VATIS UPDATE Article

A team of researchers at Drexel University, the United States, have developed a “bioreactor” system which is able to remove several chemicals from wastewater at once, shortcutting a process that, in conventional sewage treatment, takes multiple steps, expensive ingredients and quite a bit of time. Christopher Sales, at Drexel, is trying to improve wastewater treatment by adding algae – think pond scum – to the activated sludge where nitrogen is removed.

Sales said that “one of the most time-consuming and expensive components to wastewater treatment today is ridding water of nutrients such as nitrogen and phosphorus, which often make their way into water from our household toilets and sinks. It’s an essential step, because the release of excess nitrogen...into a water supply can lead to accelerated growth of cyanobacteria and algae.” The process uses a significant amount of energy, because oxygen has to be pumped through the wastewater to drive the conversion of ammonium to nitrate.

Similarly, wastewater treatment plants often need to add chemicals, such as methanol, to provide denitrifying bacteria with enough food to transform the nitrate into nitrogen gas. But Sales’s bioreactor works by continuously cycling water through an environment heavily populated with algae and bacteria. It removes nitrogen by storing it in algae that can easily be separated from water in the new reactor. According to Sales, his process can remove up to 80 per cent of nitrogen from a waste stream.