Study On Technological Characteristics Of Simultaneous Anaerobic Ammonium Oxidation, Methanogenesis And Denitrification

Biotechnology is used extremely widely for wastewater nitrogen removal among numerous denitrification technologies. Nitrification and denitrification processes constitute the traditional biotechnology of nitrogen removal, which utilizes the nitrification in the aerobic condition and the denitrification in the anaerobic condition to reduce the nitrogen. However, there are always shortages in the traditional biotechnology such as high energy consumption, long processing periods, large construction area, low organic loading and so on. In recent years, more and more researches focus on a sustainable denitrification technology of low energy consumption, short processing periods and energy recovery. On the basis of analysing the characteristics and the advantages of methanogenesis, denitrification and anaerobic ammonium oxidation, simultaneous anaerobic ammonium oxidation, methanogenesis and denitrification was achieved in the same reactor with the granular sludge as the vector. The influence of the different concentration of COD on the simultaneous anaerobic ammonium oxidation, methanogenesis and denitrification was also studied in this paper.(1) After 40-days'startup, the volumetric loading rate and COD removal rate of two UASB (1# and 2#) were respectively 0.6kgCOD/(m3·d) and over 85% under moderate temperature conditions (31-35℃). Compared with ordinary anaerobic reactors, the two reactors had the characteristics such as rapid start, stable operation and strong capacity of anti-shock loading because the seed sludge had strong anaerobic activity. The temperature, pH and other factors of the reactor were controlled to shorten the startup time, and the COD concentration of influent had would been adjusted in time according to the reactor effluent COD concentration.(2) When started over, the two UASB reactor was filled with the synthetic wastewater with nitrite and ammonium. Simultaneous anaerobic ammonium oxidation, methanogenesis and denitrification was gradually achieved when the temperature was controlled at 31-35℃, pH at 7.3 and 8.3,and the Hydraulic Retention Time(HRT)at 26.4h in the reactor.In this process,the COD removal rate was about 80-90%.The NO2ˉ-N removal rate was above 90%. The TN removal of 1#UASB and 2#UASB were 50～60% and 60～70% respectively.Ammonia nitrogen removal was in a volatile state because some nitrite was changed into ammonia nitrogen by anti-ammoniation and slow enrichment of anammox bacteria.(3) The influent COD of 1#UASB with biofilm was reduced and 2#UASB without biofilm was remained to compared the influences of different COD on simultaneous anaerobic ammonium oxidation, methanogenesis and denitrification.The COD removal rate was decreased to about 20-30% after reducing the influent COD concentration of 1# UASB. The COD removal rate remained at 70% to 80% by remaining the influent COD concentrations of 2# UASB. The effluent nitrite of 1# UASB increased and the removal rate changed little of 2# UASB. The ammonium nitrogen removal efficiency of 1#UASB and 2# UASB were 30% and 10% respectively. The nitrate nitrogen of the effluent in the 1# UASB was increased more than in the 2#UASB obviously. The function of anaerobic ammonium oxidation in the 1#UASB was enhanced from the rise of the ammonium nitrogen removal and the nitrate nitrogen of the effluent.(4) The methanogenic activity of 1# and 2#UASB were 52.8mlCH4/(gVSS·d) and 50.4mlCH4/(gVSS·d) respectively by measuring the methane production of anaerobic sludge. The denitrifying activity of 1# and 2#UASB were 20mgNO2ˉ-N/(gVSS·h) and 22.786mgNO2ˉ-N/(gVSS·h) respectively by measuring the consumption of NO2ˉ-N. The anaerobic ammonium oxidation activity of 1# and 2#UASB were 3.38mg NH4+-N/(gVSS·h) or 6.54mg NO2ˉ-N/(gVSS·h) and 2.9mg NH4+-N/(gVSS·h) or 5.91mg NO2ˉ-N/(gVSS·h) by measuring the simultaneous consumption of ammonium and nitrite under anoxic conditions.