Showing papers in "Journal of water supply: research and technology. Aqua in 2022"

A combined model based on sparrow search optimized BP neural network and Markov chain for precipitation prediction in Zhengzhou City, China

Abstract: Simulation and prediction of precipitation time series changes are important for revealing global climate change patterns and understanding surface hydrological processes. However, precipitation is influenced by a variety of factors together, showing the characteristics of nonlinear variation patterns. Given that backpropagation (BP) neural network has a strong mapping ability for nonlinear fitting, we consider using BP neural network for precipitation prediction, then use Sparrow Search Algorithm (SSA) to optimize BP network initial threshold and weight information to improve the efficiency of precipitation prediction. To further enhance model predictive performance, the Markov model is employed to predict the residual series of the SSA-BP model, so as to finally construct a combined SSA-BP-Markov model of precipitation. In this paper, the model is used to simulate the rainfall prediction in Zhengzhou City, Henan Province, China, and to compare and analyze with the other traditional models. The empirical prediction results show that the SSA-BP-Markov model is more accurate and the convergence of the algorithm is better. The model provides a new way of thinking for precipitation prediction and is also useful for predicting precipitation in other regions.

Fuzzy logic-based integrated performance evaluation of a water distribution network

Abstract: A water distribution network (WDN) is an essential component of an urban water supply scheme to deliver safe and adequate water to consumers under various operational conditions. This study focuses on the performance evaluation of an urban WDN using fuzzy logic-based aggregation of reliability, resilience, and vulnerability indices. To assess the individual performance indicators, this study advocates the pressure-dependent analysis (PDA) for the hydraulic simulation. Furthermore, it advocates a fuzzy rule-based aggregated performance index (API) that will deliver the outcome in linguistic form and help the decision-maker to prioritize the maintenance of the WDN. The proposed method is illustrated with the help of a real-time WDN for part of Dire Dawa city in Ethiopia. It has been found that the API values for this network are 0.721 and 0.624, respectively, under normal and abnormal conditions, which are just satisfactory. It has been noticed that nodes J4, J44, J47, and J49 are critical from the overall low API. Efforts should be made to improve the hydraulic and residual chlorine conditions at these nodes to increase the API. It is felt that such a methodology will help the decision-makers in improving the performance of an existing urban WDN.

Integrating a GIS-based approach and a SWAT model to identify potential suitable sites for rainwater harvesting in Rwanda

Abstract: The increasing demand of water results in the overexploitation of water resources. This situation calls for more effective water management alternatives including rainwater harvesting (RWH) systems. Due to the lack of biophysical data and infrastructure, the identification of suitable sites for various RWH systems is a challenging issue. However, integrating geospatial analysis and modeling approaches has become a promising tool to identify suitable sites for RWH. Thus, this study aimed at identifying suitable sites for RWH in the Nyabugogo catchment located in Rwanda by integrating a geo-information-based multi-criteria decision-making (MCDM) and SWAT (Soil and Water Assessment Tool) model. Moreover, the sediment yield was compared to the soil erosion evaluated using the Revised Universal Soil Loss Equation (RUSLE) owing to the lack of sediment concentration measured data. The results revealed that about 4.8 and 16.35% of the study area are classified as highly suitable and suitable areas for RWH, respectively. Around 6% of the study area (98.5 km2) was found to be suitable for farm ponds, whereas 1.6% (26.1 km2) suitable for check dams, and 25.9% (423 km2) suitable for bench terraces. Among 50 proposed sites for the RWH structures, 29 are located in the most suitable area for RWH. The results implicated that the surface runoff, sediment yield, and topography are essential factors in identifying the suitability of RWH areas. It is concluded that the integrated geospatial and MCDM techniques provide a useful and efficient method for planning RWH at a basin scale in the study area.

