Optimal Operation Of Cyclic Activated Sludge System (CASE) In Cold Areas For Municipal Wastewater Treatment

Qiqihar is one of our cities with higher latitudes, low temperatures and long period of ice. The whole city has only a 100 thousands m3/d of municipal wastewater treatment plant and a 200 thousands m3/d of the oxidation pond. With the continuous expansion of urban areas, increasing the amount of, the peak of urban sewage far beyond the oxidation pond can bear the load. After the economic and technical feasibility studies of the second phase of the sewage treatment plant is selected CASS.Currently, CASS process used for industrial wastewater treatment and municipal sewage treatment in lower latitudes. CASS process in the cold regions of the specific operating parameters and operation mode needs further study. The research project of urban sewage was treated, building a small test system of CASS process to simulate the Phase II for the southern suburbs of the sewage treatment plant in Qiqihar. Through experimental research, changes in operating parameters investigated on the effect of CASS Process. Get the optimization parameters for CASS process running in the cold regions. Master the characteristics of CASS process, exploring the law for degradation of organic compounds and nitrogen and phosphorus removal.Test regulates influent time, sludge return ratio, aeration time, ratio of reaction zone, water filling ratio, SRT and DO. The results showed that COD and ammonia nitrogen by the minimal impact of various factors, both the removal efficiency is very high and very stable. Removal of total nitrogen and total phosphorus greatly influenced by various factors. Sludge return ratio, aeration time and last paragraph of dissolved oxygen aeration of greatest impact on total nitrogen removal. SRT and last paragraph of dissolved oxygen aeration of greatest impact on total phosphorus removal. Biological nitrogen and phosphorus removal is two conflicting processes. Comprehensive impact of various factors, the optimal operating parameters for the influent time 4h, sludge return ratio 100%, aeration time 2h (2h influent after aeration), biological selection, pre-reaction zone and the main reaction zone volume ratio 1:8:27, SRT 15d , the last paragraph of dissolved oxygen aeration 3.0mg/L. Under the operating conditions when the temperature dropped to around 10℃effluent standards of the indicators can still be stable. Continuous sampling of the entire cycle, the results show that two hours without aeration for influent make a lot of nitrate nitrogen removal in the reactor. Also the reducing for the concentration of nitrate nitrogen make that the Phosphate accumulating bacteria can be more fully phosphorus release. The main reaction zone also has an obvious phenomenon of phosphorus release. The total amount of phosphorus released can reach 9.5 times as large as the amount of influent phosphorus. The mode of long influent and short aerobic is conducive to the growth of nitrifying bacteria.