Enhancing The Nitrification Performance In Wastewater Treatment Unit By The Bioaugmentation Of Accumulated Nitrifying Bacteria In Reject Water

The reject water comes from the sludge treatment process in the wastewater treatment plant is of high ammonia influent,it may lead the exorbitant ammonia loading of the whole wastewater treatment system and may influence the effluent quality if refluence to the infall. This study investigated the technology of independent treatment of the reject water and the effect of accumulated nitrifying bacteria,which were bred by the reject water in a sequencing batch reactor(SBR).The strategy of bioaugmentation using accumulated nitrifying bacteria to the wastewater treatment system to enhance the biodegradation of organic matters and nitrification performance was also performed.Then,a study on the phenomena of the aerobic denitrification in the reject water reactor was carried out.The main conclusions are as follows.(1)The SBR was started up using a high influent with ammonia concentration at 100mg/L when incubate the nitrifying active sludge which favors the high ammonia concentration.The nitrifying bacteria were successfully accumulated,and the preference flora was obtained after 25-30 days.(2)An effective nitrification performance was obtained in SBR at a high influent of ammonia when the reject water was treated independently.More than 95%of the average removal efficiency of ammonia and nitrite could be achieved at 2mg/L of DO and 8～8.5 of pH. An obvious phenomenon of pH went downward and upward was found.The result of nitrogen balance showed that the denitrification occurred immediately after the nitrification achieved in the aerobic condition,65-70%of TN was removed,but there was little denitrification in the anaerobic condition.A market effect on the nitrification in wastewater treatment system could not be found when the duration of SBR cycle was only changed as 12h,6h and 4h,in this time,the HRT,SRT and A/O ratio kept at 30h,20d and 1:3,respectively.About 60%of the average removal efficiency of TN could be achieved,the most of TN was removed in the aerobic stage.(3)In the SBR that was used to accumutated the of nitrifying bacteria by the addition of reject water,the maximum ammonia uptake rate(AUR) was 97.5 mgNH₄⁺-N/L·h,the maximum specific AUR was 32.8 mgNH₄⁺-N/gVSS·h,the maximum nitrite uptake rate (NUR) was 43.4 mgNO₂^--N/L·h and the maximum specific NUR was 14.6 mgNO₂^--N/gVSS·h.The result of fluorescence in situ hybridization(FISH) revealed that the dominant ammonia oxidizing bacteria was Nitrosomonas europaea and Nitrosococcus mobilis,the dominant nitrite oxidizing bacteria was Nitrobacter spp.(4) The ability of organism biodegradation and nitrification performance could be enhanced markedly by the bioaugmentation,and the enhancing effect may keep for some days after the bioaugment ceased,on the other hand,bioaugmentation may result in much increasing in the quantity and the diversity of protozoa.(5) The distribution of DO in the sludge flocs was determined by microelectrodes for oxygen,since a market removal of TN occurred in the aerobic stage of the reject water reactor. The behavior of denitrification of low concentration sludge in aerobic condition was also examed.The results showed that the phenomenon of the aerobic denitrification of nitrifying activated sludge bred by the reject water was due to both the asymmetry of DO transfer in flocs and the metabolism of aerobic denitrifying bacteria.