IIT Bombay Researchers Discover Natural Bacteria in Wastewater Efficiently Remove Contaminants

IIT Bombay study reveals treated refinery wastewater enhances purification through pollutant-eating bacteria in sand filtration. Know details here

IIT Bombay Researchers Discover Natural Bacteria in Wastewater Efficiently Remove Contaminants

A recent study by researchers at the Indian Institute of Technology Bombay (IIT Bombay) has uncovered a promising development in biofilter technology. Their research on biofilters - water filters that utilise microorganisms, such as bacteria, to eliminate pollutants - revealed an intriguing finding: partially treated wastewater from refineries already contains bacteria capable of degrading organic contaminants. The researchers discovered that by simply providing a substratum, specifically a column of pure quartz sand, these bacteria were able to effectively adhere and enhance the filtration process.

For their study, the researchers investigated the properties of sand as a biofilter. “Sand was chosen since it is commonly used in deep bed filters used for water and wastewater treatment,” remarks Prof. Suparna Mukherji, from the Department of Environmental Science and Engineering, IIT Bombay, who led this study.

The study also explored the microbial community within the biofilter and found that the dominant bacteria were from the Proteobacteria group. This group is renowned for its capability to decompose complex organic compounds such as polynuclear aromatic hydrocarbons (PAHs), which are detrimental to living organisms. Notable members of the Proteobacteria group, including Sphingomonadales, Burkholderiales, Rhodobacterales, and Rhodospirillales, are well-regarded for their effectiveness in mitigating hazardous pollutants.

The researchers designed a biofilter made of an acrylic cylinder measuring 45 cm in length and 2 cm in diameter. They filled it with pure quartz sand to a depth of 15 cm. The filtration process begins by allowing secondary treated refinery wastewater, which has undergone the removal of toxic chemicals, to flow through the biofilter at a controlled rate of 1 to 10 mL per minute. The wastewater flowing through the sand leads to the formation of a biofilm, made of several different types of bacteria enmeshed in extracellular polymeric substances secreted by the bacteria, on the grains of sand.

This biofilm, in turn, breaks down the organic contaminants in the water. As organic compounds containing nitrogen are degraded, they release inorganic nitrogen in the form of ammonium, which is then converted into nitrate. While some nitrate removal may have taken place, the study observed a buildup of nitrate following the biofiltration process.

The nitrates generated by the bacteria during filtration, through the conversion of other nitrogen forms, led to a buildup of nitrates in the treated water. "The observed increase in nitrates is undesirable. However, refineries often use reverse osmosis (RO) as the final treatment step, which can significantly lower the nitrate levels in the final effluent," explains Prof. Mukherji. Additionally, biofiltration can help minimize the deposition and accumulation of unwanted materials on RO membranes by reducing the presence of assimilable organic carbon (AOC).

Read More

• IIT Bombay Partners with Oilmax Energy for Research in Energy, Mining, and Green Technologies
• IIT Bombay Placements 2023-24: 22 Offers Above INR 1 Crore, 12% More Recruiters, 78 International Jobs