The Basic Study On Ammonium Oxidation,Desulfidation Under Anaerobic Conditions

In biological wastewater treatment, nitrification-denitrification process is used to removal ammonium. If nitrification was ahead of denitrification, additional electron donor was required. Otherwise wastewater should reflux. In biological treatment of sulfate-rich wastewater, sulfate reduction bacteria are dominant, which can inhibit methanogenic bacteria. The sulphide, production of reducing sulfate, can increase the sequencing process load. The new anaerobic ammonium oxidation(Anammox) process for simultaneous removal of nitrogen and sulphur can avoid these problems. In experiments we operated two kinds of reactors: anaerobic sequencing batch reactor (ASBR) and anaerobic rotating biological contactor(ARBC). The two systems are carried out under anaerobic conditions and the same hydraulic retain time, whose influents are continuous. Combining with static experiments, we study on the factors which affect Anammox. Through these experiments, we found:1. In startup period, influent COD 1 000mg/L, SO42- 200mg/L, ASBR start-up was completed in 60 days. The anaerobic rotating biological contactor start-up was completed in 50 days, which had been operated under aerobic conditions. Aerobic pretreatment accelerated start-up of anaerobic biofilm reactor.2. Serial experiments indicated: (1)sulfate reduction is relevant to COD/ SO2', at the absence of carbon,desulfidation was inhibited; (2)In anaerobic rotating biological contactor, simultaneous removal of nitrogen and sulphur occurred. The factors which affect the Anammox for simultaneous removal of nitrogen and sulphur are COD, sulfate concentration,ammonium concentration, reactor type and so on; (3)The phenomena' advent inhibited sulfate reduction completely, but accelerated methanogenesis.3. In anaerobic systems, NO2-- N or NO3-- N could inhibit sulfate reduction respectively. When raw water COD 500mg/L, SO42- 750mg/L, the efficiency of sulfate removal reducedfrom 74.9% to 15.3% and 8.5%.4. In three systems of Anammox static expriments, they used sulphate, nitrite and nitrate as electron acceptor respectively. Every system ammonium concentration figure has three phases, the corresponding microbial action are assimilation, endogenous respiration and Anammox. The decay constant b1=0.0006 h-1, b 2 =0.00088 h-1, b 3 =0.00082 h-1. In the second system which used nitrite as electron acceptor,the ratio for conversion of ammonium and nitrite to the production of nitrate was 0.68:1.32:0.27. The substrate concentration changes and kinetics analysis indiacted the Anammox occurred in these systems.