Ce2039 Municipal Solid Waste Management Lecture Notes

CE2039 MUNICIPAL SOLID WASTE MANAGEMENT LECTURE NOTES

By

G.BASKAR SINGH M.E. Assistant Professor/Civil Engineering Department

S.VEERASAMY CHETTIAR COLLEGE OF ENGINEERING AND TECHNOLOGY (NBA* & NAAC* Accredited) PULIYANGUDI,TIRUNELVELI(DIST)-627 855

MUNICIPAL SOLID WASTE MANAGEMENT

CE 2039 LECTURE NOTES

TABLE OF CONTENTS UNIT

TITLE

PAGE

1

Sources and Types of Municipal Solid Wastes

1 – 20

2

On-Site Storage & Processing

21 – 30

3

Collection and Transfer

31 – 61

4

Off-Site Processing

62 - 101

5

Disposal

102 - 122

References Glossary Anna University Question Paper Nov-Dec 2012 Informations to know – Municipal Solid Waste Management

Municipal Solid Waste Management Unit – I Sources & Types of Municipal Solid Waste Syllabus: Sources and type of solid wastes – Quantity – Factors affecting generation of solid wastes – Characteristics – Methods of sampling & characterization – Effects of improper disposal of solid wastes – Public health effects – Principle of solid waste management – Social & economic aspects – Public awareness – Role of NGO & Legislation

1. Principles of Municipal Solid waste Management - Municipal Solid waste Management involves the application of “Principle of Integrated Solid waste Management” (ISWM) - ISWM is the application of suitable techniques, technologies and management programmes covering all types of solid wastes from all sources. - ISWM has two objectives: o Waste Reduction o Effective management of waste still produced after waste reduction - Waste Reduction: It can be done by following the policy, “More with less” (i.e.) more goods / services with less use of World’s resources (raw materials & energy) and less pollution & waste. Waste reduction can also be achieved by using internal recycling of materials (or) On-site energy recovery.

1

- Effective Management of Solid wastes: Effective solid waste management systems are needed to ensure better human health and safety. They must be safe for workers and safeguard public health by preventing the spread of disease. - An effective management system must be both environmentally and economically sustainable. (a) Environmentally Sustainable: It must reduce as much as possible, the environmental impacts of waste management. (b) Economically Sustainable: It must operate at a cost acceptable to the community - An effective waste management system includes one (or) more of the following options

(a) Waste collection & Transportation (b) Resource recovery through sorting & recycling (through separation) (c) Resource recovery through waste processing (through bio / thermal process) (d) Waste transformation (without recovery of resources) (e) Disposal on land (i.e.) environmentally safe and sustainable disposal in landfill

2. Functional Elements of MSWM The activities associated with the management of municipal solid wastes from the point of generation to final disposal can be grouped into 6 elements as follows:

2

Waste Generation: - Waste generation contains activities in which materials are identified as no longer being of value (no usefulness) and are either thrown away (or) gathered together for disposal. - Waste generation is at present, an activity that is not very controllable. In the future, more control is likely to be exercised over the generation of wastes. Waste Handling, Sorting, Storage & Processing @ source: - The 2

nd

of 6 functional elements in the solid waste management.

3

- Waste handling and sorting involves the activities associated with management of wastes until they are placed in storage containers for collection. - Sorting of waste components is an important step in the handling and storage of solid wastes at source. - On site storage is of primary importance because of public health concerns and aesthetics consideration. - Processing at the source involves activities such as backyard waste composting. Collection: - The functional element of collection, includes not only the gathering of solid wastes and recyclable materials, but also the transport of these materials after collection to the location where collection vehicle is emptied. Sorting, Processing & Transformation of solid wastes: th

- It’s the 4 of MSWM’s functional elements. - Sorting of mixed materials recovery facility (MRF), transfer stations, combustion facilities and disposal sites. It includes the separation of waste components (by size), separation of ferrous & non-ferrous materials. - Waste processing is undertaken to recover, conversion products & energy. The commonly used thermal processing is incineration. - Waste transformation is undertaken to reduce volume, weight (or) size (or) toxicity of waste without recovery. It can be done by mechanical, thermal, chemical techniques. Transfer & Transport: This involves two steps. - The transfer of wastes from the smaller collection vehicle to the larger transport equipment.

4

- The subsequent transport of wastes, over a longer distances to processing disposal site. Disposal: - The final functional element in the solid waste management system is disposal. - A municipal solid waste landfill plant is an engineered facility used for disposing of solid wastes on land without creating nuisance (or) hazard to public health (or) safety.

3. Sources of solid wastes Sl.

Wastes

Sources

Examples

Residential

Single & multifamily

Food wastes, paper, card board, plastics, textiles, leather, yard wastes, metals, ashes, etc., House keeping wastes, packaging, food wastes, hazardous wastes, etc.,

No 1

dwellings

2

Industrial

3

Commercial

4

Institutional

Light & heavy manufacturing, fabrication, construction sites, power & chemical plants Stores, hotels, restaurants, markets, office buildings. Schools, hospitals, prisons, govt. centres

5

Paper, cardboard, plastics, wood, glass, metals, etc., Same as commercial

5

Construction & Demolition

6

Municipal Services

New construction sites, road repair, renovation sites, demolition of buildings Street cleaning, landscaping, parks, beaches, etc.,

Wood, steel, concrete

Industrial process wastes, scrap materials, offspecification products, slag tailings

4. Types of Solid wastes In order to plan, design and operate a solid waste management system, a thorough knowledge of the quantities generated, the composition of wastes and its characteristics are essential. Based on the source, origin and type of waste, types of solid wastes is given below: Domestic and Residential Wastes - These are originated from single & multi-family household units. - These are generated as a consequence of household activities such as cooking, cleaning, repairs, hobbies, redecoration, empty containers, packaging, clothing. Municipal Wastes - It includes wastes resulting from municipal activities and services such as street waste, dead animals, market waste & abandoned vehicles. - This term is commonly applied in a wider sense to incorporate domestic wastes, institutional wastes & commercial wastes.

6

Commercial Wastes - It includes wastes produced from offices, wholesale and retail stores, restaurants, hotels, markets, warehouses. Institutional Wastes - These are arising from institutions such as schools, universities, hospitals & research institutes. - It includes wastes which are classified as garbage & rubbish.

Garbage - It’s the term applied to animal & vegetable wastes resulting from the handling, storage, sale, preparation, cooking & serving of food - These wastes contains putrescible organic matter, which produces strong odor, so requires quick attention in its storage Rubbish - It’s a general term applied to solid wastes generating in house holds, commercial establishments & institutions, excluding garbage & ashes. Ashes - Ashes contains of a fine powdery residue, cinders & clinker often mixed with small pieces of metal & glass. - Ashes are the residues from the burning of wood, coal, charcoal, coke & other combustible materials Bulky Wastes 7

- These are house hold wastes which cannot be accommodated in the normal storage containers of house holds. So, they require special collection. - This includes large household appliances such as cookers, refrigerators, washing machines, furniture, crates, vehicle parts, tyres, wood. Street Sweeping - This term indicates that are collected from streets, walkways, alleys, parks & vacant lots. - Street wastes includes paper, cardboard, plastic, dirt, dust, leaves & other vegetable matters. Dead animals - This term applied to dead animals that die naturally (or) accidentally killed. These are divided into 2 groups; large & small. - Large animals are horses, cows, goats, sheep. Small animals are dogs, cats, rabbits & rats. Construction & demolition Wastes Industrial Wastes Hazardous Wastes Sewage Wastes

5. Quantity of Solid Wastes - The measurement of quality of solid wastes generated is becoming significant in accessing the payload capacity of the collection equipment.

8

- Also important in designing and planning a solid waste management system.

6. Factors affecting Generation of Solid wastes Effect of source reduction - Waste reduction may occur through the design, manufacture and packaging of products with minimum toxic content, minimum volume of material, source reduction can also be achieved by: - Decrease unnecessary (or) excessive packaging - Develop & use products with greater durability - Use fewer resources ( e.g: 2 sided copying) - Increase the recycled materials content of products. Extent of Recycling - The existence of recycling programmes within a community definitely affects the quantities of wastes collected for further processing (or) disposal. Effect of Public attitudes & Legislation - Public attitudes ultimately, does significant reduction in the quantities of solid wastes generated. 9

- A programme of continuing education is essential in bringing about a change in public attitudes. - It depends upon the willingness of people to change their own volition, habits & lifestyles. - Legislation perhaps the most important factor affecting the generation of certain types of wastes such as package & beverage container materials. Geographic Location - Physical factor that affects the quantity of waste generated including location, season of the year, the use of kitchen waste food grinders, waste collection frequency. - Different climate influences both the amount of certain types of solid wastes generated & the time period over which the wastes are generated. - (e.g.) substantial variations in the amount of yard & garden wastes generated in various parts of the country are related to climates. Season of the year - The quantities of certain types of solid wastes are also affected by the season of the year. (e.g.) Festivals of India is totally a various thing overall. Depending upon the type & change of festivals, waste generation is different. Frequency of Collection - In general, where unlimited collection service is provided, more wastes are collected. It does not mean that wastes are generated in more quantity. But, it means the tendency of throwing away the wastes respective of frequency of collection. 10

Characteristics of Service Area - Peculiarities of the service area can influence the quantity of solid wastes generated. (e.g.) Quantities of yard wastes generated on a per capita basis are considerably greater in many of the wealthier neighborhood than in other parts of town.

7. Characteristics of Solid Wastes 7.1

Physical Characteristics

Density (Mass per unit volume) - Knowledge of the density of a waste is essential for the design of all elements of SWM, such as community storage, transportation and disposal. - A reduction of volume of 75% is frequently achieved with normal 3

compaction equipment, so that an initial density of 100 kg / m will readily 3

be increased to 400 kg /m . - Density is an critical in the design of a sanitary landfill as it is for the storage, collection & transportation of waste. - Measurement of Density: The solid wastes should be taken in the smaller 3

0.028 m box to give a composite sample, from different parts of heap of wastes. 3

3

- After weighing, this smaller box (0.028 m ) is emptied in bigger 1m box.

