Development Of High Phosphorus Sludge Carbon Source Based On Recomag Technology

At present,the sewage treatment plant faces the problem of insufficient carbon source in the running water during operation.The insufficient carbon source limits the deep treatment of low C/N ratio sewage nitrogen and phosphorus removal.The sludge can produce a large amount of VFAs in the process of anaerobic acid production.VFAs can be used as a carbon source in the process of strengthening biological nitrogen and phosphorus removal,and solve the problem of insufficient carbon source in the process of nitrogen and phosphorus removal in wastewater treatment plants.Therefore,the development of internal carbon sources has increasingly become a research hotspot in recent years.The ReCoMag technology can produce high-phosphorus sludge rich in a large amount of organic matter,and is a good fermentation substrate.In this study,the ReCoMag sludge was taken as the research object,and the optimum temperature,hydrolysis time and optimal residual sludge addition ratio of the ReCoMag sludge hydrolysis acidification were determined by experiments.On this basis,a pilot test of ReCoMag sludge semi-continuous flow was initiated.Based on its stable operation,the relevant denitrification rate test was carried out.Finally,through high-throughput sequencing,the distribution of microbial population during the stable operation of ReCoMag semi-continuous flow was analyzed,and the mechanism of ReCoMag sludge fermentation was elucidated from the perspective of microorganisms.The main conclusions of the pilot study are as follows:（1）The fermentative acid production performance of ReCoMag sludge at four temperatures of 20,25,30 and 35℃was investigated.The results show that the increase of temperature accelerates the hydrolysis and acidification of the ReCoMag sludge,which is manifested by the increase of the peak of SCOD and VFAs and the faster output of the maximum concentration.The anaerobic acid production of the ReCoMag sludge is accompanied by the release of N element,and the higher the temperature,the more the release of N element.Due to the presence of PAC（polyaluminum chloride）in the system,there is no precipitation of phosphate.Considering that when the temperature is 30℃it can provide more SCOD and avoid excessive N and P loads.The study also found that at30℃,the concentration of SCOD increased gradually in the first 3 days,and after 3 days,the concentration gradually decreased,so the optimum hydrolysis time was 3 days.（2）The control showed was two different excess sludge on the hydrolysis and acidification of ReCoMag sludge were studied.The results showed that the dissolved amount of mixed sludge SCOD and VFAs increased with the increase of In addition,there is also the release of N element,and the more inoculated amount of excess sludge,the more N element is released;for the excess sludge W1（dewatered sludge of the sewage plant）,there is no release of P element,for W2（A secondary sedimentation tank sludge for enhanced biological phosphorus removal pilot test）is accompanied by a relatively obvious release of P element.Considering the effect of excess sludge on the hydrolysis and acidification of ReCoMag sludge,It is found that when the inoculation amount of excess sludge W1 and W2 is 12.2%and 13.6%,respectively,it can provide more SCOD for the system and avoid high N load.（3）Using CSTR reactor to control the initial SRT=3 d,by continuously shortening its SRT（2 d,1 d）,after 40 d,two parallel ReCoMag sludge semi-continuous flow tests were successfully initiated.The effluent indicator tends to be stable.The results showed that the concentration of SCOD was stable at 1200 mg·L^-1,VFAs were stable at 380mg·L^-1,NH₄⁺-N was 150 mg·L^-1,and TN concentration was 160 mg·L^-1.Due to the presence of PAC in the system,there is no precipitation of phosphate.After the adaptation and growth of the first two stages,the number of hydrolyzed acidification bacteria has increased greatly.When the load is increased,the acid-producing bacteria can continue to grow and reproduce.Thus,the hydrolysis time of the ReCoMag sludge was successfully shortened to 1 d.（4）In the stable operation stage of anaerobic small test,the mud entering No.1 was changed to the mixed sludge of ReCoMag and excess sludge at 40 d,and the VSS of the ReCoMag equipment was improved due to the shutdown of the water plant.Therefore,the indexes of the two reactors have increased greatly.The concentration of SCOD on the2nd is 1600¹900 mg·L^-1,and the concentration of NH₄⁺-N fluctuates between 160¹90mg·L^-1.There is no P element.The precipitation.The concentration of SCOD 1 increased to 2100 mg·L^-1,the concentration of NH₄⁺-N increased to 220 mg·L^-1,and the concentration of soluble TP in the supernatant was finally stabilized at 8⁹ mg·L^-1.The conclusions of the previous batch test were verified.（5）The product of anaerobic hydrolysis/acidification of ReCoMag sludge is used as the denitrification carbon source,which is compared with the denitrification rate of other carbon sources.The concentration of SCOD of the added carbon source is the same as that of the raw water,which belongs to low C/N.Denitrification rate study in the case of the case.The results showed that the denitrification rate of sodium acetate was the highest,2.15 mg/（g·h）.The denitrification rate of anaerobic hydrolysis/acidification product of ReCoMag sludge is about 1.7 mg/（g·h）,which is 1/3 and 3/4 higher than that of glucose and anhydrous methanol,respectively.The rate of nitrogen removal from carbon sources in water is increased by 3/5.Although the denitrification rate of anaerobic hydrolysis/acidification product of ReCoMag sludge is lower than that of sodium acetate,it is higher than glucose,carbon source in raw water and anhydrous methanol,which can be used as high-efficiency carbon in dephosphorization and dephosphorization source.（6）The microbial colony structure in the system was studied by high-throughput sequencing.The results showed that there were many microbial species in the two kinds of sludge,among which Firmicutes、Proteobacteria and Bacteroidetes were the dominant species.Among them,the three strains accounted for 79.15%of the total bacteria,and the proportion of the 2nd was 78.87%.In the stable operation stage,the main bacteria in the No.1 reactor,Saccharofermentans and Levilinea,are acid-producing bacteria with good acid production performance.The main genus in the No.2 reactor is Trichococcus,Levilineawei,Bifidobacterium,etc.,and all three dominant genus are acid-producing bacteria.