Design And Experimental Study On Operation Performance Of The Integrated Sewage Disposal Process

In recent years, with the expansion of medium-and-small-sized towns, there is more and more urban wastewater which is discharged into the environment at high increasingly rate. However, the construction and operation of the corresponding sewage treatment facilities far lag behind the requirement of the situation. Therefore, the construction of sewage treatment facilities in medium-and- small-sized towns will grow at high speed within some time of future, and it has great market prospect to develop the sewage treatment technology suitable for medium-and-small-sized towns. According to the social economic and sewage characteristic of the medium-and-small-sized towns and the problems of typical sewage disposal crafts, a new kind of integrated sewage disposal process was put forward. And a series of experiments were designed to study the operation performance of the integrated precess.Firstly,the research has investigated the start-up and treatment performance of the integrated process. The experiment indicated the method that accomplished the forming bio-film by draining the sludge fast and then adding the acclimated activated sludge was feasible to start the integrated precess. Based on theoretical analysis and experiments, the optimum operational condition of system was recommended that DO should be controlled at the range of 2~3mg/L in the first aerobic area and 3~4mg/L in the second aerobic area, and recirculation ratio should be controlled at 200% with HRT of 12h as well as SRT of 10d. Under the optimum condition for long-period operation, the integrated precess appeared to be very effective to eliminate pollutants from wastewater with COD removal of 89.0%, NH3-N removal of 86.7%, TN removal of 73.0% and TP removal of 73.2%. The concentration of COD, NH3-N and TN of the effluent met Category B, Class 1 specified in (GB18918-2002).In order to confirm the serviceability of the integrated process,the research has investigated the treatment performance of the integrated process under especial conditions such as low concentration wastewater, load shocks and low temperature. The experiment indicated the integrated process had perfect treatment efficiency on wastewater with low concentration, and the concentration of COD, NH3-N and TN of the effluent met Category B, Class 1 specified in (GB18918-2002). When load shocks happened, the integrated precess could be steady in removal of COD, which showed its strong shock resistance ability. The integrated precess also had good stability that the performance of system can be recovered within 4h following 400% of hydraulic load lasting 2h. Low temperature had a weak influence on the removal efficiencies of COD and TP. The removal of COD and TP reached to 85.8% and 63.3%. However, biological nitrification and denitrification were weak under the low-temperature condition that the removal of NH3-N and TN dropped to 43.5% and 35.9%. The experiment demonstrated that the denitrification efficiency was increased with the increasing of SRT. When SRT reached 20d, the removal of COD, NH3-N, TN and TP reached to 86.2%, 54.1%, 44.7% and 62.8%. Increasing SRT appropriately was an effective method that could improve the operation performance of the integrated precess under the low-temperature condition.The integrated precess is based on the traditional A/O process and it makes full use of the advantages of both activated sludge and biofilm process. With aerobic area partitioned, the integrated precess integrates reaction zone and sedimentation zone together into one unit. So the integrated precess is characterized by compact structuret, less land use, less investment for construction, and simple operation requirement. The experiment showed that the integrated precess had high removal efficiencies of COD and could remove NH3-N and TN efficaciously at the same time. The integrated precess is apt to be made into the apparatus, and suitable for medium-and-small-sized towns.