- Continue the process until bigger box is filled to the top. The waste should not be compacted by pressure. 3

3

- Fill 1m box three times, and take the average. Thus weight per m is obtained. 11

Moisture Content - Moisture content of solid wastes is usually expressed as the weight of moisture per unit weight of the wet material.

- A typical range of moisture contents is 20 - 45 %, representing the extremes of wastes in an arid climate. - Moisture content is a critical determinant in the economic feasibility of waste treatment plants. - Apart climatic conditions, moisture content is generally higher in lower income countries because of the higher proportion of food & yard wastes. Size of waste constituents - The size distribution of waste constituents in the waste stream is important because of its significance in the design of mechanical separators and shredder & waste treatment process. Calorific Value - It’s the amount of heat generated from combustion of a unit weight of a substance, expressed as Kcal / kg. - This value is measured experimentally using Bomb Calorimeter in ο

which the heat generated at a constant temperature of 25 C from the combustion of a dry sample is measured.

7.2

Chemical Characteristics Knowledge of chemical characteristics of waste is essential in 12

determining the efficacy of any treatment process. Chemical characteristics includes (i) Chemical (ii) Bio-chemical (iii) Toxic Chemical - It includes pH, Nitrogen, Phosphorous & Potassium (N-P-K), Total carbon, C/N Ratio, Calorific value.

Bio-Chemical - It includes carbohydrates, proteins, natural fibers & biodegradable factors. Toxic - It includes heavy metals, pesticides, insecticides, toxicity test for leachates (TCLP)

8. Methods of Sampling 8.1 Collection of Samples of solid wastes - When collecting samples of municipal solid waste, major collection sites are identified which are covering a large size of population?

- Based on the type of area such as residential, commercial, and industrial, market, slum etc., sampling points are distributed uniformly over the study area.

- About 10 kg of Municipal Solid waste (MSW) is collected from ten points from outside & inside of the solid waste heap.

13

- The total quantity of waste collected is thoroughly mixed & then reduced by method of quartering till a sample of such size that can be handled in the laboratory.

- Samples collected for physical and chemical analysis are double bagged in plastic bags, sealed & sent to laboratory for analysis with weight ranging 10 -12 kg.

8.2

Number of Samples to be Collected - A method of determining the number of samples by statistical technique has been suggested by Dennis. E. Carruth & Albert J. Klee

9. Effects of Improper disposal of Solid wastes 9.1

Impact on Environment When solid waste is disposed off on land, in open dumbs (or) in improperly designed landfills (low lying area), it causes the following impact on environment. 14

- Ground water contamination by the leach generated by the waste dumb. - Surface water contamination by the run-off from the waste dumb. - Bad odor, pests, rodents and wind-blown litter in and around the waste dumb. - Generation of inflammable gas (methane) within the waste dumb. - Bird menace above the waste dumb which affects flight of aircraft. - Fires within the waste dumb. - Erosion & stability problems relating to slopes of the waste dumb. - Epidemics through stray animals. - Acidity to surrounding soil & release of greenhouse gas.

9.2

Impact on Public Health - Exposure to hazardous waste can affect human health, children being more vulnerable to these pollutants. Also, it leads to chemical poisoning due to chemical mix in the wastes. - Direct handling of solid wastes contains Organic domestic wastes in various types of infectious and chronic diseases with the waste workers & the rag pickers. - Waste from agriculture and industries can also cause serious health risks such as chemical & radioactive hazards. - Waste treatment & disposal sites can also create health hazards for the neighborhood. Improperly operated incineration plants cause air pollution & improperly managed & designed landfills attracts all types of insects and rodents that spread diseases. - Recycling too carries health risks if proper precautions are not taken. Workers working with waste containing chemical & metals may experience toxic exposure. 15

10.

Occupational Hazards associated with Waste Handling

Accidents - Bone and muscle failure resulting from the handling of heavy containers. - Infecting wounds resulting from contact with sharp edges. - Burns & other injuries resulting from methane gas explosions @ landfill sites.

Chronic Diseases - Incineration operations are at risk of chronic respiratory diseases, including cancer resulting from exposure to dust & hazardous compounds.

Infections - Skin & blood infections resulting from direct contact with waste & from infected wounds. - Eye & respiratory infections resulting from exposure to infected dust, especially during landfill operations. - Different diseases that results from the bites of animals feeding on the waste. - Intestinal infections that are transmitted by flies feeding on the waste

16

11.

Role of Legislation and NGO on MSWM

11.1 Role of Legislation - River & Harbours Act, 1899 regulated the dumping of debris in navigable waters and adjacent land. The idea was to protect the navigation.

- Solid Waste Disposal Act, 1965. The intention was: o

To promote solid waste management & resource recovery o To promote technical & financial aid

o To promote national research - Public Utility Regulation & Policy Act ( PURPA) 1981, it directs public & private utilities to purchase power from waste to energy facilities.

- Comprehensive Environmental Response, Compensation & Liability Act, (CERCLA), 1980, it gives response to uncontrolled hazardous waste disposal sites.

- Resource Conservation & Recovery Act (RCRA), 1976 o It’s the Legal basis for implementation of guidelines and standards for solid waste storage, treatment & disposal.

o RCRA was amended in 1978, 1980, 1982, 1983, 1984, 1986 & 1988. The 1980 and 1984 versions emphesized with hazardous waste.

- National Environmental Policy Act (NEPA), 1969 - Resource Recovery Act, 1970. - MSW Rules 2000 (India), these rules lay down the steps to be taken by all municipal authorities to ensure management of solid waste according to best practice.

17

11.2 Role of Non-Governmental Organizations (NGO) - Non-Governmental organizations (NGOs) are yet another set of participants in waste management operations. - NGOs are often commissioned to improve the environment of the quality of life of poor marginalized populations, and may stimulate small-scale enterprises and other projects. - Since waste materials often represent the only growing resource stream, these organizations frequently base their efforts in extracting certain materials. - The

some

locations

with

insufficient

collection

(or)

where

neighborhoods are underserved, community based organizations play an active role in waste management operations. - These small-scale organizations (or) local NGOs are formed primarily as self-help (or) self-reliance units, which may evolve into service organizations that collect fees from their collection clients and from the sale of recovered materials. - NGOs working with informal workers and community based entrepreneurs often seek recognition for these organizations as part of the waste management systems. -

12.

Public Awareness and Training - Public Awareness is an important activity in solid waste management to keep the system sustainable. The information related to public awareness is necessary for creating a sustainable system.

18

12.1 Partnership Role for Public Awareness

- NGO - CBO

12.2 Mode of Implementing Public Awareness Programmes 1. Audio & Video program 2. IEC program 3. Child to child education 4. School education 12.3 Public Participation

- Total number of sweepers allotted for door to door waste collection work in each ward. - Number of sweepers getting good response from citizens in the matter of doorstep collection. - Number of sweepers not getting response from the public. - Percentage of public participation. - Improvement of the area than the previous month.

13.

Economic Aspects of MSWM - Presently a large proportion of the total expenditure is incurred on collection, a bit lesser on transportation & ameagre amount on disposal.

19

-

20

Municipal Solid Waste Management Unit II On-Site Storage & Processing Syllabus:On-Site storage methods – Materials used for containers – On-Site segregation of solid wastes – Public health & economic aspects of storage – Options under Indian conditions – Critical evaluation of options.

1.

Introduction - The handling, storage and processing of solid wastes at the source before they are collected is the 2

nd

of 6 functional elements of MSWM.

- It is important to understand, what this element involves? This unit includes a description and discussion of the Handling, Storage and Processing of waste materials at the source.

2.

On-Site Handling - On-Site handling methods and principles involves public attitude, individual belief and ultimately affects the public health.

- It’s an activity associated with the handling of solid waste until they are placed in containers.

2.1 Importance of On-Site Handling (a) Reduce volume of waste generated (b) Alter physical form (c) Recover usable material 21

2.2 On-Site Handling Methods (a) Sorting (b) Shredding (c) Grinding (d) Composting

3.

On-Site Storage - The first phase to manage solid waste is at home level. It requires facilities for temporarily storing of refuse on the premises.

- Individual house holders (or) businessman have responsibility for onsite storage of solid waste.

- Four factors that should be considered in the on-site storage of solid waste are: type of container to be used, the location of containers, public health, collection method / time.

3.1 Storage Container - Garbage and refuse generated in kitchens and other work areas should be collected and stored in properly designed and constructed water-proof garbage cans ( waste bins ).

- The cans can be constructed from galvanized iron sheets (or) plastic materials.

- They should have tightly fitting covers. They must be of such size that, when full, can be lifted easily by one man.

- They should be located in a cool place over platforms, at least 30 cm above ground level.

22

- The bins must be emptied at least daily and maintained in clean conditions.

- A typical example of garbage can, constructed from galvanized iron sheet, dimensions: 45 cm diameter, height 75 cm.

- An adequate number of suitable containers should be provided with proper platforms with stand.

- Suitable containers shall be water tight, rust resistant, tight fitting covers, fire resistant, enough size, light in weight, side handle & washable.

3.2

Storage containers as per Indian Conditions - The segregation of garbage at source is “Primarily meant to keep the two broad categories of solid waste generated separately in different containers (i.e.) bio degradable waste in one container (GREEN) and nonbio degradable waste in another container (RED). 23

- The storage of garbage used by pedestrians (or) the floating populations, bins should be located at regular intervals. The bins should be placed on “TWO BINS BASIS”

- Some types of receptacles presently used for storage are: (a)

Buckets

(b)

Plastics / HDPE / MDPE bins

(c)

Plastic bags

(d)

Metal bins with (or) without lids.

