Water Pollution

Water Pollution

• Any physical, biological or chemical change in water quality that adversely affects living organisms or makes water unsuitable for certain uses is referred as water pollution.

• When the quality or composition of water changes by any means it becomes unsuitable for any purpose and is said to be polluted.

 

1. Types, Effects and Causes of Water Pollution

• Various types of water pollution their effects and causes are summarized here.

1. Infectious agents

• Micro-organisms are naturally found in water and can cause infections to human being.

Examples : Bacteria, virus, protozoa and parasitic worms.

Human sources I causes

• Human and animal wastes

Effects

• Infectious agents may cause amoebic dysentery, skin problems, maleria etc.

2. Oxygen demanding wastes / Dissolved oxygen

• This waste when discharged in water body are degraded by oxygen demanding micro-organisms. The amount of oxygen consumed by microbes is Biochemical Oxygen Demand (BOD).

• High levels of BOD can deplete the oxygen in water.

Examples : Organic waste such as animal manure and plant debris that can be decomposed by aerobic bacteria which requires oxygen.

Human sources / causes

• Sewage, animal feed lots, paper mills, food processing units.

Effects

• Depleted oxygen level in water may kill animals of aquatic life.

3. Inorganic chemicals

• Water soluble inorganic chemicals can pollute water.

Examples

• Acids, lead (pb), arsenic (As), selenium (Se), fluorides (F).

Human sources / causes

• Surface run-off, industrial effluents and household cleanser.

Effects

• Water cannot'be used for drinking and irrigation purpose.

• Causes skin cancers.

• Damage the nervous system, liver.

• Crop yield may reduce.

• Metals exposed to water may corrode.

4. Organic chemicals

• Water soluble organic chemicals pollute water.

Examples

• Oil, gasoline, plastic, pesticides, detergents, solvents.

Human sources / causes

• Industrial effluents, household cleansers, surface run-off from farms.

Effects

• Water cannot be used for drinking.

• Can cause several disease - cancer, damage of liver, nervous system.

• Can harm aquatic life.

5. Plant nutrients

• Water soluble compounds of plant nutrient or synthetic fertilizers pollute water.

Examples

• Nitrate, phosphate and ammonium.

Human sources I causes

• Sewage, manure, run-off of agricultural and urban.

Effects

• Causes excessive growth of algae killing aquatic life.

• Excessive nitrate can lower the oxygen carrying capacity of blood.

6. Sediment

• These are suspended solids or physical pollutants. They are always naturally present in the water.

Examples

• Soil, silt.

Human sources I causes

• Land erosion.

Effects

• It reduces photosynthesis.

• Aquatic food web is disrupted.

• Carry pesticides, bacteria and other harmful substances.

7. Radioactive materials

Examples

• Radioactive isotopes of uranium, thorium and cesium.

Human sources / causes

• Nuclear power plants.

• Nuclear weapons.

• Processing of uranium.

Effects

• Genetic mutations.

• Birth defects.

• Cancer.

8. Thermal pollution I Heat

• Thermal pollution is caused by increase in rise in temperature of water.

Examples

• Excessive heat, chemical reaction.

Human sources / causes

• Water cooling in industrial process.

Effects

• Aquatic organisms become more vulnerable to diseases.

9. Point and non-point sources water pollution

• Water pollutants are categorized as point source pollution and non-point source pollution.

I Point source of pollution

• Point source pollution is defined as any single identifiable source of pollution from which pollutants are discharged.

Examples

• Industrial discharge, factory smoke stack, municipal sewage etc.

• Point source pollution sources are discrete and identifiable and hence easy to monitor and regulate.

II Non-point source of pollution

• When a source of pollution cannot be readily, identified i.e. sources are scattered or diffuse they are called as non-point source of pollution.

Examples

• Run-off from farm lands, construction sites, parking lots, agriculture logging, animal waste.

• Table 2.2.1 lists some types of pollutants and their main sources.

 

2. Effects of Water Pollution

On human beings

• On consuming polluted water following effects are observed on human beings :

1. Amoebic dysentery   

2. Skin cancers

3. Cholera  

4. Typhoid fever

5 . Damage of nervous system

6. Genetic mutations / Birth defects

7. Hepatitis

8. Malaria.

On plants and animals

1. Lower crop yields.

2. Harmful to aquatic life and wild life.

3. Excess growth of algae can kill aquatic life.

4. Reduce photosynthesis.

5. Disrupts food chain and food web.

 

3. Control Measures for Preventing Water Pollution

1. Setting up effluent treatment plants to treat waste.

2. Recycling of water must be encouraged.

3. Industrial wastes must be treated before discharge.

4. Educate public for preventing water pollution and the consequences of water pollution.

5. Strict enforcement of water pollution control act.

6. Continuous monitoring of water pollution at different places.

7. Developing economical method of water treatment.

8. River, streams, lakes and other water reservoirs must be well protected from being polluted.

 

4. Drinking Water Standards

• Drinking water is water intended for human consumption for drinking and cooking purposes from any source. It includes water (treated or untreated) supplied by any means for human consumption.

• Drinking water shall comply with the following requirements.

1. Organoleptic and Physical parameters

2. General parameters concerning substances undesirable in excessive amounts

3. Parameters concerning toxic substances

4. Parameters concerning radioactive substances

5. Bacteriological requirements

6. Virological requirements

7. Biological requirements 

Bureau of Indian Standards for Drinking Water – Specification ( BIS 10500 :1991 )

Parameters and Risks or Effects

5. Water Recycling

• Water recycling is reusing treated wastewater for beneficial purposes such as agricultural and landscape irrigation, industrial processes, toilet flushing and replenishing a ground water basin (referred to as ground water recharge).

• Water recycling offers resource and financial savings. Wastewater treatment can be tailored to meet the water quality requirements of a planned reuse.

• Recycled water can satisfy most water demands, as long as it is adequately treated to ensure water quality appropriate for the use.

• Recycled water is most commonly used for nonpotable (not for drinking) purposes, such as agriculture, landscape, public parks and golf course irrigation.

• Other non-potable applications include cooling water for power plants and oil refineries, industrial process water for such facilities as paper mills and carpet dyers, toilet flushing, dust control, construction activities, concrete mixing and artificial lakes.

• In addition to providing a dependable, locally-controlle.d water supply, water recycling provides tremendous environmental benefits. By providing an additional source of water, water recycling can help us find ways to decrease the diversion of water from sensitive ecosystems.

• Other benefits include decreasing wastewater discharges and reducing and preventing pollution. Recycled water can also be used to create or enhance wetlands and riparian habitats.

Suggested Water Recycling Treatment and Uses

Review Questions

1. Mention the reasons for water pollution and explain the control measures.

2. What are the drinking water standards for nitrates and fluorides ? What are the health impacts of nitrates and fluorides.