Whether the phosphorus removal chemical in wastewater treatment plants (WWTPs) can be accurately dosed not only affects the compliance of the effluent total phosphorus but also has a huge impact on sludge production and energy consumption during the wastewater treatment process. For the effluent from the secondary sedimentation tank of a wastewater treatment plant in southern China, based on experimental screening of the optimal pH value, chemical types and concentrations of chemicals, coagulation time, etc., a dynamic dosage prediction feedforward model for chemical phosphorus removal agents in the effluent from the secondary sedimentation tank of the WWTPs was developed to predict the most economical dosage of the chemicals. Meanwhile, combined with the adaptive fuzzy neural network P feedback control algorithm, dynamic real-time control of chemical dosing was achieved. Through micro-control design, a software model for signal collection and feedback in a specific phosphorus removal scenario was formed, and an automatic control system for chemical dosing was ultimately developed for a WWTP in a city in southern China. After stable operation for two months, the system achieved a 100% compliance rate for effluent total phosphorus (TP) concentration and a 67% improvement in effluent stability, helping the wastewater treatment plant achieve stable and precise control of the phosphorus removal process in the secondary sedimentation tank effluent, which is conducive to further promoting its implementation of low-carbon pathways.

Wastewater reclamation has gradually become an important way to cope with the global water crisis. Ultrafiltration plays an imperative part as a safeguard for the aim but is often limited by membrane fouling. Effluent organic matter (EfOM) has been known to be a major foulant during ultrafiltration. Hence, the primary aim of this study was to investigate the effects of pre-ozonation on the membrane fouling caused by EfOM in secondary wastewater effluents. In addition, the physicochemical property changes of EfOM during pre-ozonation and the subsequent influence on membrane fouling were systemically investigated. The combined fouling model and the morphology of fouled membrane were adopted to scrutinize the fouling alleviation mechanism by pre-ozonation. It was found that membrane fouling by EfOM was dominated by hydraulically reversible fouling. In addition, an obvious fouling reduction was achieved by pre-ozonation with 1.0 mg O₃/mg DOC. The resistance results showed that the normalized hydraulically reversible resistance was reduced by ~60%. The water quality analysis indicated that ozone degraded high molecular weight organics such as microbial metabolites and aromatic protein and medium molecular weight organics (humic acid-like) into smaller fractions and formed a looser fouling layer on the membrane surface. Furthermore, pre-ozonation made the cake layer foul towards pore blocking, thereby reducing fouling. In addition, there was a little degradation in the pollutant removal performance with pre-ozonation. The DOC removal rate decreased by more than 18%, while UV₂₅₄ decreased by more than 20%.

In this study, carbon emissions in three full-scale wastewater treatment plants were determined by the emission factor method. Moreover, the correlation between basic parameters (influent water parameters and pollutant removal efficiency) and carbon emissions was examined via a structural equation model (SEM). The results showed a significant variation in the total carbon emission intensity of plants over time. The average total carbon emission intensity of plants A, B and C were 0.314, 0.404 and 0.363 kg eqCO₂/m³, respectively. Meanwhile, the indirect carbon emission caused by energy and chemical agent consumption accounts for the majority of total carbon emissions (about 85%). Generally, statistical analysis results show that carbon emission intensity is positively correlated with pollutant removal efficiency. Notably, RTN showed the highest positive correlation with E_ind, followed by RTN > RCOD_Cr > RTP > TN > RNH₃-N > NH₃-N > TP. Moreover, capacity showed the greatest negative contribution to E_ind, followed by COD_Cr. In contrast, the positive contribution to E_dir was followed by the sequence of RTN > RCOD_Cr > TN > RNH₃-N > NH₃-N. Notably, COD_Cr showed a significantly negative correlation with E_dir, while TP and its removal showed little correlation with E_dir.