Research On The Fouling Characteristics Of Reverse Osmosis Membrane For Coking Wastewater And Its Pretreatment Technology

Coking wastewater has the characteristics of complex composition,high concentration of pollutants,and great environmental hazards.The reuse of coking wastewater can significantly reduce freshwater consumption and mitigate or even not discharge wastewater,which is of great significance for the green and sustainable development of the coking industry.Reverse osmosis technology is the core technology in the coking wastewater reuse system.Reverse osmosis technology has the advantages of low operating cost,strong adaptability,easy operation,automation,and difficulty in producing secondary pollution.However,membrane fouling will shorten the service life of the membrane,reduce the quality of the effluent,and hinder the application of reverse osmosis technology.The quality of the membrane influent is the critical factor causing membrane fouling.This paper establishes the correlation between membrane fouling and influent water quality by studying the influent water quality and membrane fouling characteristics.The parameters of the pre-membrane pretreatment scheme are optimized to improve the influent water quality and slow down the process of membrane fouling.The main contents and conclusions are as follows:(1)Through the analysis of the fouling characteristics of the reverse osmosis membrane,it was found that organic fouling was the main component of the fouling layer.At the same time,organic compounds and humic substances whose aromatic rings were highly substituted by carbon groups,carboxyl groups,hydroxyl groups,and ester groups in the wastewater contributed to the membrane fouling.Moreover,the Si-Mg complex,calcium sulfate and its hydrate are the paramount fouling crystals,which form fouling and blockage through organic matter bonding and stacking.(2)Through the pretreatment experiment,it is found that the best pretreatment scheme is to adsorb with 100ml/L LX-111 resin for 6 hours and then oxidize with53.7mg/L ozone for 2 hours.The final COD removal rate is 49.43%,the UV254 removal rate is 90.57%,and the chromaticity removal rate is 99.06%.Among the individual pretreatment schemes,ozone oxidation had the highest removal rate of fluorescent organics,especially tryptophan(96.514%).The combined pretreatment process can achieve a removal rate of more than 93% of various fluorescent substances.The adsorption pretreatment delays the formation of inorganic pollution,and the ozone oxidation pretreatment hinders the formation of organic pollution.(3)Through the simulation experiments of membrane fouling,it was found that the acidic components in the dissolved organic matter of wastewater will cause membrane fouling more quickly,and Si in inorganic ions has a significant effect on the decrease of membrane specific flux.Fulvic acid contaminants are also of concern.Using Ca,Si and membrane specific flux,and COD,fulvic acid and membrane specific flux to do multiple linear regression,an excellent fitting effect can be obtained,which provides ideas for establishing membrane water inflow indicators.By selecting a regression equation between the concentration of influent pollutants and the degree of membrane fouling,a suitable upper limit value of influent pollutants can be determined,which is significant for improving the treatment efficiency of membranes.