Research On Characteristics Of Half-Nitrosofication Using Moving Bed Biofilm Reactor And Start-Up Of ANAMMOX Reactor

High concentration of ammonium was usually contained in landfill leachate and gradually increased with the age of landfill, which resulted in severe contamination to environment. Therefore, it's extremely difficult to treat landfill leachate to meet the governmental regulation. In this dissertation, the combined SHARON and ANAMMOX process was used for nitrogen removal from landfill leachate.The SHARON process was carried out in aerobic moving-bed biofilm reactor(MBBR) and the start-up was investigated. The wastewater used in the study was from the effluent of an anaerobically pre-treated reactor. The inoculated sludge was collected from municipal nitrification sludge. After operation in batch feeding mode for one week, a thin layer of biofilm formed on suspended bio-carrier was observed, with the following operation in continuous feeding mode for three weeks, the SHARON reactor was successfully start-upped, 93.92% of ammonium removal efficiency and 94.97% of nitrite accumulation were achieved.In order to get suitable feed for the ANAMMOX process, the half-nitrosofication in SHARON reactor was systemicly studied. The effect of influent ammonium concentration, DO and pH on half-nitrosofication was investigated. The results showed that DO and pH were the important factors for achieving half-nitrosofication, especially; pH was the most important factor. Setting pH value constant at 7.0 in the reactor and controlling appropriate DO concentration, stable half-nitrosofication could be achieved at certain influent ammonium concentration. The proper DO concentration for half-nitrosofication of leachate whose ammonium concentration was 500 mg/L and 300 mg/L were suggested to control at 1.5 and 1.0 mg/L, respectively. The reason for high concentration accumulation of nitrite in SHARON reactor was disclosed to be the selective immobilization and accumulation of ammonia oxidizing bacteria on the biofilm in the MBBR from the indirect kinetics test and direct MPN method.In this dissertation, the effect of DO concentration and pH on the kinetic parameter of ammonium degradation in the SHARON reactor was also investigated. The results indicated that the Haldane model can be used to describe removal kinetics of ammonium, and the saturation constant Km, maximum reaction rate Vmax and inhibition constant Ki.The high loading method and low loading method with aerobic precoating microbial cultivation were conducted to comparative study the start-up of the ANAMMOX reactor. Owing to the strong inhibitory effect to microbes of high concentration of nitrite and free ammonia, the high loading method failed to grow ANAMMOX bacteria; however, low loading method with aerobic precoating microbial cultivation was successfully cultivated the ANAMMOX bacteria. After three months of cultivation using the low loading method, the removal efficiency of ammonium and nitrite was both reached nearly 100%, and the conversion ratio among NH4+-N, NO2--N and NO3--N was 1:1:0.42. The experimental results showed that pH value could be used as an indicator for the ongoing process of ANAMMOX bioreactor, in which the pH value of effluent was observed to be higher than that of influent of ANAMMOX reactor. The SEM observation of the biofilm showed that diversity of microbial species and no distinct species of dominant populations grew on the biofilm in the high loading reactor; whereas, the biofilm in the low loading reactor was predominated by staphylococcus and bacillus. So it's concluded that ANAMMOX bacteria were the main population in low loading reactor. Finally, the effect of loading rate on the performance of ANAMMOX reactor was investigated and the the results showed that the removal efficiency of ammonium and nitrite could reach nearly 100% so long as the influent ammonium and nitrite concentration was controlled below 800mg/L.