| Being increasingly strict with environmental protection, sewage discharge standards also gradually improve in recent years, combining enhanced sewage treatment and in-situ sludge reduction system is going to become both an emphasis and a nodus in future. This study developted a novel stage-aerated simultaneous wastewater treatment and sludge reduction integrated system (abbreviate for A2MO-Msystem), and selected the oxic-setting-anaerobic system (OSA system) as the compared system, to deeply and comprehensively optimize the running parameters in A2MO-M system, and investigated the mechanism of in-situ sludge reduction, nutrient removal and nitrogen and phosphorus removal in the A2MO-M systems. Meanwhile, ASM2D mathematical model and MATLAB simulation platform was applied to reveal the SMP formation and degradation in the OSA and A2MO-M systems. Consequently, this study developted the UAP and BAP mathematical model of aerobic, micro-aerobic, anoxic, and anaerobic conditions in the OSA and A MO-M systems.This study conducted the batch experiments and continuous-flow experiments to optimize the control parameters in the anaerobic sludge holding tank and oxygen-limited starvation sludge holding tank of the OSA and A2MO-M systems. Results demonstrated that when the HRT of 12 h controlled in the OSA system, the OSA3# system could achieve the minimum sludge yield. While the optimized HRT in the A2MO-M system was 9 h, which was the A2MO-M2# system in this study. When compared with the CAS, A2MO, and OSA3# systems, the reduced sludge yields in the A2MO-M2# system were 45.08%,42.46%, and 16.08. When considering the in-situ sludge reduction mechanism, this study demonstrated that there were 9.68% and 16.67% sludge reduction was induced by uncoupling mechanism in OSA and A2MO-M systems. And there were 23.23% and 21.15% sludge reduction was induced by sludge decay in OSA and A2MO-M systems. Microbial community variations investigated by high-throughput 454 pyrosequencing proved that microbial community structures were more abundant in A2MO-M system than in OSA system. Much higher relative abundances of fermentative bacterium (Osenella, Paludibacter, and Stenotrophomonas) were detected enriched in the A2MO-M system, this phenomenon demonstrated that in the A2M0-M system, sludge cryptic-growth might be another reason for in-situ sludge reduction. The relative abundances of Ramlibacter genera were 2.27% and 0.01% in OSA system and A2MO-M system, which the slow growth bacteria was found in A2M0-M system. This study demonstrated that in the A2M0-M system, the in-situ sludge reduction was induced by a series of reasons, including uncoupling mechanism, sludge decay, microorganism cryptic-growth, and slow growth bacteria.In order to understand the UAP and BAP formation and variation in the OSA and A2MO-M systems, this study also conducted the investigation of EfOM, SMP, UAP, and BAP to clearly understand the nutrient removal mechanism in A MO-M and OSA systems. Results showed that the BAP accumulation is the main factor that impacted the effluent quality, and the DO concentration was found to be an important factor that effect the BAP production in the sewage treatment system. This study also demonstrated that there were more BAP in OSA system than in A2MO-M system. By investigating the effluent nitrogen and phosphorus removal efficiencies in different OSA and A2MO-M systems, it could be concluded that the average effluent TN, ammonia nitrogen and TP removal efficiencies in A2MO-M systems increased 20.61%,12.46% and 42.20%. Microbial community variations revealed that much higher relative abundances of the primary organisms responsible for nitrogen and phosphorus removal were detected enriched in the A2MO-M system to achieve enhanced nitrogen and phosphorus removal stability.For the purpose of investigating the sewage organic contaminant degradation mechanism, this study is conducted to build the UAP and BAP mathematical modelling under different DO concentration. In this study, SMP, UAP, and BAP was introduced into the ASM2D mathematical modelling, and meanwhild, we combined the batch experiments, kinetics, and mathematical modelling to analysis the formation and degradation mechanism of SMP, UAP, and BAP under aerobic, micro-aerobic, anoxic, and anaerobic conditions. Results showed that there was little influnce of DO on UAP, while for the effect of DO on BAP formation cannot be ignored. Based on the mathematical modelling, the highest BAP production was found under anaerobic conditions, and the aerobic condition was the second, while for micro-aerobic and anoxic conditiosn, the BAP formation was lower and almost the same. Hence from the results obtained in this study it can be concluded that the different DO condition has significant influences on BAP accumulation in activated sludge sewage treatment systems. At the same time, the BAP accumulation in the anaerobic and aerobic conditions was obviously higher than it in the micro-aerobic and anoxic conditions. By building the UAP and BAP mathematical modelling, this study demonstrated that when the sludge stayed in an alternating anaerobic-aerobic environment, the OSA system would accumulate more BAP. Different DO concentration controlled in the OSA and A2MO-M systems would induced different BAP accumulation. |
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