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[Objective] The purpose of this paper is to study the optimal operation condition of AAO-MBBR mode of the new rural sewage treatment process and its treatment effect on pollutants. [Method] By comparing the pollutant removal rate under different residence time, different internal circulation ratio and different aerobic tank dissolved oxygen concentration, the optimal operation parameters of the equipment were screened out, and the equipment was set to operate under the optimal operating condition. The treatment effect on various pollutants was analyzed. [Result] The results showed that the improved AAO-MBBR process had the best removal effect when the hydraulic retention time was 8 h, the internal circulation ratio was 300% and the concentration of dissolved oxygen in aerobic pool was 2.5 mg/L. Under optimal operating conditions, the removal rates of SS, COD, BOD, NH3-N and TP of the equipment were 80%, 85%, 91%, 84.5% and 46%, respectively. And the treatment effect is significantly higher than that of other sewage treatment equipment. [Conclusion]The improved AAO-MBBR process has a good effect on pollutant removal in integrated wastewater treatment equipment. [ABSTRACT FROM AUTHOR]

Microalgae-bacteria consortium for wastewater treatment has great potential for use in nutrient removal and biodiesel acquisition. In this study, the effect of four different light/dark regimes (6/18 h , 12/12 h , 18/6 h , 24/0 h) on biomass production and pollutant degradation during the treatment of oilfield wastewater by the algae-bacteria consortium was investigated. The maximum algal biomass (0.2 g/L) and total chlorophyll content (812.76 μgmg−1 cell dry weight−1) were obtained due to an appropriate illumination cycle (18 hlight/6 h dark) with enhanced dissolved oxygen content (5.87 mg/L), thus improving bacterial biomass (0.31 g/L). The ratio of microalgae to bacteria was essentially constant under different light/dark cycles. In addition, the highest removal rates of chemical oxygen demand (55.32%), ammonia nitrogen (50.75%), total nitrogen (64.53%), and total phosphorus (65.97%) were also obtained at the 18/6 h cycle, significantly different from the results of other light/dark cycles. The degradation efficiency of ammonia nitrogen by bacteria increased and then decreased with increasing light duration, while the removal rate of ammonia nitrogen by algae showed the opposite trend. The results indicated that the light and dark regimes had an important influence on the growth of the microalgae-bacteria consortium and their performance in treating oilfield wastewater. [ABSTRACT FROM AUTHOR]

In wastewater treatment intensification, hierarchical control structures are developed to improve the plant's performance. This paper proposes two novel hybrid supervised hierarchical control structures for specifying the dissolved oxygen concentration in the last aerobic reactor of the wastewater treatment plant (WWTP) based on the nitrification rate and the ammonia level in this reactor. These structures combine the optimum disturbance rejection PI control (OPI), adaptive neuro-fuzzy inference system (ANFIS), and genetic algorithms (GA) to reduce energy consumption and operational costs, improve effluent quality, and reduce the number and percentage of times the established maximum concentration of pollutants in the effluent of the WWTP is violated. The proposed control strategy is implemented and evaluated using benchmark simulation model no. 1 (BSM1). The OPI-ANFIS-GA configuration significantly enhances effluent quality in dry, rainy, and stormy weather conditions, reducing total nitrogen violations by 50.17%, 63.35%, and 47.35%, respectively. Then, 6.79% and 7.12% of aeration energy and 1.44% and 1.46% of operational costs are reduced in dry and rain weather conditions. The OPI-ANFIS configuration enhanced significant energy savings and a cost reduction in storm weather conditions. Both configurations led to a 49.89% decrease in total suspended sludge (TSS) during stormy weather conditions. The proposed controller significantly improves the performance of the WWTP in all weather scenarios compared to the default controller and similar controllers found in the literature. [ABSTRACT FROM AUTHOR]

The vegetable oil refinery industry generates highly polluted effluents during oil production, necessitating proper treatment before discharge to prevent environmental hazards. Treating such wastewater has become a major environmental concern in developing countries. Chemical oxygen demand (COD) is a key parameter in assessing the wastewater's organic pollutant load. High COD levels can lead to reduced dissolved oxygen in water bodies, negatively affecting aquatic life. Various technologies have been employed to treat oily wastewater, but microbial degradation has gained attention due to its potential to remove organic pollutants efficiently. This study aims to optimize the biodegradation treatment process for vegetable oil industrial effluent using response surface methodology (RSM). The wastewater's physicochemical properties were characterized to achieve this, and COD removal was analyzed. Furthermore, RSM was used to investigate the combined effects of pH, contact duration, and microbial concentration on COD removal efficiency. The result showed that the microbial strain used recorded a maximum COD removal of 92%. Furthermore, a quadratic model was developed to predict COD removal based on the experimental variables. From the analysis of variance (ANOVA) analysis, the model was found to be significant at p < 0.0004 and accurately predicted COD removal rates within the experimental region, with an R2 value of 90.99% and adjusted R2 value of 82.89%. Contour plots and statistical analysis revealed the importance of contact duration and microbial concentration on COD removal. Practitioner Points: Response surface methodology (RSM) optimization achieved a significant chemical oxygen demand (COD) removal efficiency of 92% in vegetable oil industrial effluents.The study's success in optimizing COD removal using RSM highlights the potential for efficient and environmentally friendly wastewater treatment.Practitioners can benefit from the identified factors (pH, contact time, and microbial concentration) to enhance the operation of treatment systems.The developed predictive model offers a practical tool for plant operators and engineers to tailor wastewater treatment processes.This research underscores the importance of sustainable practices in wastewater treatment, emphasizing the role of microbial degradation in addressing organic pollutant loads. [ABSTRACT FROM AUTHOR]

The influence of aeration diffuser system design on electricity usage, effluent water quality, and life-cycle cost in biological wastewater treatment was investigated. A plant-wide model was implemented, and simulations were carried out with different process configurations and aeration systems. Model-aided design of new aeration diffuser systems could significantly decrease electricity usage and life-cycle cost while at the same time avoiding negative effects on the treatment performance. The optimum distribution of diffuser systems in tanks in series was found to be influenced by process configuration, volumetric loading rate, temperature, and the internal recirculation flow rate. Compared with a conventional design approach, increasing the number of diffusers, up to a critical point, led to higher energy efficiency and lower life-cycle cost. This was despite an increasing limitation of the minimum airflow rate, leading to dissolved oxygen levels significantly exceeding control targets. Aeration systems optimized by simulations were found to, independently of process configuration, exhibit 20% lower electricity usage and 16%–18% lower life-cycle costs compared with systems designed based on a more conventional approach typically applied in practice. [ABSTRACT FROM AUTHOR]

Dissolved organic nitrogen can cause undesirable environmental problems in aquatic environments, such as eutrophication, nitrogenous disinfection by-product formation, and a decrease in the amount of dissolved oxygen. 25–80% of the total dissolved nitrogen (TDN) in the effluent of wastewater treatment plants is dissolved organic nitrogen (DON) form. As a result of these concerns, the biodegradability and management of DON is important issue for domestic/industrial wastewater treatment. Dairy products are widely consumed in Turkey and dairy industry wastewater has a high organic nitrogen content. In this study, the biodegradability of wastewater samples obtained from yoghurt and cheese production industries was investigated. The biodegradability of wastewater samples was determined by using a mixed bacteria culture and identified between 72.2 and 81.7% for yoghurt production wastewater and 19.1–20.1% for cheese production wastewater. BDON/TDN ratio was found as 65.4–71.9% and 16.5–17.5% ranges for yoghurt and cheese production wastewaters, respectively. Although both are released from dairy production, it has been determined that white cheese production wastewater has a very low biodegradability compared to yoghurt production wastewater. It is thought that the results of this study will contribute to the evaluation of the removal efficiency in other industrial facilities and domestic wastewater treatment plants. [ABSTRACT FROM AUTHOR]

