soil pollution & management

8/2/2019 Soil Pollution & Management

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Solid Waste Management


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Solid waste can be classified into differenttypes depending on their source:a) Household waste is generally classifiedas municipal waste,b) Industrial waste as hazardous waste,and

c) Biomedical waste or hospital waste asinfectious waste.

Types of solid waste


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Municipal solid waste

Municipal solid waste consists ofhousehold waste, construction anddemolition debris, sanitation residue, andwaste from streets . This garbage isgenerated mainly from residential andcommercial complexes. With rising

urbanization and change in lifestyle andfood habits, the amount of municipal solidwaste has been increasing rapidly and its

composition changing.


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TYPES OF SOLID WASTES

Garbage : Putrescible wastes eg. Food Rubbish : Non-putrescible eg: paper, wood, metals Ashes : fly ash, waste after incineration Large wastes : construction waste, masonry waste Industrial solid wastes : chemicals Dead animals : household pets Agricultural wastes : crop residues, farm waste Sewage : sludge


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ar age: t e our roacategories

Organic waste: kitchen waste,vegetables, flowers, leaves, fruits.

Toxic waste : old medicines, paints,chemicals, bulbs, spray cans, fertilizer andpesticide containers, batteries, shoepolish.

Recyclable: paper, glass, metals, plastics. Soiled: hospital waste such as cloth soiled

with blood and other body fluids.


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Hazardous waste

Industrial and hospital waste is consideredhazardous as they may contain toxicsubstances. Certain types of householdwaste are also hazardous. Hazardouswastes could be highly toxic to humans,animals, and plants; are corrosive, highly

inflammable, or explosive; and react whenexposed to certain things e.g. gases .


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India generates around 7 million tonnes ofhazardous wastes every year , most ofwhich is concentrated in four states:Andhra Pradesh, Bihar, Uttar Pradesh,and Tamil Nadu.

Household waste that can be categorizedas hazardous waste include old batteries,shoe polish, paint tins, old medicines, andmedicine bottles.


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Hospital waste contaminated by chemicalsused in hospitals is considered hazardous .These chemicals include formaldehydeand phenols, which are used asdisinfectants, and mercury , which is usedin thermometers or equipment that

measure blood pressure.


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Most hospitals in India do not have properdisposal facilities for these hazardouswastes.

In the industrial sector, the majorgenerators of hazardous waste are themetal, chemical, paper, pesticide, dye,refining, and rubber goods industries .

Direct exposure to chemicals in hazardouswaste such as mercury and cyanide canbe fatal.


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Hospital waste

Hospital waste is generated during thediagnosis, treatment, or immunization ofhuman beings or animals or in researchactivities in these fields or in theproduction or testing of biologicals. It mayinclude wastes like sharps, soiled waste,

disposables, anatomical waste, cultures,discarded medicines, chemical wastes ,etc.


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These are in the form of disposablesyringes, swabs, bandages, body fluids,human excreta, etc. This waste is highlyinfectious and can be a serious threat tohuman health if not managed in a scientificand discriminate manner. It has been

roughly estimated that of the 4 kg of wastegenerated in a hospital at least 1 kg wouldbe infected.


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After the notification of the Bio-medicalWaste (Handling and Management) Rules,1998, establishments are slowlystreamlining the process of wastesegregation, collection, treatment, anddisposal. Many of the larger hospitals have

either installed the treatment facilities orare in the process


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Domestic & Municipal sewage contains microorganismswhich disposed off into soil enter food chain and causesdiseases

Addition of sludge in fields affects soil fertility Sewage irrigation also leads to lowered soil fertility and

disturbs the chemical characteristics of soil. Sewage irrigation alters the C:N ratio, affects the soil

permeability, soil pH, CEC and HUMUS CONTENT, saltcontent and availability of nutrients.

Leads to sewage sickness: Refers to the unsuitableconditions brought about in soils by the use of excessivequantities of sewage. It is more related to gross waterlogging conditions in soil. This leads to low O 2 /air ,leading to suppressed microbial growth, affecting soilfertility.


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CONTROL OF LAND POLLUTION

Soil pollutants should be collected at source anddisposed off.

Limit the use of pesticides in fields and fertilizers

Industrial effluents be treated through wastetreatment technologies Recycling of waste Animal waste like cattle dung, farm waste be

utilized in fuel generation like biogas Microbial degradation of waste: another

alternative


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SOILD WASTE MANAGEMENT

1. Minimized Usage2. Judicious disposal

3. Reuse4. Recycling


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SOIL TREATMENT Extraction & Separation TechniquesContaminated Soil is mixed with an extracting agent (acidic/basic

solution) for removal of metals, hydrocarbonsApplicable for soil, where contamination is present in the finer/coarser

fractions of the soil, or the organic component eg. Humus.

