Study On The Phosphorus Removal And The Treatment Of Sludge Pyrolysis Wastewater In A WWTP

With the development of economy, the water environment problem of our country has become more and more serious. The harmless treatment of wastewater has become one of the effective ways to protect the water environment. Jinzhong first wastewater treatment plant uses the traditional sequencing batch reactor(SBR) to treat wastewater and the low temperature pyrolysis technology to treat sludge. Owing to the demand of more stringent effluent quality standard, TP intends to be removed by synergistic chemical method, which is a kind of widely used technology as a supplement of biological phosphorus removal. The sludge pyrolysis wastewater is intended to be injected into the influent of the WWTP and to be treated in order to achieve the.harmless treatment of wastewater.At present, there is a lack of literature on the supplementary chemical phosphorus removal method, especially on the aluminum salt phosphorus removal method and their practical operations. The influence factors of biological phosphorus removal, the types of chemical phosphorus removal agent, the effect of dosage on activated sludge system and its recovery need to be studied urgently. Sludge pyrolysis is a new type of sludge treatment technology. There is little research on the composition and the treatment method of wastewater produced in the.sludge pyrolysis process. The solution to these problems will provide reference for the design and operation of phosphorus removal process in WWTP, and provide technical support for the treatment of wastewater produced in the.sludge pyrolysis process. Some conclusions are drawn from field pilot experiments and full scale experiment:Denitrification and phosphorus release can occur synchronously but phosphate accumulating organisms(PAO) began to release phosphorus obviously only after the nitrate concentrate was lower than 3mg/L during the anaerobic stage. In the aerobic stage, the oxygen supply rate only has effect on the rate of absorption of phosphorus, but has little effect on the utmost mount of absorbed phosphorus. All things considered, DO should be controlled between 2 ~ 4 mg/L. There is a high efficiency of phosphorus removal but nitrification is limited when SRT is short. Otherwise, the efficiency of nitrification is high and the efficiency of phosphorus removal is low, considering both the effect of nitrogen and phosphorus removal, the optimum SRT is suggested between 17 to 21 d.The experiment shows that the effect of PAC was better than that of PFS in chemical synergetic phosphorus removal, and the optimal dosage of PAC was 100 mg/L. The effluent TP was below 0.5mg/L. PAC had an adverse effect on both the biological anaerobic phosphorus release and aerobic phosphorus uptake. The inhibition on biological phosphorus removal increased gradually, and the biological phosphorus removal decreased obviously with the increase of the concentration of PAC. PAC mainly disturbed Ammonia-Oxidizing Bacteria(AOB) during the nitrification process. Intermittent dosing can reduce the dosage and reduce the influence of PAC on microorganisms. The process uses an 11-day PAC addition cycle which consisted 7-day dosing and 4-day cessation of dosing. Full scale and pilot field experiments showed that adding PAC cannot immediately enhance the phosphorus removal efficiency. Effluent TP can only meet the standard after 4-6 cycles of dosing. PAC has a great adverse influence on the nitrifying bacteria, but the nitrification recovered after 3~4 days domestication. The effluent TP and SS are greatly reduced and the problem of surface scum in winter is solved by the addition of PAC.When the concentration of COD is high, the concentrations of NH3-N、TP are also high in the sludge pyrolysis wastewater derived from sludge with same water content. The concentration of pollutants in the sludge pyrolysis wastewater decreases with the increase of the water content of the raw sludge. The reduction of the pollutant concentration accelerated with the increase of the water content of the raw sludge. The pretreatment experiment of sludge pyrolysis wastewater shows that the effect of PFS is better than other flocculants and the optimal dosage was 500:1. The optimum ratio of sludge pyrolysis wastewater to influent of the WWTP is 4%, which has no impact on the WWTP operation.