Water, an essential commodity available to mankind, is constantly under pollution threat. Industries are one of the major causative factors for its poor quality and therefore all organisms depending upon it, directly or indirectly are affected by various life-threatening problems. Thus, the treatment of discharge waste into the freshwater ecosystem is the dire need of the hour. The objective of the study is valorization of discarded snail shells for treatment of industrial wastewater. In the present study, industrial wastewater was treated using snail shell dust obtained from Bellamya bengalensis to assess change in water quality parameters. Various physico-chemical parameters like pH, total dissolved solids, electric conductivity, dissolved oxygen, biological oxygen demand, chemical oxygen demand, calcium, magnesium, total hardness, chlorides, bicarbonates, orthophosphates, sulfates, nitrates, and ammonia-N were assessed after its treatment with snail shell dust. Based on the present observation, it was concluded that all studied parameters except dissolved oxygen showed a remarkable decline in concentration after treatment with snail shell dust at the rate of 15 g per liter at the end of 4 days. Moreover, increased dissolved oxygen concentration also endorsed an enhancement in water quality. Statistical analysis through Pearson correlation and indices, viz., WQI (Water quality index) as well as Nemerow's Pollution index when applied to the present data, also supported an improvement in the water quality. The findings thus endorsed the utilization of snail shell dust as an eco-friendly technique and can be substituted as a sustainable method for the treatment of industrial wastewater. [ABSTRACT FROM AUTHOR]

This study presents the performance of a laboratory scale completely mixed aerobic reactor for starch wastewater treatment. The reactor was operated for 119 days, divided into 5 operational phases which included the start-up and the variation of cell-residence time. In order to determine the biokinetic coefficients for starch removal, the cell-residence time was varied between 20 to 4 days, and the system operation was set to a hydraulic retention time of 24 hours with a completely mixed reactor setup. The chemical oxygen demand concentration was 1000mg/L in the inflow of the reactor and dissolved oxygen remained above 2mg/L. In this experimentation time, the parameters such as pH, chemical oxygen demand (in the influent and effluent), dissolved oxygen and mixed liquor suspended solids were monitored. The calculation of biokinetic constants was done by an approximate method, using the graphical Lineweaver-Burk method. The biokinetic coefficients determined were for maximum substrate removal rate(Ko), half saturation rate constant or affinity constant (Km), sludge yield coefficient (Y), and microbial decay or indigenous respiration rate (Ke).The results showed that Y, (Ko) and (Km), were in the range of 0.3- 0.7 mgSSV/mgBOD5, 2- 8 day1 and 40-120 mg/L (COD- BOD5), respectively. Values of the coefficients were within the range of those reported for conventional activated sludge processes. [ABSTRACT FROM AUTHOR]

Aeration is a process of diffusing oxygen into water in order to stimulate the aerobic bacteria for starting wastewater aerobic treatment process. Zero energy aeration systems that do not require electric or mechanical power are known as passive aerators. A new technology for passive aerators using inverted bell siphon principle is innovated, which requires a lot less volume for its installation compared to other passive aeration systems as cascade, spray and perforated tray aerators. A laboratory experimental program investigated the inverted bell siphon system using deoxygenated water with almost zero dissolved oxygen concentration like anaerobic treatment effluent. The system is used to build water pressure through a distribution system used for scattering water in air to diffuse oxygen into it. Holed arm pipe with different hole diameters and numbers, showerhead, fire sprinkler and modified fire sprinkler were tested as distributors to reach the optimum type which verify good oxygen diffusion in water and ensure least possibility of clogging of distributors. Dissolved oxygen concentration was measured for each distributor water effluent. The experiments showed that the modified fire sprinkler achieved higher oxygen diffusion in water and best distribution, in addition to its geometry that prevents the distribution system from clogging. [ABSTRACT FROM AUTHOR]

Presently, the standard practices in domestic wastewater treatment fail with many prevailing challenges such as strict disposal norm, rising pollutant, abstraction, retrieval, and alleviation of nutrients; addressing these challenges requires an advance and novel wastewater treatment technique, micro-nanobubbles technology (MNB). This article improves the quality of domestic wastewater with MNB in an experimental study. The domestic wastewater with pH 6.3 was subjected to hydrodynamic oxidation to produce MNBS with enriched oxygen, and their existence was analyzed with a scanning electron microscope and nanoparticle track analyzer. Characteristic studies such as the zeta potential, pH, amount of dissolved oxygen, bubble number density, and bubble diameter were conducted to analyze the effect of MNBs on the improvement of water quality. The MNB-generated water was experimented with freezing and thawing followed by heating to room temperature effect. The oxidation period for the formation of free radicals was varied from 5 to 30 min. The 13.5% increase in dissolved oxygen, a reduction in pH value from 6.3 to 6, and −5 to −40 mV values in zeta potential at a maximum oxidation period of 30 min were observed during experimental investigations. Additionally, the water quality tests such as total dissolved oxygen, chemical oxygen demand, chromium, phosphate, and sulfide ensured the existence of MNBs in domestic wastewater and the impact of existence in improving the waste quality. This article raises the awareness of the deployment of the MNBs technology and facilitates the development of knowledge of the domestic wastewater treatment within the water resource area. [ABSTRACT FROM AUTHOR]

• Physics-informed modeling to predict parameters in a real activated sludge system. • Online validation step for physics-informed and data driven models. • Importance of physics-informed modeling when standard modeling falls short. • Physics-informed modeling may be unnecessary when standard modeling suffices. • Physics-informed modeling without the requirement for fine-tuning. Data-driven modeling is essential in chemical engineering, especially in complex systems like wastewater treatment plants. Recurrent neural networks are effective for modeling parameters in wastewater treatment process such as dissolved oxygen concentration and chemical oxygen demand due to their nonlinear adaptability. However, traditional models face challenges such as the requirement for larger datasets and more frequent sampling, noisy measurements, and overfitting. To address this, physics-informed neural networks integrate physical knowledge for improved performance. In our study, we apply both approaches to a wastewater treatment plant, enhancing prediction performance. Our results demonstrate that physics-informed models perform successfully in offline and online validation, especially when standard methods fail. They maintain effectiveness without frequent updates. Yet, integrating physics-informed knowledge can introduce noise when standard methods suffice. This result points out the need for careful consideration of model choice in different scenarios. [ABSTRACT FROM AUTHOR]

[Display omitted] Herein, a novel metal-free catalyst consisting of multiporous oxygen-rich carbon–nitrogen graphene-like nanosheets (O LAA -CN NSs) is first developed through a staged temperature-programmed calcination of l -ascorbic acid (LAA)-modified dicyandiamide precursor. It is found that the oxygen species from l -ascorbic acid (O LAA) are introduced into the graphene-like basic matrix and replace partial N atoms to form the C O C-R structure, leading to the non-uniform distribution of electrons on the catalyst surface, and the formation of electron-rich centers around the C O C microareas according to a series of characterization techniques. As a result, O LAA -CN NSs exhibits excellent performance for refractory pollutant removal in the presence of peroxymonosulfate (PMS) and dissolved oxygen. Some pollutants with complex structures are even completely degraded within only 1 min. The interface reaction mechanism is further revealed that PMS mainly acts as an active inducer to drive the electron donation of pollutants over O LAA -CN NSs. These electrons are finally utilized by dissolved oxygen to generate reactive oxygen species (ROS) through the interface process. This reaction system results in pollutants that can either be cleaved directly by surface oxidation process or degraded by the attack of the generated ROS, such as singlet oxygen (1O 2) and superoxide radicals (O 2 •−), through oxygen activation, which significantly reduces the resource and energy consumption in advanced wastewater treatment by harnessing the energy of pollutants and dissolved oxygen in the water. [ABSTRACT FROM AUTHOR]

