Nitrogen Removal Of Reclaimed Water Using Biological Filter And Membrane Bioreactor

Shenzhen City is vigorously popularizing reclaimed water reuse in recentyears.With the approaches and the amount of reclaimed water constantly expanding,safety of water quality has become the primary factor in the market of reclaimedwater. While the water quality index ammonium and total nitrogen in the secondaryeffluent from WWTP and water reclamation plant are failed to meet the Shenzhenrenewable water, rainwater quality standard (SZJG32-2010). This paper carried outa study about denitrification in pre-denitrification filter and membrane bioreactor,and analyzed the feasibility of the two treatment technology used for thedenitrification of reclaimed water. It is supposed to serve as a reference for thetransformation of water reclamation plant and the choose of process in new waterreclamation plant.The effect of HRT on filter nitrification performance and selection of filtermaterial of biological filter were studied. It showed that biological filter withceramsite, volcanic and activated carbon had the same start-up time. When HRT ofthe filters was18min, their nitrification rate reached the maximum, and the meanvalue were0.932kgNH4+-N/m3·d,0.883kgNH4+-N/m3·d,0.569kgNH4+-N/m3·drespectively. Effluent quality in biological filter with volcanic and activated carbonwas better than that with ceramsite. Ceramsite and volcanic had the same pricewhich was significantly lower than activated carbon’s. Volcanic was selected as theeconomical and effective filter in reclaimed water treatment process by comparison.The denitrification kinetics of denitrification filter with volcanic rocks has beendiscussed in the study, and lead denitrifying denitrification filter performance wasinvestigated. It showed that when C/N is3.21~4.70, HRT was not less than2.5min,the denitrifying denitrification performance was better. The denitrification processwas more aligned with first-order kinetics. By setting up the model ofdenitrification process in biological filter, the simulated value was consistent withactual value under the test water quality condition. Biofilters for denitrification hadcertain effect on removing of NH4+-N, the process mainly happened within the40cm from inlet, and concentration of NH4+-N remain the same after that, TN had alitter decrease along with the process. Under optimization condition, mean value ofNH4+-N、TN、COD and turbidity in the effluent of Pre-denitrification filter were0.39mg/L,1.48mg/L,11mg/L,0.74NTU respectively, SS is less than4mg/L. It meansthat the water quality meets the Shenzhen renewable water, rainwater qualitystandard. The study investigated the effect of C/N on denitrifying denitrification performance of membrane bioreactor. It showed that when C/N of influent was5.26~7.51, the denitrification performance was best with a highest denitrificationrate0.15kgNO3-N/MLSS·d. Concentration of NH4+-N, TN, COD and turbidity inthe effluent of system were0.22mg/L,1.39mg/L,9mg/L,0.12NTU respectivelyunder optimization condition, and SS was less than4mg/L.The economic and technical analysis of pre-denitrification filter with a dailycapacity of50000tons and membrane bioreactor water reclaimed plant showed thatthe cost of treating water were0.242and0.588yuan per ton, and the high cost ofmembrane module is the main cause of high operating cost of the latter. The effectof nitrogen removal are almost the same of the two process while NH4+-N and TN ofboth effluent meet the Shenzhen renewable water, rainwater quality standard.Membrane bioreactor is superior than biological filter in the protection of the waterturbidity and microorganisms.