Effect Of External Carbon Source On Urban Sewage Treatment With AOA-SBR Process

Along with the construction and development of modernization in China, the quantity of sewage treatment needs is increasing. Hence, the sewage treatment and reuse of city water have become urgent problems to be solved as soon as possible. At the same time, with the quantity of nitrogen and phosphorus content in sewage rising, our country and some areas have enacted higher standards on emissions of nitrogen and phosphorus. However, it is difficult to achieve the level of emissions of nitrogen and phosphorus at the same time for the current technology. This means treatment methods of sewage require more innovations and researchers need look for more efficient processing technologies.Because of the development of industrialization and urbanization rapidly in China, sludge production in urban sewage plants is more and more increasing. The untreated sludge is huge and has become heavy burden for the sewage plants. Therefore, how to utilize this part of surplus sludge into supplying system becomes a topic of increasing concern. The alkaline hydrolysis of sludge is significance of residual sludge resource utilization exhibition, which has a far-reaching development.SBR process with anaerobic/aerobic/anoxic mode operation (AOA-SBR process) is a new type of water treatment, because the competition between nitrifying bacteria and phosphorus accumulating bacteria on carbon sources that can simultaneously achieve better treatment effect of nitrogen and phosphorus removal, now has become a hot research at home and abroad.This experiment adopts the AOA-SBR technology system of urban sewage treatment for studying the influence on the effect of nitrogen and phosphorus removal system though sludge age (SRT) and carbon source (sodium acetate and micro oxygen alkaline hydrolysis and acidification sludge supernatant). The water inlet is the use of artificial water distribution, water quality concentration of COD is 400mg/L, the concentration of ammonia nitrogen is 60 mg/L, and the concentration of phosphate 7mg/LThe experiments’ results are as follow:(1)In the AOA-SBR system, SRT had little influence on the degradation of organic substance, but the effect of ammonia nitrogen removal rate increases with the increases of SRT, and the influence on the removal of phosphate has an obvious effect. This showed that the time period can have an adverse effect on the system no matter too long or too short. When the SRT is 15d, the sludge concentration is too low; the release of phosphorus incompletely inhibits the phosphorus removal. When SRT> 20d, the exhibition is that the SRT is too long so that the water content is high. This will appear sludge "autolysis" phenomenon, affecting phosphorus removal system. In summary,20d-25d is the most suitable.(2) AOA-SBR system on COD, ammonia nitrogen, total nitrogen and phosphate removal rate were improved significantly after adding sodium acetate to the reactor. However, the effluent phosphate concentration decreases. When sodium acetate dosage was 15mg/L, the parameters of the system could reach an A standard of "the outlet concentration of urban sewage treatment plant pollutant discharge standard" GB18918-2002. When the dosage was 30mg/L, anaerobic phosphorus release, phosphorus absorption in aerobic zone and anoxic phosphorus denitrification rate were all the largest, which could up to 3.54 mgPO43--P/(g MLSS h),2.54 mgPO43--P/(g MLSS h) and 1.53 mg NO X-N/(g MLSS h). When sodium acetate dosage was 9mg/L and 15mg/L, denitrifying phosphorus removal phenomenon appeared and anoxic phosphorus denitrification rate were 0.36 mgPO43"-P/(g MLSS h) and 0.02 mgPO43--P/(g MLSS h), respectively. In summary, the best dosage of sodium acetate is 30mg/L; the system will be more stable and reliable operation.(3) AOA-SBR system on COD, ammonia nitrogen, and phosphate removal rate were improved’ significantly after adding the supernatant after micro aerobic alkaline hydrolysis and acidification of seudge to the reactor. In addition, the phosphate removal rate increases with the supernatant dosage increasing. When the supernatant dosage is 30mg/L,export concentration of COD, ammonia nitrogen, phosphate and total nitrogen were the minimum, which were 13.33 mg/L,037mg/L,11.91 mg/L and 0.33mg/L, respectively which were in line with the a A standard in "urban sewage treatment plant pollutant discharge standard" GB18918-2002. When the supernatant dosage is 18mg/L, in this system, anaerobic phosphorus release rate was the maximum that was 1.02 mgPO43-P/(g MLSS h); nitrite nitrogen accumulation phenomenon was obvious that up to 2.18mg/L; the effect of denitrifying phosphorus removal in anoxic section was also obvious. Phosphorus uptake rate was 0.39 mgPO43--P/ (g MLSS h). When the supernatant dosage is 30mg/L, phosphorus uptake rate in the system in the aerobic zone reach the highest, which was 0.54 mgPO43--P/(g MLSS h); denitrification rate in the system in the anoxic section was maximum, which was 0.50 mg NO x-N/(g MLSS h). In summary, the optimal dosage of the supernatant of microaerobic alkaline hydrolysis and acidification of sludge is 30 mg/L.