Waste
Management
- Introduction
Waste is a byproduct of various human activities, which
has lack of value or reuse. There are
three types of waste which are solid waste, liquid waste and gaseous
waste. Waste can be classified by various
methods, on the basis of physical state (Solid, Liquid and gaseous) and within
the solid waste according to the original use (package waste, food waste, etc),
on the basis of material (glasses, paper etc) physical properties, (Compostable,
combustible, recyclable) source of waste generation (domestic, commercial,
industrial) or safety level (hazardous, non hazardous). The types of solid
waste associated with these sources are
a) Agriculture
waste (waste generating from Agriculture practices including livestock production
b) Mining
Waste (mainly inert materials from coal mining metal mining and other mineral production
industries).
c) Energy
production industry (waste mainly from coal burning & ash etc)
d) Industrial
waste:- Solid waste generated from various industries
e) Dredging
waste: - Organic and mineral waste from dredging operation.
f) Construction
and demolition waste:- Brickbat, concrete, asphaltic materials, pipes and other
construction materials.
g) Treatment
plant waste,
h) House
hold or residential waste (garbage including food waste, paper, furniture,
crockery, ashes in fire etc)
i)
Commercial waste – (similar to house
hold wastes but produced from office, shop, restaurant etc)
j)
Institutional waste:- (similar to household
waste plus hazardous, explosive, pathological and other wastes from hospital,
research institutions etc.
k) Market
waste:- waste generation from market such as vegetable, fish etc.
l)
Slaughter house waste produced from slaughter,
like blood, bare, etc
Quantity
of Solid Waste Generated (Million tons per year).
|
Country
|
Agriculture
|
Mining
|
Construction demolishing
|
Sewerage Sludge
|
Energy Production
|
Industry
|
Municipal
|
|
UK
|
260
|
240
|
35
|
27
|
13
|
62
|
110
|
|
USA
|
|
1400
|
31.5
|
8.4
|
63
|
430
|
133
|
|
India
|
|
700.8
|
7.2
|
|
60
|
25
|
24
|
Quantity
of Waste Generation in Different Countries
|
Country
|
KG / person / day
|
|
India
|
0.25 to 0.33
|
|
Srilanka
|
0.40
|
|
Singapore
|
0.85
|
|
UK
|
0.95 to 1.00
|
|
Japan
|
1.12
|
|
USA
|
1.25 to 2.25
|
- Management
of Solid Wastes
There are two fundamental objectives of solid waste
management, to minimize waste and to effectively utilize the waste still
produced.
The activities associated with solid waste management
involve processing of waste generated at source, collection, transportation, processing
at a central facility and final disposal on land. An effective and integrated solid waste management
system examines the following options in an order of hierarchy for all type of
waste generated.
- Waste
reduction at source
- Resource
recovery through separation and recycling
- Resource
recovery through waste processing
- Waste
transformation
- Environmentally
sustainable disposal on land
1. Waste
reduction at source
Source
reduction is the most effective way to minimize waste. Waste reduction may occur through proper
design, manufacture and packing of product with minimum toxicity, minimum
volume of material and longer useful life.
Waste reduction may also occur through selective reuse of productions
and materials.
2. Resource
recovery through recycling
Recycling involves separation
of waste material, preparation of these separated
fractions for reuse, reprocessing and remanufacture and the reuse of their
prepared materials. Recycling is an important factor which reduces the amount
of waste requiring disposal on land
3.
Resource recovery through waste processing
Waste
processing involves the physical, chemical or biological alteration of waste to
recover conversion product for reuse.
The typical processing technique used for MSW include
(a)
Biological treatment – composting (anaerobic digestion / bio gasification) and (b).
Thermal treatment – incineration (with / without energy recovery). The other processing techniques may include (a).
Physical treatment to make building blocks, bricks from inert wastes such as ash,
construction waste etc (b). Chemical treatment to recover compounds such as glucose,
synthetic oil, cellulose acetate etc.
- Waste
transformation
After
recovery of various source from a waste, the residual materials may be
subjected to a variety of processes to effectively reduce the volume of waste
requiring disposal. The treatment processes
may involve size reduction (through shredding) size separation (through
screening), volume reduction (through compaction or by thermal treatment) and
encapsulation (to reduce toxicity). The waste transformation processes helps in
reducing the final land area required for waste disposal.
