Sewage Treatment Efficiency Research Articles

A holistic model for microplastic dispersion in a free-surface wetland flow

The holistic model for microplastic dispersion is essential to conserving natural wetlands and enhancing the sewage treatment efficiency of constructed wetlands. A holistic mode is presented to analyze the microplastic transport caused by a continuous point-source discharge of substances into a wetland with an exposed water surface. The microplastic cloud's total quantity and centroid movement over each streamline are rigorously derived using the method of separation of variables and integral transform, and its longitudinal dispersion, skewness, and kurtosis are numerically analyzed using the finite difference method. Three dimensionless groups for the microplastic movement in wetland are presented. The relative importance of autonomous movement to the vertical diffusion coefficient can noticeably influence the mass center velocity and the longitudinal spread of the microplastic cloud, and its augments can enhance the amplitude of skewness and kurtosis in the initial transport stage. For the transient stage of transport during which microplastic cloud develops, the pulsating term of emission intensity shows little effect on skewness and kurtosis. The oscillation of skewness and kurtosis show less obvious for the long term evolution of microplastic cloud when the time scale across the water depth by diffusion is much larger than the oscillatory period.

Removal of sulfamethoxazole and production of cyanobacterial lipid promoted by the construction of a consortium containing a non-toxic cyanobacterium and sewage bacteria

This study evaluated the possibility of constructing a consortium containing sewage bacteria and cyanobacterial cells immobilized by Ca-alginate for the advanced treatment of antibiotic-polluted sewage coupled to cyanobacterial lipid production. Two non-toxic cyanobacterial species (Synechococcus sp. and Chroococcus sp.) were exposed to 0.5–20.0 μg/L of sulfamethoxazole (SMZ) for 4 days. Comparison between suspended and immobilized conditions indicated that immobilization increased (p < 0.05) SMZ removal percentage without reducing cyanobacterial growth performance (indicated by OD680), chlorophyll-a content, dry cell weight, lipid content and lipid weight/productivity of each cyanobacterium. Chroococcus sp. presented better antibiotic removal and lipid production ability than Synechococcus sp. After the addition of immobilized Chroococcus sp. into sewage, sewage bacteria attached to the surface and filled the pores of cyanobacterial beads. Immobilized Chroococcus sp. promoted the succession of sewage microbial community towards the dominance of Cellvibrio, Flavobacterium, Formivibrio and Pseudomonas, which participated in denitrification, phosphate accumulation and antibiotic removal. In the sewage microbial community, various functional genes upregulated by immobilized Chroococcus sp. directly showed negative correlation (p < 0.05) with sewage contaminants, including gltB, glnA and napA responsible for nitrogen removal; pstS responsible for phosphorus removal; nqrF, cbhA, glgC, malZ, pulA, uxaA and maeA responsible for COD removal; frmA, katG, maeA, uxaA, carB and cbhA responsible for SMZ removal. Coexisting sewage bacteria elevated (p < 0.05) lipid productivity of immobilized Chroococcus sp. to 29.13–36.52 mg/L/day through the upregulation of various genes related to metabolite exchange and signal transduction. Cyanobacterial cells degraded SMZ in collaboration with sewage bacteria, through deamination, nitration, bond cleavage, hydroxylation, desulfonation and nitrosation. The cyanobacteria-bacteria consortium presented 4-day removal percentages of 54.58–68.39%, 66.14–68.69%, 95.77–96.31% and 81.09–82.35% for SMZ, TN, TP and COD, respectively. In general, the cyanobacteria-bacteria consortium achieved a good combination of cyanobacterial lipid productivity and sewage treatment efficiency.

Key issues to consider toward an efficient constructed wetland-microbial fuel cell: the idea and the reality.

