Recent data suggests that India does not have the requisite sewage treatment facilities. Earlier this year, the National Green Tribunal said that 60 per cent of sewage treated by urban Indian goes untreated and enters water bodies like lakes and rivers.
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According to IIT-Hyderabad, India has the capacity to treat about 26 billion litres of sewage per day, while the total wastewater generated from Class I cities and Class II towns exceeds 75 billion litres per day. These grotesque levels of pollution discharged into our water bodies pose serious public health concerns.
How do you address this problem?
Earlier this week, IIT-Hyderabad had announced that they are developing an algal-bacterial hybrid system (algae-activated sludge system) that they believe can reduce the cost of wastewater treatment, offer better quality recyclable water and produce biodiesel and other value-added by-products.
Most wastewater treatment plants in India work on what we call an activated sludge process. The microorganisms (dominated by heterotrophic bacteria) use oxygen to respire and break down organic matter in the wastewater. Treatment essentially occurs through many different microorganisms using pollutants as a food source.
“While aerobic treatment converts organic matter into carbon dioxide and biomass, they have problems such as high energy use (primarily to satisfy oxygen demand of such processes) and production of too much sludge which is often difficult to dispose. It’s also a costly process because mechanical aeration takes up 40-50 per cent of the treatment cost. Our objective is to reduce the aeration cost without compromising quality of treatment,” says Dr. Bhattacharyya, Associate Professor, Department of Civil Engineering, speaking to TBI.
How does it work?
The research team is primarily focussing on treatment of domestic wastewater and its individual components like those originating from kitchen and laundry.
“Dr. Bhattacharya’s team has studied green micro-algae and diatoms (brown algae) for the breakdown of organic waste in wastewater. They have also combined bacteria that enable aerobic treatment, with photosynthetic microalgae. In such combined systems, the oxygen produced by the microalgae during photosynthesis is used by the bacteria for aerobic breakdown of organic waste. Carbon dioxide is released during this process. Microalgae also participate in the treatment process by assimilating this dissolved carbon dioxide as well as by taking up nutrients (for example, nitrogen and phosphorus) from wastewater for cell synthesis. Thus, a synergistic relationship is established which is likely to reduce the overall cost of wastewater treatment and also ensures a better quality effluent for reuse and recycle purposes,” says the press release issued by the institution earlier this week.
“An additional benefit of using algal-bacterial systems for wastewater treatment is that the algae that are grown in sewage treatment plants can, in turn, be used to produce biodiesel and other value-added by-products. If all sewage is treated in microalgae-based systems, the total theoretical algae-derived biodiesel production would cut our dependence on petroleum-derived diesel noticeably. However, harvesting of microalgae presents a greater challenge than operating the system for wastewater treatment,” adds Dr. Bhattacharyya.
However, they have also worked on treatment of palm oil mill effluent and wastewater originating from pharmaceutical industries and found that kitchen wastewater is amenable to algal biodegradation and is a good substrate for algal lipid (biodiesel) production. Their work on domestic wastewater treatment using a trickling filter based photo-bioreactor has also yielded promising results.
Currently, the IIT-Hyderabad team is developing a pilot-scale system and working with a gated community in Hyderabad 25 km away from campus which houses nearly 2,000 families where they are trying to upgrade an in-house wastewater treatment plant to a hybrid algal-bacterial system.
“At present wastewater treatment is seen a process imposed upon us by regulatory bodies. Our long term objective is to ensure this technology reaches a stage where it becomes a revenue generating sector. If I can reduce the cost of treatment, provide higher quality recyclable water and at the same time create useful byproducts from the sludge we generate, the process will become self-sustaining. There is a reason why we construct so many treatment plants, and quite a few of them end up not working. This exercise is not about coming up with a system for academic purposes, but a real-life and implementable process of treating wastewater. We are systematically working on scaling up. I am confident that in two years we will have a system ready that we can present this system to entrepreneurs,” he argues.
Although rural communities can benefit from this system in the long run, the immediate beneficiary of this endeavour will be people living in housing societies across various cities that have in-house plants for treating sewage. In seeking to significantly upgrade the available systems of wastewater treatment, these researchers at IIT-Hyderabad could really affect positive change to our immediate urban environment.
(Edited Saiqua Sultan)