Degradation Efficiency Of Organic Compounds In Reverse Osmosis Concentrate Produced In Water Reclamation Plants By O₃/UV Combined With Denitrification Biological Filter

Reverse osmosis(RO)process is widely used in most water reclamation plants at present,while the generated RO concentrate(ROC)cannot meet the emission standards due to its poor biodegradability and costly treatment.In this study,according to the results of ROC water quality analysis,an O3/UV combined with denitrification biological filter(DNBF)process was adopted to treat ROC produced during wastewater reuse.The effects of pH value,ozone concentration,UV intensity,reaction time,hydraulic load,carbon-nitrogen ratio and other factors on the treatment performance of the process were investigated.The results of water quality analysis showed that the pollutants in ROC were mainly non-biodegradable organics,COD was 50-80 mg/L,B/C ratio was 0.12,total nitrogen concentration was 70-90 mg/L,and most of them were inorganic nitrogen.The results of GC-MS qualitative analysis showed that there are two parts of ROC pollutants,some of which are concentrated water-retention components of sewage treatment plants,such as endocrine disruptors(EDCs),drugs and personal care products(PPCPs),and the other part is generated by RO systems,disinfection By-Products(DBPs).Three-dimensional fluorescence results showed that the major pollutants were fulvic acids and marine humic acids.Ozone has poor treatment effect on ROC,while O3/UV has obvious synergistic effect and better treatment effect.At the same ozone concentration,compared with ozone oxidation,the COD removal efficiency of O3/UV pretreatment ROC increased by nearly 10%,the average ozone utilization rate increased by 20%,and the B/C ratio increased by nearly one time.O3/UV combined with DNBF process can effectively degrade the organic compounds and total nitrogen in ROC.O3/UV process at pH equal to 8,temperature was 20℃,UV intensity was 0.4 W/m2,ozone concentration was 13 mg/L.After 20 minutes of reaction,the B/C ratio reached 0.33.At this time,the average ozone utilization rate was 69%.When the carbon-nitrogen ratio of the denitrification biofilter was 6 and the hydraulic load was 3 m3/(m2 h),the removal rates of COD,N03--N,TN,UV254,and chroma were 92.3%,90.96%,90.22%,65%,and 80%.The ROC effluent water quality index achieved the first-level A requirement of Discharge standard of pollutants for municipal wastewater treatment plant.After economic accounting,The cost of treating one ton of ROC with a combination process is 2.53 yuan.