After entering the new century, the state continues to increase the construction of urban sewage treatment projects in response to the deteriorating water pollution situation. How to collect and analyze the sewage parameter variables in the sewage treatment process to ensure the intelligent measurement and accurate operation of the parameters in the treatment application is an urgent problem to be solved. This paper is mainly based on the computer-aided control system built by the ARM9 core embedded chip, and the feasibility and effectiveness of fuzzy neural network algorithms are discussed to improve the intelligent processing of sewage treatment parameters. After analyzing the principle and implementation flow of fuzzy control and neural network, starting from the characteristics of data collected by ARM9 core chip, the hybrid algorithm model is optimized and improved to further improve the convergence speed and accuracy of the algorithm. The simulation experiment proves that the optimized fuzzy neural control algorithm can effectively identify the dissolved oxygen, nitrate nitrogen, and other parameter data in the sewage treatment, and the recognition accuracy is very close to the true precision. Based on biosensors, the ARM9 core chip control system established by a recursive fuzzy neural network can greatly improve the tracking and control ability of parameters such as dissolved oxygen concentration and nitrate nitrogen concentration in microbial degradation. This has a good development prospect in wastewater treatment control applications. The experimental results show that the recursive fuzzy neural network algorithm proposed in this paper can dynamically track and control the nitrate concentration and dissolved oxygen concentration and ensure that the control is within the accuracy range. The accuracy of recognition is very close to the real accuracy. [ABSTRACT FROM AUTHOR]

In this study, the removal of Cr(VI) using commercial FeS with the partially oxidized surface was investigated under visible light. The results demonstrated that the Cr(VI) removal using commercial FeS could be enhanced by 1.3 times in the presence of visible light. More importantly, the removed Cr(VI) was almost completely reduced to less toxic Cr(III), and most of the reduced Cr(III) was immobilized on the commercial FeS surface. In order to elucidate the plausible mechanism of the removal of Cr(VI) using partially oxidized FeS under visible-light irradiation, the role of electrons (e−) and holes (h+), the influence of dissolved oxygen, and the variation of the commercial FeS surface were carefully examined. The results revealed that the dissolved Fe(II)/S(-II), surface-bound Fe(II)/S(-II), and photogenerated electrons were directly responsible for the reduction of Cr(VI) to Cr(III). Additionally, the ·O2− derived from the dissolved oxygen activation by the photo-generated electrons also contributed to the reduction of Cr(VI). During the Cr(VI) removal process, due to the release of strong hydrophilic SO42− ions from the partially oxidized FeS surface, the continuously exposed surface Fe(II) and S(-II) maintained the Cr(VI) reduction. Besides, the photo-generated electrons and ·O2− favored the regeneration of surface Fe(II), which helped sustain the reduction of Cr(VI) by the surface Fe(II). These findings clarify the transformation process of commercial FeS during the Cr(VI) removal under visible-light irradiation and help us to further understand the mechanism of Cr(VI) removal using partially oxidized FeS with a multipronged approach. This study also offers an alternative promising commercial material for Cr(VI)-bearing wastewater treatment. [ABSTRACT FROM AUTHOR]

Rainwater discharge and human impacts produce wastewater, which is a contaminated type of water. Sediments also discharge phosphate into the water column when there is a lack of dissolved oxygen in the water. Through the manufacturing of environmentally benign nanoparticles, nanotechnology may reduce the amount of money spent by enterprises to remediate such contaminants. Because of their improved physiological, biochemical, and biomechanical qualities, nanoparticles are getting prominence. The importance of the global wastewater dilemma is discussed in this survey. The use of nanomaterials in heavy metal remediation (HMR) and wastewater treatment is covered in this survey. This paper also discusses the benefits of nanotechnology over traditional approaches in certain fields. This survey aims to gather together many recent studies on nanoparticle production and their benefits as adsorbents in the remediation of wastewater which have been done so far. The promising role of nanotechnology in wastewater remediation is surveyed in this research, which also discusses recent developments in nanotechnology-mediated remediation methods. This survey examines the vital potential of nanotechnology in wastewater treatment, as well as recent breakthroughs in nanotechnology-mediated treatment systems. [ABSTRACT FROM AUTHOR]

High biochemical oxygen demand (BOD) concentrations in water minimize oxygen availability, damage ecosystem biodiversity, impair water quality, and spoil freshwater. The increased level of BOD is an indication of severe organic pollution of freshwater. Thus, this study aims to establish empirical correlations between the 5-day biochemical oxygen demand (BOD5) and organic decomposition time to control organic pollution in various wastewater effluents. Ultimate biochemical oxygen demand (UBOD) and minimum and average BODt data sets along with their reaction rates were collected from earlier sampling analyses in the plants used for industrial, domestic (sanitary), and storm (surface) wastewater treatment. Average BOD5/COD ratios were then utilized to calculate existing 5-day dissolved oxygen (DO5) concentration for the estimation of experimental dilution factors (dfs) as a good start in sampling analysis to reach an optimum DO5 concentration. Moreover, the relationships between average BOD5 vs. COD, and BOD5 vs. DO5, were obtained based on the literature with 60–70% oxygen consumption rates required for organic decomposition. Results showed that such BOD5 relationships with time (power equations) or with COD (linear correlations) are helpful for wastewater engineers to generate valuable and accurate results for quality control, without the need to conduct laboratory experiments. The proposed regression equations would facilitate effluent quality assessment, allowing selection of optimal processes to control microbiological contamination or organic constituents in wastewaters. [ABSTRACT FROM AUTHOR]

The hospitals close to the residences can make problems for the environment as a consequence of sewage drained into the water stream. Sequencing batch biofilm reactor (SBBR) offers advantages for treating sewage; such as simple operation, flexible process, and cost-effective. The laboratory bench-scale experiments were carried out treating hospital wastewater (HWW) of one of Basrah hospital city by a fabricated SBBR reactor of 26 l working volume. The hospital wastewater has the following characteristics (average values): pH 7.3, BOD equal to 280 mg·l-1, COD equal to 550 mg·l-1, total phosphorus (TP) equal to 6.4 mg·l-1, ammonia (NH3-N) equal to 44 mg·l-1 and total suspended solid (TSS) equal to 272 mg·l-1. This research aims to estimate the performance of the SBBR system for treating hospital wastewater to enhance different effluent parameters such as COD, total nitrogen (TN), ammonia, and total phosphorous (TP) with various dissolved oxygen (DO) with range of 2.15-6.55 mg·l-1, the best DO values give these removal efficiencies for COD equal to 84.55%, NH3-N equal to 65.91% and TN between 78 and 18% for DO equal to 3.67 mg·l-1, while TP removal efficiency was 79.70% for DO equal to 6.55 mg·l-1. By comparison of the SBBR effluent with international standards for effluent sewage, it noticed COD concentration 85 mg·l-1, TN 12 mg·l-1 and TP 1.3 mg·l-1 met all standards (European, WHO, and China), while NH3-N 15 mg·l-1 was outside WHO and European standards, while satisfies only Chinese standard. [ABSTRACT FROM AUTHOR]

The water–energy nexus (WEN) has become increasingly important due to differences in supply and demand of both commodities. At the center of the WEN is wastewater treatment plants (WWTP), which can consume a significant portion of total electricity usage in many developed countries. In this study, a novel multigeneration energy system has been developed to provide an energetically self-sufficient WWTP. This system consists of four major subsystems: an activated sludge process, an anerobic digester, a gas power (Brayton) cycle, and a steam power (Rankine) cycle. Furthermore, a novel secondary compressor has been attached to the Brayton cycle to power aeration in the activated sludge system in order to increase the efficiency of the overall system. The energy and exergy efficiencies have been investigated by varying several parameters in both WWTP and power cycles. The effect of these parameters (biological oxygen demand, dissolved oxygen level, turbine inlet temperature, compression ratio and preheater temperature) on the self-efficiency has also been investigated. It was found here that up to 109% of the wastewater treatment energy demand can be produced using the proposed system. The turbine inlet temperature of the Brayton cycle has the largest effect on self-sufficiency of the system. Energy and exergy efficiencies of the overall system varied from 35.7% to 46.0% and from 30.6% to 33.55%, respectively. [ABSTRACT FROM AUTHOR]

