Study On The Operation Efficiency And Influencing Factors Of Hydrolysis-acidification In The Advanced Process—ha-a/a-mco

With the development of wastewater biological treatment, the problem of sludge should not be overlooked, so it is important to develop low sludge yield processes. Moreover, along with eutrophication aggravating, nutriment removal, such as nitrogen and phosphorus, has become a most important mission for municipal sewage treatment plant. Therefore, a new sludge reduction process is developed——hydrolysis–acidoge -nosis - Anaerobic/Anoxic- Multistep Continuous Oxic tank (HA-A/A-MCO process for short), which is composed of hydrolysis-acidification unit, Multistep Continuous aeration A2O process,side stream phosphorus removal process. This paper focuses on the performance of acidification unit,study on the influence of the operating parameters,such as returning sludge type and ratioand HRT,and the environmental parameters like pH and ORP on on the hydrolysis unit sludge acidification and phosphorus release and to explore optimum hydrolysis unit operating conditions; by DGGE patterns, analysis the influence of returning sludge type on operation and types of bacteria by analysis the structural changes of the bacterial species and study the effectiveness of community structure on the impact of acidification,The results indicate that:①The sludge is reduced, VFA and phosphorus loading are increased which are beneficial to anaerobic phosphorus release ,when no matter what sludge is returned (anaerobic or aerobic sludge).meanwhile the type of returned sludge has a great influence on the VFA composition.When the return ratio of anaerobic P-release sludge entering into hydrolysis-acidification tank is about 2% of influent flow, the amount of VFA from hydrolysis acidification process reaches the maximum (275mg/l), the proportion of acetic acid and propionic acid reachs 70%, Which is the max,and the phosphorous content from anaerobic release reaches the maximum (42 mg/l). When the return ratio of anaerobic P-release sludge entering into hydrolysis-acidification tank is about 1% of influent flow, the sluge reduction is the maximum (70%). With the increase of the returning sludge rate, the reduction rate reduced. Comprehensive consideration of phosphorous release and sludge reduction 2% is the best, which is the returning sludge ratio.②The variation of HRT is reached by changing the volume of the hydrolysis-acidification tank. when HRT=1.5h,some sludge is pushed away from the tank, which makes the sludge lower.so the reaction time between bacteria and substrates reduces,which go against hydrolysis-acidification. For the character of the tank, the hydrolysis-acidification efficenecy does not go higher with the higher HRT(when HRT>2.5h). The varition of sludge reduction ratio with the HRT is the same as the varition of COD and VFA with the HRT. the varition of acid proportion with the HRT can be overlooked.so the phosphorous realease efficenecy is positively correlated with the VFA yield,that is higer VFA yield is helpful to the phosphorous realease,with this in mind,HRT=2.5h or 3.5h can be chosen,while,for effective utilization of the tank volume,HRT=2.5h is better.③Changing pH, the habitats of the bacteria can be changed. Thereby affecting the growth of microbes and enzymes activity and thus affecting hydrolysis efficiency. In this study, when pH = 8, the activity of micro-organisms and enzymes are the highest. So the VFA is the highest, which is 339 mg/L.Changing the pH, also can affect the dominant species of microorganisms, so that the acetic and proportion of VFA changes. The pH is lower, the propionic acid content is relatively higher; while butyrate acid on the contrary. For the anaerobic phosphorus release, the VFA required by unit phosphorus release, it not only relate to the proportion of the acetic and propionic in the VFA but also to the influent pH changes. improving influent pH aslo can enhance the phosphorus release.④The changing of ORP in the habitat affects the growth and the activity of microbes and has impact on the hydrolysis and fermentation.when ORP =- 230mV, the activity of microbial and enzyme are the relatively highest, the efficiency of hydrolysis and acid production are the highest,so does sludge reduction rates. ORP changes,the proportion of each acid changes. ORP higher, the propionic acid content is relatively higher;while butyrate acid on the contrary.Considering that higher ORP is not beneficial to acidification bacteria growth,so, the ORP should be maintained at a lower level.⑤the bacterial community structure is analyzed by DGGE fingerprinting,the results show that: returning anaerobic p-release sludge enriched the bacterial community diversity of hydrolysis-acidification tank and it has higher strains similarity while returning aerobic sludge could result in impairing its bacterial community diversity and has lower strains similarity, consequently, it induces that the acid production effect of hydrolysis-acidification tank with aerobic sludge being returned into was worse than that of hydrolysis-acidification tank with anaerobic p-release sludge being returned into. In summary, HA-A/A-MCO process can achieve higher efficiency of sludge reduction and phosphate release.The studied results is provided with strong innovation, important academic meanings and practicality value.