Waste Management Systems-unit 1 & 2

Mtech Infra Sem 2 - WASTE MANAGEMENT SYSTEMS

Unit 1:

Basic Theories of Industrial Waste water Management Volume reduction Strength reduction

Neutralization Equalization and proportioning. Joint treatment of industrial wastes and domestic

sewage consequent problems.

Industrial wastes are usually dumped into the river streams causing pollution. These wastes are to be

managed before disposing. Basic Theories of Industrial Waste water Management

Volume Reduction

Strength Reduction

Neutraliztion

Equalization

Proportioning

Volume Reduction The first step in minimizing the effects of Industrial Wastes on Water Streams and Treatment Plants is to reduce

the Volume of such Wastes. This may be achieved by:

1.Classification of wastes

2.Conservation of waste water

3.Changing production to decrease wastes

4.Re-using both industrial and municipal effluents as raw water supplies

5.Elimination of batch or slug discharges of process wastes.

Classification of Wastes:

The wastes can be classified according to the extent and nature of the pollutants present in them. After

such classification is done, then the necessary degree of treatment can be adopted. By doing this, only

the most polluted ones can be treated to a higher degree than the relatively uncontaminated wastes.

The Three main classes of waste are:

Wastes from manufacturing processes

Waters used as cooling agents in industrial processes

Wastes from sanitary uses.

Conservation Of wastewater:

Water conserved is waste saved. Conservation begins when an industry changes from open to a closed

system. Introduction of conservation practices requires a complete engineering survey of existing water

use and an inventory of all plant operations using water and producing wastes, so as to develop an

accurate balance for peak and average operating conditions. For example steel mills reuse cooling

waters to coal processors reuse water to remove dirt and other non-combustible materials from coal.

Changing Production to Decrease Wastes:

This is an effective method of controlling the volume of wastes but is difficult to put into the practice. It

is hard to persuade production men to change their operations just to eliminate wastes. Normally, the

operational phase of engineering is planned by the chemical, mechanical or industrial engineer, whose

primary objective is cost savings, several measures that can be used to reduce wastes, improved process

control, improved equipment design, use of different or better quality raw materials, good house

keeping and preventive maintenance.

Re-Using Both Industrial and Municipal Effluents for Raw Water supplies:

Practiced mainly in areas where water is scarce and/or expensive, this is proving a popular and

economical method of conservation: of all the sources of water available to Industry, Sewage plant

effluent is the most reliable at all seasons of the year and the only one that is actually increasing in

quantity and improving in quality.

Many industries and cities hesitate to reuse effluents for raw water supply. Certain technical problems

such as hardness, colour and an esthetic reluctance to accept effluents as a potential source of water for

any purpose. Also treatment plants are subject to shutdown and sudden discharges, both of which may

make the supply undependable or of variable quality. However, as the cost of importing a raw water

supply increase, it would seem logical to re-use Waste- treatment plant effluents to increase the present

water supply by replenishing the ground water. The ever-available treatment plant effluent can produce

a low cost steady water source through ground water recharge. Re-use of sewage effluent will reduce

the quantity of pollution discharged by the municipality.

Elimination Of Batch or Slug Discharge Of Process Wastes

If the waste is discharged in a short period of time, it is usually referred to as a slug discharge. This type

of waste, because of its concentrated contaminants and/or surge in volume, can be troublesome to both

treatment plants and receiving streams.

There are atleast two methods of reducing the effects of these discharges:

The-manufacturing firm alters its practice so as to increase the frequency and lessen the magnitude of

Batch discharges.

Slug Wastes are retained in holding basins from which they are allowed to Flow continuously and

uniformly over an extended (usually 24-hour) period.

Strength Reduction: Waste Strength reduction is the second major objective for an industrial plant concerned with waste

treatment. The strength of wastes may be reduced by:

1.Process Changes

2.Equipment Modifications

3.Segregation of Wastes

4.Equilization of Wastes

5.By-Product Recovery

6.Proportioning of Wastes and

7.Monitoring Waste Streams

Process Changes:

In reducing the strength of wastes through process changes, the sanitary engineer is concerned with

wastes that are most troublesome from a pollution standpoint.

Equipment Modification:

Changes in equipment can effect a reduction in the strength of the waste, usually by reducing the

amounts of contaminants entering the waste stream. An outstanding example of waste strength

reduction occurred in the dairy industry. The new cans were constructed with smooth necks so that they

could be drained faster and more completely. This prevented a large amount of milk waste from

entering streams and sewage plants.

Segregation of Wastes:

Segregation of Wastes reduces the strength and/or the difficulty of treating the final waste from an

industrial plant. It usually results in two wastes: one strong and small in volume and the other weaker

with almost the same volume as the original unsegregated waste. The small- volume strong waste can

then be handled with methods specific to the problem it presents. In terms of volume reduction alone,

segregation of cooling waters and storm waters from process waste will mean a saving in the size of the

final treatment plant.