Statistical modeling of water-quality data collected at the Sacramento River at Freeport and San Joaquin River near Vernalis, California, USA, was used to examine trends in concentrations and loads of various forms of dissolved and particulate nitrogen and phosphorus that entered the Sacramento-San Joaquin River Delta (Delta) from upstream sources between 1970 and 2019. Ammonium concentrations and loads decreased at the Sacramento River site from the mid-1970s through 1990 because of the consolidation of wastewater treatment and continuously reduced from the mid-1970s to 2019 at the San Joaquin River site. Current ammonium concentrations are mostly below 4 µM (0.056 mg N L-1) at both sites, a concentration above which reductions in phytoplankton productivity or changes in algal species composition may occur. The Sacramento River at Freeport site is located upstream of the Sacramento Regional County Sanitation District's treatment facility's discharge point; nutrient water quality there is representative of upstream sources. Inorganic nitrogen (nitrate plus ammonium) concentrations and loading differed at both sites. At the Sacramento River location, concentrations decrease in the summer agricultural season, reducing the molar ratios of nitrogen to phosphorus. In contrast, inorganic nitrogen concentrations increase in the San Joaquin River during the agricultural season as a result of irrigation runoff, increasing the molar ratio of nitrogen to phosphorus. This increase suggests a possible nitrogen limitation in the northern Delta and a phosphorus limitation in the southern Delta, as indicated by the molar ratios of bioavailable nitrogen to bioavailable phosphorus. Planned upgrades to the Sacramento Regional Wastewater Treatment Plant (SRWTP) will reduce inorganic nitrogen inputs to the northern Delta. Consequently, the supply of bioavailable nitrogen throughout the upper estuary should diminish. Source modeling of nitrogen and phosphorus identifies agriculture, atmospheric deposition, and wastewater effluent as sources of total nitrogen in the Central Valley. In contrast, geologic sources, agriculture, and wastewater discharge are the primary sources of phosphorus. [ABSTRACT FROM AUTHOR]

Wastewater treatment is a problem known to humankind for centuries. The quality of treated sewage determines the condition of reservoirs around the world. Control of such a complex and nonlinear system as a wastewater treatment plant requires thorough knowledge of the process. The paper presents a hierarchical control system of a Sequencing Batch Reactor (SBR) in Wastewater Treatment Plant (WWTP) taking into account a model based on actual measurements taken from a WWTP in Swarzewo, Poland. The authors designed and implemented a nonlinear model predictive controller (MPC) that allows for the optimal implementation of the desired DO level while minimising the operation of actuators (aeration system). The design description of the predictive controller was associated with the need to specify the performance function and define the optimisation problem. In a two-layer structure, a supervisory controller was implemented based on an actual time-based controller in Swarzewo WWTP. The overview showed the improved performance of the treatment plant and the versatility of the created solution. Results of simulation tests for the wastewater treatment plant case study are presented. • Dissolved oxygen control is very important for WWTP energy efficiency. • The process of designing a hierarchical control system of a SBR has been presented. • Nonlinear MPC has been applied for optimal implementation of the set DO trajectory. • Results of simulation tests for WWTP case study have been presented. [ABSTRACT FROM AUTHOR]

Chesapeake Bay has a long history of nutrient pollution resulting in degraded water quality. However, we report improvements in chlorophyll a in surface waters and dissolved oxygen in bottom waters at one of three estuarine stations in the Choptank tributary of Chesapeake Bay. We updated a previous nutrient budget for the estuary constructed for reference year 1998 using rates of atmospheric deposition, inputs of watershed diffuse sources (primarily agriculture), and discharges of point sources (primarily human waste) for reference year 2017. Parallel trends suggest that improvements in water quality at the one station were likely due to 20% reductions in direct atmospheric deposition on the estuary's surface and 78–95% reductions in wastewater N and P due to installation of tertiary treatment. The agricultural sector, the dominant source of N and P, appeared to provide little contribution to improved water quality during this period. Although efforts to reduce nutrient losses from agriculture are common throughout the Choptank basin, widespread reductions from agricultural diffuse sources could make large contributions to improved water quality at all stations in the estuary. The response in the Choptank is similar to those observed elsewhere in the USA, Europe, Australia, and New Zealand due to improved wastewater treatment. Similar to our findings, the upper Potomac River of Chesapeake Bay saw improvements driven by reductions in atmospheric deposition. Unfortunately, few studies elsewhere have shown improvements in water quality due to agricultural management. The data presented here indicate that public and industrial investments in reductions of atmospheric emissions and upgrades to wastewater treatment plants have improved estuarine water quality in the Choptank. [ABSTRACT FROM AUTHOR]

• Small AGS (212–1000 μm) emitted higher N2O than large AGS (>1000 μm) at DO >2 mgO2/L. • Higher DO levels resulted in elevated N2O emissions for both small and large size fractions. • N2O reductase genes (nosZ) were more abundant in smaller granules. • Nitrification exhibited a positive correlation with N2O emission rates across all granule sizes. Aerobic granular sludge (AGS) at wastewater treatment plants (WWTPs) are known to produce nitrous oxide (N 2 O), a greenhouse gas which has a ∼300 times higher global warming potential than carbon dioxide. In this research, we studied N 2 O emissions from different sizes of AGS developed at a dissolved oxygen (DO) level of 2 mgO 2 /L while exposing them to disturbances at various DO concentrations ranging from 1 to 4 mgO 2 /L. Five different AGS size classes were studied: 212–600 µm, 600–1000 µm, 1000–1400 µm, 1400–2000 µm, and > 2000 µm. Metagenomic data showed N 2 O reductase genes (nosZ) were more abundant in the smaller AGS sizes which aligned with the observation of higher N 2 O reduction rates in small AGS under anaerobic conditions. However, when oxygen was present, the activity measurements of N 2 O emission showed an opposite trend compared to metagenomic data, smaller AGS (212 to 1000 µm) emitted significantly higher N 2 O (p < 0.05) than larger AGS (1000 µm to >2000 µm) at DO of 2, 3, and 4 mgO 2 /L. The N 2 O emission rate showed positive correlation with both oxygen levels and nitrification rate. This pattern indicates a connection between N 2 O emission and nitrification. In addition, the data suggested the penetration of oxygen into the anoxic zone of granules might have hindered nitrous oxide reduction, resulting in incomplete denitrification stopping at N 2 O and consequently contributing to an increase in N 2 O emissions. This work sets the stage to better understand the impacts of AGS size on N 2 O emissions in WWTPs under different disturbance of DO conditions, and thus ensure that wastewater treatment will comply with possible future regulations demanding lowering greenhouse gas emissions in an effort to combat climate change. [Display omitted] [ABSTRACT FROM AUTHOR]