The research on constructed wetland (CW) and microbial fuel cell (MFC) has been separate studies worldwide with crucial achievements being made in both fields. Due to environmentally friendly feature (of CW) and rich microbial population and excellent electrode catalytic activity (of MFC), CW and MFC have their own anticipated application prospect in wastewater purification and biological electricity generation. More significantly, the idea of embedding MFC into CW to form CW-MFC expands the scope for both of them and this has received much interest in recent years due to its striking features of sewage treatment efficiency, electricity generation, sustainability, and environmental friendliness. The increasing interest and the lack of soul of CW-MFC emerging to the new researchers reflect the need to recall the idea and summarize its development with regard to achieving its reality via some key issues This forms the basis of the paper. The paper also includes how to enhance the efficiency of electricity generation and supplement energy consumption, the degradation of emerging pollutants, and the degradation mechanism as well as the potential joint application of CW-MFC with other treatment technique. A mass of CW-MFC design parameters has been synthesized from the literature. Challenges and potential directions of CW-MFC in the future are prospected. It is expected that the paper can serve as a linkage for bridging knowledge gaps for further studies of CW-MFC.

Application of New Filling Material Based on Combined Heat and Power Waste for Sewage Treatment in Constructed Wetlands.

The filling of constructed wetlands (CWs) affects the efficiency of sewage treatment and proper operation. Mineral aggregates are most often used as filling materials. Significant environmental burdens from mineral mining operations justify the search for waste fill. This study aimed to determine the possibility of increasing the efficiency of CW by using a Certyd aggregate as a new filling. Certyd is produced in the sintering process of coal ash, a waste from combined heat and power (CHP) plant operation. Comprehensive two-year studies were conducted using two real-scale subsurface vertical flow (SS VF) CWs supplied with domestic sewage. One bed was filled with a Certyd and the other was filled with appropriate fractions of a mineral aggregate. Both beds worked in parallel, and to compare their effectiveness, account seasonality was taken into account. The SS-VF Certyd-filled bed achieved an average efficiency of 88.0% for biological oxygen demand (BOD5), 80.2% for chemical oxygen demand (COD), 80.4% for suspended solids (SSs), 80.2 for ammonia nitrogen (N-NH4), 72.2% for total nitrogen (TN), and 55.3% for total phosphorus (TP), while the gravel-filled bed achieved 84.5%, 77.0%, 86.9%, 74.2%, 69.4%, and 57.8% for the whole research period, respectively. A higher effect of the removed unit load was achieved in the bed filled with Certyd (36.2 g BOD5 m-2 d-1, 50.0 g COD m-2 d-1, 5.88 g SS m-2 d-1, 7.1 g TN m-2 d-1, 7.9 g N-NH4 m-2 d-1, 0.79 g TP m-2 d-1) compared to the gravel-filled bed (34.7 g BOD5 m-2 d-1, 47.0 g COD, 6.35 g SS m-2 d-1, 6.9 g TN m-2 d-1, 7.3 g m-2 d-1 N-NH4, 0.83 g TP m-2 d-1).

Enhancing the sewage treatment effect, reducing membrane fouling, and increasing microbial community diversity by a novel biofiller-carrying functional bacteria Rhodococcus sp. CPZ24 in a moving bed biofilm reactor

The feasibility of using a novel moving bed biofilm reactor (fbMBBR) with biofiller-carrying functional bacteria, Rhodococcus sp. CPZ24, to alleviate membrane pollution and improve wastewater treatment was studied. Three membrane reactors, namely, a biofilm reactor (MBR), a convention moving bed biofilm reactor (MBBR), and fbMBBR, were compared. The results showed that the efficiency of sewage treatment by the fbMBBR was significantly better than that of the MBR and MBBR. When the HRT and DO were 6 h and 3 mg·L−1, the removal rates of NH4+-N, COD, TN, and TP in the fbMBBR reached 92.76 %, 89.89 %, 82.24 %, and 68.23 %, respectively, and membrane fouling was effectively alleviated. Furthermore, the novel biofiller improved the abundance of dominant microbial community species on the membrane module and strengthened microbial community functions. In summary, this study presented a novel fbMBBR with excellent performance in sewage treatment, reducing membrane pollution.

