Construction Of Bacterial Agent And Its Bioaugmentation Efficiency In The Wastewater Treatment

Northeast China is the main area for petrochemical industry development. Due to long-term shortage of environmental investments and laggard technology, some enterprises had become vital industrial pollution soures. Besides, low ambient and wastewater temperature is the key factor influencing the start-up of the newly-builted municipal wastewater treatment plants (WWTPs). Through the addition of bacterial agent, bioaugmentation could effectively shorten the start-up of biological wastewater treatment systems and improve its performances and stability. Based on methods and theories of microbial physiological ecology, molecular ecology and envrionmental engineering, the present study gave a systematic expatiation on bacterial agent construction. Furthermore, practical bioaugmenation projects were conducted in the low-temperature rapid start-up of the municipal WWTPs and the upgrade of petrochemical wastewater biological system.Based on a survey of 32 municipal WWTPs in Northeast China, the construction objective of bacterial agent for municipal wastewater treatment was to realize the rapid start-up and stable operation of the biological systems under low temperatures. According to the analysis of pollutants contents, COD contribution of organics and their biodegradability, the construction objective of bacterial agent for petrochemical wastewater treatment was to enhance the degradation of refractory organics and the resistence to shock loadings.Based on microbial cometabolism, niche separation and self-adaptive acclimatization and through repeated selection, combination and acclimatization, bacterial agents against the refractory organics in petrochemical wastewater and low temperature municipal wastewater were constructed. It showed that the constructed bacterial agents were safe and economical. Besides, with the addition of bacterial agent, municipal wastewater treatment met the discharge standands rapidly; in biaugmented pilot-scale petrochemical wastewater treatment facility, the average concentration of effluent COD and NH₄⁺-N was around 80mg/L and 8mg/L, respectively. The number of the organics in the effluent of the bioaugmented system reduced to 32 compared to 69 of the original A/O process without bioaugmentation. Based on the stable existence and efficient performance of the bacterial agent for petrochemical wastewater treatment, efficiencies of different bioaugmented process type and biofilm formation methods of the contact oxidation system were compared. The bioaugmented immobilized biofilm system was superior to the bioaugmented activated sludge system both in pollutants removal and microbial activity. The indirect biofilm formation methods, which delivered granular substances like activated carbon, tourmaline and yeast for the pre-coating of the carrier, could effectively avoid the clogging of the carrier with the attachment of abundant active microorganisms within the pores. When the concentrations of the influent COD and NH₄⁺-N varied between the range of 280⁴20mg/L and 5²5mg/L, the corresponding effluent could keep stable below 70mg/L and 3mg/L, respectively. The addition of inorganic granular carriers and organic granular nutrients provided favorable environment for the degradation of organic pollutants in the petrochemical wastewater.Based on lab-scale and pilot-scale tests, the conventional A/O process was upgraded to a two-stage bioaugmented oxidation process with polyurethane foams as its carrier. PCR-DGGE results showed that under the same operational conditions, stable and diverse microbial community was formulated in the bioagumented system. Remarkable improvements were achieved on pollutants removal efficiency and shock loadings resistance ablility. Period for system start-up was also shortened to about 10 d.By applying bioaugmentation with the addition of bacterial agent, three different types of municipal WWTPs were started rapidly within 12¹5d as temperature lower than 15℃. Their effluent quality was stable with varied temperature and the biological systems kept similar metabolic activity. Different bioaugmented biological system showed similar metabolic activity under low temperatures. 50% microorganisms in the biomass samples from winter and spring were similar to the stains diliveried during the bioaugmentation, which mainly included Chryseobacterium, Hyphomicrobium, Nitrospira sp., Xanthomonadacea, Flavobacteriales, and Bacteroides sp.. Among all the cloned sequences, 36% were similar toβ- andγ-Proteobacteria, 36% were similar to Flavobacteria and Sphingobacteria and 23% were similar to Nitrospirales. These bacteria were always predominant in the biological systems. Besides, the predominances of some bacteria in different biological processes were dynamic with the variations of wastewater quanlity and quality and other environmental conditions. The coexistence of predominant bacteria and potential functional bateria was vital for the stable operation of municipal WWTPs in cold winter and seasonal transition periods.Engineering practical experiences and theoretical achievements presented in the present study systematically elaborated upon the contruction, production and evaluation methods of the bacterial agent, the selection and optimization of bioaugmentation process, the regulation and control of operational parameters, which provided powerful guidance and reference for spreading the application of bioaugmentaion technology. Bioaugmentation with bacterial agent could remarkablely shorten the start-up period and improve the pollutants removal and shock loading resistence ability of the biological wastewater treatment systems. Besides, a great many cost for start-up and upgrade was saved. The application of bacterial agent reduced the discharge of pollutants in Northeast China, especially in frozen periods, which was a fesible and effective pathway for the wastewater treatment and control of the Northeast China.