Equalization of Wastes:

Plants, which have many products, from a diversity of processes, prefer to equalize their wastes. This

requires holding wastes for a certain period of time, depending on the time taken for the repetitive

process in the plant. For example, if a manufactured item requires a series of operations that take eight

hours, the plant needs an equalization basin designed to hold the wastes for that eight hours period.

The effluent from an equalization basin is much more consistent in its characteristics than each separate

influent to that same basin.

Stabilization of pH and B.O.D and settling of Solids and Heavy Metals are among the objectives of

equalization. Stable effluents are treated more easily and efficiently, than unstable ones by industrial

and municipal treatment plants.

By-Product Recovery:

All wastes contain by products, the exhausted materials used in the process. Since some wastes are very

difficult to treat at low cost, it is advisable for the Industrial Management concerned to consider the

possibility of building a recovery plant which will produce a Marketable By-Product and at the same time

solve a trouble some Wastes problem.

Proportioning Wastes:

By Proportioning its discharge of concentrated wastes into the main sewer a plant can often reduce the

strength of its total waste to the point where it will need a minimum of final treatment or will cause the

least damage to the stream or treatment plant.

It may prove less costly to proportion one small but concentrated waste into the main flow. According to

the rate of the main flow, than to equalize the entire waste of the plant in order to reduce the strength.

Monitoring Waste Streams:

Accidental spills are often the sole cause of stream pollution or malfunctioning of treatment plants and

these can be controlled, and often eliminated completely, if all significant sources of wastes are

monitored.

Neutralization

Excessively acidic or alkaline wastes should not be discharged without treatment into a receiving stream.

A stream is adversely affected by low or high pH values. This adverse condition is even more critical

when sudden sludge of acids or alkalis are imposed upon the stream.

Acceptable Methods of Neutralization:

1.Mixing wastes so that the net effect is a neutral pH.

2.Passing acid wastes through beds of limestone.

3.Mixing acid wastes with lime slurries.

4.Adding the proper proportions of concentrated solutions of caustic soda(NaOH) or soda ash

(Na2CO3)to acid wastes.

5.Adding compressed CO2 to alkaline wastes.

6.Adding sulfuric acid to alkaline wastes.

The material and method used should be selected on the basis of the overall cost, since material costs

vary widely and equipment for utilizing various agents will differ with the method selected. The volume,

kind and quality of acid or alkali to be neutralized are also factors in deciding which neutralizing agent to

use.

Equalization: Equalization is a method of retaining wastes in a basin so that the effluent discharged is fairly uniform in

its characteristics (pH, colour ,turbidity ,alkalinity , B.O.D etc). A secondary but significant effect is that of

lowering the concentration of effluent contaminants. A retention pond serves to level out the effects of

peak loadings on the plant while substantially lowering the B.O.D and suspended solids load to the

aeration unit.

Air is sometimes injected into these basins to provide:

1.Better mixing

2.Chemical oxidation of reduced compounds

3.Some degree of biological oxidation

4.Agitation to prevent suspended solids from settling.

The size and shape of the basins vary with the quantity of waste and the pattern of its discharge from

the industry. The capacity should be adequate to hold and render homogeneous, all the wastes from the

plant. Almost all industrial plants operate on a cycle basis; thus if the cycle of operations is repeated for

every two hours, an equalization tank which can hold a two -hour flow will usually be sufficient.

The mer holding of waste, however is not sufficient to equalizing it. Each unit volume of waste

discharged must be adequately mixed with other unit volumes of waste discharged many hours

previously.

This mixing may be brought about in the following ways:

1.Proper distribution and baffling

2.Mechanical agitation

3.Aeration and

4.Combination of all three.

Proportitioning: Proportioning means the discharge of industrial wastes in proportion to the flow of municipal sewage in

the sewers or to the stream flow in the receiving river. In most case sit is possible to combine

equalization and proportion in the same basin. The effluent from the equalization basin is metered into

the sewer or stream according to a predetermined schedule. The objective of proportioning in sewers is

to keep constant the percentage of industrial wastes to domestic sewage flow entering the municipal

sewage plant.

This procedure has several purposes:

1.To protect municipal sewage treatment using chemicals from being impaired by a sudden

overdose of chemicals contained in the industrial waste.

2.To protect biological treatment devices from strong loads of industrial wastes, which may

inactivate the bacteria.

3.To minimize fluctuations of sanitary standards in the treated effluent.

The rate of flow of industrial waste varies from instant to instant, as does the flow of domestic sewage

system. Therefore the industrial waste must be equalized and retained, then proportioned to the sewer

or stream according to the volume of domestic sewage or stream flow.