The cultivation of microalgae has important interests from the economic point of view with the production of medicines, antiseptics, protein-vitamin supplements and biofuels such as hydrogen, ethanol and biodiesel, as well as for bio remediation of the environment contributing to the mitigation of CO2 in the atmosphere and wastewater treatment. In this work, a dynamic model is presented that describes the symbiotic growth of the microalgae Chlorella vulgaris and bacteria, in an open-air thin-film photobioreactor of 3,500 m², used for the treatment of liquid pig waste. A novel procedure is developed to estimate the pH value and a new kinetic equation for the growth of microalgae is proposed. MATLAB software R2009b was used to develop a program that allows estimating the temperature of the culture suspension and the variation of the process parameters (concentration of algae and bacteria, concentration of organic matter in terms of biochemical oxygen demand, pH, concentration of dissolved oxygen, dissolved carbon dioxide concentration, dissolved ammonia nitrogen concentration, and dissolved ortho-phosphates). The correlation between the experimental process parameters and those obtained with the program is demonstrated, with an error of less than 10% in all cases. The productivity per unit of cultivation area obtained with the program is compared with the real data obtained and the maximum error is ± 4%. [ABSTRACT FROM AUTHOR]

Ammonium removal is a key step in wastewater treatment which can be accomplished biologically. An interesting process option for this purpose is coupling partial nitritation with the Anammox process. The goal of the partial nitritation process is to convert half of the ammonium in the influent stream into nitrite, so both can be later converted into dinitrogen gas by the Anammox reaction. To obtain a stable partial nitritation, ammonium oxidizing bacteria (AOB) have to prevail over nitrite oxidizing bacteria (NOB) so as to avoid further conversion of nitrite into nitrate. The dissolved oxygen concentration is a key variable for the functional group selection. In this study, a constrained combination of cascade and feedforward control is proposed for reactors with biomass retention, aimed at suppressing unwanted NOB while keeping a nitrite:ammonium ratio suitable for coupling with Anammox. The master controller, aimed to regulate this effluent ratio, generates the set-point for the dissolved oxygen concentration slave controller. In addition to the cascade controller feedback loop, a feed-forward controller calculates the optimal dissolved oxygen concentration based on the current influent stream flow rate and concentrations. The resulting dissolved oxygen concentration set-point is compared to constraints that guarantee the suppression of NOB and survival of AOB. The proposed control strategy is simple to apply in common wastewater treatment plants with biomass retention. A sensitivity analysis is performed to assess the effect of model parameters uncertainty on the controller constraints and to determine which parameters need to be identified with more precision to avoid instability or poor results. The performance and the effect of the uncertainty of the most sensitive parameters on the proposed control algorithm are assessed through simulation using realistic streams as inputs of the process. • A combination of cascade control, feed-forward and constraints is proposed. • Objectives are suppressing unwanted bacteria and setting the nitrite:ammonium ratio. • Sensitivity analysis is performed on the feed-forward and constraints. • The analysis shows the significance of the maximum growth rates. • Simulation results show that the controller can achieve both objectives. • When the effluent ratio cannot be set, the unwanted bacteria are still suppressed. [ABSTRACT FROM AUTHOR]

Pollutions caused by livestock industry have posed substantial concerns on ecological environment. The random discharge of swine wastewater has resulted in excessive nutrients transport to rivers and lakes, in turn inducing eutrophication of surface water. Given that China is one of the largest pork producers in world, the treatment of swine wastewater is becoming a very urgent issue. In this study, 9 pilot-scale surface flow constructed wetlands vegetated with M. elatinoides were constructed to treat swine wastewater, in order to investigate nitrogen removal effect and influence factors of myriophyllum elatinoides wetlands. The pilot-scale M. elatinoides wetlands were exposed to swine wastewater under three strengths: low loading rates (swine wastewater diluted with fresh water at a 1:2 ratio), medium (swine wastewater diluted with fresh water at a 2:1 ratio), and high (pristine swine wastewater without dilution). The M. elatinoides wetlands were operated using an intermittent flow regime with a total volume of 180 L/d, and the theoretical hydraulic retention time was 33 d in the surface flow constructed wetlands. Water samples (inflow and outflow) were collected once a month from July 2014 to May 2015 for measuring ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3--N), total nitrogen (TN), and chemical oxygen demand, and concurrently the water temperature, pH, and dissolved oxygen were determined in the field. Monthly sediment samples were collected to determine NH4+-N, NO3--N, TN, and dissolved organic carbon. The linear mixed-effect model was used to explore the key factors affecting NH4+-N removal in the M. elatinoides wetlands. The results showed that during the whole test period (July 2014 -May 2015), the removal rates of NH4+-N and TN in low, medium, and high load wastewater were relatively high, where the removal rates of NH4+-N and TN were 85.0%-98.7% and 83.6%-97.1%, respectively. Nitrogen removal was different under different pollution loads, whereas, the removal rates of NH4+-N and TN decreased with the increase of pollution loads. The results of linear mixed model analysis showed that the key environmental factors affecting NH4+-N removal in the wetland were the dissolved oxygen and NO3--N in wastewater, and the content of NH4+-N in sediment, where the dissolved oxygen in wastewater presented the greatest impact on NH4+-N removal in the wetland. In every unit increased in the concentration of dissolved oxygen, the effluent concentration of NH4+-N decreased by 1.33% on average. With the accumulation of NH4+-N in sediment, the effluent NH4+-N concentrations increased significantly (P<0.001). As the dissolved oxygen in wastewater decreased as the pollution loads increased, the sediment NH4+-N increased as well, indicating that the variation in nitrogen removal of different pollution loads in the M. elatinoides wetlands. The removal rates of NH4+-N and TN in wetlands under different pollution loads were above 80.0%, although gradually decreased with the increase of pollution loads. Therefore, the M. elatinoides can be used as an ammonia-tolerant plant to treat high-load swine wastewater. The finding can provide a promising potential application of M. elatinoides wetlands in large-scale farms. [ABSTRACT FROM AUTHOR]

Dissolved oxygen (DO) concentration is a key variable in the activated sludge wastewater treatment processes. In this paper, an auto control strategy based on Euler method and gradient method with radial basis function (RBF) neural networks (NNs) is proposed to solve the DO concentration control problem in an activated sludge process of wastewater treatment. The control purpose is to maintain the dissolved oxygen concentration in the aerated tank for having the substrate concentration within the standard limits established by legislation of wastewater treatment. For that reason, a new proposed control strategy based on gradient descent method and RBF neural network has been used. Compared with RBF neural network PI control, the obtained results show the effectiveness in terms of both transient and steady performances of proposed control method for dissolved oxygen control in the activated sludge wastewater treatment processes. [ABSTRACT FROM AUTHOR]

Laboratory assessments of organism responses to wastewater are inexpensive, easily replicated, and offer control and precision, yet are often so reduced in temporal and spatial scale that results are difficult to apply to receiving environments. Whole-system experiments are expensive, lack true replication, and can be logistically challenging, yet offer the best insight as to how ecosystems will respond to effluent inputs. Advancing Canadian Wastewater Assets (ACWA), which includes a wastewater treatment plant, analytical labs, and research streams, provides unique infrastructure to test new wastewater treatment technologies, demonstrate technology benefits by direct analytical chemistry, and determine receiving environment effects. The ability to measure temperature, conservative ions, and dissolved oxygen in 12 replicated, naturalized streams allows physical modelling and biological monitoring consistent with larger, natural rivers. Assessments of receiving environment data could guide policy development for safe discharge of emerging contaminants and develop strategies to reduce development and persistence of antimicrobial resistance. [ABSTRACT FROM AUTHOR]

In order to solve the problem of wastewater treatment control, a computer system based on ADP iterative algorithm is proposed. Sewage treatment system is a highly nonlinear industrial process control system, because of the uncertainty of the water into the component, and the surrounding environment such as weather, temperature and pH influence factors such as mixture, the sewage treatment process is extremely complex, present a big time delay, strong coupling, time-varying and serious interference, etc. Therefore, this paper aims to control and optimize the concentration of dissolved oxygen and nitrate nitrogen in the process of sewage treatment, proposes an optimal control strategy for sewage treatment based on the iterative ADP algorithm, and realizes the online control and optimization of sewage treatment by combining the basic principle of adaptive dynamic programming and the characteristics of neural network. [ABSTRACT FROM AUTHOR]

