| Wastewater treatment under low temperature is a difficult problem in the field of wastewater treatment. The growth and metabolic activities of microorganism slow down under low temperature, even lose activity at10℃. Due to the degradation of metabolic activity, microorgnasim cannot become the advantage bacterium group at low temperature, which seriously affact the efficiency of wastewater treatment in winter. The start up of biological reactor and stable operation became the obstacal in implementation of project. Therefore, bioaugmentation with two screened psychrotroplis strains with high organic matter degradation ability and high activitises Pseudoalteromonas. A3-10and Photobacterium. D1-2was applied to accelerate the start-up of reactor at low temperature. The screening of psychrotroplis, effet of bioaugmentation on dynamic membrane reactor (DMBR) start-up, wastewater treatment performance, dynamic membrane formation, and membrane fouling under different temperature shocks were studied.The result of screening of membrane materials showed that the removal efficiency of COD, NH4+-N, TN and TP of200g/m2non-woven membrane module was better than that of80g/m2non-woven fabric moduld. Dynamic membrane formed on the former membrane modual was much stable and had higher biological purify ablity under operation. The200g/m2non-woven membrane module was much suitable to be used in dynamic membrane bioreactor.The effects of sudden decrease of temperature (25℃、20℃、15℃、10℃and5℃) and gradual decrease of temperature (15℃、12℃、10℃、7℃and5℃) on the treatmemt efficiency of two reactors were investigated. The results showed that inoculation with two strains into reactor could improve the ability of resisting to different temperature shocks, shorten start-up period and improve the wastewater treatment efficiency. With temperature decreased from25℃to20℃, no significant change was observed. But as temperature decreased to15℃, the removal efficiency of RB was much better than that of RA. At5℃, the removal efficiency of RA and RB was82%and86.7%for COD,75.6%and84.2%for NH4-N, respectively. The removal rate of TN and TP was low for both reactors, but the romoval of RB was still better than that of RA.The removal efficiency of TN for RA and RB was39.3%and49.7%and that of TP was41.3%and53.2%, respectively. The wastewater treatment for RB was better than RA under gradual decrease of temperature at low temperature. The difference of treatment effecincy between two reactors was obviously observed for TN and TP at10℃while that for COD and NH4--N was not obviously observed until temperatre decreased to7℃.Dehydrogenase activity of two reactors was investigated as temperature decreased from25℃to5℃. FISH analysis was also carried out for RB at5℃. The dehydrogenase activity decreased82.6%of its activity for RA and62.4%for RB at5℃. which indicates that inoculation of two strains could improve the biomass activity in DMBR. FISH analysis further confirmed the presence of two psychrotroplis, which confirmed that bioaugmentation process was fully operative in DMBR at low temperature.The effect of bioaugmentation on membrane fouling was also investigated. Both turbidity and flux of RB were larger than that of RA at the beginning, but once the dynamic membrane was formed, the flux became much stable and the turbidity was lower nearly to zero for both reactors, indicating that inoculation of two psychrotroplis did not significantly affect the formation of dynamic membrane. Serious membrane fouling was not observed under normal temperature for two reactors. As temperature gradually decreased to5℃, membrane fouling resistance of two reactors increased, whicn indicated that Low temperature could aggravate membrane fouling. |
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