Treating community wastewater takes a lot of energy. Eawag is currently supporting a project that not only presents an alternative to conventional treatment processes but is also designed to enabled increased throughput within a smaller amount of space.
More and more people are moving to cities and agglomerations in Switzerland, which is putting extreme pressure on some wastewater treatment plants: Because they are having to treat greater volumes of wastewater, their energy consumption is skyrocketing. And some WTPs are close to reaching capacity.
Together with various project partners from industry, Eawag has now been testing out a new kind of technology for the past six months at the Sihltal WTP. The technology is designed to allow a space-saving extension to be built at the plant whilst also lowering the plant’s energy consumption. The key to this is a special sieve that looks like an over-sized washing machine drum, which is installed before the activated sludge tank. Because this apparatus holds on to any solids larger than 0.2 mm, only the dissolved substances pass through to the activated sludge tank. “This means that fewer bacteria are needed in the activated sludge tank for treating the wastewater”, says engineer Nicolas Derlon, from the Department of Process Technology, who is leading the project at Eawag. The advantage of this is that less oxygen needs to be pumped into the tank, which in turn makes big energy savings for the plant — up to 30 percent, says Derlon. The aeration of the activated sludge tank is the most energy-hungry part of the treatment process at a WTP.