Dr. DharmendraAssistant Professor

Department of Civil Engineering Office Location: Environmental Laboratory

Civil Department (Ground Floor)

CE 481 Solid waste & ‐Environmental Pollution

byDr. Dharmendra

CE 481 SOLID WASTES AND ‐ENVIRONMENTAL POLLUTION

L T P3 1 0

• Municipal Solid Waste: Generation, Rate Variation, Characteristics (Physical,

Biological and Chemical); Management Options for Solid Waste, Waste Reduction at the Source, Collection techniques, Materials and Resources Recovery / Recycling. Transport of Municipal Solid Waste, Routing and Scheduling, Treatment, Transformations and Disposal Techniques (Composting, Vermi Composting, Incineration, Refuse Derived fuels, Landfilling).

• Hazardous waste management: Exposure and risk assessment, environment legislation, characterization and site assessment, waste minimization, incineration, transportation, storage, landfill disposal

• Air Pollution, Meteorology of Air Pollution, Particulate Emission Control Devices, Gaseous Pollutants Control, environmental assessment, acts relating to air pollution, standards.

•

Books:

• Hzardous Waste management : M.D. LaGrega, P.L. Buckingham, J.C.Evans

• Introduction to Environmental Engineering: M.L.Davis and D.A.Cornwell.

• Integrated solid Waste Management,Principles and Management Issues : G. Tchobanoglous, H.Theisen, S.Vigil.

• Air Pollution Control and Design for Industry - Paul N. Cheremiseriniff.

• Air Pollution and Industry - R.D. Ross• Introduction to Air Pollution and Control - Muralikrishna

Examination & Marks Distribution

• First mid : 15 marks• Second Mid: 15 marks• Final Mid: 50 marks• Tutorial & Assignments : 20 marks• Class environment : Late comer not allowed

between the commencement of class.

Lecture Plan (20-25 Lect.)• Lecture 2: Municipal Solid Waste: Generation, Rate Variation,

Characteristics (Physical, Biological and Chemical)• Lecture 2: Management Options for Solid Waste, Waste Reduction at the

Source, Collection techniques.• Lecture 2: Materials and Resources Recovery / Recycling. • Lecture 2: Transport of Municipal Solid Waste, Routing and Scheduling,

Treatment, Transformations and Disposal Techniques• Lecture 2:(Composting, Vermi Composting, Incineration, Refuse Derived

fuels, Landfilling).• Lecture 2: Hazardous waste management: Exposure and risk assessment.

characterization and site assessment.• Lecture 2:

waste minimization, incineration, transportation, storage, landfill disposalenvironment legislation, 

• Lecture 2 :Air Pollution, Meteorology of Air Pollution, • Lecture 2 :Particulate Emission Control Devices, Gaseous Pollutants

Control, • Lecture 2:

environmental assessment, acts relating to air pollution, standards. 

Importance & Significance of the subject

Solid Waste

9

HEAPS

10

WASTE PLASTIC :

TERI Projections on Waste Generation In India

Composition of MSW in Mumbai

Composition of Municipal solid waste in Mumbai

15%0.75%

0.80%

0.40%

35%

37.50%

10.55%

Paper and cardboardPlasticsMetals (ferrous)GlassSand & fine earthCompostable matterOthers

CITIES / TOWNS CLASS I CLASS IINo. of Cities 299 345Total Population 1281138655 22375588Waste Generation (MT/d)

48134 1454

Mode of collectionManually 50% 78 %Trucks 49 % 21 % Others 1 % 1 %DisposalDumping 94 % 93 %Composting 5 % 6 %Others 1 % 1 %

Status of Solid Waste Management in Class I Cities and Class II Towns

Composition of Municipal Solid WasteComposition of Municipal Solid Waste

Description Percent by weightVegetable, leaves 40.15Grass 3.80Paper 0.81 Plastic 0.62Glass/ceramics 0.44Metal 0.64 Stones/ashes 41.81 Miscellaneous 11.73

Quantity of Municipal Solid Wastes Generation in Metro CitiesS.No City Municipal solid Waste (TPD) Per capita waste (Kg/day)

