Achieving rapid endogenous partial denitrification by regulating competition and cooperation between glycogen accumulating organisms and phosphorus accumulating organisms from conventional activated sludge.

In anaerobic/aerobic/anoxic (A/O/A) process, endogenous denitrification (ED) is critically important, and achieving steady endogenous partial denitrification (EdPD) is crucial to carbon saving and anammox application. In this study, EdPD was rapidly realized from conventional activated sludge by expelling phosphorus accumulating organisms (PAOs) in anaerobic/anoxic (A/A) mode during 40 days, with nitrite transformation rate (NTR) surging to 82.8 % from 29.4 %. Competibacter was the prime EdPD-fulfilling bacterium, soaring to 28.9 % from 0.5 % in phase II. Afterwards, balance of high NTR and phosphorus removal efficiency (PRE) were attained by well regulating competition and cooperation between PAOs and glycogen accumulating organisms (GAOs) in A/O/A mode, when the Competibacter (21.7 %) and Accumulibacter (7.3 %, mainly Acc_IIC and Acc_IIF) were in dominant position with balance. The PRE recovered to 88.6 % and NTR remained 67.7 %. Great balance of GAOs and PAOs contributed to advanced nitrogen removal by anammox.

Perfluorinated compound correlation between human serum and drinking water: Is drinking water a significant contributor?

Perfluorinated compounds (PFASs) are a new artificial chemical. Due to its substantial toxicity and complex degradation in the natural environment, monitoring PFASs has become a hot issue for many researchers. Currently, the relationship between the concentration of PFASs in serum and the concentration of PFASs in drinking water is unclear. This paper aims to study the concentration levels of PFASs in drinking water and residents' serum in a city in northern China and the relationship between them. The results show that the concentration of PFASs in drinking water is low, and the average concentrations of perfluorooctanoate (PFOA) and perfluorooctane sulfonate (PFOS) were 2.57 ± 0.69 ng/L and 0.30 ng/L, respectively, which were lower than the limits specified in China's newly introduced Standards for drinking water quality (GB 5749-2022). In the serum of residents, PFOA and PFOS were the two PFASs with the highest concentration. Spearman correlation analysis showed that perfluorohexane sulfonate (PFHxS) and PFOS concentrations were positively correlated with age, and PFHxS, PFOA, PFNA, and PFOS varied with sex. At the same time, the correlation analysis also showed no correlation between PFAS in drinking water and serum, indicating that drinking water was not the main factor causing the physical burden of PFAS in residents. The HI method was used to assess the health risks of PFASs to human beings. The risk entropy of all PFASs for human hepatotoxicity and reproductive toxicity is below 1.