Study On Simultaneous Partial Nitrification And Denitrification In A Silastic Tube Membrane-aerated Biofilm Reactor

Recently, it is of great concern that membrane-aerated biofilm reactor (MABR) can remove organic pollutants, ammonia nitrogen and other contaminants through combining membrane technology with biological treatment. Non-porous membrane or microporous membrane used as the MABR membrane module can provide microbial adhesion and supply oxygen. Compared with the traditional bioreactors, MABR is more benefit for the treatment of ammonium pollution.A non-porous and hydrophobic silastic tube membrane-aerated biofilm reactor (SMABR) was developed to study the feasibility of achieving partial nitrification and denitrification under long-term operation test. Moreover, the effects of dissolved oxygen (DO), ratio of organic carbon to nitrogen (C/N), hydraulic retention time (HRT), influent loads and membrane fouling on the reactor performance had been discussed. Finally, the dominant bacterial species on the biofilm were also identified. The results were showed as followed:(1) Silastic tube membrane, as the membrane module, had stronger oxygen transfer capability and could satisfy the requirements for oxygen.(2) After one month of sludge acclimation, the partial nitrification and denitrification could be detected simultaneously under the conditions of32℃, pH of7.5-8.5, DO of0.5mg/L, HRT of12h, influent CODCr and NH4+-N concentrations of250mg/L and50mg/L. Tracking experiments showed that the ammonia nitrogen in SMABR were mainly oxidized to nitrite nitrogen by ammonia oxidizing bacteria.(3) In continuous experiment, the highest removal rates of CODCr, NH4+-N and TN were90%,82.9%and71%, respectively, under the conditions of32℃, pH of7.5-8.5, DO of0.5mg/L, HRT of12h, influent CODCr and NH4+-N concentrations of300mg/L and60mg/L. In the effluent, the remaining NO2--N decreased to7.3mg/L and no N03--N was detected. The results suggested that SMABR could achieve steady partial nitrification and denitrification-by changing the reaction conditions.(4) The removal rates of CODCr, NH4+-N and TN would decline while increasing the influent loads with invariant C/N ratio, suggestting the poor resistance of the reactor to impact loading. Moreover, the removal rate of TN was higher under the condition of low dissolved oxygen concentration (with the DO value of0.5mg/L). Compared with the traditional microporous membrane, silastic tube membrane had great advantage in resistance to membrane fouling.(5) The DGGE results showed the changes of microbial species and quantities on the biofilm. Twelve kinds of microbial species were coexistent on the biofilm during the partial nitrification and denitrification process, four of which were dominant microorganisms.