Study On The Preparation Of Immobilized Drilling Wastewater Degrading Bacteria And Its Application

With the rapid development of China's petroleum industry,a large amount of drilling wastewater is discharged every year,which undoubtedly causes a heavy burden to the environment.The drilling wastewater exhibits high chroma,high suspended solids,high COD,low BOD₅,and extremely poor biodegradability,which will cause severe environmental and ecological problems if discharged directly into the water.In order to achieve the low-cost and stable standard treatment of drilling wastewater,it is necessary to seek an efficient advanced treatment technology for pollutants.According to the characteristics of the pollutant components of drilling wastewater,a three-step development thought was developed,including the screening of degrading bacteria,the construction of compound bacteria,and the immobilization of compound bacteria.Moreover,the application of the immobilized bacteria in the treatment process was studied.The main research results are as follows:(1)Using the concentration gradient method,one strain of degrading bacteria was selected from the drilling wastewater contaminated soil and identified as Pseudomonas aeruginosa after16S r DNA sequencing.The screened strain was highly productive,environmentally safe,and easily inactivated,and the COD degradation rate of the drilling wastewater reached 63.0%after domestication.In order to achieve the simultaneous degradation of COD and ammonia nitrogen,this research introduced 1%Biwofeng nitrifying bacteria to build a highly efficient microflora for the drilling wastewater treatment.This microflora was able to achieve an 89.6%degradation rate of ammonia nitrogen in drilling wastewater.(2)The immobilization of complex bacterial flora was achieved using diatomaceous earth adsorption,and an immobilized microbial consortium for drilling wastewater was obtained in this study.The preparation process of the immobilized microbial consortium was determined as mixing100m L bacterial suspension with 10 g diatomaceous earth at 35?,adjusting p H to 7.5,and shaking at 120 rpm for 16 h,and the final immobilization rate could reach 97.5%.The performance of the bacterial agent was systematically evaluated.The bacterial agent's capability of salt-resistant was up to 5%,and the capability of temperature-resistant was from 15?to 50?.The agent's optimum p H was 6.0?8.0,and the agent's environmental release safety was high.The pretreated drilling wastewater's degradation performance was excellent.The degradation rate of COD in wastewater was 89.1%?96.2%,and the degradation rate of ammonia nitrogen was 90.6%.(3)After the pretreatment with micro-electrolysis and ozone catalytic oxidation process,the BOD₅/COD of drilling wastewater could reach above 0.35,and the biodegradability of wastewater was significantly improved.The developed microbial agent was then used for hydrolysis acidification and biological contact oxidation processes.The hydrolytic acidification reactor showed good biofilm growth after 34 days of start-up.When the hydraulic retention time(HRT)was 6 h,the removal rate of COD was 35.6%.The biological contact oxidation reactor was stable after 30 days of start-up.When the HRT was 12 h and the aeration time was 7h,the final effluent COD was lower than 82.35 mg/L,and the effluent ammonia-nitrogen was lower than 8.21 mg/L.The microbial treatment technology of drilling wastewater immobilized bacterium solves the high cost of drilling wastewater treatment in oil and gas fields,the high organic content of drilling wastewater,and the difficulty of ammonia nitrogen removal.After the treatment,all the water quality indexes reached the first-level standard of the Integrated Wastewater Discharge Standard(GB8978-1996),making the drilling wastewater treatment process more environmentally friendly and efficient.