Joint treatment of industrial wastes and domestic sewage consequent problems

Industrial waste waters can be received in large amounts into the municipal sewerage system and into

the treatment plant only, if they comply to certain conditions.

The combined treatment of these waters is recommended whenever the sewerage system operation is

not degraded or impeded and the operation and maintenance of the treatment plant is not prejudiced.

The discharge of industrial waste waters into the municipal sewerage system and their treatment as part

of the municipal waste waters have several advantages :

An efficient cooperation between industry and town is facilitated with the reduction of waste

water maintenance and operational cost being their common purpose.

The existence of only a single joint treatment plant leads to decreased capital cost : sometimes

the industrial waste waters contain nutritive matters (N.P.K.) necessary for the progress of purification

process under optimum conditions (in the case of separate purification these must be added artificially)

The existence of only one body in charge of the waste water treatment leads to better

management and greater efficiency of the purification process. Sometimes, the joint treatment of

industrial and municipal waste waters is impeded because the industry delivers inhibitive of the

purification process.

The preliminary researches, carried out before designing a plant treating added industrial waste

waters, have to establish whether the purification process will be inhibited. Should this be so, the

separation of the deleterious components before the waters reach the joint sewerage system is to be

strongly recommended.

Researches must also yield information about such a preliminary treatment. During these

investigations, the possibility of intervening in the industrial-technological process must be considered

with a view to the possible replacement of inhibitory substances hampering the joint treatment .

The collaboration between industrial technologies and designers of the treatment plant is of

major importance, since the most appropriate treatment solutions can be reached only as the result of

such a collaboration.

The requirements for the discharge of municipal waste waters and industrial waste waters in the

municipal sewerage system are dealt with in the "Norms on Conditions that Should Be Met for the

Discharge of Waste Waters in the Municipal Sewerage System of Populated Centres, C 90-83".

These norms forbid the discharge of : suspended solids whose quantity, size, and nature of which

represent an active factor in channel erosion, which create deposits or impede the normal flow i.e.

suspended solids or unsettleable materials ; solid, floating or entrained materials that do not pass

through screens with a 20 mm clear space between bars ; hard, entrained solid materials that can erode

sewers ; crude oil, oil, fats or other materials whose shape and amount can create adherence areas

leading to the accumulations of deposits on the sewer walls

various substances which may coagulate in the waste waters of the sewerage system*? leading to

deposits in sewers

substances which are chemically aggressive upon the materials commonly used in the construction of

sewerage systems and waste water treatment plants

Any type of suspended or dissolved matters which in the original state or by evaporation impede the

normal operation of sewerage system or treatment plants, or which together with air, can lead to

explosive mixtu-res, for example: gasoline, benzene, ether, chloroform, acetylene, dichlor-ethylene,

other chlorocarbon substances, carbon sulphide and other solvents, water and sludge from acetylene

generators, etc.;

Noxious substances that can endanger the operating personnel of the sewerage system ; inhibitives

of the purification process (e.g. Cu, Cr, Zn and Pb) in such amounts that would adversely effect the

operation of biological treatment units or of the sludge treatment units ; hot waters, the temperature

of which exceeds 40C, etc. It is also necessary to avoid the discharge into the sewerage system of those

substances producing a colouration of waste waters, and which pass still coloured through the

treatment units. The retention of colour in the pre-treatment units is much more economical.

The additional amounts of suspended solids brought by industrial. waste waters affect mainly the

settling tanks, the sludge digestors, the sludge drying beds, etc. Possibly, these will require additional

processing-volumes in comparison with those necessary for municipal waste waters. Likewise, certain

suspended matters brought by industrial waste waters can disturb either the existent settling process

(by either quicker or slower settling) or the sludge digesticin process. Sludge pumping units and the

piping used for its transport are also affected by the industrial waste waters discharged into the

municipal sewerage system. The organic loading, expressed in BOD5, is generally changed whenever

industrial waste waters are discharged into the sewerage system, deviating from the usual average

characteristics of municipal waste waters. Small amounts of industrial waste waters can significantly

increase the BODE quantity in municipal waste waters. Researches carried out to establish the design

parameters for municipal treatment plants must consider the influence of BOD5 amount on the sizes of

the various units. Considering the above problems, the construction of pre-treatment units for industrial

waste waters is highly indicated ; by this means it can be ensured an operation scheme and sizes for the

municipal waste water treatment plants close to those treating municipal waste waters having average

characteristics. The discharge of all categories of waste waters, and specifically of the industrial ones,

into the sewerage system under the provisions of the above-mentioned norms (C 90 83) should within

the control section (pro-perty limit of the utility) comply to the quality conditions given in Table 1 1 .