- The MSW Rules, 2000 describes, “ The littering of municipal solid waste shall be prohibited in cities, towns and in urban areas notified by the State Government ”

3.3 Container Size ( Capacity ) Considerations should be given for the size of the loaded container that must be hauled to the collection vehicle (or) to the disposal site. Therefore, container size for: -

Ash up to 80 to 128 lit

-

Mixed refuse up to 120 to 128 lit

-

Rubbish up to 200 lit

-

Office waste is 10 to 20 lit

-

Kitchen waste is 40 lit

-

Garbage is 48 to 80 lit

- Plastic liners for cans and wrapping for garbage reduce the need for cleaning of cans and bulk containers. It avoids bad odors, rat and fly breeding. 24

- Galvanized metal is preferable for garbage storage because it is resistant to corrosion. - Bulk containers are recommended where large volumes of refuse are generated such as hotels, restaurants, apartment houses, shopping centres.

4.

On-Site Processing / Segregation On site segregation is intended: (a)

To improve disposal options

(b)

To recover valuable resources

(c)

To prepare materials for recovery as new products (or) energy

4.1 Objectives of On-Site waste Processing / Segregation -

Compound Separation ( Hand sorting, screening )

-

Volume reduction ( baling, shredding )

-

Size reduction ( shredding, grinding )

-

Resource recovery ( composting )

4.2 Critical Evaluation of Options -

In case of On-Site processing of solid wastes, there are more number of methods may be available.

-

But, one engineer should know to evaluate the various methods and should be able to pick up a better and better solution suitable to the local conditions.

-

The various factors that enters in, when deciding the best suitable method are: 25

(a)

System’s impact on local & global environment

(b)

Reliability

(c)

Safety to workers and to local community

(d)

Ease of operations

(e)

Efficiency

(f)

Economics & aesthetics (noise, odors. Litter, increased traffic)

- A number of processing technologies have been developed for solid waste management and one of the jobs of an engineer is to select and design the most sustainable and cost effective methods for a given community.

5.

On-Site Segregation, Storage & Processing – Options under Indian Conditions Over all process of MSWM is shown here:

26

5.1 Definition of Segregation

- Segregation indicates separation and storage of individual constituents of waste materials on site.

Fig: On-Site Storage containers located in Tindivanam (2011)

27

5.2

Segregation at Dwellings There are three classifications most often used, (a) Low rise buildings ( < 4 stories ) a. Single family detached b. Single family attached (b) Medium rise buildings ( 4-7 stories ) (c) High rise buildings ( > 7 stories )

5.2.1 Low rise detached dwelling -

Here, the residents are responsible for placing the solid waste and sorting out recyclables.

-

In many communities, the decisions have been made, not to require the residents to separate the waste.

-

But, it should be mandated.

-

The equipments & facilities required are, household compactors, large wheeled containers, small wheeled hand carts .

5.2.2 Medium size apartments - The collection and sorting process differs according to location and type of waste generated. -



Some of the solid waste storage locations are:

 

Basement Storage / Curb Storage Outdoor / Mechanized Storage

28





5.2.2.1

Basement Storage Usually owner provides basement storage rooms and the recycling containers located near (or) next to solid waste storage. -

The residents are responsible for storing waste in the curb side.

The maintenance staff is responsible for curb side collection to the street collection.

5.2.2.2

Outdoor Storage -

Here, the large containers are located at the outdoor (or) near the apartments.

-

The residents are responsible for disposing their waste in the containers.

-

The collection vehicles with unloading mechanism are always preferred here .

5.2.3 High rise Apartments -

Wastes are picked up by building maintenance personnel (or) porters from the various floors and taken to the basement (or) service area.

-

Wastes are taken to the basements by tenants.

-

Wastes discharged in chutes (or) collected in large containers, compacted in to large containers.

-

In many high rise apartments, solid waste chutes are used with large compactors.

29

6.

Public health & Economic Aspects of On-Site Storage

6.1 Problems related to On-Site Sorting, Storage The main problems of sorting of waste as it is carried out manually at various stages are listed below: (a) Waste gets scattered at the bins. (b) Some types of waste does not get recycled, since it is not currently recyclables. (c) Toxic (or) hazardous waste does not get collected and ends up either in landfills (or) in composting operation. Both cause other contamination such as of groundwater. (d) Recycling takes place in very poor health and environmentally unsafe conditions .

6.2

Desirable Changes to be happened The following long-term changes are desirable: (a) Organized colony-wise collection systems involving rag pickers, with proper gear and protection. (b) Investments in the recycling sector to ensure that the units are safe and operate at economic scales. (c) Development of recycling laws for specific types of wastes. (d) Promotion of simple disinfection techniques and devices such as needle cutter for infectious waste to be pre-treated before disposal. (e) Pre-sorting of waste for composting operations, through mechanical means.

30

Municipal Solid Waste Management Unit III Collection & Transfer Syllabus:Methods of collection – Types of vehicles – Manpower requirement – Collection routes – Transfer Stations – Selection of locations, operations & maintenance –Options under Indian conditions

1. Introduction: In the Municipal Solid waste Management system, Collection is an important aspect. -

It is carried out in 5 different phases as discussed below:

31

Phase 1: The individual house owner must transfer whatever is considered as waste to the refuse can, which may be inside (or) outside the home.

Phase 2: The movement of the refuse can to the truck, which is usually done by the collection crew, called backyard collection. It the can is moved to the street by the home occupant, the system is called, curbside collection

Phase 3: More & more separated materials and yard wastes are collected separately either in same truck (or) in separate vehicles from house to house.

Phase 4: This phase is known as “truck routing”. The trucks must collect the refuse from many homes in the most efficient way possible.

Phase 5: The fifth phase of the collection system involves the location of the final destination (e.g: MRF, disposal site, transfer station)

2. Collection Components: Components of a solid waste collection system can be listed as below: - Collection Points - Collection Frequency - Storage Containers - Collection Crew - Collection Route - Transfer Station Collection Points :It depends on the locality that may be residential, commercial (or) industrial. It has the deciding factors such as size & storage which ultimately affect the cost of collection. 32

Collection Frequency: -

Climatic conditions and requirements of a locality as well as containers and costs determine the collection frequency.

- In hot and humid climates, solid wastes must be collected atleast twice a week because the decomposing solid wastes produce bad odour & leachate. - In residential areas (food & other putrescible wastes), frequent collection is desirable for health & aesthetic reasons. - While deciding the collection frequency, following factors must be kept in mind; cost, storage space, sanitation. Storage Containers: - Proper container selection can save the collection energy, increase the speed of collection and reduce crow size, while evaluating residential waste containers, the following factors must be kept in mind. - Efficiency: The containers should help to maximize the over all collection efficiency. - Convenience: The containers must be easily manageable both for residents and collection crew. - Compatibility The containers must be compatible with collection equipment. - Public Health & Safety: The containers should be securely covered and stored.

33

Collection Crew: - The optimum crew size for a community depends on labour and equipment costs, collection methods and route characterization. - It also depends on the size and types of collection vehicle used, space between houses, waste generation rates & collection frequency. - Nowadays as the increase in collection costs, the trend in recent years is towards: i.

Decrease in the frequency of collection

ii.

Increase in the dependence on residents to sort waste materials.

iii.

Increase in the degree of automation used in collection.

Collection Routes: - The collection programme must consider the route that is efficient for collection. - An efficient routing of collection vehicles reduces the costs by reducing the labour expended for collection. - Proper planning of collection route also helps conserve energy and minimize working hours and vehicle fuel consumption. - Routing (road network) analysis and planning can, i.

Increase the likelihood of all streets being serviced equally and consistently.

ii.

Help supervisors to locate (or) track crew quickly.

iii.

Provide optimal routes that can be tested against driver judgment and experience. 34

Transfer Station: - A transfer station is an intermediate station between final disposal option and collection points in order to increase the efficiency of the system, as collection vehicles and crew remain closer to routes. - A centralized sorting and recovery of recyclable materials are also carried out at transfer station. - The unit cost of hauling solid wastes from a collection area to a transfer station and then to a disposal site decreases when the size of the collection vehicles increases.

3. Methods of Primary Collection of wastes 3.1 Door step Collection through Containerized Hand carts: - A bell may be affixed to the handcart given to the sweeper (or) a whistle may be provided. - Each sweeper maybe given a fixed area (or) stretch of houses for the collection of wastes. Area

Allotment / Sweeper

(i)

Thickly Populated

-

250 to 350 RMT

(ii)

Less Populated

-

400 to 600 RMT

(iii)

Low density

-

650 to 750 RMT

35

3.2 Role of Sweeper: - The sweeper should ring the bell (or) blow the whistle indicating his arrival at the place of his work and start sweeping the street. - On hearing the bell (or) whistle, people should deposit their domestic biodegradable waste into the handcart of sweeper. - No sweeper may be expected (or) directed to do house-to-house collection by asking for waste at the door steps, as this will affect his energy & productivity.

3.3 Collection through Motorized Vehicles: - Local bodies, as an alternative to door step collection through containerized handcarts may deploy motorized vehicles having unconventional horn for doorstep collection of waste. - Driver of vehicle should blow the horn to indicate his arrival, and householders should deposit their domestic wastes directly into the vehicle without loss of time.

3.4 Primary Collection of waste from Societies / Complexes: - It is made compulsory for the management of the societies, complexes and multi-storied builders to keep community bins (or) containers in which dry & wet wastes may be stored separately by their residents. - To facilitate collection of waste from societies (or) complexes, the local bodies should act by a rule, make it obligatory for them to identify an appropriate site within their premises for keeping such bins for waste storage. 36

3.5 Collection of waste from slums: - Local bodies should collect waste from slum by bell ringing / whistle system along their main access-lanes. - Residents should bring their wastes from their houses to handcarts. - Performance certification by a “Mohalla (Local level) Committee” may be insisted upon in such cases.

