Treatment Of Reverse Osmosis Concentrated Water Of Coking Wastewater By Combined Process Of O₃/H₂O₂-A/O/Denitrification Filter-activated Carbon Adsorption

A steel company in Hebei Province produces a large amount of coking wastewater reverse osmosis concentrated water in its coking production.The organic pollutants contained in the wastewater are complex and difficult to biochemically degrade.At the same time,the wastewater contains high NH₃-N and TN content,which makes it difficult to meet the discharge standards.Therefore,it is of great significance to develop a set of treatment processes that can make the wastewater discharge up to the standard.This research takes the reverse osmosis concentrated water of coking wastewater as the research object,proposes the O₃/H₂O₂-A/O/Denitrification filter-AC adsorption combined process to treat it,and study the optimal process parameters for removing COD,NH₃-N and TN.It provides a certain reference for the treatment of similar wastewater.Experimental results show:Improve and compare the standard method HJ 828-2017 and HJ/T 399-2007 of COD determination.The results show that when the chloride ion concentration changes in the range of 0?4000 mg/L,By increasing the concentration of mercury sulfate,the interference of chloride ions can be effectively shielded.For the actual coking wastewater samples SY1 and SY2,the determination results of the standard method HJ828-2017 and HJ/T 399-2007 are consistent and meet the requirements of experimental accuracy.O₃/H₂O₂ catalytic oxidation is used as the primary treatment process.For this reverse osmosis concentrated water,through the design of single factor and response surface experiments,the order of each factor affecting the COD removal rate is ozone mass flow>oxidation time>H₂O₂ dosage>initial p H.At the same time,there is a very significant interaction between ozone mass flow and oxidation time,oxidation time and p H.The interaction between ozone mass flow rate and H₂O₂ dosage,oxidation time and H₂O₂ dosage is significant.The optimal process parameters determined by the model which the ozone mass flow is 0.38 g/h,oxidation time is 47.7 min,initial p H is 9,H₂O₂dosage is 26.9 mg/L,The actual value of COD removal rate under this condition is40.3%,which is only 0.3%relative to the 40.6%predicted by the model.A/O/Denitrification filter is used as the biological treatment process.After 30cycles of continuous operation of the A/O reactor,the indicators and conditions of the sludge in the A/O reactor were good,and the effect of removing pollutants in the wastewater was stable.Through the A/O/denitrification filter process,the final effluent COD,ammonia nitrogen,nitrate nitrogen,and total nitrogen effluent concentrations are85.0,11.4,5.1,41.7 mg/L,respectively.The removal rates were 21.5%,86.2%,97.6%,and 87.0%,respectively.The effluent COD,ammonia nitrogen,and total nitrogen meet the indirect emission standard requirements of the"Coking Chemical Industry Pollutant Emission Standard GB 16171-2012".Activated carbon adsorption is used as the three-stage treatment process.For this experimental wastewater,the adsorption effect of wood powder activated carbon is better than that of coal powder activated carbon.Through single factor experiments,the optimal process parameters was that p H is4,methylene blue value is 18 ml/g,temperature is 298 K,adsorption time is 120 min,and activated carbon dosage is 1.5 g/L.Under these conditions,the effluent COD,ammonia nitrogen,and total nitrogen concentrations were 40.1,10.8,and 35.9 mg/L,respectively,and the removal rates were 52.8%,5.6%,and 13.8%,respectively.At this time,the effluent COD meets the direct emission standard requirements.Ammonia nitrogen and total nitrogen meet the requirements of indirect emission standards.The Langmuir model can better simulate the adsorption process of activated carbon.This model shows that the adsorption process of activated carbon is a process controlled by chemical adsorption.The correlation coefficient R²fitted by the pseudo-second-order kinetic equation is 0.9991,and the calculated qe(34.07 mg/g)is relatively close to the experimental qe(32.6 mg/g).It shows that the quasi-second-order kinetic equation can better predict the adsorption process of activated carbon.