Depth Treatment Of Urban Sewage

A small urban sewage treatment plants, effluent ammonia design specifications duringsummer was5mg/L, in winter was8mg/L. But the river discharge standards was2mg/L.Even this plant effluent discharge standards, it can not meet the rivers emissions standards.Excessive ammonia can cause a range of problems. For example cause eutrophication. Algalblooms, resulting in decreased dissolved oxygen in the water, seriously affected the normalgrowth of aquatic organisms, and even death, especially for aquaculture, it will causeirreparable economic losses. It will also cause some harm to the environment, this is not onlyaffects the appearance, but also will produce odor and so on, causing adverse effects on theenvironment, and even damage the ecological balance. Finally, the high ammonia wasoxidized to nitrite after entering the groundwater system, it would causing adverse effects tohuman health, if have a long-term drinking. Thus, the sewage plant effluent needed a depthtreatment in order to achieve the purpose of reuse.A/O process have a simple system, Low running costs and small footprint. It put rawsewage in organic carbon and endogenous metabolites as a carbon source, saving the cost ofadding external carbon. The aerobic tank in the back, the organic matter can be furtherremoval. Because denitrification consume some organic carbon, it reduce aerobic tank load.Alkalinity produced by denitrification can compensate consume nitrification process. Biofilmhave a strong adaptability on water quantity, water quality, water temperature changes. It havea good effect and with good nitrification function.It have a small amount of sludge and easy tosolid-liquid separation. And a small power cost. Biological fluidized bed have a highconcentration of biological solids. Water residence time is shortened by the high volume load.It does not exist sludge bulking problem and clogging. It can adapt to different waterconcentration range and have a small covers. Using the sand as a filler, the concentration was2000mg/L. Sand have a large surface area, structural stability, ease of microbial growthcharacteristics. Therefore, this paper uses A/O technology combined with biofilm andbiological fluidized bed process for municipal sewage plant secondary sedimentation tankeffluent in-depth treatment. After treatment the ammonia can reach the river dischargestandards2mg/L or less. When the depth treatment by biofilm, TN hardly reduced and water pH declined.When using the activated sludge process, the temperature is30℃, influent ammoniacontent of15mg/L, the effluent ammonia content of5mg/L. The use of biofilm process,ammonia can be reduced to2mg/L or less even to zero from20mg/L. For summer effluentammonia5mg/L can be reduced to2mg/L or less. At this moment the biofilm mass ratio ofthe filler was0.6%. When the temperature is24~23℃, biofilm can removal ammonia from20mg/L almost to zero, then the maximum processing capacity of22mg/L. When thetemperature is22℃~18℃, the process can remove11mg/L of ammonia. When thetemperature is17℃~15℃, the process can remove10mg/L of ammonia. When thetemperature is12℃, the process can handle8mg/L of ammonia. Winter effluent ammonia8mg/L, can be reduced to2mg/L or less.Using SBR reactors, with chiller control the temperature. Research on the impact oftemperature changes of activated sludge. The results show that the temperature rise was twodays gradually increased from16℃to20℃, respiratory rate did not change, COD removal isnot affected, and no change in effluent ammonia. Moment when the temperature rises from16to20℃, respiratory rate accelerated, the degradation rate of ammonia accelerated, CODremoval unaffected. Instantaneous temperature decreases from20℃to16℃, the respiratoryrate and ammonia degradation rate has declined, COD removal unaffected. The respirationrate is low when running in a high DO.