Research On Advanced Treatment For Coke Wastewater By Combined Process Of Coagulation-microwave-fenton Oxidation

Biological denitrification and coagulation are the most commonly-used cokingwastewater treatment technologies, however the discharging water is usually difficultto meet the new revised emission standard of pollutants for coking chemical industry.According to this, the thesis focused on the advanced treatment research of cokingwastewater by coagulation, microwave-Fenton oxidation and combination process ofcoagulation-microwave-Fenton oxidation respectively. The experimental resultsshowed that the combination treatment could be a promising technology satisfying farmore rigorous environmental requirements and achieving wastewater reuse.In this study, the coking wastewater after biochemical treatment was furthertreated by coagulants of polyaluminium chloride (PAC) and polyacrylamide (PAM).The optimal processing parameters of coagulation were as follows: the doses of PACand PAM were150mg/L and8mg/L respectively and sedimentation time was35min.Under the optimum conditions, the removal of COD, chromaticity and turbidity were72.81%,84.43%and98.15%respectively. However, the remaining COD was103.28mg/L which was higher than that of emission standard of pollutants for cokingchemical industry (GB16171-2012).Meanwhile, the coking wastewater after biochemical treatment was treated bymicrowave-Fenton oxidation. The optimal process conditions were: the dose of FeSO4was250mg/L, the dose of H2O2was1300mg/L, the microwave power was450Wand the treatment time was40min. Under these conditions, the removal of COD,chromaticity and turbidity could reached83.39%,93.55%and97.26%respectively,but the remaining COD was60.05mg/L, still higher than that of emission standard forindustrial recirculating cooling water treatment (GB50050-2007).Then, combination of coagulation and microwave-Fenton oxidation was appliedto treat coking wastewater after biochemical treatment. The results showed that thecombination treatment was superior to the other treatments studied, such ascoagulation, microwave-Fenton oxidation and coagulation after microwave-Fentonoxidation. It was found that it could be much more effective when H2O2was added infor three times gradually in Fenton oxidation process.When120mg/L PAC,5mg/L PAM,120mg/L FeSO4and600mg/L H2O2wereadded, initial value pH of supernatant liquid was6, the microwave power was450W and the treatment time was35min, the removal of COD, chromaticity and turbidityarrived at the highest values, which were87.69%,98.87%and99.16%respectively.The remaining COD was45.28mg/L, which met the emission standard for design ofindustrial recirculating cooling water treatment (GB50050-2007).