New technology to turn wastewater into freshwater: Researchers

Washington, PTI | Updated : 23 February 2015, 02:28 PM

Researchers have developed a new technology that turns wastewater into freshwater more efficiently than conventional methods.

Dr Jianmin Wang, a Missouri University of Science and Technology professor developed multiple wastewater treatment technologies that produce freshwater that is not only cleaner than wastewater treated using traditional methods, but also requires less maintenance and energy.

Wang said 0.8 per cent of America’s energy use is spent on wastewater treatment. Much of that energy is used to aerate the tanks where wastewater is treated.

The energy is used to feed oxygen to the microorganisms that consume the waste, and traditionally wastewater treatment plants maintain an oxygen concentration of 2 milligrammes per litre to feed the bugs in the tanks, Wang said.

The prevailing thought has been that providing less than 2 milligrammes per litre of oxygen would make the microorganisms “unhappy.”

But Wang does not believe that is an issue, saying that if you feed them at a lower concentration, such as 0.5 milligramme per litre, it makes them a little less happy, but the microorganisms will live longer and enrich more - plus you use 30 per cent less energy during oxygen infusion to produce the same results.

He has also developed another treatment system called an Alternating Anaerobic-Anoxic-Oxic (A3O) process that “can achieve superior effluent quality since it can remove organic pollutants plus nitrogen and phosphorus nutrients.”

It does this without chemicals, and its effluent contains only 5 milligrammes per litre of total nitrogen and 0.5 milligramme per litre of total phosphorus.

It also saves more than 10 per cent of energy compared to the conventional pre-anoxic process, which has significantly less total nitrogen and total phosphorus removal.

With its high performance, high energy efficiency and low operational costs, on a large scale the technology could help curb global surface water eutrophication.

Eutrophication is the enrichment of an ecosystem with chemical nutrients, typically nitrogen, phosphorus or both.

Wang has also developed a self-mixing anaerobic digester, which can effectively convert wastewater sludge and other organic waste to biogas energy.

It improves environmental quality by removing the sludge, and it also recovers a useful resource during the process.  Additionally, his high-rate digester operates itself, without an external energy hookup.

Based on his calculations, Wang said a combination of his technologies can produce a net 10 per cent energy gain in contrast to the 27 per cent net energy use the wastewater industry currently operates on. 

First Published: Monday, February 23, 2015 02:25 PM
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