Treatment of petrochemical wastewater by combined process of ferric-carbon microelectrolysis-Fenton oxidation-biological contact oxidation

Using a combined process of ferric-carbon microelectrolysis-Fenton oxidation-biological contact oxidation to treat petrochemical wastewater, the effects of different factors on the efficiency of each treatment unit were investigated. The results showed that: for the ferric-carbon microelectrolysis pretreatment unit, when the ratio of m(Fe) to m(C) was 1.5 : 1, the pH value was 4.0, the HRT was 120 min, the mass concentration of CODCr in its effluent water was 420 mg/L with the removal rate of 67.57%, the value of m(BOD5)/m(CODCr) was increased from 0.02 0.03 to 0.30; for the Fenton oxidation unit, when the H2O2 dosage was 3.0 mL/L, the pH value was 3.5, the reaction time was 60 min, the mass concentration of CODCr in its effluent water was 130 mg/L with the removal rate of 72.17%, and the value of m(BOD5)/m(CODCr) was further increased from 0.30 to 0.58. The effluent water from the pretreatment unit was further treated by biological contact oxidation, and then, the mass concentration of CODCr was reduced to lower than 20 mg/L. the total removal rate of CODCr by the said combined process reached 98.76%, which indicated that, physical-chemical pretreatment combined with biological process was effective when treating wastewater with complex composition and poor biodegradability and the treatment effect was satisfied.