Soild Waste Management Alappat

7/31/2019 Soild Waste Management Alappat

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SOLID WASTE MANAGEMENT

Babu Alappat, Ph.D

ProfessorDepartment of Civil Engineering

I.I.T. Delhi, Hauz KhasNew Delhi, India 110 016.

[email protected]


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Solid Waste Engineering

Dealing with Solid Waste: It is More

Management than Engineering

This may be true..but management alonecannot solve the problem, for sure.


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Various Solid Wastes and their

Management in India

Municipal Solid waste (MSW): Municipal SolidWaste (Management and Handling) Rules 2000 Biomedical waste (Healthcare waste):

Biomedical Waste (Management and Handling) Rules 2002

Hazardous (Industrial) wastes: hazardous Waste(Management and Handling) Rules 1998, 2000, 2002

Nuclear Wastes: Nuclear Waste (Management andHandling) Rules 1998

E-waste draft rules are ready Agro-wastes:


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Municipal Solid Waste (MSW)

MSW = Trash+Rubbish+Refuse+Garbage MSW is the waste that is collected in the

municipal bins / containers Sources of MSW: Domestics, hotels,

markets, offices, commercial

establishments,etc. It does not contain Wastes from: Hospitals,

Industries, nuclear installations, etc.


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Municipal Solid Waste (MSW)

It is consistently INCONSISTENT Design of the treatment facilities is difficult It is not hazardous; but the problem is its very

large Quantity/Volume It is a problem in Cities / Towns / Municipalities;

but not a big issue in Villages / Rural areas The problem is MSW can be seen and smelled


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MSW Generation Rate

Generation rate varies from season toseason, place to place It depends upon the affluence, season,

education, living habits, traditions, etc. In India: 0.15 kg/person/day in rural areas

0.40 kg/person/day in urban areas Possible to estimate the total quantity

generated


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SOLID WASTE MANAGEMENT

Waste Collection and Storage Waste Transportation Recovery through Sorting & Recycling Recovery through Processing (Biological or

Thermal Route)

Waste Transformation (Volume reduction,Toxicity reduction, etc.)

Final Disposal


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HIERARCHY OF SOLID WASTE

MANAGEMENT OPTIONS

1. Waste minimization at source2. Material Recycling

3. Waste Processing (Energy / Materialrecovery)

4. Waste Transformation (no recovery)5. Land-filling


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Sorting and Materials Recovery

Sorting: separating/segregation of variouscomponents Sorting can be done at any stage Primary Sorting: at any stage (rag pickers) Secondary Sorting: sorting on the primary

sorted materials (kabaris, middlemen) Tertiary Sorting: sorting on the secondary

sorted materials (for recycling)


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MSW Storage Depots

Wastes collected (primary collection) go to thelarge municipal depots the collection vehicles carry the waste from these

depots for treatment/transformation The depots must be suiting the primary collection

system and the transportation vehicles. Depots should be properly positioned along the

road side


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For container size 3-10 m3

capacity, distancebetween 2 depots should not be more than 500m Shorter distance for smaller depots: 1 m 3

Container size depends upon the density of thewaste and the quantity of waste produced

In India: density is about 500 kg/ m 3

1 tonne MSW requires about 2 m 3 volume Provide double the capacity calculated


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Transportation of MSW

Transportation vehicles should be compatible withthe storage depots vehicles either empty the depot (manually or

mechanically) or haul it along with Manual loading: unhygienic/inefficient/time

consuming Loader loading: spoils the floor/walls of the depot Ordinary truck capacity: 5 tonnes/trip


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Routing of MSW collection

vehicles

This is for: minimizing the distance of transport

minimizing the time of transport minimizing the pollution during

transportation minimizing the traffic jams and other

inconveniences


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For MSW collection &

transportation: the 2 nd method

Node routing: to construct a tour through n points keeping the total distanceminimum

It is difficult to solve. Three methods to solve it1. The Exhaustive procedure

2. Heuristic algorithm


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Heuristic Algorithm

Based on the Hill climbing idea (at each node, findout the next cheapest node to visit) Here the problem is: it picks up cheap nodes in the

beginning; but towards the end, it may have to gofor very expensive nodes.