Thermal Treatment of the soil:Removal of the contaminants by evaporation either by heat treatmentor by open furnace

Destruction of the contaminants by direct or indirect exposure of soil toan appropriate temperature

Steam stripping is followed for treating volatile contaminants: Steam is

injected into soil to aid evoporation of volatile components.Ex. Polyaromatic hydrocarbons, cyanides conti


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SOIL TREATMENT Chemical TreatmentTreatment of the soil in suspension in a suitable liquid, eg. Cyanide may

be oxidized to CNO or hydrolyzed to CO 2 Without slurrying & long time contact between the soil and the chemical

contaminant.

Microbial Treatment Microbes are released in the soil which are capable of degrading thecontaminant.

Excavation of soil is a also practised in some cases.A community of microbes already existing on the site is collected

and cultured in the laboratory

Strains of microbes are developed that are capable of metabolizingparticular chemicals.Very promising technique for organic contaminants. Ex. Phenols,

polychlorinrted Hc, oil and oil products, dioxins.


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SOIL TREATMENT Stabilization/Solidification processessUsed to physically or chemically eliminate or reduce the

hazardous nature of the soil contaminant.The reduction in the mobility or leachability of contaminants

can be achieved by: A chemical reaction to form practically insolublecompounds

Isolating contaminants from water by addinghydrophobic compunds

Adding chemicals to fixate water and reduce microleachability Vitrification. Control of pH to minimize solubility


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SOIL TREATMENT

In situ treatment Contaminated soil is treated to remove,

destroy or fix the contaminants withoutexcavation.

Application of lime to raise the pH of soilscontaining elements such as Cd

Deep ploughing to invert the top layer ofthe soil Leaching with water or chemical solution


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SOIL TREATMENT

Leaching with water or chemical solution Proper contact between treatment agent

and the soil. Neutralization, precipitation, oxidation,

reduction and ion exchange can befollowed.


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Landfills A landfill s designed as a modular series of 3D control cells. Garbage is sent out in thin layers, compacted and covered with clay

or plastic foam. The landfill is covered with impermeable liner of clay, plastic and

sand. There is a double liner beneath the wastes.

The liner protects the ground water from being contaminated due topercolation of leachate. The upper liner is a flexible membrane lining (FML) of plastic or

rubber. The lower liner is clay . When landfill is full it is covered with clay, sand, gravel on the top to

prevent seepage. Landfill monitiring is done periodically to prevent ground water

contamination. Soil monitoring is done using lysimeters.


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Landfills

Methods: Area & trench In an area method, the solid wastes are

spread over an area, compacted and thencovered with soil or similar materials

In trench method, a trench up to 10-15 feetdeep and 20 feet wide is dug and therefuse is filled into it, futher compacted,and covered with soil.


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Landfills

1. Advantages associated with landfills: Better as compared to open dumps Asthetic Disease spread is minimized as flies, rodents,

pests are unable to breed, no health hazard

1. Hazards associated with landfills: Methane, H 2S, CO 2,generation Leaching into underground water, pollution of

ground water

Land subsidence


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Surface Impoundments

SI are excavated areas used to store liquid orhazardous wastes.

They are cheap and the wastes remain

accessible allowing treatment during storagealso.

Treatment technologies in surfaceimpoundments are neutralization, precipitation,settling and biodegradation .

DIS: Source of contamination to nearby aquifer .


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Incineration Wastes are subjected to very high temperature burning. By products of incineration are ashes and clinkers . Very effective for organic wastes , not only, in soils, but

for other solids, liquids, gases,sludges. Carcinogens, mutagens, & pathological wastes are all

completely detoxified in an incinerator. Liquid injection incinerator: For gases, liquids, sluries. Rotatary kiln incinerator: For solids and sludges besides

liquids & gases. Disadvantages: Noxious gases, unburned organic

compounds, odour, unburnt ash.


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Composting

Aerobic method of decomposing solidwastes.

Involves the segregation of wastes intoorganic and inorganic components

Bacterial decomposition of organic wastes Results in the formation of compost

(humus)


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Pyrolysis

Is the use of intense heat to causechemical changes in the waste but notcombustion

Solid wastes are heated in a reactor at inabsence of oxygen

Trash is pyrolysed to generatecombustible gases.


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Underground injection Most popular way to dispose of liquid hazardous waste . Hazardous wastes are forced underground through deep

injection wells . To assure that the undergound water supplies are not

conaminated, injection wells used to dispose offhazardous industrial wastes are required to extendbelow the lowest formation containing undergroundsources of drinking water.

Injection depth more than 700m b elow the surface. Disadv: leekage problems.

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