The maximum concentrations at the treatment plant intake for substances disturbing the aerobic or

anaerobic treatment processes are shown in Table 1-2, according to the above noted Norms C90-83

[261]. These Norms also include several indications concerning the disposal of waste waters coming

from medical equipment of the curative-prophy-lactic type (or from those using radioactive isotopes)

and the use of waste waters for irrigation purposes, etc. [270].

1.3 Preliminary Measures to Facilitate Waste Water Treatment and to Reduce the Capital Operating

Costs Generally, the capital and operating costs used for waste water treatment are only partially

recovered. This explains why, both during designing and later, during operation, the minimization of

these expenses remains a constant task. Industrial waste waters often convey inhibitive matters of the

puri-fication process. These matters can be chemical substances, fats, fibres, etc. which, after recovery,

can be re-used in the industrial technological process whose results they are. The recovery can lead in

certain cases even to reduced capital costs by diminishing the unit volumes [98]. Although the

replacement of noxious matters with less-noxious sub-stances for the purification process seems

advantageous only for purifi-cation proper, it an also lead, as for the re-used case, to the reduction of

the volumes of certain units of the treatment plant. Reciroulation, while rarely and only partially

applied for municipal waste waters, must still be considered for industrial waste waters discharged into

the municipal sewerage system. It leads to the reduction of the amount of supply and discharged water,

and accordingly of the capital costs required for the treatment plant. If municipal waste waters are to be

used for irrigation (subchapter 9.2), this leads to waste water treatment and better crops as well.

Capital and operating costs can also be decreased by taking into account the self-purification capacity of

streams. Without using the self-purification capacity to a maximum, it must still be considered even if

only temporarily, for a limited number of years. The unit volume of the treatment plant will be reduced

accordingly.

1.4 Discharge of Other Domestic Wastes into the Sewerage System together with the Waste Waters

Small amounts of domestic wastes, especially from kitchens (vegetable waste, papers, leaves, etc.) are

most of the time discharged together with the domestic waste waters instead of being stored in garbage

cans and conveyed to the garbage pits or incinerators.

In certain countries, the organized discharge of domestic wastes from kitchens into the sewerage

system is under testing. The wastes especially the small ones are chopped to avoid the blocking of

pipes. Since the chopping of domestic wastes within each flat is expensive, a larger chopping unit

servicing an entire block of flats is used [34]. No problems have been found in the treatment of waste

waters with domestic wastes ; however, the volumes of the units in the treatment plant were

incremented accordingly. Researches carried out in West Germany [1001 show that if all kitchen wastes

were discharged into the sewerage system after their chopping, the volumes of biological filters and

activated sludge units would be increased by about 50% and the cost of the treatment plant would rise

by about 30 %.

1.5 Capitalization : Waste Waters and Sludge

The purification of waste waters in municipal waste water treatment plants is only rarely profitable

from a. financial point of view. The final product of the purification is a treated waste water; the by-

products obtained are sludge gas and sludge. In a good operation, the sums obtained by the

capitalization of products and by-products would equal the capital and operating costs. The agricultural

value of waste waters is a function of the concentra-tion of dissolved and colloidal solids. Generally, the

decrease of capital costs as the result of constructing irrigation lands instead of artificial biological

treatment units is low or even non-existent. However, since the increase of agricultural production is of

major importance, often, irrigation lands are constructed even if they are sometimes more expensive

than the artificial biological units. Sludge gas resulted from sludge digestion is commonly used for the

heating of sludge digestors, dwellings or for generating etiergy. The energy resulting from the use of

sludge gas is usually sufficient for the operation of a biological treatment plant.

Sludge. can successfully replace manure ; however, if the transport distance is too long its profitability

decreases. Sometimes it is more advantageous to produce a dry fertilizer even within the treatment

plant especially if the fertilizing value is high. Although the cost of the product increases by its

transportation to the using place, it is compensated by the product's lower weight and volume. The

preparation and use of a. humus rich fertilizer obtained by mixing the digested sludge with domestic

wastes is another useful method of sludge capitalization. Since the sludge, like the waste waters,

contains pathogenic organisms, a permanent sani-tary control must be exercised whenever the sludge is

to be capitalized. Activated sludge is lat the basis of the production of vitamin B12, penicilline as well as

other antibiotics. The protein-rich plants growing in stabilization ponds can also be used for various

purposes.

Unit 2:

Solid Wastes, Collection and Transportation, Waste Disposal Systems, Land Treatment, Wastewater

Management Methods, Landfilling, Incineration, Energy from Wastes, Recycling, Composting, Reuse

and Recovery.

The main problem of solid waste management is the collection of solid waste. The household

waste consists of all types of general waste. At present there is no scientific, clean, hygienic,

efficient practice of waste collection in most of the cities of India including the metro cities.