3.6 Collection-at-the doorstep in Posh Areas: - In posh residential areas where the residents as a whole might not be willing to bring their wastes to the municipal handcart, system of collection from the doorstep on full cost recovery basis may be introduced.

4. Types of Collection Vehicles - Almost all collections are based on collector and collection crews, which move through the collection service area with a vehicle for collecting the waste material. - The collection vehicle selected must be appropriate to the terrain, type and density of waste generation. - The most commonly used collection vehicle is the dump truck fitted with a hydraulic lifting mechanism. A description of some vehicles types follows: (i) Small-Scale Collection & Muscle-powered Vehicles 37

(ii) Non-Compactor Trucks & Compactor Trucks

4.1 Small-scale Collection & Muscle Powered Vehicles: - These are common vehicles used for waste collection in many countries and are generally used in rural hilly areas.

- These can be small rickshaws, carts, (or) wagons pulled by people (or) animals, and are less expensive, easier to build and maintain compared to other vehicles.

- They are suitable for densely populated areas with narrow lanes, and squatter settlements, where there is relatively low volume of waste generated.

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4.2 Non-Compactor Trucks: - Non-Compactor trucks are efficient and cost effective in small cities and in areas where wastes tend to be very dense and have only little potential for compaction. When these trucks are used for waste collection, they need a dumping system to easily discharge the waste. It is generally required to cover the trucks in order to prevent residue flying off (or) rain soaking the wastes.

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Trucks with capacities of 10-12 m are effective, if the distance

between the disposal site and the collection area is less than 15Km. -

Non-compactor are generally used when labour cost is high.

4.3 Compactor Trucks: - Compactor vehicles are more common these days, generally having 3

capacities of 12-15 m due to limitations imposed by narrow roads. 39

- The weight of solid wastes collected per trip is 2 to 2.5 times larger since the wastes are hydraulically compacted.

- A compactor truck allows waste containers to be emptied into the vehicle from the rear, front (or) side.

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- The advantages of the compactor collection vehicles include the following: (a) Container are uniform, large, covered and relatively visually inoffensive. (b) Waste is set out in containers so that the crew can pick them up quickly. ( c ) Health risks to the collectors and odor on the streets are minimized. (d) Waste is relatively inaccessible to the waste pickers.

5. Collection Vehicle Routing - Efficient routing and re-routing of solid waste collection vehicles can help to decrease the cost by reducing the labour expended for collection. - Routing procedures usually consists of the following two separate components: (a) Macro Routing – Defining size of routes (b) Micro Routing – Defining exact path of each route

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5.1 Macro Routing: - It consists of dividing the total collection area into routes, in such a way as to represent a day’s collection for each crew. - The size of each route depends on the amount of wastes collected per stop, distance between stops, loading time and traffic conditions. - Natural barriers such as rail road embankments, rivers and roads with heavy competing traffic, can be used to divide route territories. - As much as possible, the size and shape of route areas should be balanced.

5.2 Micro Routing: - Using the results of the macro-routing analysis, micro-routing can define the specific path that each crew and collection vehicle will take on each collection day.

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- Results of micro-routing analysis should also be done by the review of experienced collection drivers.

5.3 Deciding Factors for Collection Vehicle Routing: - The heuristic (trial & error) route development process is a relatively simple manual approach that applies specific routing patterns to block configurations. - The map should show collection, service locations, disposal (or) transfer sites, one-way streets, natural barriers and the area of heavy traffic flows. - Then, routes should be traced out onto the tracing paper using the following factors: (a) Routes should not be fragmented (or) overlapping. (b) Total collection (+) Hauling time reasonably constant for each route in the community.

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( c ) The collection route should be started as close to the garage (or) motor pool as

possible. (d) Heavily travelled streets should not be visited during rush hours. (e) In case of one-way streets, it is best to start the route near the upper end of the street. (f) In case of dead-end streets, wastes must be collected by walking down, reversing the vehicle (or) taking a U-turn. (g) Higher elevations should be at the start of the route. (h) For collection from one side of the street at a time, it is generally best to route with many anti-clockwise turns around the blocks.

Based on the above rules, a typical vehicle routing is illustrated below:

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6. Transfer Stations - When the waste disposal unit is remote to the collection area, a transfer station is employed. - A transfer station is an intermediate station between final disposal option and collection point in order to increase the efficiency of the system, as collection vehicles & crew remain closer to routes. - In some situations, the transfer stations serves as a pre-processing plant, where wastes are dewatered & compressed. - A centralized sorting and recovery of recyclable materials are also carried out at the transfer station.

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6.1 Basic Transfer Technologies:

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6.2 Types of Transfer Stations: - Depending upon the size, transfer stations can be either of the following types: (i) Small to Medium Transfer Stations (ii) Large Transfer Stations

6.2.1 Small to Medium Transfer Stations: - These are direct discharge station that provides no intermediate waste storage area.) - The capacities are generally small ( < 100 tons/day) and medium ( 100-300 tones/day ) - These stations includes a recyclable material separation and processing units. - The required over all station capacity (number & size of containers) depends on the size and population density of the area served and the frequency of the collection.

6.2.2 Large Transfer Stations: - These are designed for heavy commercial use by private and municipal collection vehicles. The typical operational procedure for a larger station is as follows: - When collection vehicles arrive at the site, they are checked in for billing, weighted and directed to the appropriate dumping area. 49

- Collection vehicles travel to the dumping area and empty the wastes into a waiting trailer, a pit (or) a platform. - After unloading, the collection vehicle leaves the site, and there is no need to weigh the departing vehicle, if its weight (empty) is known. - Transfer vehicles are weighed either during (or) after loading, trailers can be more consistently loaded to just under maximum legal weights and this maximize payloads and minimizes weight violations.

6.3 Benefits of Transfer Stations: - Reduces overall community truck traffic by consolidating smaller loads into larger vehicles. - It offers more flexibility in waste handling and disposal options. - It reduces air pollution, fuel consumption and road wear by consolidating trash into fewer vehicles. - Allows for screening of wastes for special handling. - Reduces the traffic at disposal facility. - Offers citizens facilities for convenient drop-off of waste and recyclables.

6.4 Factors Affecting Site Selection (or) Location of Transfer Stations - Transfer stations will generate additional amount of traffic in its immediate area. This traffic can contribute to increased road congestion, air emissions, noise and wear on roads. So, site selection should be based on following criteria: 50

- Selecting sites that have direct access to truck routes, highways and rail terminals. - Providing adequate space within the facility site so that customers waiting to use the transfer station do not interrupt traffic on public roads. - Arranging the site so that traffic flows are not adjacent to properties that are sensitive to noise. - The site should large enough to accommodate all required functions and possibly future expansion should be centrally located in the area where waste is generated.

6.5 Operation & Maintenance of a Transfer Station - Six categories can be finalized and can be explained under “Operation & Maintenance of a Transfer Station”. They are: (i) Operation & Maintenance plans (ii) Facility Operating Time (iii) Interacting with the people (iv)Waste Screening (v)Emergency Situation (vi)Record Keeping

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Operation & Maintenance Plans: - Although a transfer station’s basic function as a waste consolidation and transfer facility is straightforward, operating a successful station involves properly executing many tasks. - They should be written specifically for a particular facility and include the following elements: - Facility operating schedules, including days of the week, hours each day & holidays. - Staffing plan that lists duties by job title, minimum staffing levels and typical work schedules. - Description of acceptable & unacceptable wastes. - Operating methods for each component of the facility & description of maintenance procedure for each component. - Employee training

- Safety rules & regulations

- Recordkeeping procedures

- Emergency Procedures

Facility Operating Hours: - A transfer station’s operating hours must accommodate the collection schedules of vehicles delivering wastes to the facility. - Operating hours need to consider the local setting of the transfer station, including neighboring land uses, as well as the operating hours of disposal sites collecting wastes from the transfer station.

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- Operating hours considerable depends on individual circumstances. Many large facilities located in urban industrial zones operate 24 hours, 7 days / week. - Suburban & rural transfer stations of various sizes commonly open early in the morning (6.am to 7.am) and close in the late afternoon (4.pm to 5.pm) - In many cases, the best trailer must be loaded with sufficient time to reach the disposal site before it closes (4.pm to 6.pm)

Interacting with the Public: - Every transfer station has its neighbors, whether they are industrial, commercial, residential (or) merely a vacant land. - An important part of a successful transfer station operations is engaging in constructive dialogue with the surrounding community. - When developing a community outreach plan, transfer station operators should consider the following: - Develop a clear explanation of the need for the transfer stations & its benefits. - Develop a clear process for addressing community concerns. - Designate one person as official contact for neighborhood questions & queries - Organize periodic facility tours. - Establish positive relationships by working with community based organizations

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Waste Screening: - Transfer station operators should screen for unacceptable materials before, during & after customers unload. - And operators should tell customers where they can dispose off wastes inappropriate for that transfer stations with the medium of fact sheets.

Emergency Situations: - Transfer station operators should prepare for emergency, at minimum, the following emergency events should be anticipated. - Power Failure: The plan should address how to record customer information, collect fees and load transfer trailers during a power outage.

- Unavailability of Transfer Vehicles: The plan should address what to do if poor weather, road closures (or) strikes prevent empty transfer vehicles from arriving at the transfer station. - Unavailability of Scales: The plan should describe record keeping and fee assessment in the event that scales are inoperable. - Fire: Fire response and containment procedures should address fire’s found in incoming loads, temporary storage, compaction equipment, transfer vehicles and other locations. - Injuries to employees (or) customers: The plan should include first aid procedures and emergency phone numbers of nearby hospitals.

