Solid Waste Management (Municipal Solid Waste)

Introduction

Solid waste is the unwanted or useless solid materials generated from combined residential,
industrial and commercial activities in a given area.

Management of solid waste reduces or eliminates adverse impacts on the environment and
human health and supports economic development and improved quality of life. A number of
processes are involved in effectively managing waste for a municipality. These include
monitoring, collection, transport, processing, recycling and disposal.

Municipal solid waste

 Consists of household waste, construction and demolition debris, sanitation residue, and waste
from streets.
 This garbage is generated mainly from residential and commercial complexes.
 The amount of municipal solid waste has been increasing rapidly.
 The composition of MSW is also changing. Earlier it was mainly food and other biodegradable
refuse but nowadays plastics and aluminium cans form a large chunk of the daily MSW
generation.

Classification of MSW

Quick facts
Annual MSW pattern in U.S

Percentage composition of MSW

 Moisture – An important factor

Collection of MSW

Collection is an expensive part of waste management, and many new devices and methods have
been proposed in order to cut costs.

They are as follows:

 Garbage grinders
 Pneumatic pipes
 Kitchen garbage compactors
 Green cans on wheels
 Transfer stations
 Route optimization
 Garbage grinders:

 Garbage grinders reduce the amount of garbage in refuse.

 Frequency of collection could be reduced.
 Twice-a-week collection is only needed in warm weather when garbage decomposes rapidly.
 Garbage grinders do put an extra load on the wastewater treatment plant, but sewage is
relatively dilute and shredded garbage can be accommodated in both sewers and treatment
plants.
 The increased burden may be problematic in water-short communities.

Pneumatic pipes:

The refuse is ground at the residence and sucked through underground lines. Mainly present in
Japan and Sweden.

Kitchen garbage compactors:

 They can reduce collection and MSW disposal costs.

 Costs about as much as other large kitchen appliances.
 Uses special high strength bags. High operation costs.
 Stationary compactors for commercial establishments and apartment houses have already had
significant influence on collection practices.
 Green cans on wheels:

 The cans are pushed to the curb by the householder and emptied into the truck by a hydraulic
lift.
 It also reduces the occupational injuries for collection workers dramatically.

Transfer station:

 A typical system includes several stations, located at various points in a city, to which collection
trucks bring the refuse.
 The drive to each transfer station is relatively short. This is to increase collection efficiency.
 At the transfer station, bulldozers pack the refuse into large containers that are trucked to the
landfill or other disposal facility.
 Alternatively, the refuse may be baled before disposal.

Effects on Health
 Disease vectors are the means by which disease organisms are transmitted, such as water, air,
and food. The two most important disease vectors related to solid waste are rats and flies.
 70,000 flies can be produced in one cubic feet of garbage, and they carry many diseases like
bacillary dysentery.
 Rats not only destroy property and infect by direct bite, but also carry insects like fleas and ticks
that may also act as vectors.
 Infiltration of leachate from MSW disposal into groundwater, particularly drinking water supplies
is a public health issue.
 Leachate may be a major groundwater and surface water contaminant, particularly where there
is heavy rainfall and rapid percolation through the soil.

Sanitary landfills

 Sanitary landfills are engineered operations, designed and operated according to acceptable
standards as opposed to open dumps which are simply places to deposit waste.
 Sanitary landfilling is the compaction of refuse in a lined pit and the covering of the compacted
refuse with an earthen cover.
 A landfill continues to subside after closure, so that permanent structures cannot be built onsite
without special foundations.
 Closed landfills have potential uses as golf courses, playgrounds, tennis courts, winter recreation,
or parks and green belts.
 The sanitary landfilling operation involves numerous stages, including siting, design, operation,
and closing.

Process of landfilling

 The liner is made of plastic and a layer of clay that further reduces the chance of leakage into
the groundwater of the liquid produced by the landfill during the decomposition of the waste.
 The liquid produced is collected by pipes laid into the landfill as it is constructed.
 Gases produced by the decomposing waste must be collected and either vented or collected and
burned.
 When the landfill is full, a cover must be placed on it such that the seepage of rainwater into the
landfill is minimized.
 Vegetation must then be established on the landfill, and its effect on groundwater must be
monitored by wells sunk around it.

