Integration Of Biological Nutrient Removal Device And Its Treatment Of Domestic Wastewater

The tranditional biological removal process of phosphorus and nitrogen has the disadvantages of high construction cost and equipment investment,more land occupation,high cost to operate and the requirement of multiple units to realize the recycle of swedge and nitrate solution. In the study, an integrated A/O equipment was designed based on the principle of A/O process and a batch of laboratory experiment. This equipment was used for the disposal of sewage on pilot experiment. The disposal efficiencies of phosphorus and nitrogen were investigated at 1 m3/h of influent rate,200% of sludge reflux ratio,5-8 h of total hydraulic retention time and 4-14℃of water temperature. The microbial characteristics of active sludge were determined by using an electron microscope. In addition, bases on comparing the performance of the integrated A/O equipment with the other typical biological removal processes, the project investment and operation cost of the integrated A/O equipment are analyzed. The following results were obtanied:(1)After two weeks operation, the concentration of TP, TN, NH4+-N, CODcr, BOD5 declined from 4.2-12.9 mg/L,40-80 mg/L,8.96-30.68 mg/L,150-450mg/L and 43-96 mg/L in influent to 0-2 mg/L,10-20 mg/L,0-5mg/L,0-50 mg/L and 0 to 20 mg/L in effluent. The results indicate that the integrated A/O equipment can steadily operate, and have high capacity of resisting impact load.(2) During the stable operation procedure, the average removal efficiencies of TP, TN, NH4+-N, CODcr and BOD5 were 86.7%,69.5%,80%,84.7%,84.9%, respectively. TN, NH4+-N, CODCcr and BOD5 can come up to the first level standard of "Discharge standard of pollutants from municipal wastewater treatment plant" (GB 18918-2002) and TP meets the reqirement of the second level standard of "Discharge standard of pollutants from municipal wastewater treatment plant" (GB 18918-2002).(3)There was few filamentous bacterium in active sludge in the integrated A/O system, implying the sludge has good setting ability. A lot of protozoa and metazoa were observed, indicating there is a high acitivity of sludge to keep high performance and treatment efficiency of sewedge in the integrated A/O system.(4) The energy consumption of the integrated A/O system was 0.104 kw·h/m3,which can save energy by 20% as comprared with the traditional treatment processes.Moreover, the integrated A/O equipment can link aerobic zone, anaerobin zone and sedimentation zone, which have a compact equipment constructure. The occupied area was 1.3m2 per one ton waste water, which can save land area by 9.1-48%.(5)As compared with the traditional sewage treatment technologies, the integrated A/O system has advantages of automatic backflow of sludge, less land occupation, and easy management and high capacity of resisting impact load. It can be applied to treatment of domestic waste water discharged from residential communities, tourist attractions and townlets where network drains can not or be difficult to extend.