SOLID WASTE MANAGEMENT

DEFINITION

Solid wastes comprise all the wastes arising from human and animal activities and are normally solid and that are discarded as useless or unwanted.

Solid waste management may be defined as the discipline associated with the control of generation, storage, collection, transfer and transport, processing and disposal of wastes in a manner that is in accord with the best principles of public health, economics, engineering and conservation.

Functional Elements of Solid Waste Management System

Waste generation

Waste handling, separation,storage and processing at the source

Collection

Disposal

Transfer and transportSegregation & processing &

transformation of solidwaste

Factors Contributing to Increasing Amounts of MSW

Increasing population Changing lifestyles Disposable materials* Excessive packaging*

*two largest contributors to waste volume

Increasing Population

TYPES OF SOLID WASTES

Based on the source of generation Residential wastes

• Commercial wastes: Packaging material• Institutional wastes: Hospital• Construction and demolition wastes- campus• Municipal services • Treatment plant wastes• Industrial wastes: Biogas from distillery waste• Agricultural wastes: fodder to animals and

energy resource

Domestic/household wastes (including kitchen refuse), wastes from commercial units and markets that are related to items sold, e.g. foodstuffs, vegetable choppings, cloth cuttings and sweepings from streets and shops, institutional refuse and wastes from public places and that generated by hawkers

Medical or clinical waste from medical institutions. These can be classified into the following types; general waste, sharp objects such as used needles, blades and scissors; syringes, pathological wastes, including contaminated bandages, dressings, linens, dead tissues, organs etc; and radioactive wastes

Industrial wastes generated by industrial processes and some of which is hazardous

Debris from construction, excavation and/or demolition sites.

TYPES OF SOLID WASTES

TYPES OF SOLID WASTES

Based on the contents of the waste Rubbish Food waste Ashes Dead animals Treatment plant waste Industrial waste Mining waste

Classification of MSW

Based on decomposability• Non-decomposable • Decomposable waste: Biogas generation

Based on combustibility• Combustible waste: useful from energy point of view

• Non-combustible waste

Biodegradable waste (mainly organic wastes such as peelings of potatoes, bananas, saw dust and water hyacinth dumped within the municipal environs, etc), and these constitute the bulk of the wastes generated

Non-biodegradable waste, e.g. polythene bags, plastic products, pesticide residues, process wastes, highly inflammable and volatile substances, furniture, abandoned vehicles, used tyres; industrial wastes including metal scrap and medical wastes such as used needles, plastic and glass bottles and syringes.

Classification of MSW

Classification of MSW

MSW can be classified into "dry and "wet" materials, on the basis of their moisture content.

The unpleasant odors and liquids associated with "garbage" are due to the putrescible organic components of food and plant wastes in the ‘wet form’. These materials are less than 30% of the total MSW.

From the perspective of energy recovery, the non-recyclable ‘dry fraction’ can be divided into combustible materials, such as paper, plastics and wood; and non-combustible or "inert" materials, are metals and glasses.

Options for handling the "wet" fraction: combustion, aerobic - anaerobic bioconversion and land filling.

Small towns 100g/p/day Medium towns 300-400g/p/day Large towns 500g/p/day

In general varies between 0.3-0.6 kg/p/day TOTAL WASTE GENERATION IN INDIA

@0.45kg/P=120,0000000*.45/1000=0.54MT/day

and 197.1 MT/annum

TYPICAL WASTE GENERATION TYPICAL MSW GENERATION

Characteristics of Municipal Solid Waste Generated by Metro Cities

Sl. No

Metro city Paper Textile Leather Plastic Metal Glass Ash, Fine

earth & others

Compostable matter

1 Mumbai 10.0 3.6 0.2 2.0 - 0.2 44.0 40.0

2 Delhi 6.6 4.0 0.6 1.5 2.5 1.2 51.5 31.78

3 Hyderabad 7.0 1.7 - 1.3 - - 50.0 40.0

4 Jaipur 6.0 2.0 - 1.0 - 2.0 47.0 42.0

5 Kanpur 5.0 1.0 5.0 1.5 - - 52.5 40.0

6 Chennai 10.0 5.0 5.0 3.0 - - 33.0 44.0

7 Visakhapatnam 3.0 2.0 - 5.0 - 5.0 50.0 35.0

Characteristics ( Percent by wt. )

Composition of Waste

Characteristics of the waste

Physical Composition Density Moisture content

CHARACTERSTICS OF THE WASTECHARACTERSTICS OF THE WASTE

Physical properties of MSW (These properties are important to estimate volume or weight of waste for transportation, disposal, or processing)

Specific weight or density Moisture content Particle size and size distribution Permeability or hydraulic conductivity

CHARACTERSTICS OF THE WASTECHARACTERSTICS OF THE WASTE

Chemical properties of MSW Proximate analysis: moisture, volatiles, ash and fixed carbon

Fusing point of ash Ultimate analysis: C, H, N and O Energy content: Heating value Leaching properties (applicable to Hazardous

waste fraction in MSW waste): permeability in soil

CHARACTERSTICS OF THE WASTECHARACTERSTICS OF THE WASTE

Biodegradable fraction is important for estimation of gas generation potential of waste or odor potential

Majority of odors from decomposition of waste are due to conversation of

sulfur into H2S, NH3, methyl mercaptan (CH3SH) and/or aminobutryic acid.