The limitations of in-depth specific studies about industrial discharges have led more and more professionals to make use parameters that clash with reality, due to the adoption of tabulated coefficients which do not always correspond to the real characteristics of the aforementioned effluents. This study aims above all to determine the deoxygenation coefficient of the water body that receives the discharges of a dairy plant in the interior of the state of Goiás. A self-depuration study was also conducted along the lines of the Streeter-Phelps method, thanks to which it was possible to analyze the differences between the theoretical and experimental coefficients. The theoretical deoxygenation coefficient used was that found in the literature of Von Sperling for secondary treatment wastewater, varying between 0,12 d-1 (minimum), 0,18 d-1 (medium) and 0,24 d-1 (maximum), in which each of these values was corrected on the basis of the temperature of the effluent, resulting in K1 26°C = 0,16d-1, 0,24 d-1 e 0,32 d-1, respectively. As for the experimental coefficient, it was determined using the Thomas method. The figure found for coefficient K1 corrected on the basis of the temperature resulted in K1 26°C = 0,46 d-1. Thanks to the self-depuration data modeling, it was possible to establish that the industrial discharge had the major impact on the receiving water body, the experimental K1 26°C showed a smaller amount of critical concentration of dissolved oxygen and consequently, after the active decomposition zone, there was a gradual improvement in the levels of the dissolved oxygen by means of the experimental K1 26°C, which in turn led to the restoration of the initial characteristics of the clean waters zone in an area smaller when compared with the theoretical K126°C. [ABSTRACT FROM AUTHOR]

Success of design and high operational efficiency may basically stand or fall on the quality of measured (or estimated) input data. Even small mistakes committed in the initial steps of sampling and analysis may become large once scaled up in the design process or during full-scale operation. The paper provides several experiment-based practical recommendations and easily implemented, powerful methods for appropriate sampling and analysis practice in wastewater treatment. Representative wastewater characterization is crucial for satisfactory design and cost-effective operation. The paper highlights hidden problems and challenges of sampling and analysis in activated sludge wastewater treatment which may strongly affect the quality of input data, and thus basically determine the modelling outputs. Full-scale results proved that wastewater quality may change significantly in the sampling tubing and vessels; during the sampling process even nitrification can happen. Regarding sludge settling measurements, effects of dilution, temperature, floc structure, nitrate and dissolved oxygen concentrations as well as current biochemical condition of the sludge sample have been studied and important recommendations provided. A combined comparative method including SVI and DSVI measurements has been elaborated for indication and early warning alert of undesired floc structure transformations. Influent BOD5 concentration is a key factor for describing biodegradability and denitrification capacity of wastewater to be treated. Results of the two most commonly used BOD testing methods were compared for preclarified wastewater. An electrochemical measurement technique provided significantly lower BOD5 concentrations compared to manometric analysis results with a difference of 23% and 15% on average for unfiltered and filtered samples, respectively. Effects of BOD-based fractionation deviations on predictable denitrification efficiency were studied at different inlet C/N ratios by simulating existing full-scale wastewater treatment plants resulting in remarkable differences in effluent nitrate concentrations. Based on the results, application of the manometric BOD measurement method proved to be preferable. [ABSTRACT FROM AUTHOR]

Dissolved oxygen (DO) concentration is a key variable in the operation of wastewater treatment processes (WWTPs). In this paper, an adaptive fuzzy neural network-based model predictive control (AFNN-MPC) is proposed for the control problem of DO concentration. The main contributions of AFNN-MPC are threefolds: First, an AFNN, based on a novel learning method with adaptive learning rate, is designed to model the unknown nonlinearities of WWTPs with high predicting performance. Second, a gradient method is used to solve the optimal control problem of AFNN-MPC to reduce the computational cost. Third, the convergence of AFNN, as well as the stability analysis of AFNN-MPC, has been given in detail. Finally, the proposed AFNN-MPC is applied to the benchmark simulation model No. 2. The promising results indicate that the proposed AFNN-MPC is a suitable solution to control DO concentration. Moreover, the comprehensive experiments clearly show the superiority and efficacy of the proposed AFNN-MPC. [ABSTRACT FROM AUTHOR]

In the present study, the effect of carbon to nitrogen (C/N) ratio, suspended biomass concentration (X), hydraulic retention time (HRT) and dissolved oxygen (DO) on chemical oxygen demand (COD) and nutrient removal from wastewater was investigated in a lab-scale activated sludge (AS)-biofilm reactor. Furthermore, in order to improve the quality of the treated wastewater, photocatalysis by TiO2 was investigated as a post-treatment technology, using solar and UV irradiations. The AS-biofilm reactor provided a substantial removal efficiency in terms of COD, ammonia nitrogen , total nitrogen (TN) and total phosphorous when the system was maintained at C/N ratio 6.66, X in the range 2-2.5 g/L, HRT 10 h, DO in the range of 3.5-4.5 mg/L and organic loading rate (OLR) of 0.96 kg COD/m3 d during Run 1. Similarly, when the reactor was maintained at C/N ratio 10, X in the range of 3-3.5 g/L, HRT 8 h, DO in the range of 3.5-4.5 mg/L and OLR of 1.8 kg COD/m3 d during Run 2. The microstructure of suspended and attached biomass comprised a dense bacterial structure of cocci and bacillus microorganisms. The UV photocatalysis was found to be better than solar photocatalysis during the comparative analysis. The maximum removal efficiencies of COD, most probable number and phosphorous at optimum conditions in the case of UV and solar irradiations were 72%, 95%, 52% and 71%, 99%, 50%, respectively. [ABSTRACT FROM AUTHOR]

Highlights • Rotating drum contactors filled with random carriers were implemented. • The volumetric oxygen transfer coefficient was measured by abiotic tests. • The post-denitrification process was proposed for advanced nitrogen removal. • Both aerobic AOB and ANAMMOX contributed the TN loss in anoxic tank. Abstract A lab-scale rotating drum biological contactor (RDBC) was implemented and accessed concerning abiotic oxygen transfer rate and treatment capacity for domestic sewage. The dissolved oxygen (DO) transfer test showed that the rotational speed and the submergence level of drum greatly affected the DO in bulk liquid with the volumetric oxygen transfer coefficient K L a of 2.3-25.9 h−1, effectively achieving anaerobic/anoxic/aerobic conditions in the reactor. The post-denitrification process was proposed using the RDBC to degrade the synthetic nitrogen-containing sewage wastewater. When the hydraulic retention time was 16 h, the flow distribution ratio was 3:1 and the anoxic rotational speed was 6 rpm, the effluent NH 4 +-N and TN were 2.3 mg L−1 and 7.3 mg L−1 with the NH 4 +-N and TN removal efficiency of 94.1% and 80.9%, respectively. The Nitrosomonas europaea and Candidatus Kuenenia dominated in the anoxic carried-biofilm, indicating that the coexisting of aerobic and anaerobic ammonium oxidation bacteria enhanced the TN loss in the post-anoxic tank. This study provides an innovative non-aeration technology for biological wastewater treatment and has implications to simplify operation and save energy. [ABSTRACT FROM AUTHOR]