1. Ahmadabad 1,683 0.585

2. Bangalore 2,000 0.484

3. Bhopal 546 0.514

4. Bombay 5,355 0.436

5. Calcutta 3,692 0.383

6. Coimbatore 350 0.429

7. Delhi 4,000 0.475

8. Hyderabad 1,566 0.382

9. Indore 350 0.321

10 Jaipur 580 0.398

11 Kanpur 1,200 0.640

12 Kochi 347 0.518

13 Lucknow 1,010 0.623

14 Ludhiana 400 0.384

15 Madras 3,124 0.657

16 Madurai 370 0.392

17 Nagpur 443 0.273

18 Patna 330 0.360

19 Pune 700 0.312

20 Surat 900 0.600

21 Vadodara 400 0.389

22 Varanasi 412 0.400

23 Visakhapatnam 300 0.400

Solid Waste in India• 7.2 million tones of hazardous waste

• One Sq km of additional landfill area every-year

• Rs 1600 crore for treatment & disposal of these wastes

• In addition to this industries discharge about 150 million tones of high volume low hazard waste every year, which is mostly dumped on open low lying land areas.

Source: Estimate of Ministry of Environment & Forest

Present Scenario of Solid Waste Management in India

• 100-500 grams per capita waste• Dirty streets and cities • Unhygienic conditions • Loss of reusable / recyclable material • Pollution due to burning of waste • Local as well as global air pollution

Definition of solid waste(Volume 40 of the U.S. Code of Federation Regulation (CFR))

• Garbage, refuse, sludges, and other discarded solid materials resulting from industrial and commercial operations and from community activities.

• It does not include solid or dissolve material in domestic sewage or other significant pollutants in water resources, such as silt, dissolved or suspended solids in industrial wastewater effluents, dissolve materials in irrigation return flows or other common water pollutants.

Categories of wastes

• Municipal• Industrial• Medical• Agriculture• Construction and

demolition

• Hazardous• Radioactive• Mining• Universal

Classification of Wastes• Solid waste- vegetable waste, kitchen waste, household

waste etc.

• E-waste- discarded electronic devices like computer, TV, music systems etc.

• Liquid waste- water used for different industries eg tanneries, distillaries, thermal power plants

• Plastic waste- plastic bags, bottles, buckets etc.

• Metal waste- unused metal sheet, metal scraps etc.

• Nuclear waste- unused materials from nuclear power plants

Municipal Solid waste (MSW)• It is also known as domestic waste or sometimes household

waste, is generated within a community from several sources.MSW generation as a function of source

Residential(Single and multi-family homes)

Food scraps, food packaging, cans, bottles, newspapers, clothing, yard waste, old appliances

Commercial (office bldg., retail companies, restaurants)

Office paper, corrugated boxes, food wastes, disposable tableware, paper napkins, yard waste, wood pallets

Institutional (school, hospitals, prisons) Office paper, corrugated boxes, cafeteria waste, restroom wastes, yard waste

Municipal Litter, street sweepings, abandoned automobiles, some construction and demolition debris

Physical Composition of municipal solid waste

Chemical Class

General composition

Organic

Paper products Office paper, computer printout, newsprint, wrappings, corrugated card board

Plastics Polyethylene terephthalate (PETE/1), High density polyethylene(HDPE/2), polyvinyl chloride(PVC/3), Low density polyethylene(LDPE/4) , Polypropylene(PP/5), polystyrene (PS/6), Other multi-layer plastic (7)

Food Food (putrescible)

Yard waste Grass clippings, grden trimmings, leaves, wood, branches

Textiles/rubber Cloth, fabric, Carpet, Rubber, Leather

Physical Composition of municipal solid waste

Chemical Class

General composition

Inorganic

Glass Clear (flint), Amber, green, brown

Metals Ferrous, aluminium, Other non-ferrous (copper, zinc, chromium)

Dirt Dirt, stones, ash

Bulky wastes Furniture, refrigerators, stoves, etc.

Physical properties of MSW

• Specific weight– Specific weight is defined as the weight of

material per unit volume (kg/m3). MSW generally reported as loose, as found in containers, un-compacted and compacted.

