Ammonium removal from concentrated waste streams with the anaerobic ammonium oxidation (anammox) process in different reactor configurations

Many concentrated wastewater streams produced in food and agro-industry are treated using sludge digestion. The effluent from sludge digesters frequently contains ammonium in high concentrations (up to 2 kg m(-3)). This ammonium-rich effluent is usually treated by a normal wastewater treatment plant (WWTP). When ammonium removal from this concentrated stream is considered, steam stripping or a combination of two biological processes, aerobic nitrification and anoxic denitrification, are the (costly) options. Recently a novel process was discovered in which ammonium is converted to dinitrogen gas under anoxic conditions with nitrite as the electron acceptor. It has been named Anammox (anaerobic ammonium oxidation). The aim of this study was to demonstrate the feasibility of ammonium removal from sludge digestion effluents with the Anammox process. Using a synthetic wastewater, it was shown that a fixed-bed reactor and a fluidised-bed reactor were suitable reactor configurations. The effects of sludge digestion effluent on the Anammox process were investigated; during 150 days, 82% ammonium removal efficiency and 99% nitrite removal efficiency was achieved in a fluidised-bed reactor inoculated with Anammox sludge and fed with sludge digestion effluent from a domestic WWTP. The maximum nitrogen conversion capacity was 0.7 kg NH4+-N m(reactor)(-3) day(-1) and 1.5 kg total N m(reactor)(-3) day(-1). (C) 1997 Elsevier Science Ltd.