Application Of Bioaugmentation Technology In Wastewater Denitrification Treatment

Bioaugmentation is an effective method to improve the efficiency of wastewater treatment by adding functional microbes,nutrients or substrate analogues into systems,while the isolation and identification of heterotrophic nitrification and aerobic denitrification bacteria provide a new direction.In recent years,because of serious nitrogen pollution,a variety of denitrification processes have appeared such as anaerobic reactor,membrane bioreactor,USMB reactor and sequencing batch reactor(SBR).Among them,the SBR reactor has been widely used due to its simple and efficient operation.In this article,Pseudomonas putida HJH1 and Bacillus sp.K5 were introduced into SBRs to treat piggery wastewater and municipal wastewater,respectively.Effects of augmented SBRs on wastewater treatment were invtigated,and stabilities and nitrogen removal mechanisms were respectively explored during the long-term operation.The main results obtained are as follows:1)Piggery wastewater treatment by the SBR augmented with Pseudomonas putida HJH1To begin with,a strain was isolated from a eutrophic water body and identified as Pseudomonas putida HJH1.The strain HJH1 could not only remove up to 72.4 mg/L NO2--N under aerobic conditions,but also has a good performance for simultaneous nitrification and denitrification(SND)with no nitrite accumulation.The SBR system augmented with this strain was able to consistently remove(1)76.4-100%ammonium nitrogen and 71.4-100%COD from artifical wastewater in stage 1,and(2)89.2-99.1%ammonium nitrogen and 82.4-100%COD from piggery wastewater in stage 2.DGGE showed that the strain HJH1 predominated in the SBR all the time to function together with other bacteria during the whole operation period,indicating that the SBR system inoculated with Pseudomonas putida HJH1 can efficiently remove ammonium nitrogen from piggery wastewater,thereby having potential applications for the future nitrogen removal.2)Muicipal wastewater treatment by the SBR augmented with Bacillus sp.K5Municipal wastewater was treated successfully by the bioaugmentation of Bacillus sp.K5 capable of simultaneous nitrification and denitrification(SND)within a sequencing batch reactor(SBR).During the long-term operation,the bioaugmentation system exhibited an excellent and steady COD and NH4+-N removal without nitrite and nitrate accumulation.The average removal efficiency for COD and NH4+-N achieved to 98%and 95%,respectively.The fluorescence in situ hybridization(FISH)demonstrated that the abundance of nirS that is a key gene participating in denitrification increased and thus resulting in an increasing removal efficiency of TN(total nitrogen),but it did not exert a significant impact on both ammonium and COD removal.Meanwhile,PCR-DGGE and the morphology of active sludge by SEM revealed that the introduced Bacillus sp.K5 should be an important functional strain and exerted a critical influence on the structure of microbial community.Additionally,some functional genes involved in nitrogen removal from activated sludge were quantified by qPCR,and results indicated that the concentration of most genes elevated,suggesting the strain K5 facilitated aerobic nutrients removal capabilities.As a result,on the basis of those mentioned above,the simultaneous nitrification and denitrification(SND)pathway that might exist in this SBR system was proposed.