Energy Recovery and Disposal
• Most common methods of energy recovery
and disposal for non hazardous solid waste are
--Incineration, composting and Landfill
• Final Disposal: No more conversion, remains
as waste and unused.
• Before putting on Land If it has some
biodegradable fraction then compost (organic
manure) should be made out it.
23
24. Contd…
• Organic Manure: Environmental friendly,
provides micronutrients that increase soil
fertility.
• Vermi-Composting: If this work is done more
efficiently by some special worms then it is
known as vermi-Composting.
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25. INCINERATION
• Incineration means burning of solid waste in controlled
conditions.
• It is more efficient than usual practice of burning solid
waste in open burning.
• Incinerator: enclosed device using controlled flame
combustion
• Incineration uses heat to convert complex toxic organic
compounds in to mostly CO2 and water.
• Combustion Temperatures: 760 – 870 oC
• Modern Incinerators: 1650 oC to convert metal and
glases into ashes
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27. Factors to be controlled
• Thermal feed rate
• Waste feed rate
• Minimum combustion gas temperatures
• Suspended particulate matter (SPM)
• Other Air pollutants
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28. Advantages
• Volume and weight reduced (approx. 90% vol. and 75%
wt reduction)
• Waste reduction is immediate, no long term residency
required
• Incineration can be done at generation site
• Air discharges can be controlled
• Ash residue is usually non-putrescible, sterile, inert
• Small disposal area required
• Cost can be offset by heat recovery/ sale of energy
28
29. Disadvantages
• High capital cost
• Skilled operators are required (particularly for
boiler operations)
• Some materials are noncombustible
• Some material require supplemental fuel
29
30. Flue gas pollutants
• Particulates
• Acid Gases
• NOx
• CO
• Organic Hazardous Air Pollutants
• Metal Hazardous Air Pollutants
30
31. Devices
• Electrostatic Precipitator
• Baghouses
• Acid Gas Scrubbers
• Wet scrubber
• Dry scrubber
• Chemicals added in slurry to neutralize acids
31
32. Landfill Technology
• The most Common and Easy way of disposal of
SW
• The decomposition of Solid waste produces gases
(Methane) and dark colored water (leachate)
• The two major environmental concerns in a
landfill are gases and leachate.
• Harmful chemicals (if present in solid waste)and
Leachate mix with ground water and rain water.
• Appears costly, but for long life time it is efficient.
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37. Composting
• Composting is the biological
decomposition of organic
waste such as food or plant
material by bacteria, fungi,
worms and other organisms
under controlled aerobic
conditions.
• The end result of composting
is an accumulation of
partially decayed organic
matter called humus.
37
38. Contd…
• The organic matter (consisting of carbon,
hydrogen, nitrogen, oxygen, and sulfur) has a
tendency of being converted into inorganic
matter as the later is a stable form.
• The food, excreta and other organic waste gets
decomposed (changed into inorganic form) and
produce gases like biogas (mainly methane) and
solids of decomposition like sulfates, nitrates,
phosphates etc.
• Compost is more useful as it contains the
nutrients like N, P, K as well as the micronutrients.
38
39. Contd…
• Organic matter can be decomposed in two ways
in the presence of oxygen or in the absence of
oxygen, composting (aerobically or anaerobically)
• Aerobic: micro-organisms oxidize the organic
compounds to carbon dioxide, nitrite and nitrates
(Exothermic)
• Anaerobic: Bacteria, while metabolizing the
nutrients, break down the organic compounds
through a process of reduction (The gases
evolved are mainly CH4 and CO2)
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40. Vermi-Composting
• The stabilization of
organic solid waste
through special
earthworm by conversion
of the organic matter to
worm casting
• Pheretima sp, Eisenia sp,
and Perionyx excavatus
sp.
40
41. Contd…
• Earthworms feed on any organic waste and
consume two to five times of their body weight,
excrete the mucus coated undigested matter as
wormcasts
• Wormcasts consists of organic matter that has
undergone physical and chemical breakdown
through the muscular activity that grinds the
material to a particle size of 1 to 3 micron.
• The nutrient present in the wormcast are easily
soluble in water and are thus readily available for
the plant growth
41
42. Contd…
• Special worms survive in the temperature range
of 20- 40 oC and moisture range of 20-80%.
• do not survive in pure organic substrate
containing more than 40% fermentable organic
substances.
• So fresh waste is mixed with partially or fully
stabilized waste
• Unfavorable Conditions: particle size of biomass
and extent of its decomposition, very high
temperature increase, anaerobic condition,
toxicity of decomposition products, etc.
42
43. Contd…
• The worms are also adversely affected by high
concentrations of such heavy metals as
cadmium, chromium, lead and zinc
• Due to these problems the vermi-compostin is
successful more on the household level
(vegetables etc, organic waste) than the
municipality level.
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45. • Energy is recovered from organic matter present
in waste by incorporating suitable techniques.
Along with gain of energy , Other benefits:
• The total quantity of waste gets reduced by nearly
60 to 90% depending upon the characteristics of
waste and the adopted process.
• As the quantity reduces the demand for land
required for landfill as disposal also reduces.
• The cost of transportation also reduces as the
quantity reduces.
• The overall environmental pollution reduces.
46. Basic techniques of energy recovery
• Thermo-chemical conversion:
This process entails thermal decomposition of
organic matter to produce either heat energy or fuel oil
or gas.
• Useful for wastes containing high percentage of
organic non-biodegradable matter and low moisture
content.
• Technological Option:
Incineration,pyrolysis/gasification.
47. Bio chemical conversion
This process is based on enzymatic
decomposition of organic matter by microbiological
action to produce methane gas or alcohol.
• Preferred for wastes having high percentage of
organic bio-degradable (putrescible) matter and high
moisture content.
• Technological Options: Anaerobic Digestion also
known as Biomethanation.