Mercaptans: R–SHR represents an alkane, alkene, or other carbon-containing group of atoms. 

Various functional elements of municipal solid waste management system

Storage Movable bins - Type I: Bins with lid (5-20 litre), Type II: Bins of

50 litre capacity, Type III: Bins of capacity from 50-200 litres, Type IV: M.S. Bins (4.5 cum)

Fixed bins - Masonry bins of 3.6 cum capacity (Type V)

Collection (H/H (house to house) collection system, Community bin system

Transportation Hand cart (Type I), Hand cart with six containers (Type II),

Trycycle, Animal cart, Tipper trucks, Dumper placer, Bulk refuse carrier

Waste Transfer Stations (Relay Centre Facility) Transfer stations near or far off

Collection system Low rise buildings

Curb or Alley Setout-setback Backyard carry

CURB SET OUT: Place your cart in the street with its wheels up against the curb and the front of the cart facing the street.

ALLEY SET OUT: Place your cart in the alley with the front of your cart facing towards the alley and at least 4 feet from any obstructions, including your garage, dumpsters or cars. Do not block access to your neighbors' driveway, gate or garage.

High rise buildings Crew can collect waste Waste taken to service area by tenants Tenants putting the waste in chute

Garbage chute works in the same way as a chimney; with odours and harmful airborne microorganisms being sucked up the chute (hot air rising), to be inhaled by residents as they open the chute doors to dispose of their waste.

Types of Collection system

Haul container system (HCS)

Stationary container system (SCS)

NEED OF NEED OF TRANSPOTATION TRANSPOTATION SYSTEMSYSTEM

Illegal dumps Disposal site too far Small capacity collection truck Low density area More waste to large distance

Transportation system

Motor vehicle: most common Railways Hydraulic Pneumatic Compressed air/vacuum

MSW = Pollution or Resource?

“Ecosystems dispose of wastes and replenishnutrients by recycling all elements”

PROCESSING OF WASTES

Segregation To reduce the volume, quantity and separate

components

Compaction

Shredding

Biomethanation

Processing facility of municipal solid waste

Source reduction Reduce the amount and toxicity of trash you discard Reusing items by repairing them, donating them to charity and

community groups, or selling them also reduces waste Recycling to turn materials that would otherwise become waste into

valuable resources Composting It is nature's way of recycling organic wastes into new soil used in

vegetable and flower gardens, landscaping, and many other applications

Energy recovery by incineration/pyrolysis In addition to minimizing volume, combustors, when properly

equipped, can convert water into steam to fuel heating systems or generate electricity. A variety of pollution control technologies reduce the toxic materials emitted in combustion smoke.

TRANSFORMATION OF SOLID WASTETRANSFORMATION OF SOLID WASTE

Efficient storage, handling and transport Reduce disposal cost Stabilize waste Destroy toxic element (chemical or biological

entities) Generate electrical energy Re-use

TRANSFORMATION OF SOLID WASTE

Physical method Chemical method Biological method

PHYSICAL TRANSFORMATION

1.Component separation or sorting Done mechanically or manually, at source or at a transfer

station Key process to recover recyclable and remove hazardous

waste component

2. Mechanical volume reduction or densification Reduce storage, transport and disposal cost Waste collection vehicles are equipped with compaction

mechanisms

PHYSICAL TRANSFORMATION

3. Mechanical size reduction Makes waste more uniform and reduces the average

size. Shredding, grinding and milling Tree mulchar (shreds trees into wooden chips for

landscaping application ) Tire shredder

Tires Shredding- Off-The-Road_OT(D) - YouTube.MP4

Shredding of organic waste improves efficiency of composting

CHEMICAL TRANSFORMATION

COMBUSTION Thermal processing of solid waste by chemical

oxidation with stoichiometric or excess amounts of air.

End products-hot gases, water vapour (flue gas), and non-combustible residue (ash).

Energy can be recovered by heat exchange from the hot combustion gases.

Incineration

Pyrolysis

Thermal processing of waste in the complete absence of air.

End products-solids (char), liquids (tar/oil) and gases (hydroggen, methane, carbon monoxide, carbon dioxide etc.)

Endothermic process, external source of heat is required.

PYROLYSIS OF URBAN WASTE

Gasification

Thermal processing of waste with limited air.

End products- gases (hydrogen, methane, carbon monoxide, carbon dioxide etc.) and ash

Waste to Energy: WTE

Waste to Energy: WTE

ENERGY ROUTES OF URBAN WASTE TO ENERGY

BIO-CHEMICAL CONVERSION

The process makes use of the enzymes of bacteria and other micro-organisms to break down biomass to produce liquid and gaseous fuels

In most cases micro-organisms are used to perform the conversion process: anaerobic digestion, fermentation and composting.

Other chemical processes such as converting vegetable or animal oils (waste) into biodiesel is transesterification.

