Study On Biological Immobilization Treatment Of Refinery Wastewater

With the country's emphasis on environmental protection,pollutant discharge standards have become increasingly stringent.The "Emission Standards for Pollutants in the Petroleum Refining Industry"(GB31570-2015)requires the use of effluent COD?50 mg/L in areas where the ecological environment is vulnerable to serious water environment pollution problems.Ammonia nitrogen?5 mg/L,TN?30 mg/L,oil ?3mg/L pollutant emissions limits.Due to capital and land restrictions,most enterprises can only perform in-situ upgrade process technological transformation on the basis of the original structures,of which biological immobilization is one of the hot spots in the industry.Bio-filler is a key material for the immobilization of microorganisms.Based on the prevalence of hydrophilicity and insufficient bio-affinity of commercially available fillers,this paper carried out filler modification,evaluation and comparison of filler properties,A/O and MBBR process and the optimal operating conditions of the process.The main findings are as follows:(1)Comparing the fillers with different compositions by measuring the hydrophilicity,bio-affinity of the fillers and the biomass of the unit fillers.The experimental results show that the addition of activated carbon and metal oxides can effectively improve the hydrophilicity and bioaffinity of the fillers.After modification,the contact angle of the fillers is changed from 80°to 53°,and the modified filler packing speed is improved.And the amount of hanging film has been improved compared to before.(2)A/O process and MBBR process are determined by examining the effect of operating conditions such as DO,C/N,HRT,and reflux ratio on the removal of petroleum,COD,ammonia nitrogen,and total nitrogen in the A/O process and the MBBR process.The best operating conditions of A/O process: DO is 4 mg/L,C/N is 9,HRT is 10 h,reflux ratio is 300%;the best operating condition of MBBR process: gas to water ratio is 5:1,C/ N is 9,HRT is 8h,and reflux ratio is 150%.Compared with the A/O process,the MBBR process has better impact resistance and can have better total nitrogen removal efficiency at low C/N,low reflux ratio,and low HRT conditions.(3)The best operating conditions for the Biofilm activated sludge mixing process are DO concentration of 3 mg/L,HRT of 12 h,and reflux ratio of 200%.Through the staged water intake method,the carbon source can be more reasonably distributed.The final ammonia nitrogen removal rate can reach 97%,and the total nitrogen removal rate can reach 79.3%.The effluent ammonia nitrogen and total nitrogen are 1.46 mg/L and10.96 mg/L,respectively.