Temporal and spatial variations in the physical and chemical properties of anaerobic granular sludge within a Pilot Spiral Symmetry Stream Anaerobic Bioreactor

Anaerobic granular sludge (AGS) determines the high performance of the bioreactor. To study the regionalization of granular sludge in the bioreactor, a Pilot Spiral Symmetry Stream Anaerobic Bioreactor (P-SSSAB) was established over 216 days, divided into three zones (I, II, and III) from bottom to top. AGS at the bottom of P-SSSAB had a higher porosity (60.35 %–83.27 %) and more suitable settling velocity (60 m/h) when the particle size range was 1.0–2.0 mm. This proved the better metabolic activity and superior settling performance in zone I than in zones II and III. In addition, the elemental composition of AGS in various zones was analyzed. The relative content of iron (5.66 %, 3.36 %, and 1.38 %, respectively) and sulfur (2.47 %, 2.19 %, and 1.49 %, respectively) in zone I, II, and III tended to decrease with the height of P-SSSAB. This also verified the better mass transfer performance and operational stability in lower zone than in upper zone. However, the monitoring of bed temperature in various zones revealed that the microbial activity in zone I was 6.7×10−12~3.5×10−2 times and 1.8×10−15~1.4×10−3 times that in zones II and III, respectively, which indicated that the unit activity of AGS in zone I was the worst. It indicated that AGS in lower zone had poor unit activity but had the highest unit capacity due to the high sludge concentration. Besides, the unit capacity of the upper zone was too weak to produce enough alkalinity to neutralize acid produced by excessive hydrolysis and acidification in lower zone, resulting in the worst treatment efficiency of the upper zone. Therefore, temperature and concentration ratios under various spatial distributions in bioreactors are vital to the overall sewage treatment stability and efficiency of bioreactors in actual engineering applications.

Converting pomelo peel biowaste into multifunctional sponges integrated underwater superoleophobicity and catalytic ability for sewage treatment

Fabricating practical multitasking materials integrating efficient oil-water separation ability and excellent catalytic performance is significant for water remediation but challenging for substrates and subsequent surface modification causing high cost, high power consumption, and poor reusability. Herein, a multitasking sponge was designed for water purification by successively modifying the biomass pomelo peel (PP) with polypyrrole (PPy), Au nanoparticles (NPs), and polydopamine (PDA). The cost-effective and renewable PP substrates, facile surface decoration of PP with PPy coating, in-situ spontaneous growth of Au NPs, and the protection of the outermost PDA coating endowed the as-obtained PP/PPy-Au/PDA sponges high sewage treatment efficiency and the potential for large-scale preparation. The PP/PPy-Au/PDA sponges exhibited high catalytic reduction activity for 4-nitrophenol (4-NP) and excellent reusability without remarkable decline in catalytic activity even after 10 recycles due to the synergistic effect among PPy, Au NPs and PDA. In addition, this sponge also displayed superior separation efficiency and high filtration flux towards both immiscible oil-water mixtures and O/W emulsions due to its underwater superoleophobicity. Integrating above properties, the PP/PPy-Au/PDA sponge could perform catalytic degradation of organic molecules and meanwhile separation of oil-water mixtures.

The regulating role of applied voltage on methanogenesis in an up-flow single-chamber microbial electrolysis assisted reactor

Applied voltage was introduced into the anaerobic system for improving the efficiency of sewage treatment and bioenergy production. For better energy efficient applications, it was necessary to have a good understanding of the effect of applied voltage, which is different from the conductive materials. In this study, the effects of applied voltage at different positions were investigated, considering the concentration gradients. Results showed that the maximum COD removal efficiency was 96.7% and the methane production rate was 0.434 ± 0.018 m3 CH4/m3/day in the reactor with two pairs of electrodes. The effect of the applied voltage on the organic matter conversion and methane production were dominant in the lower electrode. The increased energy output could content the required electric energy, and additional energy could be generated by CHP. The contribution of electrochemical direct action was lesser, and the increase of applied voltage led to the enrichment of functional microbes in this system, especially the hydrogenotrophic methanogens dominated by Methanocorpusculum.

