Water Pollution and its Control

Water Pollution

· Water is very essential for the maintenance of life on earth.

· Due to human activities, water bodies have become polluted all over the world.

Some of the common pollutants and their sources are:

Domestic sewage

It mainly contains organic matter, which is biodegradable. Microorganisms involved in their degradation consume a lot of oxygen and the BOD of the water body increases leading to the death of fishes and other aquatic life. Sewage also contains many pathogenic microbes, which may cause the outbreak of many diseases such as typhoid, jaundice, etc.

Industrial Effluents

Industrial effluents contain inorganic toxic substances, which may undergo biomagnification (increase in concentration of a toxin at successive trophic levels). The toxin gets accumulated in the body of an organism and is passed on to the next level. For example, DDT and other heavy metals such as mercury, cadmium, etc.

Biomagnification of DDT in an aquatic food chain

Thermal wastewater discharge

Heated water flowing out of the thermal power plants increase the temperature of the water body. It eliminates the cold water species and promotes the warm water species. In the long run, it causes damage to the indigenous biodiversity of the water body.

Eutrophication

· It is the ageing of a water body due to nutrient enrichment of its water. It can be natural or artificial.

· The natural process takes thousands of years, but due to human activities, this process has got accelerated (accelerated/cultural eutrophication).

· Release of nutrient rich sewage and industrial effluents lead to introduction of nutrients such as nitrogen and phosphorus and increase in temperature and BOD of the water body, causing increased biological activity, thereby leading to algal blooms. This results in the loss of indigenous flora and fauna.

· In some cases, large masses of floating plants (bog) develop, finally converting the water body into land.

Control of Water Pollution

Ø Raw sewage can be treated using biological and other means to remove the solid, suspended, and inorganic materials before it is released back into the environment.

Ø Nitrogenous fertilizers can be denitrified using microbes, which can convert nitrate and nitrite into gaseous nitrogen by a process called de-nitrification.

Integrated wastewater management as practiced in Arcata, California- In this approach, the water is first treated by conventional means such as filtration, sedimentation, and chlorine treatment, followed by bioremediation. (Marshes having appropriate plants, bacteria, fungi, and algae were seeded, which assimilate dangerous pollutants such as heavy metals).

A Case Study of Integrated Waste Water Treatment

Wastewater including sewage can be treated in an integrated manner, by utilising a mix of artificial and natural processes. An example of such an initiative is the town of Arcata, situated along the northern coast of California. Collaborating with biologists from the Humboldt State University, the townspeople created an integrated waste water treatment process within a natural system.

The cleaning occurs in two stages – (a) the conventional sedimentation, filtering and chlorine treatments are given. After this stage, lots of dangerous pollutants like dissolved heavy metals still remain. To combat this, an innovative approach was taken and (b) the biologists developed a series of six connected marshes over 60 hectares of marshland. Appropriate plants, algae, fungi and bacteria were seeded into this area, which neutralise, absorb and assimilate the pollutants. Hence, as the water flows through the marshes, it gets purified naturally.

The marshes also constitute a sanctuary, with a high level of biodiversity in the form of fishes, animals and birds that now reside there. A citizens group called Friends of the Arcata Marsh (FOAM) are responsible for the upkeep and safeguarding of this wonderful project.

Ecological sanitation is a sustainable system for handling human excreta, using dry composting toilets. This is a practical, hygienic, efficient and cost-effective solution to human waste disposal. The key point to note here is that with this composting method, human excreta can be recycled into a resource (as natural fertiliser), which reduces the need for chemical fertilisers. There are working ‘EcoSan’ toilets in many areas of Kerala and Sri Lanka.