- Environmentally
sustainable disposal on land
Despite all efforts to minimize waste,
the requirement for storage / disposal of the following type of waste will
continue to remain a). Solid wastes that cannot be recycled b). The residual
waste after subjecting to all type of processing.
The
long term options available in this regard are (i) Dispersal on earth surface
(ii) Dispersal on deep, below the earth’s surface. (iii) Dispersal at the ocean bottom. Dispersal on the earth surface is the most
commonly adopted method of ultimate disposal of solid waste materials.
When waste is stored on land, it becomes a part of the hydrological cycle.
Above diagram presents
the hydrological cycle with the various paths that, water takes, as it
circulate in nature. During infiltration
of water through waste, as well as during rain, numerous contaminants are
removed from the waste to the adjacent areas as well as to the strata below the
waste by the action of percolating water.
This action of water along with the action of wind as well as the
reaction occurring within the waste, can have significant impact on the
adjacent environment. To minimize the
impact of waste on the environments, the final disposal is done in engineered
land fill which offer an environmentally sustainable methodology for disposing
waste on land
Changes
Occurring in a Waste Dump:-
(1)
Biological changes:- Biological
reactions occurring in waste dumps are those involving the organic materials that lead to the evolution
of landfill gases and liquid. The biological decomposition of the waste process
usually proceeds aerobically for some short period of time until it exasperates
after decomposition. The oxygen initially present immediately after
decomposition of the waste, becomes anaerobic. In the aerobic decomposition,
available oxygen has been consumed and the organic matter converted to carbon
dioxide, methane, ammonia, Hydrogen sulfide.
(2)
Chemical changes:-Important chemical
reaction that occur within waste dump include dissolution and suspension of
waste materials and biological conversion of products in the liquid (leachate)
percolating through the waste, evaporation and vaporization of chemical
compound.
(3)
Physical changes:- The important
physical changes in waste dump are the lateral movements of gases in the waste
and emission of gases to the surrounding environment, movement of leachate
within the waste and in to underlying soils and settlement caused by
consolidation and decomposition of the waste.
(4)
Impact on Environment: - The potential
impacts are air pollution, surface water pollution, ground water pollution and
subsoil pollution. The pathways of potential impact are (a) precipitation (b)
infiltration (c) seepage (d) evaporation (e) surface run off (f) prevailing
wind (g) ground water flow (h) river and
storm water drains (i) rodents and pests (j) vegetative growth on waste dumps.
Minimization of
Environmental Impact through Waste Containment
The
impact of a waste dump on the environment can be minimized by isolating the
source or by eliminating the pathways. This can be achieved through containment
of the waste dump.
The
waste containment can be effected through engineered design,
(1)
Based on lining system as well as cover
system to isolate the waste dump from the hydrological cycle.
(2)
Leachate collection system.
(3)
Gas collection system.
Engineered
Landfills:-
Schematic Design of Engineered Land fill
The
land fill is generally described as facility used for the disposal of solid
waste on the surface of the earth. The term Engineered land fill, is used to denote
a landfill designed and operated to minimize environmental impact. The various
components of a modern engineered landfill are.
(1) Liner
system at base and sides of the landfill, which prevents migration of leachate or
gas to the surrounding soil. The liner materials have more impermeability
property and comprise of compacted clays or geo-membranes.
(2) A
Leachate collection facility which collects and extracts Leachate from within
and from the base of the land fill and then treating the leachate.
(3) A
gas control facility which collect and extracts gas from within and from the
top of the land fill and then treats it or uses it for energy recovery.
(4) A
final cover systems which enhances surface drainage, intercepts infiltrating
water and support surface vegetation The final cover system comprises of
multiple layers of soils and membrane materials
(5) A
surface water drainage system which collect and removes all surface runoff from
the land fill site.
(6) An
environmental monitoring system which periodically collect and analyses air,
surface water and ground water samples around the landfill site.
(7) A
closure and post closure plan which list the steps that must be taken to close
and secure a land fill site once the filling / dumping operations has been
completed and the activities for long-term monitoring and maintenance of the
completed land fill shall be ensured.
Geethakrishnan
K.I, SAJIKUMAR P.R, MTech
Asst
Exe Engineer, LSGD
Chief
Engineer, LSGD