Efficiency Calculation and Evaluation of Environmental Governance Using the Theory of Production, Life, and Ecology Based on Panel Data from 27 Provinces in China from 2003 to 2020

Promoting green development and promoting harmonious coexistence between humans and nature are strategic tasks for the construction of ecological civilization in China in the new era. Currently, the growing environmental governance investment in China has not performed well, and the low efficiency of environmental governance has become the main problem facing the development of ecological civilization in China. Therefore, it is of great practical significance to scientifically measure the efficiency of environmental governance and improve the efficiency of environmental governance input factors to achieve green development and overcome the difficulties in the construction of ecological civilization. In this study, an improved three-stage SBM model and cloud model combined with the Theory of production, life, and ecology were used to measure the environmental governance efficiency of 27 provinces in China from 2003 to 2020 and conduct in-depth analysis and evaluation. The results show that: First, the influence of random error factors and external environmental conditions on the efficiency of rural domestic sewage treatment in China is significant. Their existence will underestimate the environmental governance efficiency in the central and western regions of China and overestimate the environmental governance efficiency in the eastern regions of China, except for Hainan Province. Second, after excluding the influence of random errors and external environment conditions, the adjusted efficiency mean value of the central and western regions significantly increases, while the environmental governance efficiency of most provinces in the eastern region, except for Hainan Province, decreases significantly. Third, the overall environmental governance efficiency of the 27 provinces in China still presents a situation wherein the western region is ranked first in efficiency, the eastern region ranks second, and the central region ranks third. The environmental governance efficiency of the 27 provinces shows a “large at both ends, small in the middle” and “low efficiency in the eastern and central regions, and instability in the western region” state, and there is a large difference in the degree of environmental governance efficiency among the various provinces. In this regard, for the eastern and central regions, special attention should be paid to their government’s transformation of development thinking, placing greater emphasis on balanced and coordinated development between urbanization, industrialization, and the environment. As for the western region, due to its harsh environmental conditions, it attaches more importance to environmental governance. However, efforts should be made to strengthen its economic development to ensure sufficient provision of material conditions such as infrastructure and equipment required for environmental governance in order to achieve stable environmental governance efficiency in the western region. For the central region, both the economy and the environment need to be further strengthened.

하수처리시설 수질인자의 머신러닝 예측 모델

The purpose of this study is to develop a machine learning-based prediction model for the value of COD, a key factor that measures the quality of sewage flowing from a sewage treatment facility. Considering that the inflowing sewage water quality data has a time-series characteristic, a machine learning model using ARIMAX, RNN, and LSTM was developed as a predictive model for COD. For each model, after learning based on big data collected from domestic J sewage treatment facility, the prediction performance was evaluated by RMSE. ARIMAX model showed an accuracy of 7.83% compared to the average, RNN was 3.62%, and LSTM was 3.56%. Overall, the LSTM model was evaluated as the best performing predictive model. If our model is used in a sewage treatment facility, it is possible to predict the sewage water quality in real time, which is expected to greatly contribute to improving the efficiency of sewage treatment.

Optimal Design and Simulation for the Intelligent Control of Sewage Treatment Based on Multi-Objective Particle Swarm Optimization

With the continuous increase in emphasis on the environmental protection industry, sewage treatment plants have been built in many places, and these sewage treatment plants undoubtedly occupy an important position in protecting the local environment. The sewage treatment process is generally complicated and the treatment environment is difficult, which means that the treatment plant must have an excellent control system. At this stage, the sewage treatment systems in many cities have the issue of possessing backward technology and huge costs, which hinder the development of urban sewage treatment. In this paper, a new intelligent control method for sewage treatment is proposed, combined with the multi-objective particle swarm optimization (MOPSO) algorithm. The MOPSO algorithm is used to optimize the parameters and control rules of the controller globally, thereby improving the performance and work efficiency of the controller. Practice has shown that the intelligent control system combined with the MOPSO algorithm can make chemical oxygen demand (COD) in the sewage treatment quickly meet the expected requirements, and the control accuracy is also very accurate, which greatly improves the sewage treatment performance. Through our calculations, the new method improved the sewage treatment efficiency by 7.15%.

