Study On Treatment Of Refinery Wastewater By Biological Enhanced Carrier Fluidized Bed Biofilm

The research object of this paper is the wastewater from a large-scale comprehensive refinery wastewater treatment plant.The wastewater has many sources of pollutants and complex components.The concentration of COD_cr,ammonia nitrogen and oil vary greatly.After being treated by"oil isolation-air flotation-biochemical"process,the drainage indicators can not meet the requirements of the national wastewater discharge standards.Field experiments were carried out on a commercial scale for carrier fluidized bed biofilm Reactor?CFBR?.The Enhanced denitrification mechanism of Shortcut Nitrification-Denitrification?SCND?and Simutaneous Nitrification and Denitrification?SND?in aerobic process was studied.Benzene was the characteristic pollutant in wastewater.The biodegradation of 1,4-Benzenedicarboxylic acid Dimethyl Ester?DMT?was studied.Five strains of DMT biodegrading bacteria were screened and the dominant bacteria were constructed.Fixed-bed Membrane Bioreactor?FBMBR?was designed.The main influencing factors and mechanism of membrane fouling were analyzed.The effluent of wastewater treatment plant was treated in depth,and the possibility of partial reuse of effluent was explored.The conclusions are as follows:The wastewater treatment effect of CFBR process is obviously better than that of Actived Sluge technology?AS?process,and the biological denitrification effect is good.It is suitable for the transformation of wastewater treatment plant,and has the advantages of simple operation and convenient maintenance.The effluent from the wastewater treatment plant can meet the national first-class discharge standard?GB8978-1996?.Petroleum is less than 5 mg/L,COD_cr is less than 60 mg/L and ammonia nitrogen is less than 15 mg/L.CFBR process can strengthen SCND function and realize SND function synchronously.The accumulating rate of NO₂^--N in SCND can reach more than 80%,the saturation constant of NO_x^--N in SND is 5.33,the denitrification effect of SND is improved obviously,and the removal rate of TN can reach more than 80%.The optimum operation parameters of CFBR process are DO 2.0-3.0 mg/L,pH 7.5-8.0,temperature 30-35?,HRT 10-12h and alkali consumption 20g/m³ per ton of wastewater.Five strains of DMT-degrading bacteria were screened and isolated by batch domestication of DMT.16SrDNA sequence analysis confirmed that strains were Pasteurella multocida,Bacillus cereus,Mesophilic methyl bacillus,acid-eating bacterium and Sphingomonas olitica.The optimum conditions for DMT degradation of strains showed that the optimum conditions for DMT degradation of bacteria were:temperature between 28?and 36?,pH value between 7.5 and 8.0,and the proportion of strains added was 5%.Under the conditions of HRT 1.25h,gas-water ratio 0.5:1 and packing A,the effluent CODcr less than 35mg/L,BOD5 less than 5mg/L,ammonia nitrogen less than 3mg/L,suspended solids less than 5mg/L and turbidity less than 5NTU of FBMBR process all meet the requirements of industrial circulating water recharge index.The main influencing factors of membrane fouling in FBMBR plant are soluble microbial products?SMP?in the mixed solution,and the specific resistance and extracellular polymeric substances?EPS?of the mixed solution can be neglected.The structure design of the device can effectively alleviate the SMP pollution to the membrane,reduce the transmembrane pressure difference of the ultrafiltration membrane,and prolong the cleaning cycle and service life of the ultrafiltration membrane.