Study On The Distribution Of BTEX And PAHs In Refinery Wastewater And Environmental Risk Assessment

Refinery effluents,generated from petroleum refining,hydroskimming and oil-washing,are made up of many different chemicals,have high Concentration,diffcult degradation and high residue,which are dangerous to environmental.General refinery effluents are concern with removing routine pollutants such as COD,BOD,sulfide,rarely considered these compounds have toxic,mutagenic and carcinogenic properties such as BTEX(Benzene,Toluene,Ethybenzene.p-xylene,m-Xylene,o-Xylene)and PAHs(Polycyclic aromatic hydrocarbons).So,research on the distribution and decrease of BTEX and PAHs in the refinery effluent treament and environmental effect to surface water is good to improve effluent treatment technology,guarantee water environmental security,have important theory and application value.In this study,on the basis of the review analysis menthod of BTEX and PAHs in refinery effluent,treatment technology and environmental effect,by lots of investigation, research and field survey,mainly summarize and analyze the available treatment technology of refinery effluent in china,and integrate the treatment efficiency,the monitoring and analyzing unit was established.On this basis,because of large of interference chemicals,difficult isolation,low concertration,it is difficult to analyze BTEX and PAHs in refinery effluent,So mainly consult and completely review the isolation, Purification,and analysis technology,completely researching on the method of pretreatment and improving system analysis condition were adopt,establish a new method to determine the treatment efficiency of BTEX and PAHs in effluent treatment,and access environmental risk.This dissertation included the following contents and conclusions:(1)Silicon column was optimized in orfer to achieve effective isolution of other chemicals.the optimized conditions were listed as followed:silicon is 5.0g,the colum is 20cm×10mm,first use 5ml n-pentane to remove alkane impurities,and use 70ml mixed eluants(CH₂Cl₂/n-pentane=2/3)to eluate(2ml/min),and collect organic compounds,and concentrate to 1.5ml by rotary evaporator,exchange organical solution with n-hexane, concentrate to 1ml by rotary evaporator.On this basis,the method of analysis PAHs in refinery effluent with GC/MS was established.To chang the temperature of water bath and the time of heating,Head-space GC method was established.And it shows better sensitivity and accuracy than common method.The RSD of PAHs was within 1.28%～17.38%and the recovery of PAHs was about 76.3%～129.0%.The RSD of BTEX was within 93.5%～103.6%and the recovery of PAHs was about 2.35%～12.29%.(2)Adopting established analysis method to determine the concentration of BTEX and PAHs in refinery effluent treatment process,we analvsed 6 BTEX and 16 PAHs primarily.The research result shows that:the removal efficiency of 6 BTEX is very high, close to 99%;the total concentration of PAHs was 309.2μg/L～7097.46μg/L.The biochemical treatment process can removed 67%PAHs,the biological activity carbon technology can removed 94%PAHs.This refinery effluent treatment technology can remove 65%～99%PAHs,the 16 total removal efficiency is 96%.The removal efficiency of 2-3 low PAHs.85%,lower than the removal efficiency of 4-6 PAHs.99%. The high ring PAHs have better removal efficiency.(3)Four monitoring section follow by effluent outfall in xiaoqing river were investgated,the result shows that the concentration of 16 PAHs in sediments was 2.56～307.62mg/kg,the average concentration is 19.39mg/kg.The concentration of 2-4 low PAHs is higher than other from rings,the highest concentration in sediment is H2, 263.83mg/kg.The concentration of 16 PAHs in water is 46.19～1847.60ng/L,the highest concentration in water is H2.The concentration of low PAHs is higher than that of high PAHs.By spatial distribution laws,reference to control profile,the total concentration of 16 PAHs in water decreased gradually.From single PAHs,the concentration of Phenanthrene was maximum,followed by Pyrene,Benzo(a)anthracene,Chysene.(4)These results showed that the concentration of PAHs in sediment had correlation with the concentration of PAHs in water,have the same change trend.The concentration of PAHs had good Correlation with the content of TOC in sediment.The higher content of TOC in sediment,the higher content of PAHs in sediment.The content of TOC is importment to influence concentration of PAHs in sediment.(5)According to the data of the PAHs,reference to oversea environmental risk assessment index,environmental risk assessment for water and sediment in xiaoqing river was made,showed that xiaoqing river has generatied a certain negative ecological effect, existed a certain high ecological effect.