The research status of several technologies capable of integrating wastewater treatment with carbon capture

Since the Paris Agreement was proposed, many industries need to make efforts to save energy and reduce emissions. It is understood that the sewage treatment industry accounts for about 3% of global greenhouse gas (GHG) emissions, and with the acceleration of urbanization and industrialization in some countries, the total sewage treatment capacity will further increase. This will also lead to a further increase in the industry's greenhouse gas emissions, exacerbating global climate change. Therefore, the sewage treatment industry needs to make technical changes, but under the premise of not affecting the effect and efficiency of sewage treatment. Under such basic requirements, technologies that combine sewage treatment with carbon capture have gradually emerged in recent years. This review selects 3 technologies, including microbial electrosynthesis (MES), constructed wetland and microalgae cultivation, with good development prospects in this area, then summarizes their carbon capture principles and capabilities, sewage treatment principles and capabilities, research status in recent years, and current problems, in order to provide some ideas for the carbon emission reduction plan of the sewage treatment industry.

A simple system for ozone application in domestic sewage for agricultural reuse

The increasing demand for water in food production highlights the need to seek alternative sources of supply. Treated domestic sewage is a way to mitigate this problem, but it must comply with legislation to be used safely in agriculture. Ozone has been used for disinfection of domestic effluents due to its strong oxidizing character, allowing the adjustment of its parameters for agricultural reuse. This study therefore aimed to evaluate the sanitary and agricultural viability of domestic effluent treated with ozone. The experiment was carried out on laboratory benchtops and doses of 0, 8, 15, 30, 45, and 60 mg L−1 of ozone were applied. The application time for each dose was 0, 14, 27, 54, 81, and 108 seconds, respectively. Microbiological, physical, and chemical parameters were evaluated: total coliforms, Escherichia coli, pH, turbidity, dissolved oxygen, electrical conductivity, total organic carbon, total nitrogen, total phosphorus, potassium, magnesium, calcium, and sodium. Ozonation did not significantly alter the physical and chemical composition of wastewater, indicating an important advantage in terms of potential agricultural reuse. However, the pathogenic load of E. coli was not reduced enough for the effluent to be used in agriculture. The results suggest an investigation of the effects of ozone on the efficiency of sewage treatment, seeking to understand these interactions to identify ideal doses and exposure time, making wastewater safe for agricultural reuse.&#x0D; Keywords: agriculture, ozonation, treated effluent.

Extensive abundances and characteristics of microplastic pollution in the karst hyporheic zones of urban rivers

Cities are potential areas for microplastic pollution due to large-scale production and the use of plastic products. The karst ecosystem in southwestern China is fragile, and pollutants are more likely to be transported over long distance, resulting in higher pollution risks. Understanding the abundance and composition of microplastics in karst urban water systems is crucial for microplastic pollution management in a karst region. This study investigates the abundances and characteristics of microplastics typically found in river sediments in 10 cities in karst regions of Southwest China. The results show that the abundance of microplastics in sediments ranged from 800 items·kg−1 to 4400 items·kg−1, with an average of 2273 ± 775 items·kg−1 (n = 30), indicating high abundance. Polyamide (PA) was the most common plastic polymer types in all sediment samples. The abundance of microplastics in the downstream (2527 ± 698 items·kg−1) was higher than that in the midstream (2350 ± 999 items·kg−1) and upstream areas (1943 ± 370 items·kg−1), indicating a gradual accumulation effect in the karst water systems. Microplastic abundance in cities (2119 ± 838 items·kg−1) was lower than in counties (2427 ± 671 items·kg−1). No significant correlation was found between microplastic abundance in rivers of urban areas and the level of regional population and economy, but significantly negatively correlated with the efficiency of urban sewage treatment. The results obtained from this study provided insights into the management of microplastic pollution in urban river of a karst region.