1.Moisture content– It is expressed as percentage of dry and wet material– Moisture content (M) = (w-d/w)*100– W= Initial weight & d = Final weight after drying at 105 0C

Physical properties of MSWCont..

• Particle size– Sc = L or Sc = (L+w/2) ; Sc = (L+w+h/3)– Sc = (L x W)1/2

; Sc = (LxWxh)1/3 – Where Sc = Size of component in mm– W = width in mm & h = height in mm

• Field capacity– Of solid waste is holding capacity of moisture.– Water in excess of the field capacity will be released

as leachate.

Physical properties of MSWCont..

• Permeability of compacted solid waste– The hydraulic conductivity of compacted waste is a physical

property by which we can estimate the movement of liquids and gases in a landfill.

– Where K = Coefficient of permeability– C = dimensionless constant or shape factor– D = average size of pores– = specific weight of water– μ = Dynamic viscosity of water and k = intrinsic permeability

Chemical properties of MSW• Proximity analysis

– Moisture (loss of moisture when heated to 105 0C for 1 h)– Volatile combustible matter (additional loss of weight on ignition at 950

0C in a covered crucible)– Fixed carbon ( combustible residue left after volatile matter is removed)– Ash

• Fusing point of ash– Is defined as that temp. ( 100 to 1200 0 ) at which ash form a solid

(clinker) by fusion and agglomeration.

• Ultimate analysis (major element) : of C, H, O, N, & S.

Energy content or Calorific value

• Energy content: by bomb calorimeter Btu/lb or Btu/lb x 2.326 = kJ/kg

• By calculation based on chemical composition:• Btu/lb = 145C + 610 H2O – 1/8 O2) + 40S + 10 N

Where C = carbon, percent by weightH2 = hydrogen, percent by weight

O2 = Oxygen, Percent by weight

S = Sulfur, Percent by weightN = nitrogen, percent by weight

Q. Estimation of energy content of typical residential MSW based on chemical composition C760H1980O874.5N12.7S. Determine the energy value?

Component Number of atoms per

mole

Atomic Weight

Weight contribution of each element

% by weight

Carbon 760 12 9120 36.03

Hydrogen 1980 1 1980 7.82

Oxygen 875 16 14,000 55.30

Nitrogen 13 14 182 0.72

Sulfur 1 32 32 0.13

Total 25,314 100

Btu/lb = 145(36.03) + 610 (7.8- 55.3/8) + 40(0.1) + 10 (0.7)= 5772

Essential Nutrients and other elements

• Essential nutrient such as NH4-N, NO3-N, P, PO4-P, K, SO4-S, Ca, Mg, Na, Mn, B, Se, Zn, Fe, Cu, Co, Mo, and Ni etc. are required for biological conversion of MSW.

• These nutrient not only help to microbes to grow but also essential for achieved good quality of compost.

Biological Properties of MSW• Excluding plastic, rubber and leather components, the organic

fraction of MSW can be classified:– Water soluble contents, such as sugars, starches, amino acid and

various organic acids– Fats, oils and waxes– Lignin, a polymeric material containing aromatic rings with– Eg. 2CH3CHOHCOOH + SO4

2- 2CH3COOH + S2- +H2O+ CO2

– Lactate Sulfate Acetate Sulfide ion

– 4H2 + SO42- S2- + 4H2O

– S2- + 2H+ H2S

Transformation Processes used for the management of solid wasteTransformationProcess

Transformation means or method Transformation or Principal conversion Products

PhysicalComponentSeparation

Manual and/or mechanical separation

Individual components found in commingled municipal waste

Volume reduction

Application of energy in the form of force or pressure

The original waste reduced in volume.

Size reduction Application of energy in the form of Shredding, grinding, or milling

The original waste components altered in form and reduced in size.