To avoid this: repeat the algorithm for the sameinitial nodes going back taking the cheapest route.Then compare the cheapest route.


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TREATMENTTECHNIQUES FOR MSW


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Biological route: the most acceptable option Composting

Vermi-composting Chemical Route: not popular for MSW

Physico-chemical Route: not popular for MSW Thermal Route: Costliest; but rapid

Incineration Gasification Pyrolysis


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Composting of MSW

Composting: organized method of producing compost by adopting andaccelerating the natural decomposition

phenomenon Compost : an organic manure containing

N,P,K and other micro-nutrients Compost should be used with other

chemical fertilizers for optimum results


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Composting: aerobic or anaerobic Aerobic composting:

using aerobic microorganisms,end products are CO 2 , nitrates, etc

Carbon is the source of energyexothermic reaction and temp. rises

all pathogens are killed overall, it takes 2-4 months

no foul smell


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Anaerobic composting:using anaerobic microorganisms

reduction reaction

end products are CH 4 , CO 2 , etc

temperature does not increases

pathogens are not killed

it takes 4 to 6 months

odour problem

large space requirements


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Factors affecting Aerobic

Composting

Microorganisms Shredding of refuse

C/N ratio Temperature

Moisture content Windrow details

Aeration/turning


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Bacteria: breaks down mostly protein andother organic matter

Fungi and Actinomycetes decomposes

lignin and cellulose Most of the organisms for composting are

readily available in the MSW itself. But there are inoculums and enzymes

claiming to hasten composting. This isrequired for sure for agricultural andindustrial wastes


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Shredding of the MSW

For better bacterial invasion Shredding destroy the natural resistance of the

vegetation to microbial invasion Provides larger surface area Better availability of oxygen

Uniform and rapid decomposition Materials become more homogeneous Better fly control/moisture control


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Desirable size for composting: less than 2inch

Material size governs (to certain extent) thesize of the finished product

Compost for flower gardens/lawn: < 1 cm


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C/N ratio C/N ratio available is important as all C present

may not be available for degradation For rapid composting, initial C/N ratio of the

waste = 30 is ideal. (range 26 to 31) If C/N ratio is >>30, add N sources like blood,

sewage sludge, slaughter house wastes, etc . If C/N ratio is


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Temperature

MSW has good insulation properties; so thetemperature shoots up in aerobic composting. It may increase to 65 to 70 oC. But optimum temp

is 50 to 60o

C If temp is > 70 oC, it may inactivate theenzymes/organisms

All pathogens shall be killed if 50 to 60 oC ismaintained for 5-7 days

No temp. rise in anaerobic composting


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Moisture Content

Optimum : 50 to 60 % by weight If moisture is considerably less than the optimum,the physiological needs of the organisms are not

met. If moisture is considerably greater than theoptimum, pores may be blocked affecting the

oxygen supply. System may turn anaerobic If moisture is < 40%, just add water No composting if moisture is < 12 %


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Height is in between 1.8 to 2.7 m for thewindrows with air circulation arrangementat the center. In this case, width is 3.6 m to

6.1 m Turning / mixing equipment also decides

the height of the windrows


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Finished Product - Compost

Colour: black brown or black Odour: earthy

Crumbly in nature Weight: about 50 % of the original waste

It is neither very dry nor watery N,P,K content > 1% (each)

C/N ratio about 20


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MSW Compost Plant

Major expenditure (capital and operational)is for the SEPERATION of the bio-degradable from the inerts

An array of separation techniques may berequired

Separation may be carried after or beforeComposting


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Air Classification

Magnetic Separator

Screens

Manual Separation

To separate light

materials

For ferrous metals

Size Separation

Materials that can behand picked


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Vermi-Composting (Rapid Composting)

Bio-degradable are degraded by the earthworms Earthworms feed on the organic matter. Duringthe passage through the worms alimentary canal,

it is converted to a simpler humus rich materialdue to the action of the enzymatic secretions andbacteria.