RS-SVM Machine Learning Approach Driven by Case Data for Selecting Urban Drainage Network Restoration Scheme

ABSTRACT Urban drainage pipe network is the backbone of urban drainage, flood control and water pollution prevention, and is also an essential symbol to measure the level of urban modernization. A large number of underground drainage pipe networks in aged urban areas have been laid for a long time and have reached or practically reached the service age. The repair of drainage pipe networks has attracted extensive attention from all walks of life. Since the Ministry of ecological environment and the national development and Reform Commission jointly issued the action plan for the Yangtze River Protection and restoration in 2019, various provinces in the Yangtze River Basin, such as Anhui, Jiangxi and Hunan, have extensively carried out PPP projects for urban pipeline restoration, in order to improve the quality and efficiency of sewage treatment. Based on the management practice of urban pipe network restoration project in Wuhu City, Anhui Province, this paper analyzes the problems of lengthy construction period and repeated operation caused by the mismatch between the design schedule of the restoration scheme and the construction schedule of the pipe network restoration in the existing project management mode, and proposes a model of urban drainage pipe network restoration scheme selection based on the improved support vector machine. The validity and feasibility of the model are analyzed and verified by collecting the data in the project practice. The research results show that the model has a favorable effect on the selection of urban drainage pipeline restoration schemes, and its accuracy can reach 90%. The research results can provide method guidance and technical support for the rapid decision-making of urban drainage pipeline restoration projects.

Bioelectrochemical processes and cellulosic carbon source enhance the autotrophic and heterotrophic denitrification of low C/N ratio wastewater in tidal flow constructed wetland - Microbial fuel cells

To solve the problem of poor nitrogen and phosphorus removal efficiency of low C/N ratio wastewater, a siphon constructed wetland - microbial fuel cell (CW-MFC) reactor was constructed. And the influence of electrochemical process on autotrophic denitrification and nitrogen removal was studied. The effects of agricultural waste as cellulose carbon source on heterotrophic denitrification and electricity generation were also investigated. In addition, related electrochemical processes and microbial mechanisms were studied. The results indicated that MFC enhanced autotrophic denitrification. The addition of cellulose carbon source could significantly promote the heterotrophic denitrification process ( P < 0.05). In 137 days, the reactor with carbon source added to both cathode and anode (CS CW-MFC) had the best removal effect on COD , NH 4 + -N and TN, with removal rates of 98.38%, 79.31% and 84.43%, respectively. The removal efficiency of TP reached 89.92%. Adding carbon sources facilitated biological electricity production. The maximum voltage was 450 mV, and the maximum power density was 113.95 mW m −3 . However, methane emissions increased slightly with the addition of carbon sources. Compared with previous studies, tidal flow via siphon aeration could significantly improve TN removal efficiency. Bioelectrochemical processes had significant impact on the autotrophic denitrifying bacteria, the relative abundance of Bacteroidota and Proteobacteria was the highest. This study suggests that the addition of cellulose carbon source and the operation of tidal flow CW-MFC can enhance treatment of low C/N ratio wastewater. This technology not only enables agricultural waste to be recycled, but also improves the efficiency of sewage treatment and energy recovery. • Bioelectrochemistry affected autotrophic denitrification and nitrogen removal. • Cellulose carbon source was beneficial to heterotrophic denitrification. • The addition of cellulose carbon source increased the system electricity generation. • The tidal flow in CW-MFC can enhance the treatment of low C/N ratio wastewater. • Autotrophic/heterotrophic denitrification and bioelectroactive bacteria coexisted.