ANAEROBIC DIGESTION

Biological treatment can be done either in presence of oxygen (aerobic) or in absence of oxygen (anaerobic).

In India, anaerobic digestion plants are commonly known as Biogas Plants or Gobar Gas Plants. In such plants slurry of cow dung and water is fed to the digester and is allowed to ferment for a few weeks. The biogas is released. The biogas contains methane and carbon dioxide. This gas is used as a fuel.

There are two types of Biogas Plants Fixed dome Floating dome

ENERGY ROUTE OF BIOGAS

TYPICAL BIOGAS COMPOSITION

Sl. No. Constituents % (V/V)

1 CH460

2 CO238

3 H2S < 1

4 H2O vapors ~ 1

Heating value = 18-20 MJ/Nm3

SCHEMATIC OF A FIXED DOME TYPE BIOGAS PLANT

SCHEMATIC OF A FIXED DOME TYPE BIOGAS PLANT

Position a of dome with less gas in the dome. Position b of dome with more gas in the dome.

COMPARISON OF FIXED AND FLOATING HEAD BIOGAS PLANT

Janta/Fixed dome type Floating Dome type Biogas Plant

1 Gas is released at variable pressure Gas is released at constant pressure

2 Identifying defects is difficult Identifying the defects in gas holder easy

3 Cost of maintenance is low Cost of maintenance is high/corrosion

4 Capital cost is low Capital cost is high (for same capacity)

5 Space above the drum can be used Floating drum does not allow the use of space for other purpose

6 Temperature is high during winter Temperature is low during winter

7 Life span is comparatively longer Life is short

8 Requires more excavation work Requires relatively less excavation

Composting

Conventional Composting Vermi-composting

Composting Biological transformation of the waste. Transformation of biodegradable waste into

biologically stable matter using micro organisms. Reduces the volume of waste. Destroy pathogens/insects. End product is a humus like material called compost

that is rich in nutrients. Compost can be used to support plant growth and as a

soil amendment.

Vermicomposting

Worms

Eudrilus eugineae Eisena foetida

DISPOSAL Open dumping

Land filling Disposal of residual solid wastes in the surface

soils of the earth.

Barging into sea

Feeding to pigs/hogs

LANDFILL

Primary means of MSW disposal Disposal of residual solid wastes in the surface

soils of the earth.

Land fillingLandfills include: any site which is used for more than a year for the temporary

storage of waste; and, any internal waste disposal site, that is to say a site where a

producer of waste is carrying out its own waste disposal at the place of production.

Landfills do not include: any facility where waste is unloaded in order to permit its

preparation for further transport for recovery, treatment or disposal elsewhere;

any site where waste is stored for a period of less than one year prior to disposal.

LANDFILL CLASSIFICATION

1. Secure landfills /Class 1 landfills Designed to handle hazardous wastes.

2. Monofills /Class 2 landfills Designed to handle particular types of wastes such as

incinerator ash or sewage sludge that are relatively uniform in characteristics and require special handling.

3. Sanitary landfills /Class 3 landfills Engineered facilities designed to handle MSW.

TemporaryHolding area

Environmentalmonitoring facilities

Equipmentworkshop

Inspection/Screening facility

Weighingscale

Accessroad

Leachatetreatmentfacility

Gasflaringfacility

Surfacewatercollectionfacility

Typical Layout of a Landfill

Completed fill

Active filling area

Future fill area

Stock piled cover material

Office

Landfill Cell

Postclosure care Activities associated with the long-term monitoring

and maintenance of the landfill (typically 30-50 years).

Numerical Problem:Estimating Landfill Requirements

Estimate the landfill area needed to handle one year’s MSW for a town of 100,000 people. Assume US national average discards (146.6 million tonnes of MSW per year for US population of roughly 260 million), no combustion, a landfill density of 600 kg/m³, and a single 3m lift. Assume that 20 percent of the cell volume is soil used for cover.

Vmsw=(146.6×10^6 tonne ×10³ kg/tonne ×100000 people)

260 × 10^6 people × 600 kg/m³

= 93,975 m³

Since only 80 percent of a cell is landfill, the volume of cell needed is

Vcell = 93,975 m³/0.8 = 117,468 m³

The area of lift, at 3 m cell depth, is

A = 117,468/3 = 39,155 m²

The actual sizing of a landfill would include a number of additional factors, such as additional area requirements for access roads and auxiliary facilities, reduction in landfill volume as biological decomposition takes place and increas in compaction as additional lifts are added.

Biological Reactions in Landfills Four stage process

1. Aerobic Phase

2. Acid Phase

3. Methanogenesis, unsteady

4. Methanogenesis, steady

INTEGRATED SOLID WASTE MANAGEMENT

Selection and application of suitable techniques, technologies and management programs to achieve specific waste management objectives and goals.

3 R’s in waste management Reduce Recycle Reuse

Why reduction and recycling?

To reduce the waste to burry To reduce the pollution by reusing the resources. To reduce the rate of consumption of resources

The waste has three values

* The bulk value

*The food value or nutrition value

*The energy value