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Record Keeping: -Medium & large transfer stations typically record the following information as part of their routine works. -Incoming Loads: date, time, company, driver name, truck number, origin of load, fee charged. - Outgoing Loads: date, time, company, driver name, truck number, type of waste. - Facility operating log: Noting any unusual events during the operating day. - Complaint Log: Noting the date, time, complaining party, nature of the complaint. - Accidents (or) releases: Details of any accident (or) waste releases into the environment. - Maintenance Records: For mobile and fixed equipments.

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7. Collection and Transfer Operations – Under Indian Conditions Let’s all know about the collection and transfer operations in Municipal Solid Waste Management of Coimbatore city.

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Municipal Solid Waste Management Unit IV Off Site Processing Syllabus:Processing techniques & Equipments – Resource Recovery from solid wastes – Composting – Incineration – Pyrolysis – Options under Indian conditions.

1. Processing Techniques & Equipments 1.1 Purpose of Processing - The processing of wastes helps in achieving the best possible benefit from every functional element of the solid waste management (SWM) system and, therefore, requires proper selection of techniques and equipment for every element. - Essentially, the purposes of processing are: (a) Improving efficiency of SWM system (e.g.) Shredding (b) Recovering material for reuse ( c ) Recovering conversion products & energy

1.2 Various Techniques & Equipments: (a) Mechanical Volume & Size reduction (b) Component Separation

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- Air Separation - Magnetic Separation - Screening ( c ) Drying & Dewatering

1.3 Mechanical Volume & Size Reduction - Mechanical volume and size reduction is an important factor in the development and operation of any SWM system. - The main purpose is to reduce the volume and size of waste, as compared to the original form, and produce waste of uniform size.

1.3.1 Volume Reduction (or) Compaction: - Volume reduction (or) compaction refers to densifying wastes in order to reduce their volume. The benefits of compaction are: (a) Reduction in the quantity of materials to be handled at the disposal site (b) Improved efficiency of collection and disposal of wastes ( c ) Increased life of landfills (d) Economically viable waste management system

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Equipments for Volume reduction (or) Compaction: Stationary Equipments: - This represents the equipment in which wastes are brought to, and loaded into, either manually (or) mechanically.

Movable Equipment: - This represents the wheeled and tracked equipment used to place and compact solid wastes. 2

Low Pressure ( < 7 kg / cm ) Compactors: -

These compactors are used at apartments, commercial

establishments. Example: Baling equipment – For waste papers & card boards Stationary compactors – For transfer station - In low pressure compaction, wastes are compacted in large containers. 2

High Pressure ( > 7Kg / cm )Compactors:

this category. Compact systems with a capacity up to 351.5 Kg / cm2 came under Here, specialized compaction equipment are used to compress solid wastes in to blocks (or) bales of various sizes. 64

- Typically, the reduction ranges from about 3 to 1 through 8 to 1 Compaction Ratio = V1 / V2 V1 = Volume of waste before compaction V2 = Volume of waste after compaction

1.3.2 Size Reduction (or) Shredding - This is required to convert the large sized wastes into smaller pieces. - Size reduction helps in obtaining the final product in a reasonably size in comparison to the original form.

Equipments for Size Reduction (or) Shredding: Hammer Mill: - These are used most often in large commercial operations for reducing the size of wastes. - Hammer mill is an impact device consisting of a number of hammers, fastened flexibly to an inner disk, which rotates at a very high speed. - Solid wastes as they enter the mill, are hit by sufficient force, which crush (or) tear them with a velocity so that they do not adhere to the hammers. - Wastes are further reduced in size by being struck between breaker plates & cutting bars fixed around the periphery of the inner chamber.

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Hydro-pulper: - An alternate method of size reduction involves the use of a hydropulper as shown below: - Solid wastes and recycled water are added to the hydro-pulper. - The high speed cutting blades, mounted on a rotor in the bottom of the unit, convert palpable and friable materials in to slurry with a solid content varying from 25 to 35%

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- The rejected material passes down a chute that is connected to a bucket elevator, while the solid slurry passes out through the bottom of the pulper tank and is pumped to the next processing operation.

1.4 Component Separation - Component separation is a necessary operation in which the waste components are identified and either manually (or) mechanically to aid further processing.

1.4.1 Air Separation This technique has been in use for a number of years in industrial operations for segregating various components from dry mixtures. - Air separation is primarily used to separate lighter materials from the heavier ones.

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- The lighter materials may include plastics, paper products and other organic materials.

Equipments used for Air Separation Conventional Chute Type: - Its one of the simplest type of air classifier. - In this type, when the processed solid wastes are dropped into the vertical chute, the lighter materials are carried by the air flow to the top while the heavier materials fall to the bottom of the chute. - A rotary air lock feed mechanism is required to introduce the shredded wastes into the classifier.

Zig-Zag Classifier: - It consists of a continuous vertical column with internal zig-zag deflectors through which air is drawn at high rate. - Shredded wastes are introduced at the top of the column at a controlled rate, and air is introduced at the bottom of the column.

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- As the wastes drop into the air stream, the lighter friction is fluidized and moves upward and out of column, while the heavy fraction falls to the bottom.

1.4.2 Magnetic Separation - The most common method of recovering ferrous scrap from shredded solid wastes involves the use of magnetic recovery system. - Ferrous materials are usually recovered either after shredding (or) before air separation.

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Equipments used for Magnetic Separation Suspended Magnet: - In this type of separator, a permanent magnet is used to attract the ferrous metal from the waste stream.

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- When the attracted metal reaches the area where there is no magnetism, it falls away freely. - This ferrous metal is then collected in a separate container.

Magnetic Pulley: - This consists of a drum type device containing magnets (or) electromagnets over which a conveyor (or) a similar transfer mechanism carries the waste stream. - The conveyor belt conforms to the rounded shape of the magnetic drum and the magnetic force pulls the ferrous material away from the falling stream of solid waste.

1.4.3 Screening

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- Screening is the most common form of separating solid wastes, depending on their size by the use of one (or) more screening surfaces. - Screening has a number of applications in solid waste resource & energy recovery systems. - Screens can be used before (or) after shredding and after air separation of wastes in various applications dealing with both light & heavy fraction materials.

1.5 Drying & Dewatering - Drying and dewatering operations are used primarily for incineration systems with (or) without energy recovery systems. - These are also used for drying of sludges in wastewater treatment plants, prior to their incineration (or) transport to land disposal.

1.5.1 Drying The following methods are used to apply the heat required for drying the wastes.

Convection Drying: In this method, hot air is in direct contact with the wet solid waste stream.

Conduction Drying: In this method, the wet solid waste stream is in contact with a heated surface.

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Radiation Drying: In this method, heat is transmitted directly to the wet solid waste stream by radiation from the heated body.

1.5.2 Dewatering - When drying beds, lagoons (or) spreading on land are not feasible,

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Other mechanical means of dewatering are used. - The objective is to reduce the liquid volume in the solid waste stream. - Once dewatered, the sludge can be mixed with other solid waste, and the resulting mixture can be: (i) incinerated to reduce volume (ii) used for the production of recoverable by-products (iii) used for production of compost (iv) buried in a landfill

2. Resource Recovery from solid wastes – MRF - A Materials Recovery Facility (or) Materials Reclamation Facility (or) Materials Recycling Facility (MRF) is a specialized plant that receives, separates and prepares recyclable materials for marketing to end-user manufacturers. - Generally, there are two different types of MRF are there: Clean MRF & Dirty MRF

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Clean MRF: - A clean MRF accepts recyclable commingled materials that have already been separated at the source from municipal solid waste generated either by residential (or) commercial sources. - There are varieties of clean MRFs. - The most common are “Single Stream Type” where all recyclable material is mixed (or) “Dual Stream Type” where source separated recyclables are delivered in a mixed container stream.

Dirty MRF: - A dirty MRF accepts a mixed solid waste stream and then proceeds to separate out designated recyclable materials through a combination of manual and mechanical sorting. - The sorted recyclable materials may undergo further processing required to meet technical specifications established by end-markets while the balance of the mixed waste stream is sent to a disposal facility such as a landfill.

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3. Composting Composting is one of the important technologies for solid waste management. - Any organic material that can be biologically decomposed is compostable. - Today, composting is a diverse practice that includes a variety of approaches, depending upon type of organic materials being composted and the designed properties of final product. The overall composting process can be explained as follows: Organic matter + O2 + Aerobic bacteria → Co2 + NH3 + H2O + other end products + Energy

3.1 Principles of Composting - Decomposition and stabilization of organic waste matter is a natural phenomenon. - Composting is an organized method of producing compost manure by adopting this natural phenomenon. - Composting can be carried out in two ways, aerobically & anaerobically.

3.1.1 Aerobic Composting - During composting, aerobic micro-organisms oxidize organic compounds to Co2, Nitrite and Nitrate 77

- Carbon from organic compounds is used as a source of energy while nitrogen is recycled. - Due to exothermic reaction, temperature of the mass rises.

3.1.2 Anaerobic Composting - During composting, the anaerobic micro-organisms, while metabolizing the nutrients, breakdown the organic compounds through a process of reduction. - A very small amount of energy is released during the process and the temperature of composting mass does not rise much. - The gases evolved are mainly Methane & Carbon dioxide. - An anaerobic process is a reduction process and the final product is subjected to some minor oxidation when applied to land.

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3.2 Methods of Composting - Manual composting was systemized by Howard and his associates. - It was further developed by Acharya & Subramanyam and the methods are conventionally referred as Indore and Bangalore methods of Composting.

3.2.1 Bangalore Method - This is an anaerobic method conventionally carried out in pits. - Formerly the waste was anaerobically stabilizes 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. 79

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

3.2.2 Indore 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 tuning 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 days. Further turning is normally not required and the compost is ready in 2 to 4 weeks.

Comparison of the methods: - The Bangalore method requires longer time for stabilization of the material & hence needs larger load space. - The gases generated in this anaerobic process also pose smell & odour problems. - The Indore method on the other hand stabilizes the material in shorter time & needs lesser land space. - As no odourous gases are generated in this process, it is environment friendly & hence commonly preferred.