Optimization of the Internal Circulating Fluidized Bed Using Computational Fluid Dynamics Technology

The computational fluid dynamics (CFD) technology is analyzed and calculated utilizing the turbulence model and multiphase flow model to explore the performance of internal circulating fluidized beds (ICFB) based on CFD. The three-dimensional simulation method can study the hydrodynamic properties of the ICFB, and the performance of the fluidized bed is optimized. The fluidization performance of the ICFB is improved through the experimental study of the cross-shaped baffle. Then, through the cross-shaped baffle and funnel-shaped baffle placement, the fluidized bed reaches a coupled optimization. The results show that CFD simulation technology can effectively improve the mass transfer efficiency and performance of sewage treatment. The base gap cross-shaped baffle can improve the hydraulic conditions of the fluidized bed and reduce the system energy consumption. The cross-shaped baffle and funnel-shaped baffle can perfect the performance of the reactor and effectively strengthen the treatment in the intense aerobic process of industrial sewage.

Kitchen waste hydrolysate enhances sewage treatment efficiency with different biological process compared with glucose

Insufficient carbon source is the primary factor that limits biological nitrogen and phosphorus removal during sewage treatment. This study investigates the feasibility and biological process of kitchen waste hydrolysate (KWH) replacing glucose to improve pollutant removal efficiency. It was found that using KWH as carbon source achieved better removal effect than glucose during sewage treatment. And more than 96% of total nitrogen (TN), total phosphorus (TP), and the chemical oxygen demand were removed after 48 h of acclimation. Nitrogen and phosphorus introduced by adding KHW had no negative effect on the effluent quality. Compared with glucose, KWH decreased the diversity of bacteria and significantly promoted the accumulation of acid-producing bacteria (Propionibacterium) and denitrifying bacteria (Rhodobacteraceae). Moreover, KWH significantly improved the relative abundance of the amo A, nap A, and nos Z genes. This result further indicated that KWH was beneficial for denitrification and was a favorable external carbon source.

Simulation and Computational Study of CFD on Tube MBR Membrane Assembly

When using tubular MBR to treat sewage, the water production is an important parameter to measure the efficiency of the tubular MBR system. The problem to be solved in this paper is to calculate the water yield of the tubular MBR system, so as to evaluate the sewage treatment efficiency of the MBR system. This research uses the CFD simulation software ANSYS 16.0 to study the water yield of the tubular MBR system. The MBR model of a single membrane filament tube was established using the ICEM CFD preprocessor in ANSYS 16.0, and the structured grid was divided to obtain a grid file. Then, the fluid solver was used to solve the mesh file and through the flow monitoring window to obtain the water output of the tubular MBR system. Finally, the CFD postprocessor in ANSYS 16.0 was used to visualize the calculation results and compare them with the waste-water treatment results of some actual MBR systems. The results show that the water yield calculated by the fluent solver is basically the same as that of the actual MBR system. This research realizes the purpose of calculating the water yield of the tubular MBR system with CFD technology, solves the problem of evaluating the working efficiency of the tubular MBR system with water consumption, and realizes the MBR before deployment The evaluation of the working efficiency of the system has certain reference value for the planning, design, and deployment of MBR.

Can public-private partnerships (PPPs) improve the environmental performance of urban sewage treatment?

Insufficient sewage treatment facility is one important reason for wastewater entering and affecting aquatic ecosystems. The PPP mode, serving as one of the fastest-growing mechanisms for public service provision in recent decades, is considered to be an effective way to alleviate the pressure of funding shortages and to improve the efficiency of sewage treatment. However, the performance of PPPs has been questioned, especially the service quality given the inherent nature of the private sectors' pursuit of maximizing economic profit and the shortcoming of incomplete contracts. This paper evaluates the service quality, namely the environmental performance, of the PPP mode in China's urban sewage treatment sector. Based on detailed firm-level data in Jiangsu Province, China, we find that the PPP mode has improved the pollutant treatment performance, and increased operation cost and promoted sewage treatment efficiency serve as the main mechanism for the improvement of environmental performance. The research findings could help both developed and developing countries to apply and design a public-private partnerships mechanism.