Earthworms are effectively used for maximizingthe growth of aerobic bacteria Residence time: 30 days (one month)


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Earthworms

They are invertebrates, Phylum: Annelida More than 3000 species In India, there are about 500 species Only surface dwelling earthworms are

useful a composters

Deep burrowing type is not preferred Most suitable species: Eudrilus Eugeinae,

Eisenia Foetida and Perionyx Excavatus


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+ and of vermi-composting

Simple to construct and operate No mechanical/electrical parts Minimum cost High process stability Elimination of pathogens

Large land requirements Uncertainty and lack of understanding

Slow nature


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Vermi-Composting is a viable and eco-friendly technology for MSW management

But mostly feasible for small community orcampus

There should be a good market for vermi-

compost for self-sustainability of a vermi-compost project


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Advantageous of Incineration Incineration is a total destruction process, if carried out

properly. The incineration residue, if any, is free of any organic or

other biologically active material.

Modern incinerators can burn a great variety of wastematerials under different conditions of temperature. Adverse weather condition has no effect on incineration . Potential for large scale energy recovery. Faster than Biological / Chemical techniques More reliable and fool-proof Useful when other technologies fail to do the job


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Waste /Coal

Preparation

Waste /Coal

Feeding FURNACE

Bottom Ash HeatRecovery

ParticleRemoval

Acidic GasRemoval

STACK

Waste/

Coal Aux Fuel

ID Fan

FD Fan

Heat

Flue Gas

For treatment & disposal

Gas out


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TYPES INCINERATOR FURNACES

Stocker / Grates Type Rotary Kiln Type Fixed Hearth Multiple Hearth Cyclonic

Fluidized Bed

MSW Mass Burning Any type of waste Biomedical wastes Sewage Sludge High heat content

Any kind of waste


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Thermal Properties of Indian MSW

For self-sustaining combustion, there should be a heatcontent of atleast 2500 kcal/kg. Usually below 1500kcal/kg, it is not recommended for incineration

Indian MSW is infamous for its low heat content (700 to 1000kcal/kg)

high moisture content (30 to 55 % by weight) & high inertcontents (30 to 50 % by weight)

These make it a poor candidate for direct incineration.


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Incineration of MSW is not popular in India

But Incineration is very famous (in fact,infamous) for the treatment of Biomedicalwastes

It is also extensively used for the treatment

of hazardous wastes in India


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Biomedical Waste Incineration

Only infectious wastes go for Incineration Mostly using Double Chambered Fixed

Hearth type Rules do not specify the type of Incinerator Rules specify only the emission limits


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Bi di l t I i t


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Biomedical waste Incinerator

Performance is Unsatisfactory Reasons for that: Improper handling of the unit Lack of waste segregation

Batch operation of the unit Excess capacity of the Unit Lack of mixing (Turbulence)

Absence of Air Pollution Control EquipmentsThe Fixed Hearth type incinerators cannot givehigh combustion efficiency


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Remedial Measures Suggested

Proper Segregation of Wastes Continuous operation as far as possible Central Facilities rather than small individual units Avoid excess capacity Install Air Pollution Control Equipments

Operate Primary Chamber in the Starved AirMode and the Secondary in the Excess Air Mode


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Landfilling

This is un-avoidable This comes at the end of the entire solidwaste management system

Even after composting or vermi-compostingor incineration, some thing always remain

for the burial In India, mostly MSW goes straight to alandfill


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Engineered Landfills

Sanitary Landfills for MSW

Secured Landfills for hazardous wastes

Designated Landfills for a typical waste

Sustainable Landfill new concept


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Leachate is then sent to Treatmentand/or Storage Facility

Landfill

PumpStation

Gravity Drainage

Leachate

StorageTreatment


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Landfill Gas is Typically Extractedto a Blower-Flare Station

Landfill

Note:Must Drain

Condensate

BlowerFlare

Station

Gas Wells


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We rarely have Engineered Landfills

Most of the Landfills are actually Land

Dumps

These dumps do not have Leachate and GasCollection Arrangements

No proper Cover and monitoringmechanism after the closure


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Land-dump can inflict serious damage tothe ground water, surface water and ambientair in the near by areas

Also it causes damage to the flora and fauna

and aesthetics of the area

All new facilities to dispose waste have tobe Engineered landfills

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Soild Waste Management Alappat