| This topic is based on a new homemade Fe2O3 nanoparticles modified sand called NMS (Nano-Modified Sand). NMS being filled in conlander bag and being ultilized in Biological pretreatment was called BNMSC(Biological Nano-Modified Sand Conlander).NMS was also uesed in subsequent biological filter material called BNMS(Biological Nano-Modified Sand). A new process called ’Combined Process’ was combined with BNMSC pretreatment,conventional coagulation-sedimentation process,and BNMS filtration.In this rerearch ’Combined Process’was ultilized to handle micro-polluted raw water in the south with the concentration of NH3-N 2.5-3.0 mg/L, turbidity 5-20 NTU, TOC 2.0 mg/L and Trichloromethane 30～45μg/L. The results are shown as follows:1. Removal efficiency to ammonia nitrogen pretreatment by BNMSC:After 7d for biofilm formation, NH3-N removal rate of BNMSC is 40%, biomass on BNMSC is 40nmol-P/g. Under the condition of continuous aeration, when the air-water ratio was 1:1, the NH3-N removal rate reached the the best,to 41%. Concentration of NH3-N in is effluent below 2mg/L.Turbidity removal rate by BNMSC is 40% when turbidity was below 10 NTU in raw water.Due to BNMSC pretreatment, NH3-N removal rate by subsequent conventional coagulation -sedimentation process increased 15%. Biofilm formation period in BNMS filter reduced to 8 days, otherwise which is 12 days without BNMSC.2. Ammonia nitrogen removal efficiency under the best filter speed:The best filter speed of BNMS is 6m/h. Removal rate to NH3-N is 92% and removal quantity of NH3-N by BNMS accounted for 45% in raw water. Turbidity degreed of BNMS effluent is below 0.1NTU. Particle size distribution Significantly decrease to 50nm when it is 200nm in raw water.And Zeta potential was dropped to-6m V when it is-17m V in raw water.The biomass in upper-middle-stratum (0 cm to 50cm) of BNMS column is plentiful,which is about 40nmol-P/g. Biomass in the surface 0 cm to 10cm of BNMS column is highest, it is 60nmol-P/g, and it is 35-40nmol-P/g in 25 to 50cm stratum,and lest than 20 nmol-P/g in middle-lower stratum.Relatively high head loss appeared in the surface (0 cm to 30cm) of BNMS column without the phenomenon of very high loss appearing and short cycle filtration cycle. The head loss in layers below surface from 0 cm to 1 Ocm,10 cm to 30cm,30 cm to 70cm and 70cm to 100cm were 65cm,67cm,7.5cm and 6cm.3. Removal efficiency to Trichloromethane by Combined Process:Due to the synergistic action by aeration and biological membrane adsorption in BNMSC pretreatment, Trichloromethane removal rate is more than 50% as Trichloromethane concentration is 33.81 μg/L in raw water but it was 17.0μg/L in effluent. Trichloromethane removal rate by conventional coagulation sedimentation process,BNMS filter and Ordinary quartz were 30.30%,6.0% and 4.4%.Concentration of Trichloromethane in effluent from Combined Process is 4.5μg/L.4. Removal efficiency TOC(Trichloromethane precursors) by Combined Process:TOC Concentration is 2mg/L, and Trichloromethane-formation-trend is 46μg/L in raw water. Removal rate to TOC is 7.5% and Trichloromethane-formation-trend was reduced 12.5% by BNMC pretreament. Removal rate to TOC is 25% and Trichloromethane-formation-trend was reduced 22.5% by conventional coagulation sedimentation process. Removal rate to TOC is 15.3% by BNMS filter.TOC Concentration is 1.0mg/L in effluent from Combined Process,50% lower than which in raw water. And Trichloromethane-formation-trend is 24.8μg/L in effluent from Combined Process,45% lower than which in raw water. |
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