1st Prize – Cost and Energy Savings Nitrifying Downflow Hanging Sponge Reactor: Addressing Water Supply Disruption Challenge

Down-flow hanging sponge (DHS) reactor is a potential treatment system for low-cost ammonia-polluted drinking water treatment in developing countries. Polluted water supplied at the top of the reactor trickles down the polyurethane sponge media to the bottom. The sponge carriers are exposed to the atmosphere, in which oxygen easily diffuses into the downflow water through natural ventilation. Therefore, DHS can provide an aerobic environment for nitrification without external aeration device, reducing the energy cost significantly. Moreover, the sponge media can retain more biomass and reduce excess sludge production. The long sludge retention time in DHS promotes the growth of slow-growing autotrophic nitrifiers, hence ensuring effective and complete nitrification. The DHS system was proven to remove ammonia efficiently for treatment of different forms of industrial wastewaters. Apart from wastewater, we found that high quality effluent can be achieved in ammonia-polluted drinking water treatment at a short hydraulic retention time (1 hour), indicating that NH4+-N can be treated quickly. This lowers the capital cost by reducing the size of the reactor, featuring the compactness of the DHS system. Hence, an innovative concept for drinking water treatment by DHS reactor is introduced, no need for chemicals and aeration, with a smaller surface footprint.