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3.2.3 Windrow Composting - The organic material present in Municipal Waste can be converted into a stable mass by aerobic decomposition. - Aerobic micro-organisms oxidize organic compounds to carbon di oxide and oxides of Nitrogen and carbon from organic compounds is used as a source of energy, while Nitrogen is recycled. - Due to exothermic reactions, temperature of mass rises. - In areas / regions were higher ambient temperatures are available, composting in open windrows is to be preferred. - In this method, refuse is delivered on a paved / unpaved open space but leveled and well drained land in about 20 windrows with each window 3m long x 2m long x 1.5m high with a total volume not exceeding 9.0 m th

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- Each windrow would be turned on 6 & 11 days outside to the centre to destroy insects larvae and to provide aeration. th

- On 16 day, windrow would be broken down and passed through manually operated rotary screens of about 25mm square mesh to remove the oversize contrary material. - The screened compost is stored about 30 days in helps about 2m x 1.5m high and up to 20m long to ensure stabilization before sales

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Indian Standards for compost:

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3.2.4 Mechanical Composting - Though manual methods are preferable in countries where labour is comparatively cheap, processes are preferred where higher labour costs and limitations of space exist. - Mechanical composting plant is a combination of various units which perform specific functions.

- Solid waste collected from various areas reaches the plant site at a variable depending upon the distance of collection point. - As the compost plant operates at a constant rate, a balancing storage has to be provided to absorb the fluctuations in the waste input to the plant.

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- The waste is then fed to a slowly moving ( 5m / minute ) conveyor belt and the non-decomposable material such as plastics, glass, metals are manually removed by labors standing on either side of the conveyor belt. - And the removed material is stored separately. - The metals are then removed from the waste by either a suspended magnet system (or) a magnetic pulley system.

- The waste is thus subjected to size reduction when the surface area per unit weight is increased for faster biological decomposition. -Size reduction is commonly carried out either in Hammer mills (or) Rasp mill. Hammer mills are high speed ( 600 – 1200 rpm ) compact machines consumes large energy. - Rasp mills are slow moving large units that requires lesser energy. - The stabilization is carried out in open windrows provided over cement concrete paved ground. - These windrows are turned every 5 days to ensure aerobic decomposition, various types of equipment such as front end loaders are used to turn windrows. - At the end of the 3 to 4 weeks periods, the material is known as green (or) fresh compost where in the cellulose has not been fully stabilized.

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- It is hence stored in large sized windrows for 1-2 months either at the plants (or) farms.

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3.3 Factors affecting Composting (i) Organisms (ii) Use of cultures (iii) Moisture (iv) Temperature (v) C/N Ratio (vi) Aeration (vii) Addition of sewage & sewage sludge

Organisms: - Aerobic composting is a dynamic system where in bacteria, actinomycetes, fungi and other biological forms are actively involved. - The relative preponderance of one species over another depends upon the constantly changing food supply, temperature and substrate conditions.

- When the temperature drops, actinomycetes & fungi are confined to 5 to 15 cm outer surface layer. - Thermophilic actinomycetes and fungi are known to grow well ο in the range of 45 to 60 C

Use of Cultures: - During the development of composting process, various innovators came forward with inoculum, enzymes claimed to hasten the composting process.

- Investigations carried out by various workers have shown that they are not necessary. 89

- Under proper environment conditions, the indigenous bacteria adopted to MSW rapidly multiply as compared to the added cultures.

- However, such inoculum will be required during composting of industrial and agricultural solid waste which do not have the large mix of indigenous bacterial population.

Moisture: - The moisture tends to occupy the free air space between the particles. - Hence, when the moisture content is very high, anaerobic condition set in. - The composting mass should have a certain minimum moisture content in it for the organisms to survive. - The optimum moisture content is known to be between 50 to 60% - Higher moisture content may be required while composting straw and strong fibrous material which is often the fibre and fills the large pore spaces.

Temperature: -The aerobic decomposition of a gram mole of glucose releases 484 to 674 kilo calories energy under controlled conditions, while only 26 kcal are released when it is decomposed anaerobically. - Under properly controlled conditions, temperatures are known to rise beyond 70 C in aerobic condition. ο

- This increased temperature results in increased rate of biological activity and hence result in faster stabilization of materials.

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- The temperature range of 50 C - 60 C is optimum for nitrification and cellulose degradation. - Thus, if the process is so controlled that the temperature is kept ο between 50 C to 60 C for 5 to 7 days, destruction of pathogens and parasites can be ensured. ο

Carbon to Nitrogen Ratio: - The organisms involved in stabilization of organic matter utilizes about 30 parts of carbon for each part of nitrogen and hence an C/N ratio of 30 is most favorable. - It has reported that optimum value to range between 26 – 31 depending upon other environmental conditions. - Whenever the C/N ratio is less than the optimum, carbon source such as straw, sawdust, paper are added while if the ratio is to high, the sewage sludge, slaughter house waste, blood are added as a source of nitrogen.

Aeration: - It is necessary to ensure that oxygen is supplied throughout the mass and aerobic activity is maintained. - During the decomposition, the oxygen gets depleted and has to be continuously replenished. - This can be achieved either by turning of windrows (or) by supplying compressed air. - In case of artificial supplying, the quantity of air supply is normally maintained at 1 – 2 cu m / day / kg of volatile solid.

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- It have shown that the optimum turning interval which will reduce the cost and simultaneously maintain aerobic conditions in 5 days.

Addition of sewage & sewage sludge: - The optimum C/N ratio for composting is 25-30. - MSW in developed countries has a C/N ratio of nearly 80. - To bring it down to the optimum value and to reduce the cost of sewage sludge treatment, it is mixed with sewage sludge. -MSW in India, has an initial C/N ratio of around 30 which does not need blending.

4. Incineration 4.1 Definition - Incineration process can be defined as an engineered process using controlled flame combustion to thermally degrade waste materials in presence of oxygen.

4.2 Necessity of Incineration - Waste volume reduced to less than 5% - At sufficiently high temperature, and residence time, any hydrocarbon vapour can be oxidized to carbon di oxide and water. - Relatively simply devices capable of achieving very high removal efficiencies. - Heat can be recovered - Most gases are burnt – well designed systems

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- Easy to maintain - Only solution for certain waste types.

4.3 Incineration system components - Waste pre-treatment ( pre-heating (or) shredding ) - Waste loading systems ( conveyors, hoppers, sprayers ) - Burner management system - Combustion chambers - Heat recovery - Air pollution control device - Slack discharge - Ash disposal - Emission monitoring systems

4.4 Process Description The System concept consists of the following three (3) essential main components: 1. Rotary kiln with subsequent afterburner chamber 2. Heat exchanger or steam boiler for energy utilization 3. Multi-layer flue gas purification, including catalyst

- The solid and paste-like hazardous wastes are pushed into the rotary tubular kiln by a spiral-like screw conveyor or a stopper. - Liquid wastes are injected via an injection nozzle into the rotary tubular kiln and into the afterburner chamber. - The rotary tubular kiln is the most universal method of incineration of hazardous wastes of different composition.

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- Solid as well as pasty and liquid materials can be fed into the furnace for incineration at the same time. - Through a high excess of air and through the constant addition of supplemental fuel, thorough incineration is guaranteed. - The hazardous waste and the incineration air is introduced into the system from the front side of the rotary kiln. - From the opposite end the slag and flue gas is being discharged. - The following incineration temperatures are achieved: Maximum furnace temperature in rotary kiln: 1050 degrees C Maximum post-combustion temperature: 1300 degrees C

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5. Pyrolysis 5.1 Definition - Pyrolysis is a thermochemical decomposition of organic material at elevated temperatures without the participation of oxygen. - It involves the simultaneous change of chemical composition and physical phase, and is irreversible. - Pyro = fire;

lysis = separating

5.2 Applicability - The waste conversion Pyrolysis system is well suited to handle various feed stocks as follows: - Municipal Solid waste - Automobile tires - Biomass - Industrial waste - Hazardous waste - Sewage sludge 95

5.3 Advantages of Pyrolysis - Conversion of up to 100% - No Green house and other harmful gas emission into the atmosphere

- No toxic waste to dispose of - Reduced public health risk - Simultaneous treatment of various types of waste materials - Reliable energy source, high energy output - High conversion efficiency - Low capital and operation cost - Low energy consumption

5.4 System Components - Pre-processing & feeding system - Pyrolysis reactor - Thermal oxidizer - Energy generator - Off gas depuration system

5.5 Process Description Step 1: Waste pre-processing and feeding system. - Municipal solid waste is conveyed to the system through a specifically designed pre-processing line which includes filittering out materials that are not suitable for pyrolysis (metals, glass and inerts), - Shredding and drying of the remaining waste stream.

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- Filtered out recyclable materials make for 15-20% of the initial amount of waste, depending on its composition, and can be sold to the market, providing a significant source of revenue. - The remaining waste stream is chipped into small pieces up to 50mm in diameter. In the dryer its moisture content is reduced down to 20% in order to provide higher conversion results. - The properly prepared waste is finally collected in the storage bin.

Step 2: Pyrolysis of waste - The high-temperature pyrolysis process takes place in an indirectly heated pyrolytic chamber (a retort) at 700-750%C in an oxygen-free environment, allowing conversion of the waste into synthesis gas (90-98%) and a solid cocking residue, or carbon char (2-10%), without any liquid tar fractions being formed. - The specific temperature regime, continuously maintained in the process chamber, eliminates any dioxins or furans in the carbon char residue thereby allowing further use of this byproduct. Dioxins are contained in syngas only.

Step 3: Thermal Oxidizer - Syngas is mixed with air in the main burner and directed to the oxidizer for ο combustion at 1200 C. - Specific controlled conditions in the oxidizer ensure complete destruction of dioxins and furans contained in the syngas and prevent their re-formation.

