Research On Treatment Of Tailwater From Urban Sewage Treatment Plant By Biological Activated Carbon Filter (BACF)

The tailwater from urban sewage treatment plant has low level of C/N,and has high content of nitrogen and phosphorus. It has some difficulties in removing nitrogen and phosphorus. In this paper, biological activated carbon filter (BACF) was combined with simultaneous nitrification and denitrification (SND) technology, and shortcut nitrification-denitrification technology,in order to strengthen the effect of nitrogen removal.The comparative study of BACF with different particle size filler showed that, in the same experimental conditions, during the biofilm formation and early time of sta-ble operation, the BACF both with small (diameter:(?)1.5mm, length:2-4mm, colum-nar granular activated carbon) and big (diameter:(p4mm, length:4-10mm, columnar granular activated carbon) particle size filler had highly efficient decontamination capa-bility,but the BACF with smaller particle size filler had advantage in removing contaminants than the BACF with bigger particle size filler. But during the long-term stable operation, the BACF with bigger particle size filler had more stable treatment effect. The filter of BACF with smaller particle size filler had appeared that, the phen-omenon of compaction, and the quality of effluent became worse. In order to ensure the stable opetation of technology system, reducing backwashing and backwashing cycl-e power, and reducing the energy consumtion, the follow-up experiment would use the bigger paticle size activated carbon as the filler of BACF.The experiment of BACF simultaneous nitrification and denitrification process dealing with the simulation wastewater of the tailwater from urban sewage treatment plant, showed that, the best operating condition was:T:25±1℃; the ratio of gas to water:4; DO: 2.5-3.5mg/L; hydraulic loading:9m3/(m2.d); pH:7.5-8.0; height of packing:70cm. Under this experimental conditions, the effluent of BACF was COD:10.3mg/L, NH4+-N:1.0 mg/L,TN:16.6mg/L, removal effciency was 86.7%,92.9%,36.2%. The concentration of COD, NH4+-N in effluent had meet the design requirements, but TN hadn t. BACF simultaneous nitrification and denitrification process in this experiment had some certain limitations.The experiment of Pre-denitrification BACF which was based on shortcut nitrification-denitrification technology, dealing with simulation wastewater of the tailwater from urban sewage treatment plant, showed that, the best operating condition was:T:25±1℃; pH:7.5±0.2; the ratio of gas to wate:2; reflux ratio:200%; hydraulic loading:11.3m3/(m2.d). Under this experimental conditions, the effluent of process was COD:10.7mg/L, NH4+-N:1.2 mg/L,TN:10.6mg/L, removal effciency was 88.2%,92.5%,71.2%. The concentration of COD, NH4+-N, TN in effluent has meet the design requirements. But TP concentration in effluent was 1.3 mg/L,removal effciency was 45.6%, which had t meet the design requirements. The coagulation technology should be introduced to enhance phosphorus removal.