BENGALURU: A novel product developed by Nualgi Nano Biotech (NNB), a low-profile biotech company here, is helping clean up sewage-polluted Ulsoor Lake where thousands of fish were found dead last week owing to depletion of dissolved oxygen.

Ulsoor Lake, famous for army rowing competitions as well as for boating among tourists, was seen covered with thousands of dead fish that left people here stunned.

“Called Nualgi, it is a mixture of micro-nutrients in the form of nano-particles including silica, iron and manganese,” said Thothathri Sampathkumar, who founded the company which patented the product in India in 2008.

“Nualgi triggers the rapid growth of a type of algae called ‘diatoms’ and the oxygen released by the diatoms through photosynthesis quickly increases the dissolved oxygen level of water and thus keeps the pond clean,” Sampathkumar told IANS.

According to Sampathkumar, one kg of Nualgi can treat four million litres of water, adding that the affected fishermen — who have the contract for fishing in Ulsoor lake — have purchased 40 litres of Nualgi from his company to increase the dissolved oxygen level and stop further fish death.

“We can see the results very soon,” added Sampathkumar.

“Nualgi can be used to grow diatom algae in any water including sewage polluted water. The growing diatoms absorb carbon dioxide from the air and, by photosynthesis, release oxygen at the micro plant level. The oxygen released, helps aerobic bacteria breakdown organics in the water into base constituents, thereby eliminating the stinking odour from the water.

The growing diatoms are eaten by zooplankton that, in turn, is consumed by fish. “The fish clean up the lakes of all diatoms, zooplankton and organics, thus restoring the polluted lakes and water bodies to its original glory,” said Sampathkumar.

According to him, the mass fish death in Ulsoor lake took place perhaps because the fishermen ran out of their stock of Nualgi or missed its timely application.

The tragedy could have been averted, had the authorities installed monitors to continuously record the level of dissolved oxygen (DO) in the lake water and alert them when DO falls below critical level. These DO monitors, he said, are now commercially available.

“Nualgi has been patented also in the US, Britain, Germany and South Africa. Five years ago, the three-acre Duck Pond in New York state in the US that was in a highly impaired state with a variety of water quality issues was restored to normal health thanks to Nualgi.”

Nualgi, that requires no skilled labour, is an economical alternative to treat sewage and organic wastes in eutrophic lakes and ponds contaminated by nitrogen or phosphorus compounds, such as by laundry detergents, untreated sewage and fertiliser run-off from agricultural lands.