The industrial waste is also handled in the same way. The collection and storage of waste is the

most neglected operation in any industry.

The best way would have been the segregation of waste at the generation point. Segregation

means collecting it in different bins, or plastic bags. The domestic waste can be broadly

separated as reusable (paper, plastic, metal etc.), and non reusable. The non reusable may have

organic matter like kitchen waste or inorganic matter like dust, dirt etc. The organic matter is

liable to decomposition (putrescible) and thus requires immediate attention.

This separated waste should be regularly collected by the worker directly from the houses at

some well defined time. Then it should be transported in (covered vehicles)to some waste

collection depots for utilization/transportation to different sites. The organic waste can be used

for the production of biogas or for the extraction of energy, incineration (controlled burning

or making organic compost, and vermi-composting.

Transportation

The waste is transported from the storage depots to the disposal sites in tractor trollies or ill

designed open trucks.

Though it has been instructed by the law that the transportation must be done in closed

containers only. The industrial waste must be transported separately and must be disposed in a

safe way after suitable treatment.

Any type of the Hazardous waste should be labeled and coded so that in case of an accident

the emergency services know how to handle a spillage.

Energy Recovery and Disposal

The waste has to be treated before disposal for the protection of environment.

In the treatment the biodegradable waste can be processed by composting, vermi-

composting, anaerobic digestion or any other appropriate biological processing for stabilization

of waste.

In any case the solid waste should be reduced in quantity at the source, segregated, then

carefully transported and the economically treated before the final disposal.

The most common methods of energy recovery and disposal for non hazardous solid waste

are incineration, composting and landfill. The final disposal of waste should be done in such a

way that it remains a waste in actual sense, i.e. nothing can be recovered out of it and it could

not be used any where.

Collection Services For Solid Wastes

Municipal Collection Service

Although a variety of collection services are available the three most common are curb, alley

and backyard collection. Curb collection has gained popularity because labour costs for

collection can be minimized. In

be emptied mechanically with an articulated container pickup mechanism will be the most

common method used for the collection of municipal wastes.

Curb Service: The house owner is responsibl

on the scheduled day. The workmen come, collect and empty the container and put back at

the curb. The house owner is required to take back the empty containers from the curb to his

house.

Alley Service: The containers are placed at the alley line from where they are picked up by

workmen from refuse vehicle who deposit back the empty container

Set out Set Back Service: Set out man go to the house collect containers and empty them in

the refuse vehicle. Another group of persons return them to the house owners yard

Backyard Service: The workers with the vehicles carry a bin, wheel

the yard and empty the solid waste container in it

solid waste vehicle where it is emptied.

Commercial-Industrial Collection Services

The collection service provided to large apartment buildings, residential complexes, and

commercial and industrial activities typically is centered around the use of large movabl

stationary containers and large stationary compactors.

used to compress material directly into large container or to form bale that are then placed in

large containers.

Types of Collection Systems

Solid Wastes

Municipal Collection Service


. Curb collection has gained popularity because labour costs for

collection can be minimized. In the future, it appears that the use of large container which can


common method used for the collection of municipal wastes.

Curb Service: The house owner is responsible for placing the solid waste containers at the curb


. The house owner is required to take back the empty containers from the curb to his

The containers are placed at the alley line from where they are picked up by

workmen from refuse vehicle who deposit back the empty container.


other group of persons return them to the house owners yard

Backyard Service: The workers with the vehicles carry a bin, wheel-barrow or sack or cloth to

the yard and empty the solid waste container in it. The wheel barrow or bin is then taken to

ste vehicle where it is emptied.

Industrial Collection Services


commercial and industrial activities typically is centered around the use of large movabl

stationary containers and large stationary compactors. Compactors are of type that can be



. Curb collection has gained popularity because labour costs for

the future, it appears that the use of large container which can


e for placing the solid waste containers at the curb


. The house owner is required to take back the empty containers from the curb to his

The containers are placed at the alley line from where they are picked up by


other group of persons return them to the house owners yard

barrow or sack or cloth to

. The wheel barrow or bin is then taken to


commercial and industrial activities typically is centered around the use of large movable and

Compactors are of type that can be


Based on the mode of operation, collection systems are classified into two categories:

container systems and stationary

Hauled Container Systems

Collection system in which the containers used for the storage of waste are hauled to the

processing, transfer, or disposal site, emptied, and returned to either their original location or

some other location are defined as hauled

There are two main types of container Tilt

responsible for driving the vehicles, loading full container and unloading empty containers, and

emptying the contents of the container at the disposal site. In some cases, for safety reasons,

both a driver and helper are used.

