Study On Bioaugmentation Of High-salty Wastewater In Offshore Drilling Platform

With the rapid development of China's economy and the great development of marine resources, the pollution of the marine environment has been paid more and more attention.According to the International Maritime Organization (IMO), the emission standards of sewage from offshore platform has been strictly defined since 1973. And the indicators of sewage such as BOD5 (<25mg/L), SS (<35mg/L), Escherichia coli (<100 /100mL), COD(<125mg/L), pH (6.0-8.5), chlorine (<2.5mg/L), TN (<20mg/L) and TP (<1mg/L), were contained in the IMO. The offshore drilling platform high-salty sewage (3.5%NaCl salinity)were selected as research object, the integration of MBR technology were selected as hard-core. Meanwhile, it examines the comparative advantages of the two kinds of salt tolerant activated sludge. Then, the 16S rDNA high-throughput gene sequencing was used for classifying the four strains of halophilic bacteria that obtained by screening. Finally, the characteristics such as treatment efficiency, membrane fouling and sludge reduction, were used as the performance evaluation index of the device.The results of sludge acclimation showed that: The system of activated sludge naturally acclimated by gradiently adding salt concentration , by contrast, has better ability of restoration than the one that domesticated by using bioaugmentation under the conditions of stable salinity. The former is less resistant to shock load, and is not suitable for the treatment of salt containing wastewater with high load. Otherwise, it can shorten the acclimation period of salt tolerant activated sludge by inoculation sludge with high background salinity.The results of bacterial identification showed that: After the four strains of halophilic bacteria were screened and analyzed by 16S rDNA sequencing, it initially identified that strain Y-1 belonged to Virgibacillus sp.,strain Y-2 belonged to Nitratireductor sp., strain Y-3 belonged to Arthrobacter sp., and strain Y-4 belonged to Arenibacter sp..Moreover,the removal rate of organic compounds by strain Y-1 and ammonia nitrogen by strain Y-3 was respectively highest among them.The results of removal efficiency of the integrated effluent treatment plant showed that:The system of activated sludge naturally acclimated by gradiently adding salt concentration was used as the inoculated sludge . And under the conditions of MLSS=9500mg/L,HRT=22h and SRT=60d, the removal efficiency of the integrated wastewater treatment equipment is as follows.The average removal rate of COD was 90.9%, the average removal rate of BOD5 was 88.5%,the average removal rate of TOC was 88.9%, the average removal rate of NH4+-N was 60.4%, and the average removal rate of TP was 58.9%.The results of membrane fouling and recovery showed that: The influence of operating conditions such as salinity,aeration rate and membrane flux (or HRT) on membrane fouling is great as well as the concentration polarization. Besides , the cleaning method of membrane is made up of three parts: firstly physical cleaning, then pickling(H2SO4), and finally alkali washing(NaC10), and experimental results show that the means of cleaning returned to the original level.