【正文】 average velocity. Microbial oxidation process consumes dissolved oxygen in water, until the value to zero in the DO, mixture in hypoxia state. 3. The CD method and application widely in the largespan tunnel, the CRD construction method in this System, BOD degradation is a continuous process, nitrification and denitrification occurred in the same pool. Because of the limitation of structure of the oxidation ditch can be effective for BOD, but phosphorus removal denitrification ability is limited. Carrousel Moseley oxidation ditch the influence factors of biological nitrogen removal Influence factors of phosphorus removal from Carrousel Moseley oxidation ditch is primarily a sludge age, nitrate concentration and substrate concentration. Research shows that when the total sludge age of 8 ~ 10 d, the lion39。s share of the activated sludge phosphorus content is 4% of the dried sludge quantity, 11% of the quality of heterotrophic bacteria, but when sludge in sludge age more than 15 d maximum phosphorus content significantly decreased, but cannot meet the maximum phosphorus removal effect. So blindly extend sludge age (for example, 20, 25 d, 30 d d) is not necessary, appropriate within 8 ~ 15 d choose. At the same time, high nitrate concentration and low substrate concentration of phosphorus removal process. 4. Carrousel Moseley oxidation ditch existing problems and solutions Though Carrousel Moseley oxidation ditch have effluent water quality is good, strong ability to resist impact load, high efficiency of nitrogen removal and sludge is stable, power consumption province, easy to automatic control, etc. However, in the actual operation process, a series of problems still exist. Sludge bulking problem When carbohydrates in the waste water is more, N, P content in imbalance, low pH, high oxidation ditch in sludge load, dissolved oxygen concentration, dredge not free and easy to sludge bulking caused by filamentous bacteria sex。 Non filamentous bacteria mainly in wastewater sludge bulking sludge load at high temperature is low. Microbial load is high, the bacteria absorb a large amount of nutrients, because of the low temperature, metabolic speed is slow, product storage on a large amount of high viscosity polysaccharide substances, the adhered on the surface of the activated sludge in the water increase greatly, SVI value is very high, the formation of sludge bulking. Aiming at the cause of sludge bulking, can adopt different countermeasures: caused by a lack of oxygen, high water temperature, can increase air or cut into the water to lighten the load, or decrease the MLSS (control sludge return flow), reduce oxygen demand。 Such as sludge loading is too high, can improve the MLSS, in order to adjust the load, when necessary to stop water, boring exposure for a period of time。 Can be adjusted by adding the nitrogen fertilizer, phosphate fertilizer, mixture of nutrient balance (BOD5: N: P = 100:5)。 PH value is too low, but adding the lime to adjust。 Chlorine bleaching powder and liquid (% ~ % in dry sludge dosing), inhibit filamentous fungi reproduction, bined with water sludge bulking control. Bubble problem Due to water with a large number of oil, processing System can39。t effectively remove it pletely, part of the oil concentration in the sludge, turn the brush oxygen filling mixing, produce a large number of bubbles。 The sludge age slightly long, sludge aging, also easy to produce foam. With surface spray water or remove foam deforming agent, deforming agent monly used engine oil, kerosene, silicone oil, turnover of ~ mg/L. By increasing the sludge concentration in aeration or reduced air, also can effectively control the bubble. When the wastewater contains surface active material is large, easily removed by foam separation process or other method in advance. Also can consider adding a set of oil removal device. But the most important is the better water management, reduce the high oilbearing wastewater and other toxic wastewater into. Sludge upfloating problem When the oil content in waste water is too large, qualitative light, the whole System in the process of operation can39。t well control the residence time in the second pond, easy cause lack of oxygen, produce sludge upfloating decay。 When the aeration time is too long, high nitrification occurred in the pool, the nitrate concentration is high, in the second pond, prone to denitrification, produce nitrogen gas, sludge floating。 In addition, the oil content in the waste water is too large, the sludge may carry oil to rise. After sludge floating water shall be suspended, break or removal of the sludge, ascertain the reason, adjust the operation. Sludge settle ability is poor, can dosing coagulant or inert material, improve the precipitation。 Such as water load should be reduced into water or step back flow。 Such as the sludge particles small can decrease the aerator speed。 Denitrification is found, should reduce air, increasing the backflow or mud。 Sludge decay is found, should increase air, and clean up mud, hydraulic conditions and try to improve in the pool. And uneven velocity of sludge deposition problem In Carrousel Moseley oxidation ditch, for its unique mixing and processing results, the mixture must be circulating in the groove at a certain velocity. It is generally believed that the minimum flow rate should be m/s, the average velocity of sedimentary does not occur should be ~ m/s. Oxidation ditch aeration equipment generally brush turn for aeration and aeration rotary brush turns the submerged depth of 250 ~ 300 mm, submerged depth of the wheel is 480 ~ 530 mm. With oxidation ditch depth ( ~ m), pared to brush only 1/10 ~ 1/12 of the water depth, turntable also accounts for only 1/6 ~ 1/7, so the oxidation ditch caused by upper flow velocity is larger (about ~ m, or even more), and at the bottom of the flow rate is small (especially in depth below twothirds or 3/4,