Enhanced Nitrogen And Phosphorus Removal By Combined Process Of BAF And Multi-soil-layering Biofiltration

This paper based on a novel solid-phase denitrification technology，namelyutilizing water insoluble and biodegradable polymer poly butylene succinate (PBS)as the carbon source and biofilm carrier of denitrifying bacteria. The research used anew combination process of biological aerated filter (BAF)+multi-soil-layering(MSL) system，and a two-stage biological aerated filter based on ceramic and PBS，for domestic wastewater and municipal secondary effluent treatment of enhancednitrogen and phosphorus removal.The combined process of BAF+MSL was designed for purifying domesticwastewater. PBS and sawdust were used as carbon source in MSL-1and MSL-2，respectively. Comparative studies on performance of nitrogen and phosphorusremoval between MSL-1and MSL-2were also investigated. The result showed thatthe average removal efficiency of SS and COD were94.08%and80%，respectively，and the COD concentration in the effluent was below20mg/L. The influence of HLRon denitrification of MSL was more significant than that on nitrification of BAF.When the HLR of BAF were0.5，1and2m~3/m~2/d respectively， the removalefficiency of NH4~+-N was above90%，and the TN removal efficiency were26.53%，11.09%and5.71%，respectively. The corresponding HLR of MSL were0.25，0.5and1m~3/m~2/d，the TN removal efficiency of MSL-1were87.39%，65.09%and45.56%，respectively，while the removal efficiency of MSL-2were61.51%，42.52%and31.32%，respectively. Although the TN removal efficiency of MSL-1was better thanthat of MSL-2，the TP removal efficiency of MSL-1was similar to MSL-2. As theHLR increased，the TP removal efficiency reduced. The highest average TP removalefficiency of MSL-1was91.97%.BAF+MSL combined process was used in different hydraulic loading rate(HLR) for municipal secondary effluent treatment of enhanced nitrogen andphosphorus removal. Comparative studies on performance of nitrogen andphosphorus removal between MSL-1and MSL-2were also investigated. The resultshowed that the TN concentration of effluent from MSL-1and MSL-2underdifferent HLR was below15mg/L，which can meet the first class of A standard.With the HLR increased form0.5m~3/m~2/d to1m~3/m~2/d and2m~3/m~2/d，the removalrate of TN decreased gradually. During the three stages，the TN removal efficiencyof MSL-1were73.28%，63.20%，39.97%，respectively，while the TN removal efficiency of MSL-2were44.99%，36.64%，22.23%，respectively. However，theremoval efficiency of phosphorus between MSL-1and MSL-2had little difference.When the HLR is less than1m~3/m~2/d，the effluent concentration of TP was below1mg/L，which can meet the first class of A standard. With the HLR increased，the TPremoval efficiency of MSL-1were83.31%，74.99%，57.08%，respectively，whilethe TP removal efficiency of MSL-2were83.74%，72.40%，52.46%，respectively.A two-stage biological aerated filter based on ceramic and PBS，for domesticwastewater treatment of enhanced nitrogen removal was also investigated. Theresults showed that the hydraulic residence time (HRT) has greater effect on the TNremoval efficiency. When the HRT were120min and90min， the TN removalefficiency could reach above80%，while the HRT were60min and30min，the TNremoval efficiency rapidly decreased to50%~60%. With the HRT decreased，theeffluent TN removal efficiency were3.12mg/L，8.62mg/L，11.24mg/L，respectively，which can meet the first class of A standard from “Discharge standard of pollutantsfor municipal wastewater treatment plant”.