Pilot Study Of AAO Process Sewage Treatment Plant`s Operation And Control During The Rainy Season In Dianchi Lake Watershed Running Regulation

With the development of social economy and technology, water pollution has become increasingly serious in China, attracting much attention on water source. Therefore, wastewater treatment is necessary to protect water environment during the development of economy nowadays. On the east coast of Dianchi Lake, a cycling main canal to cut wastewater was established. It aimed to lead wastewater from non-point source pollution within region and municipal domestic wastewater to wastewater treatment plant or mixed water purification plant of Luolong River before emitted. During the rainy season in Kunming Province, there is large precipitation with strong rainfastness. The influent quality is also different from that of dry season. AAO technology, a conventional wastewater treatment process with simultaneous nitrogen and phosphorus removal, was adopted in wastewater treatment plant of Luolong River. It has been widely used in China, with good removal rate of nitrogen and phosphorus. The work was the mission 3 and 4 of “Key of Efficient Collection of Early Urban Rainwater and Joint Operation of Treatment Facilities”—joint operation of wastewater treatment plant and storable facilities and their mode operation research and engineering demonstration(No. 2012ZX07102-001-003). These missions belong to a sub-project of “Water Environment Comprehensive Control and Water Remediation Technology and Demonstration Projects in Dianchi River Basin” of national major projects “Water Pollution Control and Governance Technology”. Starting from abnormal inlet water of AAO technology during rainy season in Dianchi River basin, the work studied the control direction of technology under the condition of abnormal inlet water.Based on the spot investigation of wastewater treatment plant of Luolong River in Kunming Province, the work ascertained the current condition of facilities. Then, basic parameters and quality characteristics of influent and effluent of process operation was obtained by studying water quality of mixed water purification plant of Luolong River. Results showed that there was a great fluctuation of the water quality in dry season and rainy season. Therefore, it was necessary to propose this subject in proper time. In this study, pilot experimental device was reduced according to AAO technology of wastewater treatment plant of Luolong River, with a scale of 50m3/d. The same hydraulic retention time and sludge were used. The work further studied the model establishment, customization, reactor installation and operation, sludge cultivation and water impact in rainy season. Through the adjustment of key parameters in AAO, such as sludge return ratio, mixed liquid reflux ratio and aeration rate, equation relation and changing trend of effluent effect and control factors were obtained based on the analysis of data. During experiment, there was large number of chemical foam in aeration tank and sludge corruption in secondary sedimentation tank. These problems can be solved by referring to literature data and consulting experienced staff.Through pilot-scale study of AAO system in Dianchi River basin, several conclusions have been obtained under the influent condition in rainy reason:(1) During rainy season(May to September), the TN concentration of influent was 19.05±3.72mg/L. Apart from the average concentration 23.70mg/L of May and 23.70mg/L of July, concentration of other months were all below standard B of Class 1 20mg/L. TP concentration in rainy season was 1.57±0.47, higher than the discharge standard of national standard B of Class 1. Therefore, phosphorus removal of wastewater should be given prior consideration in AAO system in Dianchi River basin during rainy season.(2) In rainy season, the main means to improve the removal rate of TP was the reduction of aeration rate and sludge return ratio. There was an increase of the value of DO and decrease of biodegradability in rainy season. Reduction of aeration rate can reduce the dissolution of zoogloea particles in aerobic zone and endogenous respiration of microorganism, thus ensuring sludge settling ability. Reduction of sludge return ratio enabled to reduce bottom disturbance of secondary sedimentation tank and nitrate concentration that return sludge bring to anaerobic zone. Thus, anaerobic environment was ensured to improve removal rate of TP. Meanwhile, it can also be realized by reducing return ratio of mixed liquid.(3) Reducing return ratio of mixed liquid was also beneficial to improve removal rate of TP, which was contrary with traditional theory.(4) Using intermittent aeration to reduce the aeration rate in rainy season to two-thirds of dry reason also benefited the removal of nitrogen and phosphorus. However, further decrease of aeration rate will restrain microbial activity, thus decreasing the removal rate of TN and TP.In this work, full consideration has been paid to equipment power of wastewater treatment plant of Luolong River. Thus, the conclusions was useful in practical production.