- The oxidized gasses have high thermal capacity and are partly utilized by the system to maintain the temperature in the pyrolytic chamber, thereby decreasing outside energy consumption (natural gas, or propane-butane) by 60%.

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Step 4: Energy Generation. - As oxidized gas leaves the thermal oxidizer, its high temperature is heat exchanged to a waste heat boiler. - Thermal energy captured from the oxidized gas is converted into high temperature steam supplying energy to turbine generators which in turn produce clean electric power

.Step 5: Pollution Control System. - The cooled (flue gasses are passed through a multi-stage pollution control system to be cleaned of harmful impurities and safely released into the environment. - Waste off gasses utilized for pyrolysis reactor heating are also directed to the waste heat boiler, and, after being cooled, pass through a similar depuration system.

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Municipal Solid Waste Management Unit V Disposal Syllabus:Dumping of solid waste; sanitary landfills – Site selection, design and operation of sanitary landfills – Leachate collection & treatment

1. Introduction - The term ‘landfill’ can be treated as synonymous to ‘sanitary landfill’ of Municipal Solid Waste, only if the latter is designed on the principle of waste containment and is characterized by the presence of a liner and leachate collection system to prevent ground water contamination. - The term ‘sanitary’ landfill has been extensively used in the past to

describe MSW disposal units constructed on the basis of ‘dump and cover’ but with no protection against ground water pollution. - Such landfills do not fall under the term ‘municipal solid waste

landfills’

2. Sanitary Landfill -The term ‘landfill’ is used to describe a unit operation for final disposal of ‘Municipal Solid Waste’ on land, designed and constructed with the objective of minimum impact to the environment by incorporating eight essential components.

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3. Dumping of Solid wastes (a) Landfilling will be done for the following types of waste: (i) Comingled waste (mixed waste) not found suitable for waste processing; (ii) Pre-processing and post-processing rejects from waste processing sites; (iii) Non-hazardous waste not being processed or recycled. (b) Landfilling will usually not be done for the following waste streams in the

municipal solid waste: (i) Bio waste/garden waste; (ii) Dry recyclables.

(c) Landfilling of hazardous waste stream in the municipal waste will be done at a hazardous waste landfill site; such a site will be identified by the State Government and is likely to be operated by industries of a district/state.

(d) Landfilling of construction and demolition waste will be done in a separate landfill where the waste can be stored and mined for future use in earthwork or road projects.

(e) All existing and old landfills will be inspected and boreholes will be drilled for (i) recovery of leachate samples from the base of the landfill, (ii) recovery of subsoil samples beneath the base of the landfill for evaluation of permeability and soil properties and (iii) recovery of waste samples for waste characterization.

(f) If the leachate quality is observed to be of poor quality with respect to the local ground water quality or with respect to the CPCB norms.

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4. Essential Components of a Landfill The seven essential components of a MSW landfill are: (a) A liner system at the base and sides of the landfill which prevents migration of leachate or gas to the surrounding soil.

(b) A leachate collection and control facility which collects and extracts leachate from within and from the base of the landfill and then treats the leachate.

(c) A gas collection and control facility (optional for small landfills) which collects and extracts gas from within and from the top of the landfill and then treats it or uses it for energy recovery.

(d) A final cover system at the top of the landfill which enhances surface drainage, prevents infiltrating water and supports surface vegetation. 104

(e) A surface water drainage system which collects and removes all surface runoff from the landfill site.

(f) An environmental monitoring system which periodically collects and analyses air, surface water, soil-gas and ground water samples around the landfill site.

(g) A closure and post-closure plan which lists the steps that must be taken to close and secure a landfill site once the filling operation has been completed and the activities for long-term monitoring, operation and maintenance of the completed landfill.

5. Site selection for Landfill Selection of a landfill site usually comprises of the following steps, when a large number (eg. 4 to 8) landfill sites are available:

(i) Setting up of a locational criteria (ii) Identification of search area (iii) Drawing up a list of potential sites; (iv) Data collection (v) Selection of few best-ranked sites (vi)Environmental impact assessment and (vii)Final site selection and land acquisition.

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I Locational Criteria A locational criterion may be specified by a regulatory agency (e.g. Pollution Control Board). In the absence of regulatory requirements, the following criteria are suggested. (a) Lake or Pond: No landfill should be constructed within 200 m of any lake

or pond. Because of concerns regarding runoff of waste water contact, a surface water monitoring program should be established if a landfill is sited less than 200m from a lake or pond.

(b) River: No landfill should be constructed within 100 m of a navigable river or stream. The distance may be reduced in some instances for no meandering rivers but a minimum of 30 m should be maintained in all cases.

(c) Flood Plain: No landfill should be constructed within a 100 year flood plain. A landfill may be built within the flood plains of secondary streams if an embankment is built along the stream side to avoid flooding of the area.

(d) Highway: No landfill should be constructed within 200 m of the right of way of any state or national highway. This restriction is mainly for aesthetic reasons. A landfill may be built within the restricted distance, but no closer than 50 m, if trees and berms are used to screen the landfill site.

(e) Habitation: A landfill site should be at least 500 m from a notified habituated area. A zone of 500 m around a landfill boundary should be declared a NoDevelopment Buffer Zone after the landfill location is finalized. 106

(f) Public parks: No landfill should be constructed within 300 m of a public park. A landfill may be constructed within the restricted distance if some kind of screening is used with a high fence around the landfill and a secured gate.

(g) Critical Habitat Area: No landfill should be constructed within critical habitat areas. A critical habitat area is defined as the area in which one or more endangered species live. It is sometimes difficult to define a critical habitat area. If there is any doubt then the regulatory agency should be contacted.

(h) Wetlands: No landfill should be constructed within wetlands. It is often difficult to define a wetland area. Maps may be available for some wetlands, but in many cases such maps are absent or are incorrect. If there is any doubt, then the regulatory agency should be contacted.

(i) Ground Water Table: A landfill should not be constructed in areas where water table is less than 2m below ground surface. Special design measures be adopted, if this cannot be adhered to.

(j) Airports: No landfill should be constructed within the limits prescribed by regulatory agencies (MOEF/ CPCB/ Aviation Authorities) from time to time.

(k) Water Supply Well: No landfill should be constructed within 500 m of any water supply well. It is strongly suggested that this locational restriction be abided by at least for down gradient wells.

(l) Coastal Regulation Zone: A landfill should not be sited in a coastal regulation zone. 107

(m) Unstable Zone: A landfill should not be located in potentially unstable zones such as landslide prone areas, fault zone etc.

(n) Buffer Zone: A landfill should have a buffer zone around it, up to a distance prescribed by regulatory agencies.

(o) Other criteria may be decided by the planners.

II Search Area - To identify the potential sites for a landfill a ‘search area’ has to be delineated. The search area is usually governed by the economics of waste transportation. - It is usually limited by the boundaries of the municipality. Typically search

areas are delineated on a map using a ‘search radius’ of 5 to 10 km, keeping the waste generating unit as the centre. - Alternatively, the search area may be identified by adopting a range of 5 km all around the built-up city boundary. One should start with a small search area and enlarge it, if needed.

III Development of a list of Potential Sites - After demarcating the search area, as well as after studying the various restrictions listed in the locational criteria, areas having potential for site development should be identified. - A road map may be used to show the potential sites that satisfy the locational criteria. Preliminary data collection should be undertaken with an aim of narrowing the list of sites to a few best-ranked sites. 108

- In areas where land availability is scarce, degraded sites such as abandoned quarry sites or old waste dump sites can be considered. Special design measures are required for such sites.

IV Data Collection Several maps and other information need to be studied to collect data within the search radius. Some are discussed below.

(a) Topographic Maps: The topography of the area indicates low and high areas, natural surface water drainage pattern, streams, and rivers.

(b) Soil Maps: These maps, primarily meant for agricultural use, will show the types of soil near the surface.

(c) Land Use Plans: These plans are useful in delineating areas with definite zoning restrictions. There may be restrictions on the use of agricultural land or on the use of forest land for landfill purposes.

(d) Transportation Maps: These maps, which indicate roads and railways and locations of airports, are used to determine the transportation needs in developing a site.

(e) Flood Plain Maps: These maps are used to delineate areas that are within a 100 year flood plain. Landfill siting must be avoided within the flood plains of major rivers.

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(f) Ground Water Maps: Ground water contour maps are available in various regions, which indicate the depth to ground water below the land surface as well as regional ground water flow patterns. Such maps should be collected from Ground Water Boards or Minor Irrigation Tube well Corporations.

(i) Rainfall Data: The monthly rainfall data for the region should be collected from the Indian Meteorological Department.

(j) Wind Map: The predominant wind direction and velocities should be collected from the Indian Meteorological Department.

(k) Seismic Data: The seismic activity of a region is an important input in the design of landfills Seismic coefficients are earmarked for various seismic zones and these can be obtained from the relevant BIS code or from the Indian Meteorological Department.

V Site Walk-over & Establishment of Ground Truths - A site reconnaissance will be conducted by a site walk-over as a part of the preliminary data collection. All features observed in various maps will be confirmed. - Additional information pertaining to the following will be ascertained from nearby inhabitants: (a) Flooding during monsoons (b) Soil Type (c) Depth to G.W. Table (as observed in open wells or tube wells) (d) Quality of groundwater and (e) Depth to bedrock. 110

VI Preliminary Boreholes and Geophysical Investigation - At each site, as a part of preliminary data collection, one to two boreholes will be drilled and samples collected at every 1.5m interval to a depth of 20m below the ground surface. - The following information will be obtained: (i) Soil type and stratification (ii) Permeability of each stratum (iii) Strength and compressibility parameters (optional) (iv) Ground water level and quality and (v) Depth to bedrock.

