Hyderabad: Indian Institute of Technology Hyderabad Researchers are developing algal-bacterial hybrid systems that can reduce the cost of wastewater treatment, in addition to providing practical routes to producing recyclable water and biodiesel. These systems serve the dual purposes of wastewater treatment and biodiesel production.
The Research team hopes that their system will help rural communities in the long-run. The immediate intended beneficiaries of the research, however, are gated urban communities that have in-house plants for treating sewage.
The research team comprised Dr. Debraj Bhattacharyya, Associate Professor, Department of Civil Engineering, IIT Hyderabad, and research students, Ms. Anjana Babu, Ms. Keerthi Katam, Mr. Marttin Gundupalli, Ms. Aishwarya Pandey, Mr. Raj Kumar Oruganti, and Mr. Vinod Vadithya from the Department of Civil Engineering, IIT Hyderabad.
The results of this socially relevant work have been published in the past couple of years in reputed peer-review journals such as Journal of Industrial and Engineering Chemistry, Water Environment Research, and Environmental Science and Pollution Research.
Speaking about the research, Dr. Bhattacharyya, Associate Professor, Department of Civil Engineering, IIT Hyderabad, said, “Decentralised wastewater treatment is essential in cities of a country like India where the total wastewater generated from Class I cites and Class II towns have exceeded 75 billion litres per day.”.
Current sewage treatment facilities in the country can only treat about 26 billion litres per day. The unavailability of an extensive centralized system of wastewater treatment in class I cities and class II towns results in the discharge of untreated wastewater into water bodies and land, resulting in severe pollution and contamination issues.
Dr. Bhattacharyya added. “One step in current sewage treatment systems is aerobic biological treatment (for example, Activated Sludge Process) in which, microorganisms, dominated by heterotrophic bacteria, use oxygen to break down organic matter.”
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.
Microalgae have the ability to eliminate the problems faced in conventional aerobic biological treatment processes. However, a lot of research is needed to develop an algae-bacterial high-rate hybrid system and study its application to a wide variety of wastewaters.
Dr. Bhattacharya’s team has studied green micro-algae and diatoms for the breakdown of organic waste in wastewater. They have also combined bacteria that enable aerobic treatment, with photosynthetic micro-algae. 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.
“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 systems for wastewater treatment,” adds Dr. Bhattacharyya of the immense promise of the technology.
The research team has assessed the performance of mixed microalgae-activated sludge consortia in real wastewater treatment and simultaneous production of biofuel using bench-scale and semi-pilot scale systems. The team primarily focuses on treatment of domestic wastewater and its individual components, like those originating from kitchen and laundry.
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 team is developing a pilot-scale system and working with a gated community in Hyderabad where they are trying to upgrade an in-house wastewater treatment plant to a hybrid algal-bacterial system. Dr. Bhattacharyya also has active research and academic collaboration in the area wastewater treatment with a few Japanese Universities.