ChemicalCombustion Thermal oxidation Carbon dioxide (CO2), sulfur

dioxide (SO2), other oxidation products

Pyrolysis Destructive distillation A gas stream containing a verity of gases, tar and or oil and a char

Gasification Starved air combustion A low-Btu gas, Char containing carbon, and pyrolytic oil

Transformation Processes used for the management of solid waste

TransformationProcess

Transformation means or method Transformation or Principal conversion Products

Biological

Aerobic compositing

Aerobic biological conversion Compost (humus-like material used as a soil conditioner)

Anaerobic digestion (low- or high-solids)

Anaerobic biological conversion Methane (CH4), carbon dioxide (CO2), trace gases, digested humus or sludge

Anaerobic composting (Occurs in landfil)

Anaerobic biological conversion Methane (CH4), carbon dioxide (CH2), digested waste

Importance of waste transformation

1. To improve the efficiency of solid waste management operation and system.

2. To recover and reusable and recyclable materials.

3. To recover conversion products and energy.

Solid waste management

• Collection• Separation and recovery• Transfer and transport• Ultimate disposal

Collection of Solid waste

• The types of collection services that are provided.• The types of collection systems and some of the

equipment now used as well as the associated labor requirements.

• An analysis of collection systems, including the component relationship that can be used to quantify collection operation.

• The general methodology involved in setting up collection routes.

Collection services1. Curb-side/Alley: Residential place containers to be emptied at curb or in alley on

the collection day. Collection crew empties containers into collection vehicle. Residents return the containers to their storage location until next schedule time.

Advantages:• Crew can move quickly• Crew can not enter private property, so fewer accidents and trespassing

complaints arise.• This method is less costly than backyard collection because it is generally requires

less time and fewer crew members.• Adaptable to automated and semi-automated collection equipmentDisadvantage:• On collection day waste containers are visible from the street• Collection day must be scheduled• Residents are responsible for placing containers at proper collection point

Collection servicesCont..

3. Backyard collection: In this method collection crews enter property to collect refuse. Containers may be transported to the truck, emptied, and return to their original storage location, or emptied into tub or cart and transport to the vehicle so that only one trip is required.

Advantages:• Collection days need not be scheduled• Waste container are not visible from the street• Resident are not involved with container setout or movement• This method required fewer crew members than setout/setback methodDisadvantages:• Because crew enter private property, more injuries and trespassing complaints

likely • The method are more time consuming than curb-side and alley or setback

method• Spill may occur where waste is transferred.

Collection servicesCont..

2. Backyard Setout-setback collection: Containers are carried from backyard to curb by a special crew and emptied by the collection crew. The special crew then transports the container to their original storage location.

Advantages:• Collection day need not be scheduled• Waste containers are not usually visible from the street• Use of additional crew members reduces loading time as compared to back yard

collection systemDisadvantages:• Because crew enter private property, more injuries and trespassing complaints

likely • The method are more time consuming• Resident are not involved and more crew members than for curb-side and alley

collection are required.• This is more costly than curb-side and alley collection because additional crew are

required

Collection servicesCont..

4. Drop-off at specified collection point: Resident transport waste to specified point. This point may be transfer station or the disposal site.

Advantages• Drop-off is the least expansive of methods• Offers reasonable strategy for low population densities• This method involves low staffing requirements.• Disadvantage• Residents are inconveniencedDisadvantages:• Residents are inconvenienced• There is risk of injury to residents• If drop-off site is unstaffed, illegal dumping may occur

Waste Collection in India• Primarily by the city municipality

-No gradation of waste product eg bio-degradable, glasses, polybags, paper shreds etc-Dumps these wastes to the city outskirts

• Local raddiwala / kabadiwala (Rag pickers)-Collecting small iron pieces by magnets-Collecting glass bottles-Collecting paper for recycling

• MCD- Sophisticated DWM (Delhi Waste Management) vehicle

How solid waste affected us in recent years?

• Cloudburst in Mumbai (2005) clogged the sewage line due to large no. of plastic bags

• Blast in the Bhusan Steel factory at Noida, caused due to imported scrap from Iran

• Reduction in the number of migratory birds due to consumption of contaminated foods

• Stray animals dying on streets and farmland due to consumption of plastic bags, which blocks the food movement in their stomach

Waste Separation at the source

• At the source usually done by manually• Separation of components depend on Programme• Additional separation required before reused and

recycling• Waste separation also depend on material

recovery facilities (MRFs) and material recovery and transfer facilities (MR/TFs).

