The Treatment Of Petrochemical Secondary Effluent By Fenton Oxidation

The characteristics of petrochemical wastewater are that of large quantity of emissions,complex components and difficult to degrade so that the petrochemical wastewater has been ahotspot in the field of industrial wastewater treatment. The petrochemical wastewater treatedby the conventional biological treatment also contains large amounts of refractory organicmatter, and it needs deep treatment to meet increasing water discharge requirements. In thispaper, the petrochemical secondary effluent was used to conduct a deep treatment by theFenton oxidation. The main conclusions are as follows.The Fenton reagent was used to do oxidation treatment to the petrochemical secondaryeffluent directly, the influent flow was60L/h, the dosage of H2O2(30%) is0.2,0.4,0.6,0.8and1.0mL/L and the dosage of FeSO47H2O is0.1,0.2,0.3,0.4and0.5g/L. The resultsshowed that: the influence of H2O2on COD removal rate is bigger than that of FeSO47H2O,the most cost-effective dosage of the petrochemical wastewater treatment by Fenton reagentdirectly is that the dosage of H2O2(30%) is0.4Ml/L and the dosage of FeSO47H2O is0.4g/L,at this time, the COD removal rate reached the highest of59.2%; the PO43-P removal ratewas more than89.0%and the sludge production was187mg/L.The pH, dosage of H2O2(30%), FeSO47H2O and PAM were chose as the four mainfactors to conduct an orthogonal experiment. The results showed that the importance offactors that affect the COD removal rate were as follows: initial pH> FeSO47H2O dosage>PAM dosage> H2O2dosage. When the petrochemical secondary effluent quality was different,the best operating conditions for the experiment were different. When the secondary effluentCOD≦65mg/L, the optimal operating conditions are as follows: HRT was90min, initialpH was4, the dosage of H2O2was0.4mL/L, the dosage of FeSO47H2O was0.4g/L anddosage of PAM was1.2mg/L, under this condition, when the average secondary effluentCOD concentration was61.73mg/L, the COD average concentration of Fenton oxidationreaction effluent was49.53mg/L and the highest COD removal rate was26.4%; the averageremoval rate of PO43–P could reach96.9%; the average amount of sludge production was671mg/L. When the secondary effluent COD≧65mg/L, the optimal operating conditionsare as follows: HRT was90min, initial pH was4, the dosage of H2O2was0.4mL/L and thedosage of FeSO47H2O was0.8g/L, under this condition, when the average secondaryeffluent COD concentration was77.32mg/L, the COD average concentration of Fentonoxidation reaction effluent was58.10mg/L and the highest COD removal rate was33.2%;the average removal rate of PO43–P could reach94.2%; the average amount of sludge production was868mg/L.TOC/TN analyzer, gas chromatography chromatography-mass spectrometry andthree-dimensional fluorescence spectrophotometer are also used to analyze the characteristicsof the wastewater which is not treated and the wastewater which is treated by Fentonoxidation under optimum operating parameters.TOC/TN analysis show that the TOC of thepetrochemical secondary effluent is29.83mg/L, and the TOC of organics whose molecularweight are under1kDa in this wastewater is23.99mg/L which take up80.4%of all. The TOCof the Fenton oxidation reaction effluent is29.83mg/L, and the TOC of organics whosemolecular weight are under1kDa in this wastewater is15.46mg/L which take up95.6%of all.The gas chromatography chromatography-mass spectrometry and three-dimensionalfluorescence spectrophotometer analysis show that most organics in the petrochemicalsecondary effluent are oxidized and removed after the Fenton oxidation treatment.The sludge of the wastewater which is treated by Fenton oxidation is also analyzed. Afterthe Fenton oxidation treatment, some sludge in which PAM is threw is placed one month, andsome sludge in which nothing is threw is placed one month too. Then these two kinds ofsludge and the sludge which is treated without any measures are all dried and scanned byelectron microscopy. This SEM images show that the sludge which PAM is threw in andplaced one month is coarse and irregular. The sludge which nothing is threw in and placed onemonth is smooth, and it’s surface groups are closely. There are some small grains on thesurface of the sludge which is treated without any measures, and the gap between the surfacegroups is small. Under optimal reaction conditions, physical and chemical properties of allkinds of sludge, such as moisture content, ash and volatiles, are measured and analyzed. Theresults show that, as the time increases, both the moisture content and volatiles of the sludgewhich is treated by PAM are increasing gradually, but the ash has no changes. And as the timeincreases, the moisture content, ash and volatiles of the sludge which is not treated by PAMhave few changes.The costs of the processing technology are analyzed based on the above experiments. Ifthe unit price of industrial electricity is0.8yuan per kilowatt-hour，and the handling capacityis6500ton per hour, then the power costs are0.083yuan per ton. when the COD is under65mg/L, the pharmacy costs are1.68yuan per ton, and when the COD is higher than65mg/L,the pharmacy costs are0.716yuan per ton.