Effect of granular matrix on functional flora in EBPR system

Abstract

Enhanced biological phosphorus removal (EBPR) is a very mature phosphorus removal technology, but there is still a problem of unstable treatment effect in the operation of actual wastewater treatment plants, so the study on the effect of phosphorus removal performance still needs to be further studied. Because there are a lot of granular matrix in municipal wastewater, it occupies an important proportion in the total Chemical Oxygen Demand (COD) of municipal wastewater, and the fluctuation of granular matrix concentration is also related to the instability of phosphorus removal effect. Therefore, it is of practical guiding significance to further explore the influence of granular matrix on the functional bacteria community of phosphorus removal in the enhanced biological phosphorus removal system. The acetic acid was used as a carbon source to enrich and cultivate phosphorus accumulating bacteria. After the enrichment and the system was stable, soluble starch was added into the water to study the effects of granular matrix on phosphorus removal performance and functional bacteria community in EBPR system. The results showed that acetic acid was beneficial to the proliferation of phosphorus-accumulating bacteria in the enrichment stage, and the phosphate removal rate of the system could reach more than 99%. After the system is stabilized, granular matrix with different concentrations is added to the system in three stages, and the phosphate removal rate of the system gradually decreases. With the increasing of granular matrix concentration in the influent, the phosphorus removal performance of sludge decreased gradually, the maximum phosphorus release rate and maximum phosphorus uptake rate of sludge decreased, and the acetic acid utilization rate ΔP/ΔHAc value also decreased. Fluorescence in situ hybridization was used to measure the changes of functional bacteria in activated sludge under different conditions. With the increase of the concentration of soluble starch, the proportion of PAOs gradually decreased, and the proportion of GAOs gradually increased. Granular matrix exists in the internal of floc sludge and cannot be utilized by PAOs, which results in inhibition of the growth of PAOs and weakened activity. This indicates that the higher concentration of granular matrix will lead to a decrease in the proportion of PAOs in EBPR system, and then lead to a decrease in the phosphorus removal activity of activated sludge, and ultimately reduce the phosphorus removal effect of EBPR system.