 Refuse is unloaded, compacted with bulldozers, and covered with compacted soil.
 The landfill is built up in units called cells.
 The daily cover is between 6 and 12 inches thick depending on soil composition.
 The final cover of at least 2 feet thick is used to close the landfill.
 Factors influencing the siting

 Drainage: Rapid runoff will lessen mosquito problems, but proximity to streams or well supplies
may result in water pollution.
 Wind: It is preferable that the landfill be downwind from any nearby community.
 Distance from collection sites.
 Size: A small site with limited capacity is generally not acceptable since finding a new site entails
considerable difficulty.
 Rainfall patterns influence the production of leachate from the landfill.
 Soil must be used as cover so soil type is an important factor.
 Depth of the water table: The bottom of the landfill must be substantially above the highest
expected groundwater elevation.
 Treatment of leachate requires proximity to wastewater treatment facilities.
 All landfills attract birds to some extent and are therefore not compatible with airports in vicinity.
 The final use of the land has to considered before undertaking the project.

Byproducts of landfilling

 During the operational period and even afterwards there is always a cost of maintenance
involved to monitor the environmental impact and mitigate it accordingly and within laws of the
state. The environmental impact is mainly caused due to the byproducts of the landfills.
 There are mainly two types of byproducts

–Leachate

–Gases

Leachate

 The liquid produced during decomposition, as well as water that seeps through the groundcover
and works its way out of the refuse, is known as leachate.
 This liquid contains pollutants in high concentration.
 If the leachate escapes the landfill, its effects on the environment are severe. In a number of
instances, leachate has polluted nearby wells to a degree that they have ceased to be sources of
potable water.
 Leachate production depends on rainfall patterns as well as on total amount of precipitation.
 Gases

 Since landfills are anaerobic biological reactors, they produce CH and CO .

4 2

 The first stage is aerobic and may last from a few days to several months, during which time
aerobic organisms are active and affect the decomposition.
 As the organisms use up the available oxygen, the landfill enters the second stage, when
anaerobic decomposition begins but methane-forming organisms have not yet become
productive.
 During the second stage, the acid formers cause a build up of CO .
2

 In methane production stage, during which the percentage of CH progressively increases and
4

the landfill interior temperature rises to about 55°C.

 The final, steady-state condition occurs when the fractions of CO and CH are about equal and
2 4

microbial activity has stabilized.

 Unwanted gas migration may be prevented by installing escape vents in the landfill
 Landfill gas can be burned to produce electric power. Alternatively, the gas can be cleaned of
CO2 and other contaminants and used as pipeline gas.

Closing and final use of landfills

 Municipal landfills must be closed according to state and federal regulations. Such closure
includes the permanent control of leachate and gas and the placement of an impermeable cap.
 The cost of closure is very high and must be incorporated in the tipping fee during the life of the
landfill.
 Landfills settle unevenly, and it is generally suggested that nothing at all be constructed on a
landfill for at least two years after closure, and that no large permanent structures ever be built.
 Disturbance may cause structural problems, and trapped gases can present a hazard.
 Buildings constructed on landfills should have spread footings (large concrete slabs) as
foundations, although some have been constructed on pilings that extend through the fill onto
rock.

Solid Waste Management(Hazardous Waste)

 What is Solid Waste?

 Municipal solid waste (MSW), commonly known as trash or garbage (US), refuse or rubbish (UK)
is a waste type consisting of everyday items that are discarded by the public.

Typical classification :

 Biodegradable waste: food and kitchen waste, green waste, paper (can also be recycled).
 Recyclable material: paper, glass, bottles, cans, metals, certain plastics, fabrics, clothes,
batteries etc.
 Inert waste: construction and demolition waste, dirt, rocks, debris.
 Electrical and electronic waste (WEEE) - electrical appliances, TVs, computers, screens, etc.
 Composite wastes: waste clothing, Tetra Packs, waste plastics such as toys.
 Hazardous waste including most paints, chemicals, light bulbs, fluorescent tubes, spray cans,
fertilizer and containers, Toxic waste including pesticide, herbicides, fungicides, medical waste.