VII Assessment of Public Reaction - The public/nearby residents should be informed of the possibility of siting of a landfill in a nearby even as soon as a list of potential sites is developed. A preliminary assessment of public opinion regarding all the sites in the list is essential. - Public reaction is less hostile if landfilling is done in an area already degraded by earlier municipal waste dumps or other activities such as quarrying, ash disposal etc.

VIII Selection of Few Best-Ranked Sites - From amongst a large number of sites, the selection of a final site will emerge from a two -stage approach.

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(a) Selection of a few best-ranked sites (usually 2 sites, sometimes 3) on the basis of pathway and receptor related attributes.

(b) Selection of final site on the basis of environmental impact assessment, social acceptance and cost of disposal.

IX Environmental Impact Assessment (EIA) - Wherever feasible, environmental impact assessment will be conducted for two alternate sites (in exceptional circumstances up to 3 sites) - The impact of the landfill on the following will be quantified: (a) Ground water quality; (a) Ground water quality; (b) Surface water quality; (c) Air quality – gases, dust, litter; (d) Aesthetics – visual, vermin, flies; (e) Noise; (f) Land use alteration; (g) Traffic alteration; (h) Drainage alteration; (i) Soil erosion; (j) Ecological impacts

X Final Site Selection - The final selection of the site from amongst the best-ranked alternatives should be done by comparing: (a) The environmental impact; (b) Social acceptance; and (c) Transportation and landfilling costs.

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6. Design of Landfill - Design of a landfill can be described through following aspects 6.1 Design Life - A landfill design life will comprise of an ‘active’ period and an ‘closure and post-closure’ period. - The ‘active’ period may typically range from 10 to25 years depending on the availability of land area. - The ‘closure and post-closure’ period for which a landfill will be monitored and maintained will be 25 years after the ‘active period’ is completed.

6.2 Waste Volume and Landfill Capacity - The volume of waste to be placed in a landfill will be computed for the ‘active’ period of the landfill taking into account (a) the current generation of water per annum and (b) the anticipated increase in rate of waste generation on the basis of past records or population growth rate. - The required landfill capacity is significantly greater than the waste volume it accommodates. - The actual capacity of the landfill will depend upon the volume occupied by the liner system and the cover material (daily, intermediate and final cover) as well as the compacted density of the waste. - In addition, the amount of settlement a waste will undergo due to overburden stress and due to biodegradation should also be taken into account. - Densities may range as low as 0.40 t/cu.m. to 1.25 t/cu.m. - For planning purposes, a density of 0.85 t/cu.m. may be adopted for biodegradable wastes with higher values (typically 1.1 t/cu.m.) for inert waste.

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- The total landfill area should be approximately 15% more than the area required for landfilling to accommodate all infrastructure and support facilities as well as to allow the formation of a green belt around the landfill. - There is no standard method for classifying landfills by their capacity. However the following nomenclature is often observed in literature: Small size landfill : less than 5 hectare area Medium size landfill : 5 to 20 hectare area Large size landfill : greater than 20 hectare area. Landfill heights are reported to vary from less than 5 m to well above 30 m.

6.3 Layout - A landfill site will comprise of the area in which the waste will be filled as well as additional area for support facilities. - Within the area to be filled, work may proceed in phases with only a part of the area under active operation. - The following facilities must be located in the layout: (a) Access roads (b) Equipment shelters (c) Weighing scales (d) Office space (e) Location of waste inspection and transfer station (if used) (f) Temporary waste storage and/or disposal sites for special wastes (g) Areas to be used for waste processing (e.g. shredding) (h) Demarcation of the landfill areas and areas for stockpiling cover material and liner material (i) Drainage facilities (j) Location of landfill gas management facilities 114

(k) Location of leachate treatment facilities; and (l) Location of monitoring wells. A typical site layout is shown below

- It is recommended that for each landfill site, a layout be designed incorporating all the above mentioned facilities

7. Operation of a Landfill - To secure public acceptability, landfill operations require careful planning and determination of the extent of environmental effects. - The basic factor influencing the planning of site operations is the nature and quantity of incoming waste. - The various aspects of operation of a landfill are as follows

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7.1 Methods of Filling - Trench Method: This involves the excavation of a trench into which waste is deposited, and the excavated material is then used as cover. - Area Method: Wastes may be deposited in layers and so form terraces over the available area. However, with this type of operation, excessive leachate generation may occur.

- Cell Method: This method involves the deposition of wastes within preconstructed bounded area. It is now the preferred method in the industrialized world, since it encourages the concept of progressive filling and restoration.

- Canyon / Depression: This method refers to the placing of suitable wastes against lined canyon or ravine slide slopes. Slope stability and leachate gas emission are critical issues for this type of waste placement.

7.2 Refuse Placement - The working space should be sufficiently extensive to permit vehicles to man oeuvre and unload quickly and safely without Impeding refuse spreading, and allow easy operation of the site equipment. - Depositing waste in thin layers using a compactor enables a high waste density to be achieved. - Various systems for monitoring the leachate level are in use, and are mostly based on pipes installed prior to land filling. - Placing pipes within a column or tyres may, however, offer some protection.

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7.3 Covering of Waste - At the end of each working day, all exposed surfaces, including the flanks and working space, should be covered with a suitable inert material to a depth of at least 15 cm. - This daily cover is considered essential, as it minimizes windblown litter and helps reduce odours.

7.4 Site Equipment and Workforce Orientation - The equipment most commonly used on landfill sites includes steel wheeled compactors, tracked dozers, loaders, earthmovers and hydraulic excavators. - Scrapers are used for excavating and moving cover materials. In addition to appropriate equipment, proper training must be ensured for the workforce.

7.5 Leachate / gas Monitoring - Monitoring of leachate plays a vital role in the management of landfills. - Data on the volume of leachate and their composition are essential for proper control of leachate generation and its treatment. - Placing pipes within a column or tyres may, however, offer some protection.

7.6 Groundwater Monitoring - A continued groundwater monitoring programme for confirming the integrity of the liner system is essential. 118

- At an early stage of site preparation, therefore, a number of monitoring boreholes need to be provided around the site. - However, the location, design and number of boreholes depend on the size of the landfill, proximity to an aquifer, geology of the site and types of wastes deposited.

8. Leachate Collection & Treatment 8.1 Leachate Control - Leachate control within a landfill involves the following steps: (a) Prevention of migration of leachate from landfill sides and landfill base to the subsoil by a suitable liner system

(b) Drainage of leachate collected at the base of a landfill to the sides of the landfill and removal of the leachate from within the landfill. - Three types of liner systems are usually adopted and these are described

hereafter: (a) Single Liner System: Such a system comprises of a single primary barrier overlain by a leachate collection system with an appropriate separation/protection layer. A system of this type is used for a low vulnerability landfill.

(b) Single Composite Liner System: A composite liner comprises of two barriers, made of different materials, placed in intimate contact with each other to provide a beneficial combined effect of both the barriers. Usually a flexible geo membrane is placed over a clay or amended soil barrier.

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(c) Double Liner System: In a double liner system a single liner system is placed

twice, one beneath the other. The top barrier (called the primary barrier) is overlaid by a leachate collection system. Beneath the primary barrier, another leachate collection system (often called the leak detection layer) is placed followed by a second barrier (the secondary barrier).

8.2 Leachate Collection - A leachate collection system comprises of a drainage layer, a perforated pipe collector system, sump collection area, and a removal system. - The leachate drainage layer is usually 30 cm thick, has a slope of 2% or higher and a permeability of greater than 0.01 cm/sec. - A system of perforated pipes and sumps are provided within the drainage layer. The pipe spacing is governed by the requirement that the leachate head should not be greater than the drainage layer thickness. - Leachate is removed from the landfill by (a) pumping in vertical wells or chimneys, (b) pumping in side slope risers, or (c) by gravity drains rough the base of a landfill in above -ground and sloped landfills. - The design steps for the leachate collection system are: (a) Finalization of layout pipe network and sumps in conjunction with drainage layer slopes of 2% (b) Estimation of pipe diameter and spacing on the basis of estimated leachate quantity and maximum permissible leachate head (c) Estimating the size of sumps and pump (d) Design of wells/side slopes risers for leachate removal; and (e) Design of a holding tank.

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8.3 Leachate Treatment (a) Discharge to Lined Drains: This option is usually not feasible. It can only be adopted if the leachate quality is shown to satisfy all waste water discharge standards for lined drains, consistently for a period of several years.

(b) Discharge To Waste Water Treatment System: For landfills close to a waste water treatment plant, leachate may be sent to such a plant after some pretreatment. Reduction is organic content is usually required as a pretreatment.

(c) Recirculation: One of the methods for treatment of leachate is to recirculate it through the landfill. This has two beneficial effects: (i) The process of landfill stabilization is accelerated (ii) The constituents of the leachate are attenuated by the biological, chemical and physical changes occurring with the landfill. - Recirculation of a leachate requires the design of a distribution system to ensure that the leachate passes uniformly throughout the entire waste.

(d) Evaporation of Leachate: one of the techniques used to manage leachate is to spray it in lined leachate ponds and allow the leachate to evaporate. -Such ponds have to be covered with geo membranes during the high rainfall periods. - The leachate is exposed during the summer months to allow evaporation. Odour control has to be exercised at such ponds.

(e) Treatment of Leachate: The types of treatment facilities to be used depend upon the leachate characteristics.

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- Typically, treatment may be required to reduce the concentration of the following prior to discharge: Degradable and non-degradable organic materials, Specific hazardous constituents, Ammonia and nitrate ions, Sulphides, Odorous compounds, and Suspended solids. - Treatment processes may be biological processes (such as activated sludge, aeration, nitrification (dentrification), chemical processes (such as oxidation, neutralisation) and physical processes (such as air stripping, activated adsorption, ultra filtration etc.). - The treated leachate may be discharged to surface water bodies.

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