Systems that use tilt-frame

ideally suited for collection of all types of solid wastes and rubbish from locations where the

generation rate warrants the use of large containers.

warehouses and construction sites. Large Containers used in conjunction with stationary

compactors are common at commercial and industrial services and at transfer stations. Because

of the large volume that can be hauled, the

become widespread, especially among private collectors servicing industrial accounts.

The application of trash-trailer is similar to that of tilt

are better for the collection of especially heavy rubbish, such as sand, timber, and metal scrap,

and often are used for the collection of demolition wastes at construction sites

Stationary-Container System (SCS)

Collection systems in which the containers used for the storag

of waste generation, except when moved for collection are defined as stationary

systems. There are two main types of stationary

(1) Those in which self-loading compactors are used and

(2) Those in which manual loaded vehicles are used.

of operation, collection systems are classified into two categories:

container systems and stationary-container systems.


transfer, or disposal site, emptied, and returned to either their original location or

some other location are defined as hauled-container system.

There are two main types of container Tilt-frame Container, and Trash-Trailer.

for driving the vehicles, loading full container and unloading empty containers, and


both a driver and helper are used.

frame-loaded vehicles and large containers, often called drop boxes, are


generation rate warrants the use of large containers. Open-top containers are used routinely at



of the large volume that can be hauled, the use of tilt-frame hauled container systems has


trailer is similar to that of tilt-frame container systems. Trash

ection of especially heavy rubbish, such as sand, timber, and metal scrap,


Container System (SCS)

Collection systems in which the containers used for the storage of wastes remain at the point

of waste generation, except when moved for collection are defined as stationary

There are two main types of stationary-container system:

loading compactors are used and

in which manual loaded vehicles are used.

of operation, collection systems are classified into two categories: hauled-


transfer, or disposal site, emptied, and returned to either their original location or

Trailer. The collector is

for driving the vehicles, loading full container and unloading empty containers, and


loaded vehicles and large containers, often called drop boxes, are


ntainers are used routinely at



frame hauled container systems has


frame container systems. Trash-trailer

ection of especially heavy rubbish, such as sand, timber, and metal scrap,


e of wastes remain at the point

of waste generation, except when moved for collection are defined as stationary-container

Container size and utilization are not as critical in stationary

collection vehicles equipped with a compaction mechanism as they are in the hauled

system. Trips to the disposal site, transfer and loading meth

wastes and litter. Manual methods are used for the collection of industrial wastes where pickup

points are inaccessible to the collection vehicles.

Processing of Solid Waste

Processing techniques are used in soli

efficiency of solid-Waste disposal systems (2) To recover Resources and (3) To prepare

materials for the recovery of conversion products and energy

Mechanical Volume Reduction

Mechanical Volume Reduction is pe

operation of solid-waste management systems. Vehicles equipped with compaction

mechanisms are used for the collection of most municipal solid wastes.

landfills, wastes are compacted

Thermal Volume Reduction

The volume of municipal wastes can be reduced by more than 90 % by incineration. In the

past, incineration was quite common.

requirement necessitating the use of expensive cleanup equipment only a limited number of

municipal incinerators are currently in operation.

available landfill sites and increased fuel costs have b

incineration.

Container size and utilization are not as critical in stationary-container systems using self

collection vehicles equipped with a compaction mechanism as they are in the hauled

system. Trips to the disposal site, transfer and loading methods is in the collection of residential


points are inaccessible to the collection vehicles.

Processing techniques are used in solid waste management systems to (1) improve the

Waste disposal systems (2) To recover Resources and (3) To prepare

materials for the recovery of conversion products and energy.

Mechanical Volume Reduction is perhaps the most important factor in development and

waste management systems. Vehicles equipped with compaction

mechanisms are used for the collection of most municipal solid wastes. To increase the life of

landfills, wastes are compacted. Paper for recycling is baled for shipping to processing centres.


past, incineration was quite common. However, with more restrictive air-pollution control


municipal incinerators are currently in operation. More recently, increased haul distances to

available landfill sites and increased fuel costs have brought about a renewed interest in

container systems using self-loading

collection vehicles equipped with a compaction mechanism as they are in the hauled-container

ods is in the collection of residential


(1) improve the

Waste disposal systems (2) To recover Resources and (3) To prepare

rhaps the most important factor in development and

waste management systems. Vehicles equipped with compaction

To increase the life of

. Paper for recycling is baled for shipping to processing centres.


llution control


More recently, increased haul distances to

rought about a renewed interest in

Manual Component Separation

The manual separation of solid waste components can be accomplished at source where solid

waste are generated, at a transfer station, at a centralized processing station or at the disposal

site. Manual sorting at the source of generation is the most positi

recovery and reuse of materials. The number and types of components salvaged or sorted

depend on the location, the opportunities for recycling, and the resale market

Disposal

Disposal on or in the earths mantle is, at present the o

(1) Solid Wastes that are collected and are of no further use,

(2) The residual matter remaining after solid wastes have been processed,

(3) The residual matter remaining after the recovery of conversion products

been accomplished.

