Water pollution.ppt

7/26/2019 Water pollution.ppt

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Water Pollution + Solid Waste


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Water Pollution

- Water pollution refers to degradation of water quality.

We generally look at the intended use of the water, how far

it departs from the norm, it effects on public health or

ecological view, a pollutant is any biological, physical or

chemical substance that in identifiable excess is known to

be harmful to other desirable living organisms.

Water in domestic usesmust be free from constituents

harmful to health. It should taste and smell good. It

should not damage plumping or household appliances.

Water quality for industrial processesvaries widely

depending on the process. Some requires distilled water

etc.


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Some sources of water pollution

Surface water Groundwater

1. Industrial Effluent

2. Urban runoff

3. Agricultural runoff

4. Accidental spills of

chemicals5. Sediments

6. Air fallouts

7. Salinity Intrusion

1. Leaks from waste disposal site

2. Saltwater intrusion into coastal

aquifers.

3. Seepage from mines and septic

systems.4. Seepage from pesticides.

5. Seepage from accidental spills.

6. Seepage polluted stream

Point Source(Transportation accidents, industrial sites, oil wells, sewage

plants)

Non-point (Dif fuse) Source(Farm fields, feedlots, golf courses, parkinglots, lawns)may be episodic.


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Major categories of Water Pollutants

Infect ious Ag entsDisease causing agents or pathogens, including bacteria,viruses, protozoa, parasites. These come from raw sewage and animalwaste and they may be responsible for 80% of the disease in developingcountries. Measured by the amount of colliform bacteria present.

Oxygen-demandin g wastescan be decomposed by aerobic bacteria. Causea reduction in Dissolved Oxygen (DO), suffocating for oxygen-consumingorganisms (fish). Measured by biological oxygen demand (BOD). Sewage,animal manure or biodegradable organic wastes.

Water soluble Inorganic chemicals Water-soluble inorganic chemicals,

including acids, salts, and metals. Make water unfit to consume and usefor irrigation. Also can harm organisms and cause material corrosion

Organic chemicals including oil, gasoline, plastics, pesticides, solvents,detergents. Present health risks to humans and other organisms.

Plant nu tr ients Nitrates, phosphates, ammoniumfrom fertilizers mostly.Cause excessive algal and plant growth that lower oxygen levels when

they decomposeAlgal bloomDO decreases. EutrophicationSediment Mud, silt, sand. Disrupt photosynthesis and transports large

amounts of other, adsorbed pollutants. Bad for Aquatic animals.

Radioact iv e materialsradon, uranium, may come either from natural oranthropogenic sources.

Heatfrom cooling water for power plants & other industrial plants. Lowerssolubility of oxygen in water. Also affect aquatic lives directly.


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EUTROPHICATION


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Wastewater Treatment

The water used for industrial and municipal purposes isoften degraded during use by the addition of suspendedsolids, salts, nutrients, bacteria, and oxygen-demandingmaterial.

By law, these wastewaters must be treated before beingreleased back into the environment.

Conventional methods include disposal and treatment ofhousehold wastewater by way of septic-tankdisposalsystems in rural areas and centralized water treatmentplantsthat collect wastewater from sewer systems incities.


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Wastewater Treatment plant: ETP

Wastewater treatment, or sewage treatment, occurs atspecially designed plants known as Effluent TreatmentPlant (ETP).

Wastewater treatment methods are usually dividedinto three categories: primarytreatment, secondarytreatment, and advancedwaste treatment.

Primary treatment removes 30% to 40% of the

pollutants volume from wastewater.

Secondary removes about 90%

Advanced treatment plan is used when it isparticularly important to maintain good water quality.


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Special Pollution Problems of Groundwater

pollution

Slow movement retards cleansing effect

Decomposing bacteria may not be present in

sufficient numbers

Cooler temperatures, lack of sunlight slow

chemical reactions that decompose wastes

Source of pollution may be more difficult to trace.

Aquifer characteristics may be poorly known.


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The value (recommended limit) for

arsenic in drinking water as per

the guideline of the World Health

Organization (WHO) is 10 mg/L

while the national standard in

most

countries, including Bangladesh,

is 50 mg/L. With varying levels of

contamination from region toregion, groundwater in 61 out of

the 64 districts in Bangladesh is

contaminated with arsenic.

According to a study conducted by

the British Geological Survey andDPHE, Bangladesh, arsenic

concentrations in the country

range from less than 0.25 mg/L to

more than 1600 mg/L.


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Groundwater pollution: Bangladesh

We have long believed that groundwater is ingeneral pure and safe to drink.

In Bangladesh, groundwater of 59 districts(126,134km2) are effected by Arseniccontamination. A total of 75 million people are atrisk. Total number of tube wells in Bangladesh = 4 million

Total number of affected tube wells = 1.12 million Number of people suffering from arsenicosis = 7,600


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Coastal Pollution: Why Should We

Care???

Around half of our

population lives within

200 km of the coast

We eat at least 15 lbs.of seafood per person

each year

Just about everything

bought & sold goes

thru ports in cargo

ships

A large variety species

in oceans & wetlands,

each one vital to

balance of nature 17% of our oil and 25%

of our natural gas come

from offshore

The oceans are fun to

be near or in...


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O d i I l f t lid


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Open dumping: In many places of our country, solidwaster is accumulated in open dumps where therefuse was piled up without being covered orotherwise protected.

Open dump creates nuisance by being unsightly,providing breeding grounds for pests, creating healthhazard, polluting air, and sometimes polluting

groundwater and surface water.

S it l dfill A it l dfill i d i d t


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Sanitary landfill: A sanitary landfill is designed to

concentrate and contain refuse without creating a

nuisance or hazard to public health or safety.

If waste buried in a landfill the liquid content of it might

seep into the ground as Leachatenoxious,

mineralized liquid capable of polluting groundwater.


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Water pollution.ppt