eg. Direct use; curbside collection and drop-off and buy-back center

The Unit operations used for the separation & Processing

Item Function/material processed

Preprocessing

Shredding - Hammer mills - Size reduction/all types of

wastes- Removal of large bulky items, removal of contaminants

-Flail mills Size reduction, also used as bag breaker, all type of waste

Removal of large bulky items, removal of contaminants

-Shear shredder Size reduction, also used as bag breaker, all type of waste

Removal of large bulky items, removal of contaminants

-Glass crusher Size reduction, All type of glass

Removal of all non-glass material

Wood grinder Size reduction/yard trimmings/all type of wood wastes

Removal of large bulky items, removal of contaminants

The Unit operations used for the separation & Processing

Item Function/material processed PreprocessingScreening Separation of over and under

sized material; trommel also used as bag breaker/All type of waste

Removal of large bulky items, large pieces of cardboard

Cyclone separator Separation of light combustible material

Material is removed from air stream containing light combustible materials

Magnetic separation Separation of ferrous metal from commingled wastes

Removal of large bulky items, large pieces of cardboard

Densification-Balers-Can crushers

-Compaction into bales/paper, cardboard, plastics, textiles, aluminum- Compaction and flattening/ aluminum and it`s cane

- Balers are used to bale separated components

Flow diagram for processing yard and other green waste

Yard waste

Collection

Receiving area

Manual Removal of Contaminants

Claw pickup unit and collection vehicle

Plastic, broken crockery etc.

Front end loader

Shredding, Tub grinder

Screening for size separationOver size material

Biomass fuel

Compost Shipping

Q. In the town of XYZ, it is determined that the per capita waste generation rate is 1.4 Kg per person per day. Collection is conducted once per week by the municipality. If the density of MSW in a typical trash container is 150kg/m3, how many 120 L container would be needed.

• 1.4Kg/person/day X 7 days/week = 9.8 Kg MSW• 9.8 Kg/person X 4 person = 39.2 Kg/Family• 39.2Kg /150kg/m3 = 0.26 m3

• 0.26 m3 X 1000L/m3 =260L• Hence three 120L capacity container required.

• Q. From the above example, Collection truck have a capacity of 11.5 m3, which can compressed the waste density of 420 Kg/m3. How many customers can a truck handle a single run, before departing for the transfer station.

• 11.5 m3 X 420 kg/m3 = 4830 kg Capacity• 4830 Kg/ 39.2 Kg/household = 123 household.

Transfer and transport• Collection vehicles used for MSW are:

– Traditional compacter-type trucks taking loose and bagged waste

– Modern single-compartment truck taking wheeled ins from single unit dwelling

– Single-compartment trucks taking wheeled bins from multi-unit apartment buildings and commercial establishments.

– Multi-compartment trucks that remove source separated waste– Truck taking container loads, either closed or opened topped– Vacuum trucks, used in areas with limited accessibility, with

tube length up to 100m– Traditional open-top trucks, commonly used in low-income

countries.

Automated waste collection• Semi-automated and fully automated system are two

innovative approach to MSW collection.– Fully automated means computer-aided equipment, mechanical lifting

devices, and electronic control or onboard computers for monitoring truck performance and collection operation

• The benefits of automated waste collection system are:– Reduce injury risk: Increased automation typically reduces work-related

lifting injuries as well as puncture wounds and lacerations.– Reduce vehicle needs– Decrease labor needs: Reduce crew size.– Reduce environmental impacts– Improved neighbored aesthetics– Reduce public health risk: Containers with lids help mitigate odor and

health concerns.

Some other mode ofTransfer & Transport

• Railroad transport• Water transport• Pneumatic• Hydraulic• Conveyors• Air-cushion• Rubber-tired trolley• Under ground conduits

Collection Routes

• Some of heuristic guidelines considering during route optimization:1. Existing policies and regulations related to such items as

the point of collection and frequency of collection must be identified.

2. Existing system characteristics such as crew size and vehicle type must be coordinated

3. When ever possible, routes should be laid out so that they begin and end near arterial streets, using topographical and physical barriers as route boundaries.

4. In hilly area, routes should start at the top of the grade and proceed downhill as the vehicle becomes loaded.

heuristic guidelinesCont…

5. Routes should be laid out so that the last container to be collected on the route is located nearest to the disposal site.

