Research On Upgrading Technology Of The Oxidation Ditch In Small-town Wastewater Treatment Plant

Improved Carrousel oxidation ditch process was adopted in the first-stage project of a small town sewage treatment plant of C hongqing, and the effluent quality comply the first level B discharge standard. In actual operation, and the effluent quality of TN 、NH3-N can not meet the required standard as a result of the changes of water quantity, water quality and aeration equipment problems. Design is upgraded through the scene reconnaissance and summary of current problems, improving the process of aeration mode, reflow method, tank volume expansion and so on, O xidation ditch process is transformed into bottom aeration oxidation ditch. Reconstruction project was completed in the end of March 2014 and the put into operation. After 3 months of debugging and running, water quality tends to be stable gradually, and to reach B standard on level 1 of《the town sewage treatment plant pollutant discharge standard》(GB18918-2002). Stable operation parameters as follows: about 8:1 gas water ratio, the reflux ratio inside is 100% ~ 150%, the mixture of sludge concentration is 3000 ~ 4000 mg/L, the reflux ratio outside is approximately 70%.This paper analyzes the debugging and running results of the sewage plant and the impact on the sewage treatment plant under the condition of winter low temperature.When the B sewage treatment plant is running at high temperature(20 ~ 25 ℃) in summer, The SS,BOD5, CODcr, N H3-N, TN, TP of effluent average are: 13.74 mg/L, 5.71 mg/L, 24.12 mg/L, 1.69 mg/L, 12.84 mg/L, 0.24 mg/L, better able to reach the level of B standard; When the B sewage treatment plant is running at low temperature(13 ~ 16 ℃) in winter, the average index of effluent are: 14.63 mg/L, 5.97 mg/L, 28.14 mg/L, 3.93 mg/L, 15.97 mg/L, 0.48 mg/L, fundamentally able to reach the level of B standard. NH3-N, TN removal efficiency are greatly influenced by low temperature in winter.The distribution of dissolved oxygen is analyzed cross section of the oxidation ditch.The dissolved oxygen distribution characteristics of the oxidation ditch are that the DO concentration of anoxic pond range from 02.to 0.5 mg/L, aerobic pond meet the aerobic condition both in winter and summer running, the DO concentration in winter is higher than the summer.The change of all pollutants along the oxidation ditch, CODcr and NH3-N are mainly removed from D section to F section in the aerobic pool, TN is mainly removed from A section to C section in the anoxic pool, TN concentration basically remain unchanged in the aerobic pool.The pollutant removal efficiency, pollutant reductions, energy consumption, operation cost, etc, Which are before and after the upgrade of the sewage plant,are compared and analyzed in terms of technology, economy and environment of the applicability of the small town sewage treatment. After the upgrade, the CODcr, NH3-N, TN of the effluent average monthly respectively reduced 7.97 mg/L, 13.9 mg/L, 8.97 mg/L; The water quality of effluent was reduced by 26.11%, 90.91% and 26.11% respectively; Compared to cut before the upgrade,Which is by the transform of 103.9 tons/month, 2.11 tons/month, 5.61 tons/month to increase to 123.1 tons/month after reforming, 6.99 tons/month, 7.14 tons/month, cut growth is 18.5%, 231.0% and 21.4% respectively; The unit power consumption of sewage processing is 0.60 k W·h/ m3 before modification,fell to 0.37 k W·h/ m3 after the upgrade, saving about 38.3% of the electricity.The running cost of the sewage treatment plant is 2.495 yuan/m3 before modification, lowered to 1.937 yuan/m3 after the upgrade, saving 22.4% of the cost. Look from the cumulative total cost, That can save ￥6159 yuan monthly on average. Greatly saving the running cost.That Should be paid attention in the debugging of sewage plant running are control alkalinity of wastewater, dissolved oxygen,organic load of inflow, reflux ratio inside, the ratio of BOD5 and TKN, discharge of excess sludge, sludge load and sludge age, etc, At the same time, the water turbidity of the second pond, biological foam, sludge bulking problem should be prevented.The long-term productive experiment showed that Bottom Aeration O xidation Ditch is effective and stable. and the effluent quality of TN、NH3-N can meet the first level B discharge standard stably.It possesses strong anti-shock loading capability.