Landfilling is the method of disposal used most commonly for municipal wastes; land farming

and deep-well injection have been used for industrial wastes. Although incineration is often

considered a disposal method, it is

Landfilling with Solid Wastes

Land filling involves the controlled disposal of solid waste on or in the upper layer of the earths

mantle.

Landfilling Methods and Operations

The principal methods used for landfilling dry

Depression.

The Area Method

The Area Method is used when the terrain is unsuitable for the excavation of trenches in

which to place the solid wastes. The filling operation usually is started by building an

against which wastes are placed in thin layers and compacted as the fill progresses untill the thickness

of the compacted wastes reaches a height of 2 to 3 m at the end of days operation a 150 mm to 300

mm layer of cover material is placed



Manual sorting at the source of generation is the most positive way to achieve the


depend on the location, the opportunities for recycling, and the resale market

Disposal on or in the earths mantle is, at present the only viable method for long

(1) Solid Wastes that are collected and are of no further use,

(2) The residual matter remaining after solid wastes have been processed,

(3) The residual matter remaining after the recovery of conversion products and energy has


well injection have been used for industrial wastes. Although incineration is often

considered a disposal method, it is in reality, a processing method.


Landfilling Methods and Operations

The principal methods used for landfilling dry area may be classified as (1) Area (2) Trench (3)


The filling operation usually is started by building an earthen bund



mm layer of cover material is placed over the compacted fill. The cover material must be hauled in by



ve way to achieve the


depend on the location, the opportunities for recycling, and the resale market.

nly viable method for long-term handling:

and energy has


well injection have been used for industrial wastes. Although incineration is often


(1) Area (2) Trench (3)


earthen bund



The cover material must be hauled in by

truck or earth-moving equipment from adjacent land or from borrow-pit areas. A final layer of cover

material is used when the fill reaches the final design height.

The Trench Method

The trench method is suited to areas where an adequate depth of cover material is available

at the site and where the water table is well below the surface. To start the process To start the

process, a portion of the trench is dug with a bulldozer and the dirt is stockpiled to form an

embankment behind the first trench. Wastes are then placed in the trench, spread into thin layers and

compacted. The operation continues untill the desired height is reached. Cover material is obtained by

excavating an adjacent trench or continuing the trench that is being filled.

Depression Landfills

At locations where natural or artificial depression exist, it is often possible to use them

effectively for landfilling operations. Canyons, ravines, fry borrow pits and quarries have all used for

this purpose. The technique to place and compact solid waste in depression landfills vary with the

geometry of the site, the characteristics of the cover material, the hydrology and geology of the site, and

the access to the site.

Land Farming

Land farming is a waste-disposal method in which the biological, chemical, and physical processes that

occur in the surface of the soil are used to treat biodegradable industrial wastes. Wastes to be treated

are either applied on top of the land, which has been prepared to receive the wastes, or injected below

the surface of the soil.

When organic wastes are added to the soil, they are subjected simultaneously to the following process:

(1) Bacteria and chemical decomposition

(2) Leaching of water-soluble components in the original wastes and from the

decomposition product.

(3) Volatilization of selected component in the original wastes and from the product of

decomposition.

Land farming is suitable for wastes that contain organic constituents that are biodegradable and are not

subjected to significant leaching while the bioconversion process is occurring.

Composting

Composting as defined earlier is a process in which organic matter of the solid waste is

decomposed and converted to humus and stable mineral compounds. The end product of

composting process is called compost which is rich fertilizer.

There are three methods of composting:

(1) Composting by Trenching

(2) Open window composting

(3) Mechanical Composting

Composting by Trenching:

In this method trenches 3 to 12 m long, 2 to 3 m wide and 1 to 2 m deep are excavated with

clear spacing of 2 m. The trenches are then filled up with dry solid waste in layers of 15 cm. On

top of each layer 5 cm thick sandwiching layer of night soil animal dung is spread in semi liquid

form. On the top layer of night soil animal dung is spread in semi liquid form. On the top layer

protruding about 30 cm above the surrounding ground layer, a layer of earth having thickness of

around 10 cm is laid so that there is no problem of flies. Intensive biological action starts in 2 to

3 days and organic matter decomposition starts. In this process considerable heat is generated

and temperature of the composting mass rises upto 75 0 C. Due to this fly breeding does not

take place. The solid waste stabilizes in 4 to 6 months and gets changed in to a brown

coloured, odourless, innocuous powdery form known as humus having high manure value

because of nitrogen content.