Highlights • An oxygen mass balance was used to account for the effects of macrophytes. • The approach was implemented in QUAL2K. • Mass transfer rates were measured to estimate oxygen equivalents of macrophytes. • Water-quality improvements following an upgrade to the municipal wastewater facility were documented. Abstract A dissolved oxygen (DO) mass balance was developed for a 5.9 km reach of the heavily eutrophied and macrophyte-rich wastewater effluent dominated Silver Bow Creek, MT, USA, to assess water-quality changes following an upgrade to the municipal wastewater facility. Surveys of diurnal DO were completed in 2015 and 2016, and various mass transfer rates were quantified including macrophyte photosynthesis and respiration, macrophyte density, sediment oxygen demand, and reaeration. A DO mass balance model was then developed in QUAL2K, where oxygen equivalents of macrophytes were incorporated as closely spaced diurnally varying point sources (sinusoids). Overall, diurnal DO swings and longitudinal oxygen profiles were reasonably replicated in the pre- and post-upgrade synoptic surveys and models, and the facility upgrade greatly enhanced DO concentrations in the stream. Improvements, however, were not enough to meet the minimum DO criterion for the waterbody. The results above have important implications for assessing DO responses and impairment status in macrophyte-rich streams. Moreover, they suggest wastewater treatment upgrades may not always achieve desired results and that modeling should be conducted a priori to understand receiving-water responses. [ABSTRACT FROM AUTHOR]

Abstract The high energy consumption associated with biological treatment of municipal wastewater is posing a serious impact and challenge on the current global wastewater industry and is also inevitably linked to the issue of global climate change. To tackle such an emerging situation, this study aimed to develop strategies to effectively suppress nitrite oxidizing bacteria (NOB) in pilot-scale mainstream nitritation-denitritation system coupled with MBR for municipal wastewater treatment. The results showed that stable nitrite shunt was achieved, while more than 90% of COD and NH 4 +-N removal were obtained via nitritation-denitritation in the pilot plant fed with real municipal wastewater. Through adjusting aeration intensity in MBR in combination with the integrated control of dissolved oxygen (DO), sludge retention time (SRT) and sludge return ratio, NOB was successfully suppressed with a nitrite accumulation rate (NAR) of more than 80%. Highlights • Pilot scale mainstream nitritation-denitritation coupled with MBR was achieved. • Integrated control of DO, SRT and sludge return ratio was crucial. • Feasible solutions for the overgrowth of NOB in MBR was shown. • Both aeration-associated energy and external organic carbon were saved. • Microbial analysis clearly showed that NOB was suppressed. [ABSTRACT FROM AUTHOR]

Abstract The use of microbial fuel cells (MFC) in the field of electricity generation and wastewater treatment is attracting considerable research attention. Nitrate removal relies on nitrification and denitrification in the cathode. Dissolved oxygen (DO) is an important factor influencing MFC. In this work, the performance of a two-chambered MFC that uses nitrogen wastewater as a substrate was investigated under three different initial catholyte DO microenvironments anoxic (1.5 mg/L), normal-value (3.4 mg/L), and oxygen-rich (4.4 mg/L) conditions. Results indicated that MFC performance depended on the initial DO concentration of the cathode. Power density was the highest under anoxic condition. Furthermore, high-throughput sequencing was used to explore the cathode biofilm and microbial-communities suspension in each stage. Results showed that the predominant genus of cathode electrodes changed from Pirellula to Thermomonas and finally to Azospira. Heterotrophic denitrifying bacterial activity was inhibited under anoxic condition, and the proportion of nitrobacteria increased. Overall, this study showed that MFC can be used for simultaneous power generation and decomposed‑nitrogen treatment by controlling the catholyte DO and improving the reduction efficiency of the cathode. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the efficiency of a novel pilot-scale passively aerated biological filter (PABF) as a low energy consumption system for the treatment of municipal wastewater. It consists of four similar compartments, each containing 40% of a non-woven polyester fabric as a bio-bed. The PABF was fed with primary treated wastewater under a hydraulic retention time (HRT) of 3.5 hr and a hydraulic loading rate of 5.5 m2/m3/d. The effect of media depth, HRT, dissolved oxygen (DO) and surface area of the media on the removal efficiency of pollutants was investigated. Results indicated that increasing media depth along the axis of the reactor and consequently increasing the HRT and DO resulted in great removal of different pollutants. A significant increase in the DO levels in the final effluent up to 6.7 mg/l resulted in good nitrification processes. Statistical analysis using SPSS showed that the reactor performance has significant removal efficiency (p < .05) for all pollutants. Overall results indicated that PABF is a viable ecological engineering approach that can be optimized and applied to improve water quality with minimal consumption of energy and low sludge production compared with conventional activated sludge and trickling filter systems. [ABSTRACT FROM AUTHOR]

Abstract To scale up microbial fuel cells (MFCs), larger cathodes need to be developed that can use air directly, rather than dissolved oxygen, and have good electrochemical performance. A new type of cathode design was examined here that uses a "window-pane" approach with fifteen smaller cathodes welded to a single conductive metal sheet to maintain good electrical conductivity across the cathode with an increase in total area. Abiotic electrochemical tests were conducted to evaluate the impact of the cathode size (exposed areas of 7 cm2, 33 cm2, and 6200 cm2) on performance for all cathodes having the same active catalyst material. Increasing the size of the exposed area of the electrodes to the electrolyte from 7 cm2 to 33 cm2 (a single cathode panel) decreased the cathode potential by 5%, and a further increase in size to 6200 cm2 using the multi-panel cathode reduced the electrode potential by 55% (at 0.6 A m−2), in a 50 mM phosphate buffer solution (PBS). In 85 L MFC tests with the largest cathode using wastewater as a fuel, the maximum power density based on polarization data was 0.083 ± 0.006 W m−2 using 22 brush anodes to fully cover the cathode, and 0.061 ± 0.003 W m−2 with 8 brush anodes (40% of cathode projected area) compared to 0.304 ± 0.009 W m−2 obtained in the 28 mL MFC. Recovering power from large MFCs will therefore be challenging, but several approaches identified in this study can be pursued to maintain performance when increasing the size of the electrodes. Graphical abstract Image 1 Highlights • Window-pane 0.62 m2 cathode successfully installed in 85 L MFC. • The large 15-panel cathode had lower abiotic performance than smaller cathodes. • Power density of 0.083 ± 0.006 W m−2 was obtained using wastewater as a fuel. • Maintaining full coverage of the electrodes maximized the power production. [ABSTRACT FROM AUTHOR]

Abstract Single-chamber sediment microbial fuel cells (SSMFCs) have received considerable attention nowadays because of their unique dual-functionality of power generation and enhancement of wastewater treatment performance. Thus, scaling up or upgrading SSMFCs for enhanced and efficient performance is a highly crucial task. Therefore, in order to achieve this goal, an innovative physical technique of using interface layers with four different pore sizes embedded in the middle of SSMFCs was utilized in this study. Experimental results showed that the performance of SSMFCs employing an interface layer was improved regardless of the pore size of the interface material, compared to those without such layers. The use of an interface layer resulted in a positive and significant effect on the performance of SSMFCs because of the effective prevention of oxygen diffusion from the cathode to the anode. Nevertheless, when a smaller pore size interface was utilized, better power performance and COD degradation were observed. A maximum power density of 0.032 mW/m2 and COD degradation of 47.3% were obtained in the case of an interface pore size of 0.28 μm. The findings in this study are of significance to promote the future practical application of SSMFCs in wastewater treatment plants. Graphical abstract Unlabelled Image [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Enzyme activity of PSB wastewater treatment were studied for the first time. • Oxygen was beneficial for COD degradation and detrimental for PSB growth. • Oxygen promoted PFK and PK activity and inhibited RuBisCO activity. • PFK and PK worked in COD degradation and RuBisCO and HK worked in PSB growth. Abstract Photosynthetic bacteria (PSB) wastewater treatment is a novel method that can simultaneously achieve wastewater purification and recourse recovery. Oxygen conditions can significantly influence PSB metabolism and wastewater treatment; however, the roles of key enzymes in this process have been unclear. This study investigated the effects of different oxygen conditions on respiratory enzymes (hexokinase, HK; phosphofructokinase, PFK; and pyruvate kinase, PK) and the photosynthetic enzyme RuBisCO of PSB. The results showed that HK activity was almost the highest under anaerobic condition; PFK activity was the highest (311 nmol/min∙g) and PK the most quickly reached its peak under aerobic condition; and RuBisCO activity was the highest (107 nmol/min g) under anaerobic condition. The above results illustrated that HK might simultaneously regulate PSB growth and COD degradation, and its main role might be PSB growth regulation. PFK and PK might function in COD degradation while RuBisCO might function in PSB growth. Further, oxygen was beneficial for COD degradation and detrimental for PSB growth. This study provides a theoretical basis for the development of PSB wastewater treatment. [ABSTRACT FROM AUTHOR]