6. Waste generated at traffic-congested locations should be collected as early in the day as possible.

7. Sources at which extremely large quantities of wastes are generated should be serviced during the first part of the day.

8. Scattered pickup points (small quantity SW generation) that received on the same day or in one trip.

Computer assisted routing

• Computer programs will help in route optimization.• First of all digitize the existing map.• To program few details are required as follows:

– detailed micro-routs, block configurations, waste generation rates, distance between the residence, distance between routes and disposal or transfer sites and loading time

• Municipalities that have a geographic information system (GIS) database can utilize data for their area to facilitating route balancing.

Disposal

• MSW RULES 2000:• Our Municipal Solid Waste (Management &

Handling) Rules are a blueprint for sustainable living: – What comes from the soil goes back to the soil.

This needs a joint effort of Citizens & their City managers.

Waste Disposal Options

• Sanitary Land-filling : Confine, Compact and Cover• Composting and Vermi-composting• Incineration: Burning of combustible wastes to gases• Pelletization: fuel pellets from MSW• Gasification / Pyrolysis: SW heated indirectly from

external source to convert waste into gas• Anaerobic treatment of solid waste• Conversion to biogas: Gasifire

Land-filling

• Importance of landfill• There are few definition of terms which generally

used when discussing the landfill • Landfill are the physical facilities used for the disposal of

residual solid wastes in the surface soil of the earth.• Sanitary landfill

– In past, the waste placed in the landfill was covered at the end of each day operation

– Today, it refer to an engineered facility for the disposal of MSW designed & operated to minimize public health and environmental impact.

Definition of terms Cont…

• Secure landfills: Landfill for the disposal of hazardous waste

• Cell is used to describe the volume of material placed in a landfill during one operating period.

• Daily cover usually consist of 6 to 12 inch of native soil.

• Lift is a complete layer of cells over the active area of landfill.

Definition of terms Cont…

• Bench or terrace is commonly used where landfill height will exceed 50 to 75 ft. it is used for maintaining the slope stability, for the placement of surface water drainage, and for land fill gas collection pipe.

• Leachate is the liquid that collected at bottom of a landfill. (In deep landfill, leachate is often collected at intermediate point)

• Landfill gas is the mixture of different gas consist of methane (CH4), carbon dioxide (CO2), atmospheric nitrogen oxygen, ammonia & terrace organic compound

Definition of terms Cont…

• Landfill liners are materials (both natural & artificial) that are used to line the bottom area and below-grade side of a landfill.– eg. Natural & artificial landfill liner clay & geo-membrane

• Landfill closure is term used to describe the step that must be taken to close and secure a landfill site once the filling operation has been completed.

• Post-closure care refers to the activities associated with the long term monitoring and maintenance – Environmental monitoring

Indian landfill condition

In planning the layout of a landfill site, the location of the following must be determine

• Access roads• Equipment shelter• Office space• Location of convenience

transfer station• Storage and/or disposal

of special wastes

• Drainage facility• Location of landfill gas

management facility• Location of monitoring

well• Plantings• Area to be used for

waste processing (composting)

Composting

• In nature- dead animals and vegetable is decomposed by the bacteria- the products of decomposition add to the fertility of the soil by improving its physical properties for the support of plants, and by the provision of plant nutrients.

• In many parts of the world, particularly villages in tropical and sub-tropical regions , where farmers still rely almost entirely on organic manures.

Cont…• The organic content of MSW tends to decompose leading to

various smell and odor problems.

• It also leads to pollution of the environment.

• To ensure a safe disposal of the MSW, it is desirable to reduce its pollution potential and several processing methods are proposed for this purpose.

• Composting process is quite commonly used and results in production of a stable product.

• Compost which depending upon its quality can be used as a low grade manure and soil conditioner.

