| The problem of water pollution is serious in China,and the demand for water resources is increasing.Compared with desalination treatment and cross-regional water diversion,wastewater reuse is more economical and guaranteed.Denitrification moving bed biofilm reactor?MBBR?was developed for the advanced nitrogen removal of reverse osmosis concentrate from the low pressure reverse osmosis unit,which was produced from the high-quality water reclaimation of municipal wastewater.The low pressure reverse osmosis concentrate has the characteristics of high TN concentration,high NO3--N accounted ratio and low C/N ratio,and the nitrogen is one of the main factors influencing the water eutrophication.So,it is urgent for treatment of the low pressure reverse osmosis concentrate.The effects of different kinds of suspended carriers,polyethylene configuration,the ratio of height to diameter of MBBR,and the different influent wastewater concentrations on the denitrification MBBR efficiency were studied extensively.The scanning electron microscopy?SEM?and fluorescence quantitative PCR?Q-PCR?were also combined to analyze the characteristics of microbial communities and gene richness of the bacteria 16S rRNA,the archaea 16S rRNA,nirK,nirS and narG.When the pH was 7.50-8.10,the temperature was 24-26?,HRT was 12 h,FR was 50%,the results showed:?1?Polyethylene?PE?,polypropylene?PP?,polyurethane?PU?and haydite were analysed as the suspended carriers for MBBRs.The results demonstrated that the NO3--N and TN removal efficiency achieved by denitrification MBBR filled with PE were better than the others,the removal rate were 79.4±3.9%and 66.0±3.4%respectively.The biomass was3.75mg/g carrier,the genes richness were highest.?2?Comparing the nitrogen removal rate of denitrification MBBRs with?25×12,?25×4,?15×15 and?10×7 four different configurations of cylindrical PE carriers,the denitrification MBBR with?15×15 PE carriers had the highest removal efficiency for low pressure reverse osmosis concentrate treatment.The removal efficiency of NO3--N,NO2--N,NH4+-N,TN and COD were 78.0±15.8%,43.8±9.3%,55.6±22.3%,68.9±12.4%,71.5±16.6%at stage I?influent NO3--N was16.70±5.99mg/L and TN was 22.25±6.36 mg/L.et al.?,and they were 85.7±10.5%,55.0±9.7%,52.2±10.3%,79.7±9.2%and 58.4±8.4%at stage II?influent NO3--N was30.36±1.83mg/L and TN was 36.83±2.12mg/L?.The carrier biomass was the highest?2.13mg/g carrier at stage I and 3.41 mg/g carrier at sage II?in the?15×15 PE denitrification MBBR compared with other configuration denitrification MBBRs.And the genes of the?15×15 PE denitrification MBBR were also the most abundant.?3?The denitrification efficiency of?25×12 cylindrical PE MBBR with 1.24 and 4.17height-diameter?H/D?ratio were compared.The efficiency of denitrification MBBR with 1.24H/D ratio were higher than the denitrification MBBR with 4.17 H/D ratio for treatment of the low pressure reverse osmosis concentrate.The removal efficiency of NO3--N,NO2--N,NH4+-N,TN and COD in the denitrification MBBR with 1.24 H/D ratio were72.5±19.0%,44.3±12.5%,49.5±20.4%,65.0±15.2%and 60.3±14.1%at stage I,and they were78.0±14.0%,50.8±9.0%,47.8±11.8%,73.3±11.2%,54.9±8.3%at stage II.The biomass was higher?1.85mg/g at stage I and 2.61 mg/g at stage II?in the denitrification MBBR with 1.24H/D ratio than 4.17 H/D ratio,and the genes were also higher.?4?Cylindrical PE denitrification MBBR with various configurations and H/D ratios had a slightly better removal nitrogen efficiency in higher influent concentration?stage II?than those in lower influent concentration?stage I?for treatment of the low pressure reverse osmosis concentrate.The biomass and the genes abundance in denitrification MBBR were also a bit higher in stage II than those in stage I.The above-mentioned results illustrated that the influent concentrations had little influence on the efficiencies of denitrification MBBRs in stage II and stage I.The conclusions obtained in this study provided theoretical and technical support for the actual operation process of the wastewater reclaimed water plant,provided data basis for actual project operation,and helped to alleviate and improve the current water environment problems. |
PDF Full Text Request