How microbes can clean polluted water, from drains to rivers
New Delhi: Can the problem of water pollution be checked by letting loose sewage-eating microbes?
The answer is yes and the technology that offers this hope—bioremediation—doesn’t cost the earth.
Indeed, authorities in India are batting for this technology, both to clean drains and to check pollution in the river Ganga, Prime Minister Narendra Modi’s dream project.
The technology has been successfully demonstrated in pilot projects by the Central Pollution Control Board. And the National Mission for Clean Ganga is now in the process of using bioremediation for cleaning up some parts of the river.
Internationally, the technology has been used in several countries.
In simple terms, bioremediation is a system of sewage treatment where microbes are used to degrade flowing sewage into carbon dioxide and water. The process also reduces the stench from raw sewage.
The microbes simply eat up contaminants such as oil and organic matter (e.g., waste food), convert them and then let off carbon dioxide and water. The process uses naturally occurring bacteria, fungi or plants to degrade substances that are hazardous to human health or the environment.
Bioremediation technology includes phytoremediation (plants) and rhizoremediation (plant and microbe interaction). At present, the process is used to check contamination in soil, groundwater and surface water. The system does not require construction or any major modification of drains or diversion of flow. It takes place in open drains without displacement of sewage. The process also does not require any additional land or power, making it a simple and easy system.
It is cheaper than conventional treatment methods, easy to handle and, importantly, does not require skilled manpower.
Under the process, bacteria are cultured in bulk and applied to the flowing sewage. Then, the microbes are activated and they multiply—with or without oxygen and food available in the form of organic matter present in sewage. Sometimes, enzymes are also added to activate the microbes.
However, bioremediation can be effective only in places where environmental conditions permit microbial growth and activity. Where the conditions are not favourable for their growth, manipulation of environmental parameters is carried out to allow microbial growth and allow degradation at a faster rate.
These microbes consume the organic mass of the waste water and utilize the nutrients from sewage for their growth, ultimately enhancing the cleaning action of waste water. The treatment can restore water quality and increases the self-cleansing capacity of the water body. The process also helps reduce biochemical oxygen demand (BOD) in sewage and reduces odour.
Waste water often contains organic materials that are decomposed by microorganisms, which use oxygen in the process, and BOD is the amount of oxygen that is used by such organisms in breaking down the waste matter.
The microorganisms that are used already exist in nature and this prevents any harm to the environment. Sometimes, they are indigenous to a contaminated area, otherwise, they need to be brought in to the targeted site.
It has been found that as a result of this process, heavy metals and toxic chemicals are also reduced. It also leads to the suppression and elimination of harmful pathogenic bacteria such as E. coli from the treated water.
For a country such as India, where there is a huge lack of adequate sewage collection and treatment systems, this process could be highly beneficial. Many Indian cities have either very poor or non-existent sewage treatment facilities; conditions in rural areas are no better.
The government claims that 25 patents have been granted by the Indian Patent Office in the field of bioremediation from 1971 to 2008.
One of the biggest advantages of bioremediation is that it can be carried out at the site that is polluted rather than by having to transport huge quantities of waste from the site. Bioremediation technology can also be used to clean oil spills.
However, the success of bioremediation depends on having the right microbes at the right place with the right environmental factors to support it. Also, for greater amounts of waste, enzymes may be needed as a catalyst to speed up the microbes’ action. This means every project has to be custom-designed, operated and maintained.