The stabilized mass is then removed from trenches screened to remove coarse inert materials

like stones brick bats, glass pieces plastic articles etc.

Indore Method of Composting:

In this method solid waste night soil and animal dung etc. are placed in brick lined pits 3 m x 3 m

x 1 m deep in alternate layers of 7.5 to 10 cm height, till the total height becomes 1.5 m.

Chemical insecticides are added to prevent fly breeding. The material is turned regularly for a

period of about 8 to 12 weeks and then stored on ground for 4 to 6 weeks. In about 6 to 8

turnings and period of 4 months time compost becomes ready for use as manure. Insecticide

used in Indore method was DDT but now because of very high half life of DDT in nature other

suitable insecticide is recommended, e.g. Gamaxine.

Bangalore Method

The solid waste is stabilized anaerobically. Earthen trenches of size 10 x 1.5 x 1.5 m deep are

filled up in alternate layers of solid waste and night soil/cow dung. The material is converse with

15 cm earthen layer and left for biodegradation. In about 4-5 months the compost becomes

ready to use, normally a city produces 200 to 250 kg/capita/year of refuse and 8 to 10 kg /

capita/year of night soil.

Open Window Composting:

In This method large materials like broken glass pieces, stone, plastic articles etc. are first

removed are first removed and remaining solid waste is dumped on ground in form of piles of

0.6 to 1 m height the width and length of pile are kept as 60%. The piles are then covered with

night soil, animal dung to supply necessary organisms for biodegradation.

The temperature rises because of biological activities in the waste piles and microbial action

shift to misophilic to thermophilic stage. After this pile is turned up for cooling and aeration to

avoid anaerobic decomposition. The temperature of pile again rises to 75 0 C and process of

turning cooling and aeration are repeated. The complete process may taker 4 to 6 weeks and

finally compost is ready to use. As fertilizers

Mechanical Composting

The composting by trenching and open window composting methods require very large area.

The process ire laborious and time consuming. In large cities the larger area may not be

available and therefore mechanical composting is adopted which is very fast mechanical devices

are employed in turning the solid waste undergoing composting. The stabilization of the wastes

takes only about 3 to 6 m days.

The operation involves

(1) Reception and refuse (2) segregation

(3) Shredding (4) Stabilization (5) Marketing the humus.

Deep-Well Injection

Deep-Well Injection for the disposal of liquid solid waste involves injecting the wastes deep in

the ground into permeable rock formations or underground caverns. The installation of deep

wells for the injection of wastes closely follow the practices used for the drilling and completion

of oil and gas wells. To isolate and protect potential water supply aquifer, the surface casing

must be set well below such aquifers, and cemented to the surface of the well. The drilling fluid

should not be allowed to penetrate the formation that is To be used for waste disposal. To

prevent clogging of the formation, the drilling fluid is replaced with a compatible solution.

Deep well injections has been used principally for liquid wastes that are difficult to treat and

dispose of by more conventional methods and for hazardous wastes. The waste may be liquid,

gases, or solids. The gases and solids are either dissolved in the liquid or are carried along with

the liquid.

Incineration

Incineration can be defined as a controlled combustion process for burn

gaseous combustible wastes to gases and residue containing non combustible material.

Incinerators are used for the process of incineration. Following important points should be

observed carefully during incineration.

Charging of solid waste should be continuous

Each batch of waste should be well mixed and proportion of fuel should be such that complete

combustion takes places and the proper temperature is maintained.

Auxiliary burners are usually installed above the refuse to ignite it

the beginning of the cycle. This is required when moisture content of solid waste is high.

The minimum temperature in the chamber should be not less than 670 0C so that all organic

matter is incinerated and foul smelling gase

Advantages of Incineration

Most hygienic method

Complete destruction of pathogens

No odour trouble

Heat generated may be used for raising steam power.

Clinkers produced may be used for road construction.

Less space Required

Adverse weather condition has no effect.

Disadvantages of Incineration

Large initial expense

Care and attention required otherwise in complete combustion will increase air pollution.

Residues are required to be disposed which needs money.

Large number of vehicles require

Incineration can be defined as a controlled combustion process for burning solid, liquid and



observed carefully during incineration.

waste should be continuous


combustion takes places and the proper temperature is maintained.

Auxiliary burners are usually installed above the refuse to ignite it and to establish the draft at



matter is incinerated and foul smelling gases are oxidized.

Complete destruction of pathogens

Heat generated may be used for raising steam power.

Clinkers produced may be used for road construction.

condition has no effect.


Residues are required to be disposed which needs money.

Large number of vehicles required for solid waste transport to the site of incineration.

ing solid, liquid and




and to establish the draft at




d for solid waste transport to the site of incineration.

Waste Management Systems-unit 1 & 2

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Transcript of Waste Management Systems-unit 1 & 2