Enhanced Treatment of Petrochemical Secondary Effluent by Biological Aerated Filter (Fe2+)-Ozonation Process

Abstract

Two parallel biological aerated filters (BAF)-ozonation,named as number 1(feeding with FeSO4·7H2O) and number 2,were used to treat petrochemical secondary effluent.The effect of FeSO4·7H2O on COD and phosphorus removal by BAF-ozonation was studied.Molecular weight distribution,three-dimensional fluorescence scan and gas chromatography-mass spectrometry (GC-MS) were used to analyze water quality before and after BAF-ozonation.The results showed the average COD and TP concentrations were 82.91 mg·L-1 and 1.37 mg·L-1,respectively.When the dosage of FeSO4·7H2O was 9 mg·L-1,the average removal rates of COD and TP were 52.20% and 71.50%,respectively.The average COD removal rate in number 1 combined process was 17.15%,which was higher than that in number 2 combined process.The TP removal rate in number 1 combined process was increased by 51.81%.The percentage of dissolved organic matters with relative molecular weight less than 1×103 was 52% in the raw wastewater.However,the percentage increased to 75% when treated by number 1 combined process and the removal rate of various molecular weight organics was increased.Three-dimensional fluorescence analysis showed that the dosage of FeSO4·7H2O could improve the removal of fluorescent substances.GC-MS results showed that the number and concentration of organics were reduced after number 1 combined process in comparison with number 2 combined process.BAF-ozone could be enhanced by FeSO4·7H2O when treating petrochemical secondary effluent.