Nitrogen And Phosphorus Removal Mechanisms Of The Sidestream Activated Sludge Process Based On Diverse Inlet Carbon Sources

In order to deal with the challenges faced by conventional mainstream activated sludge process,such as insufficient carbon source,low carbon source utilization,excess sludge,etc.To improve the removal of nitrogen and phosphorus from wastewater,the sidestream activated sludge process has been applied to sewage treatment projects around the world.As an important factor affecting activated sludge process treatment-carbon source,the hydrolysis and metabolism of sewage organic carbons affect the nutrient removal mechanism of sidestream activated sludge process.current papers are mainly based on simple carbon sources(such as sodium acetate,glucose,etc.),and the research on multi-carbon sources based on sidestream activated sludge plant is insufficient.Therefore,Diverse carbon sources similar to the composition of actual domestic wastewater(including simple carbon sources of sodium acetate,macromolecular carbon sources of glucose,starch,peptone,soybean oil and their combination)were therefore used to explore the hydrolysis and metabolism behaviors as well as microbial community changes in a sidestream activated sludge process(mainstream A/O coupled with sidestream anaerobic reactors、mainstream A/O/A/O coupled with sidestream anaerobic reactors).Nitrogen and phosphorus removal mechanisms were also discussed in the case of complex carbon sources.Phase one(mainstream A/O coupled with sidestream anaerobic reactors),The nitrogen removal efficiency of the sidestream activated sludge process was less than80%,whereas the phosphorus removal efficiency was generally above 90%.Despite of different removal efficiencies.Despite the sequencing results showed that the abundance of Nitrogen and phosphorus removal flora was low,the removal of nitrogen and phosphorus was realized in each reactor.nitrogen and phosphorus removal mechanisms may be attributed to a common assimilation process in the mainstream aerobic stage.The changes of mainstream VFA,PHA,and glycogen concentrations indicative of the process of carbon hydrolysis and metabolism could reveal the extent to which nutrients were assimilated aerobically and released anaerobically.The inclusion of the sidestream anaerobic reactor in this study did not significantly improve the nitrogen removal performance of the mainstream single stage A/O process or increase the relative abundance of phosphorus accumulating bacteria.Nevertheless,it may enhance the sludge hydrolysis and nutrients release in the system,which furnish the rapid hydrolysis of mainstream macromolecular carbon sources with ample hydrolytic microorganisms.Phase two(mainstream A/O/A/O coupled with sidestream anaerobic reactors),The nitrogen removal efficiency of the sidestream activated sludge process was significantly improved compared with the Phase one(60%-100%),and the phosphorus removal efficiency was generally higher than 80%.Although The nitrogen removal efficiency was improved compared with the Phase one,the abundance of denitrification bacteria did not increase significantly.Traditional phosphorus accumulating bacteria were almost not detected in each reactor and lack of significant anaerobic phosphorus release phenomenon.The changes of VFA,PHA,glycogen and total phosphorus may not be coupled with the classical metabolic pattern of phosphorus accumulating bacteria,but as the indexes of hydrolysis and metabolism of carbon sources.The anaerobic sidestream reactor may enhance the effective enrichment of other functional phosphorus removal bacteria(Pseudomonas and Aeromonas)by promoting the rapid hydrolysis of organic carbon in wastewater.Fermentation of polysaccharides,proteins,and lipids in mainstream and sidestream reactors produces a range of organic compounds,resulting in a more complex variety of organic compounds and a greater diversity of microbial communities and their corresponding abundance in wastewater treatment compared to the composition of effluent.