The untreated or incomplete disposal of nitrogen pollutants in the wastewater can cause great harm to the environment. A large amount of ammonia-nitrogen (NH3-N) will consume dissolved oxygen and cause eutrophication. The conventional wastewater treatment process in Malaysia is not efficient enough to remove the NH3-N. Most of the sewage treatment plants (STPs) in Malaysia are open structures which occupy a large area and emit stench. The existing STPs are not suitable for construction in the compact urban areas and some of these STPs operation are costly. This study designs a novel biological water purification system using a biofilm reactor with encapsulated microbes that is known as Mass Bio System (MBS). The MBS had been used in the east of Asia to treat high concentration of NH3-N in the industrial wastewater with high efficiency. MBS has not been reported to treat domestic wastewater. This paper reports the adaptability and verification of the new sewage treatment system based on MBS to treat domestic wastewater in Malaysia. The study will dynamically monitor the key parameters and compared with the conventional extended aeration (EA) process that is the most common STP applied in Malaysia using the same influent conditions. The aim is to verify that the MBS can treat the wastewater to meet the local emission standard where the water discharge shows the characteristics well below the discharge limits. The study showed that the average effluent and removal efficiency of NH3-N was approximately 2 mg/L and 88.6 % (with maximum 99.7 % removal). All evaluated parameters in the MBS showed stability of effluent characteristics and met the requirements of Malaysian sewerage industry guidelines. MBS also offers the co-benefits of energy, and space saving than the conventional process. The process is recommended as an efficient sewage treatment system in Malaysia and other countries with similar climatic conditions. [ABSTRACT FROM AUTHOR]

Managing waste produced from swine farming operations is a significant agricultural and environmental challenge. Confined animal feeding operations continually generate large amounts of animal waste, which necessitates adequate waste management systems. This study examines the use of multistage surface flow constructed wetlands (SFCWs) to treat pig farm sewage. The wastewater removal rate, sediment deposits, physicochemical properties, and microbial community compositions of each segment of a SFCW were examined. The results indicated that removal rates of chemical oxygen demand (COD), total nitrogen (TN), NH4+, NO3−, and total phosphorus (TP) were 89.8%, 97.9%, 98.2%, 87.6%, and 96.4%, respectively, in the multistage SFCW. The general trend showed increase in the dissolved oxygen (DO) concentrations and oxidation reduction potential (Eh) from the beginning of the SFCW to its end. Sediment concentrations of N and P in each segment of the SFCW generally decreased, suggesting their accumulation in each segment. High-throughput sequencing indicated that the bacterial diversity increased over time. Proteobacteria, Bacteroidetes, Chloroflexi, and Firmicutes were dominant in multistage SFCW bacterial communities at the phylum level. Results further indicate that DO and Eh are major environmental factors that influence the bacterial community distribution. Overall, our findings suggest that multistage SFCWs not only improve contaminant removal but also change the bacterial community composition and promote bacterial community diversity. [ABSTRACT FROM AUTHOR]

Abstract In aquatic ecosystems, ammonium is one of the dominant substances in the effluent discharge from wastewater treatment plants and its impact has been widely explored as it is thought, in its toxic form (NH 3), to cause stress on organisms. Little is, however, known about its potential effect on the release of phosphorus (P) from the sediment. In a two-month mesocosm (150 L) experiment, we tested if high loading of ammonium promotes sediment P release and investigated the dominant underlying mechanisms. A gradient of five target ammonium loading levels was used by adding NH 4 Cl fertilizer: no addition/control (N0), 3 (N1), 5 (N2), 10 (N3), and 21 (N4) mg NH 4 Cl L−1 (NH 4 Cl expressed as nitrogen). We found that: 1) significant sediment P release for N3 and N4 but minor release or retention for N0, N1, and N2 were detected both by the total phosphorus concentration (TP) in the overlying water and in situ measurements of diffusive gradients in thin-films (DGT) at the sediment-water interface; 2) overall, TP correlated significantly and positively with total nitrogen (TN) concentrations in the water. Further correlation and path analyses suggested that stimulated alkaline phosphatase activity (APA) was likely the dominant mechanisms behind the ammonium-induced sediment P release and decreased dissolved oxygen (DO) levels (an approximate reduction from 9.2 to 6.6 mg O2 L−1) was likely a contributing factor, particularly in the beginning of the experiment. Graphical abstract Image Highlights • High ammonium loading promoted sediment phosphorus release. • High ammonium increased alkaline phosphatase activity and decreased oxygen. • Phosphorus release was caused mainly by increased alkaline phosphatase activity. [ABSTRACT FROM AUTHOR]

A lab-scale aerobic-anoxic-aerobic (AE1-AN- AE2) MBBR system was tested for the removal of COD, NH+4 -N, SCN-, phenols, and nitrogen from coal gasification wastewater, using a shortcut biological nitrogen removal process. Dissolved oxygen concentration in AE1 was maintained at 1.0 to 2.0 mg/L to ensure stable NO- 2 -N accumulation. Adding methanol wastewater to AN guaranteed denitrification efficiency. AE2 ensured high removal rates of NH+4 -N, SCN-, and phenols. The effects of influent pollutant concentration and hydraulic retention time (HRT) on nitrogen removal were studied. Improving the dissolved oxygen concentration in AE1 eliminated the negative effect of increased organic loading on nitrification, but it affected the stability of nitrosation. Shortening the HRT had negative effects on the performance of the system and performance recovered after it was extended. The average total nitrogen removal rate was 82.6% with a CODmethanol/NO- x-N ratio of 3.5. Biomass and activity of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria were measured to understand the evolution of nitrification. [ABSTRACT FROM AUTHOR]

Constructed wetland (CW) is popular in wastewater treatment for its prominent advantage of low construction and operation cost. However, the nitrogen removal in conventional CW is usually limited by the low dissolved oxygen (DO) and insufficient electron donor. This paper investigated the nitrogen removal performance and mechanisms in the poly (butylenes succinate)-based CW (PBS-CW) while treating ammonia wastewater under different DO levels. The average DO contents in limited-aeration and full-aeration phases were 1.68 mg L−1 and 5.71 mg L−1, respectively. Results indicated that, with the ammonia nitrogen loading rate of 25 g N m−3 day−1, total nitrogen removal ratios in the PBS-CW under the limited-aeration and full-aeration phases were 72% and 99%, respectively. Combined analyses revealed that simultaneous nitrification and denitrification (SND) via nitrite/nitrate were the main microbial nitrogen removal pathways in the aeration phase of the PBS-CW (> 89%). The microbial carrier of biodegradable material was believed to play a significant role in prompting SND performance while dealing with low C/N wastewater. Due to the coexistence of micro-anaerobic zone and carbon supply inside the coated biofilm, the high DO level in the PBS-CW increased the abundance of the nitrifying bacteria (amoA and nxrA), denitrifying bacteria (narG, nirK, nirS, and nosZ), and even anammox bacteria (anammox 16s rRNA). These features are beneficial to many microbial processes which require the simultaneous aerobic, anoxic, and anaerobic environment. [ABSTRACT FROM AUTHOR]