Study On The Carbon Source Diversion Ratio Of Modified A~2/O Process And Feasibility Of Yellow Water As A External Carbon Source

Nowadays, A2/O process has been widely used in municipal sewage treatment plants, but there is an inherent shortcoming:it is rather difficult to remove nitrogen and phosphorus simultaneously in one system, with the competition and contradictions in carbon source, sludge age and organic load among PAOs, nitrifying bacteria and denitrifying bacteria. Therefore, in order to better mitigate the inherent contradictions of the A2/O technology and to improve the efficiency of nitrogen and phosphorus removal, the thesis study the best control of nitrogen and phosphorus removal from two aspects, carbon source diversion (process improvement) and external carbon source, to provide technical support for the sewage treatment plant upgrade.In terms of carbon source diversion, the thesis proposed a modified A2/O process (A-A2/O process), which can make full use of the original influent carbon source in priority. The results show that the increasing can effectively remove nitrate in return sludge, and when the select pool water proportion Rpre-an change from10%to20%, the NO3-removal rate of selecting pool is directly proportional to Rpre-an.To some extent, setting select pool improve the effectiveness of anaerobic phosphorus release, by changing the anaerobic pond from the traditional denitrification and phosphorus removal function into specifically phosphorus release. At the same time, the removal of COD, NH3-N of A-A2/O process are very stable, efficient with different water ratio, less affected by the different water ratio. When Rpre-an is10%,15%and20%, the pilot effluent TN average is12.63mg/L,14.19mg/L and12.04mg/L, and removal efficiency is53.1%,65.4%,51.3%. Different proportion of water only changes the selection section and the anaerobic stage of TN removal percentage, did not have a greater impact on the denitrification rate. Influent proportion have a greater impact on TP removal, the greater of the water proportion Rpre-an, the more obvious effects of anaerobic phosphorus release. Anoxic denitrifying phosphorus removal exist in the three conditions, the phosphorus performance (phosphorus uptake/release of phosphorus ratio) of system achieve maximum1.38when the Rpre-an is15%, higher than the theoretical value of traditional biological phosphorus removal systems with1.20. Taken together, the most appropriate select pool water proportion Rpre-an of the pilot system is15%, under this proportion, the pilot system can achieved relatively stable, efficient nitrogen and phosphorus removal performance.In addition, COD of influent was dramatically increased when the A-A2/O process is running, the average of which is649.8mg/L meaning the pilot system is in the high-load condition. The poor performance of nitrogen removal in the high-load condition due to the limitations of aeration system and process conditions, the nitration reaction is suppressed, at a nitration rate of0.0111gNH3-N/gVSS·d, is only a third of the normal state, the effluent of NH3-N, TN sharp rise, SND exist in the aerobic stage; on the contrary, the performance of phosphorus removal is very good, the effluent TP can reach the level of1st class A standard, the high COD of influent improve a large number of carbon source to the anaerobic phosphorus release, which is helpful for phosphorus removal.In terms of external carbon source, increase the available carbon source of system, investigate the feasibility of yellow water as a external carbon source, analysis of the pollutant removal effects wih the yellow water as a external carbon source to added to the winter A/O process. The thesis found that the yellow water as a byproduct of liquor production is rich in organic acids, alcohols, lipids and the readily biodegradable organic matter content is high, it can increase the available carbon source of the system, will not increase the nitrogen and phosphorus load at the same time, is a high quality carbon source. As a external carbon source to added to the winter A/O process, the dosing of yellow water has a big effect on the denitrification effect of A/O process, the nitrification effect is both very well before and after the addition of yellow water, the average treatment effect of the NH3-N can reach the level of1st class A standard in GB18918-2002, and the dosage of yellow water has no significant effect on the nitrification process of NH3-N removal, the NH3-N removal is mainly concentrated in the front-end of aerobic stage; at the same time, the additive of yellow water increase the available carbon sources, the removal efficiency of TN and denitrification rate of anoxic zone increase with the increase dosage of yellow water, the effluent TN value is6.41mg/L with the dosing quantity of yellow water is100mg/L; the COD consumption rate will significantly decrease when the yellow water was used as a external carbon source, the carbon source utilization of pilot system increase; a significantly loss of TN exist in aerobic zone,10.2%of TN was removed in the aerobic zone by SND.