Cont… A composting process has three products:• Compost for use as an organic fertilizer• Salvaged materials which can be sold for re-cycling• “Contraries”, which are of no value and must be

disposed of by landfill.General Equation for composting:

Organic fraction of MSW +O2 +Nutrients + m.o

Compost + New Cells + dead cells + CO2+H2O+SO2+heat

Control Parameters in CompostingParameter ValuesParticle size 25-75 mm

Moisture content 50-60%C/N 25-50pH 7-7.5

Temperature 50-55O C

Blending and seeding Controlled by blending ratioAir supply Frequent turning

Mixing and turning First turn on the 3rd day then on alternative days

Pathogen control Maintain a temperature of final compost @70O C for 1 to 2 days.

Odour Controlled by air supply

Principals of CompostingManual and mechanized methods

• Decomposition and stabilization of organic waste matter is a natural phenomenon.

• Compost is particularly useful as an organic manure which contains plant nutrients ( NPK) as well as micro nutrients which can be utilized for the growth of plants.

• Composting can be carried out in two ways i.e., aerobically and anaerobically.

• During aerobic composting aerobic micro-organisms oxidize organic compounds to CO2,NO2& NO3.

Contd………• Carbon from organic compounds is used as a source

of energy while nitrogen is recycled. • Due to exothermic, temperature of the mass rises. • In anaerobic process, the anaerobic micro

organisms, while metabolizing the nutrients ,break down the organic compounds through a process of reduction.

• A very small amount of energy is released during the process and temperature of composting mass does not rise much.

• The gases evolved are mainly CH4 and CO2.

Bangalore Method • This is an aerobic method conventionally carried out

in pits. • Formerly the waste was anaerobically stabilized in pits

where alternate layers of MSW and night soil were laid.

• The pit is completely filled and a final soil layer is laid to prevent fly breeding, entry of rain water into the pit and for conservation of the released energy.

• The material is allowed to decompose for 4 to 6 months after which the stabilized material is taken out and used as compost.

Indore MethodIndore Method

• This method of composting in pits involves filling of alternate layers of similar thickness as in Bangalore method.

• However, to ensure aerobic condition the material is turned at specific intervals for which a 60 cm strip on the longitudinal side of the pit is kept vacant.

• For starting the turning operation, the first turn is manually given using long handled rakes 4 to 7 days after filling. The second turn is given after 5 to 10 more days.

Cont…

• Further turning is normally not required and the compost is ready in 2 to 4 weeks.

• In the urban areas, due to extensive provision of water carriage system of sanitation, night soil is not available.

• Composting of MSW alone is hence often carried out.

• Aerobic composting of MSW is commonly carried out in windrows.

Comparison of the Methods• The Bangalore method requires longer time for stabilization of the

material & hence needs larger land space, which is in short supply in urban areas. The gases generated in this anaerobic process also pose smell & odor problems.

• The Indore method on the other hand stabilizes the material in shorter time & needs lesser land space. As no odorous gases are generated in this process, it is environmental friendly& hence commonly preferred.

• While the organic matter is stabilized during the composting process, the moisture content also changes. The non decomposable are also rejected. Hence the quantity of compost is much lesser that the input & is normally around 50% and the exact value depends upon the characteristics of the input material.

Earthworms help convert organic waste into valuable nutrients for crops, through a process we call “vermicomposting.”

• Why use Vermicompost?• Promotes faster growth of plants, increases crop yield • Produces crops with a better taste, luster and lasting quality,

without toxic residues: crops can therefore fetch a higher price in the market

• Increases water-holding capacity of soil • Easy to produce and low in cost • Reduces salinization and acidification • Reduces soil erosion • Induces resistance to pest and disease attack

Cont…

• Other benefits for farmers:• Enhances soil productivity • Increases crop yield with less irrigation • Lowers risk of crop loss due to pest attack

What materials are required to start a vermicompost

• Material Quantity – Cement ring ~90 cm diameter, ~30 cm height(or

pit or walled enclosure) – Polythene sheet (big enough to cover the bottom

of the cement ring) – Dry organic wastes (DOW) 50 kg Rock phosphate

(RP) – 15 kg Earthworms (EW) 500-750 worms – Water (W) 5 L every three days

Assignment-1

Q.1 What is solid waste and what are their source of generation?

Q.2 What is importance and significance of solid waste. What are impacts on nature?

Q.3 What is the role of civil engineer in solid waste management.

Q4 Write down Importance of waste transformation?