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For the upgradation and building of wastewater treatment plants in limited areas, biological wastewater treatment processes with a high pollutant removal loading rate are required. Biofilm or membrane-based systems can achieve a high pollutant removal loading rate through high microbial biomass concentrations and/or activities. The sludge separation is the primary bottleneck for achieving high biomass concentrations inside the biological reactors. In addition, low growers including anaerobic ammonia oxidation bacteria and methanogens are usually easier to form granules and induce high nutrient removal loading rates. The possible granule formation mechanisms should be clarified through physical, chemical and biological aspects, including hydraulic control, microbial extracellular polymeric substances formation, biological energy utilization control, microbial interactions and also other microbial processes. In future, the possible mechanisms should be further clarified, and then high-efficient bioreactors, new microbial ecology control strategy and novel biofilm carriers should be developed for advancing biological wastewater treatment processes with high pollutant removal loading rates.

Denitrifying anaerobic methane oxidation (DAMO) can mitigate methane emissions; however, this process has not been studied in cattle manure, an important source of methane emissions in animal agriculture. The objective of this study was to investigate the occurrence of DAMO microbes in cattle manure and examine the impacts of veterinary antibiotics on the DAMO process in cattle manure. Results show that DAMO archaea and bacteria consistently occur at high concentrations in beef cattle manure. During the long-term operation of a sequencing batch reactor seeded with beef cattle manure, the DAMO activities intensified, and DAMO microbial biomass increased. Exposure to chlortetracycline at initial concentrations up to 5000 μg L–1did not inhibit DAMO activities or affect the concentrations of the 16S rRNA gene and functional genes of DAMO microbes. In contrast, exposure to tylosin at initial concentrations of 50 and 500 μg L–1increased the activities of the DAMO microbes. An initial concentration of 5000 μg L–1TYL almost entirely halted DAMO activities and reduced the concentrations of DAMO microbes. These results show the occurrence of DAMO microbes in cattle manure and reveal that elevated concentrations of dissolved antibiotics could inhibit the DAMO process, potentially affecting net methane emissions from cattle manure.

Wastewater treatment contributes significantly to protect human health and ecological safety. With sustainable development of wastewater treatment, recovery of resources and energy from wastewater has been the focus for conventional contaminants, while reduction and control of ecological toxicity is the focus for emerging compounds. Under anaerobic conditions, especially with the enhancement of direct interspecies electron transfer, methanogenesis and/or nitrous oxide production could be achieved separately or simultaneously, and the removal efficiency of some types of emerging compounds could be improved. During nitritation, both nitrogen and emerging compounds removal could be achieved simultaneously. Therefore, a new wastewater treatment concept based on recovery of energy and control of emerging compounds was proposed, including the anaerobic treatment process by incorporating directly electron transfer enhancement and nitritation-based nitrogen removal. The proposed strategy provided a new technology concept for advancing the sustainable development of wastewater treatment through recovery of energy and control of emerging compounds.

Direct interspecies electron transfer (DIET) plays an important role in anaerobic wastewater treatment processes, and the dosage of conductive materials can enhance DIET. In this study, tryptone and starch were used to acclimate anaerobic sludge with different microbial communities. Then, the effect of ferroferric oxide (Fe3O4) dosage on batch anaerobic treatment of synthetic wastewater was examined. During methanogenesis for the tryptone acclimated anaerobic sludge, the lag phase was shortened, and the maximum methane (CH4) production rate was increased with the dosage of Fe3O4. While for the starch acclimated anaerobic sludge, the CH4 production was less affected by the dosage of Fe3O4. Furthermore, the dosage of Fe3O4 had limited effects on both hydrolysis/acidification of tryptone and methanogenesis of acetate for the tryptone acclimated anaerobic sludge. Methanosarcina (66.28% of archaea) and Methanosaeta (19.56% of archaea) were detected methanogens in the tryptone acclimated anaerobic sludge, which could accept electrons via DIET. While Methanobacterium (92.80% of archaea) was mainly detected in the starch acclimated anaerobic sludge. Therefore, the effect of Fe3O4 on anaerobic treatment performance was significantly dependent on the organic carbon acclimated microbial communities.

Aiming problems arising from the wind turbine with the frequency converter, this paper proposes a design for wind turbine based on differential speed regulation. The dynamic characteristics and parameter determination method of the structural components including differential gear train and speed regulating motor (SRM) were studied and the dynamic characteristic expression were obtained. The critical conditions about input power or output power for ring gear driven by SRM were researched. The way to determine the optimal structure parameters of SRM was put forward. The minimum peak power of SRM was regarded as the objective function while the transmission ratios of three gear sets which were placed in the different positions of overall structure scheme was optimized. A SIMULINK model of 1.5 MW wind turbine based on differential speed regulation was built and ran. The rotational speed, torque and power of the wind rotor, the SRM and the synchronous generator were obtained respectively. The simulation results can verify effectiveness of the theoretical analysis and parameter configuration.

Two-sided assembly lines are widely used in the large-size product manufacturing industry, especially for automotive assembly production. Balancing the assembly line is significant for assembly process planning and assembly production. In this study, we develop a novel and exact method to optimize the two-sided assembly line balancing problem with zoning constraints (TALBz), in which the aim is to minimize the number of mated-stations considering the task restrictions. A mixed-integer programming model is employed to exactly describe the TALBz problem. To strengthen the computational efficiency, we apply Dantzig–Wolfe decomposition to reformulate the TALBz problem. We further propose a branch-and-price (B&P) algorithm that integrates the column generation approach into a branch-and-bound frame. Both the benchmark datasets with zoning constraints and without zoning constraints are tested to evaluate the performance of the B&P algorithm. The numerical results show that our proposed approach can obtain optimal solutions efficiently on most cases. In addition, experiments on the real-world datasets originating from passenger vehicle assembly lines are conducted. The proposed B&P algorithm shows its advantage in tackling practical problems with the task restrictions. This developed methodology therefore provides insight for solving large-scale TALBz problems in practice.