Study On The Treatment Of Petrochemical Wastewater From A Petrochemical Plant Of Zibo By Thermal Coagulation-O₃/H₂O₂

According to the water quality characteristics of the petrochemical wastewatercoming from a petrochemical plant of zibo city, it was firstly pretreated by thermalcoagulation to reduce the COD and turbidity. Then Fenton reagent and O3/H2O2oxidation were used to treate the wastewater respectively, putting the COD and volatilephenol as the indicator. The two processes were compared by treatment effect andeconomic feasibility in order to determine a suitable method. At last, the optimalprocessing method was applied to engineering practice.First of all, the wastewater was pretreated by thermal coagulation. The treatmenteffects was compared with three coagulant in zhe same conditions of wastewater, suchas CuSO4·5H2O, FeCl3and FeSO4·7H2O. The consequences indicated that FeCl3wasthe best coagulant for the wastewater. The effects of FeCl3dosage, reactiontemperature, pH and PAM dosage were discussed by orthogonal experiment and therelationship between primary and secondary of the influence factors was defined. Theoptimum condition was determined through single factor analysis. The experimentalresults showed that the removal rate of COD and turbidity was up to63.26%and89.40%respectively, when pH value was8, the FeCl3dosage was4g/L, the PAMdosage was2mg/Land reaction temperature was50℃.Secondly, the petrochemical wastewater was treated by Fenton reagent afterthermal coagulation. The optimized conditions were discovered through orthogonalexperiment and single factor analysis when dosage of H2O2was60mmol/L, initial pHvalue was3, the concentration of Fe2+was15mmol/L, and reaction time was90min.The removal rate of COD and volatile phenol were up to67.58%and84.92%respectively in the condition. The indexs such as COD, NH3-N, volatile phenol andcolor were reduced after Fenton reagent oxidation treatment. But it had yet to reach thelimit of discharge standard, and higher cost.Thirdly, the O3/H2O2oxidation was applied to treat the wastewater which was pretreated by thermal coagulation. The result indicated that The COD and volatilephenol were reduced to489.79mg/L and18.28mg/L, and the removal rate was up to76.78%and96.79%respectively under the optimum conditions as follows: theconcentration of H2O2was50mmol/L, initial pH value was10, ozone flow was4g/h,and reaction time was50min. The indexs such as turbidity, color, TOC and NH3-Nwere reduced to4.70NTU,20times,578.25mg/L and25.31mg/L respectively. Theratio of BOD5to COD was increased from0.16to0.41after treated. Thebiodegradability was improved apparently and the effluent quality reached “thedischarge standards of Sewage ischarged into urban sewage discharge standards”(CJ343-2010). In addition, the reaction mechanism and kinetics on treatment ofpetrochemical wastewater was discussed. The kinetic research revealed that theremove of COD was in accordance with the first-order kinetic model, and the reactionrate constant was0.0283min-1. By comparison, the operating cost is lower than Fentonreagent method.According to the experimental results, the waste water containing phenol of theplant can be processed through thermal coagulation-O3/H2O2.The plant designed andbuilded a set of thermal coagulation-O3/H2O2device in order to treat the wastewater.The COD and volatile phenol concentrations of the effluent were498.6mg/L and20.45mg/l respectively, which had reached the design requirements.