Quantity–quality-based water allocation programming in a reservoir–river system

Abstract: Simulation–optimization approaches are useful methods for the assessment of water resource engineering plans and finding the best management policy at the watershed scale. In this study, to find the optimum operation for a reservoir with the purpose of satisfying water demands while meeting the water quantity and quality criteria, a generic reservoir and river basin simulation model (MODSIM) is coupled with the particle swarm optimization (PSO) algorithm leading to construct the PSO–MODSIM model. With the decision variables of the reservoir's monthly releases, the objective function is to maximize the supply for downstream demands while keeping the electrical conductivity (EC) in the river flow lower than a predefined level at the downstream checkpoint, which is a function of the EC in the agricultural return flows. Moreover, a safe flow rate is defined in which the streamflow should not exceed at the checkpoint resulting in mitigation of the submerging lands damage. Results obtained by the PSO–MODSIM model indicate the ability of the proposed simulation–optimization approach for solving the problem of optimal quantity–quality-based water allocation in a reservoir–river system. For instance, the EC at the checkpoint is decreased by 61% in the optimum reservoir operation state comparing the present situation, whereas the municipal and environmental demands are fully met and the agricultural demands are supplied with a desirable reliability satisfaction level.

Factors influencing economic benefit of rainwater harvesting: an empirical analysis

Abstract: This study examines key factors influencing the economic benefit of rainwater harvesting on the household at the Mongla Upazila in the Bagerhat district of coastal Bangladesh. The household survey questionnaire was used to collect primary data from 1040 households. The Ordinary Least Square (OLS) regression analysis was applied to understand the relationship between economic benefit and factors that can affect economic benefit in the household. The empirical result shows that income (1.103**), storage capacity (0.574***), water price (32708.9***), age of rainwater harvesting (100.083***), and total cost (1.627***) positively impact economic benefit while the number of children (35.531**) has a negative relationship. The finding confirms the validity of statistical hypotheses. In addition, heterogeneity analysis was employed to test the model's strength and robustness check to validate the structural function and efficiency of the regression model. The finding concludes with policy recommendations, especially for rain-intensive countries that focus on (i) formulating and implementing rainwater harvesting policy; (ii) integrating rainwater harvesting as a tool for poverty reduction and achieving sustainable development goals; (iii) minimizing mismanagement of (rain) water that causes floods; (iv) initiate programme and take necessary steps for providing financial and non-financial incentive for rainwater harvesting in commercial, and non-commercial building.

Minimization of halogenated disinfection by-product precursors by Al-based electrocoagulation–flotation (ECF) toward cyanobacteria-laden water

Abstract: The presence of toxic algae, such as Microcystis aeruginosa (MA), in drinking water treatment plants (DWTPs) would contribute to algal organic matter (AOM) as precursors toward disinfection by-products (DBPs). Electrocoagulation–flotation (ECF) has shown promising performance in minimizing algal cells from water and dissolved AOM. This study aimed to investigate the effect of current density (CD) and pH on alumina (Al)-based ECF for removing MA cell and DBPs precursors from cyanobacteria-laden water. The performance of Al-based ECF was evaluated at various CD and pH conditions within 20 min. In addition, the total halogenated DBPs formation of the treated suspension after ECF was quantified. At pH 8, the ECF process with 5 mA/cm2 exhibits the most significant reductions in MA cell and soluble AOM, accounting for 97 and 56%, respectively. Additionally, the precursors of trihalomethanes (THMs) and haloketones (HKs) can be effectively removed with flotation despite their significant release at EC. The tremendous reduction of humic acid-like (HAL) substances in extracellular organic matter (EOM) fraction by ECF leads to the minimized THMs formation potential. In summary, Al-based ECF at pH 8 is effective to remove cyanobacteria and minimize the precursors of regulated THMs along with an insignificant reduction in regulated haloacetic acids (HAAs) precursors.

Evaluating the effect of acute ammonia toxicity in a freshwater ecological environment on the growth and hematological functioning of Clarias gariepinus

Abstract: This study was carried out to evaluate the effect of ammonia toxicity on the growth and hematology of Clarias gariepinus. The mean weight gain of fish 1.52 ± 0.3 g was investigated under laboratory conditions at static bioassay for 96 h and 14 days, respectively. Five treatments of 96 h median lethal concentration LC50 were used, namely, T0 (0.00 g·l−1), T1 (0.40 g·l−1), T2 (0.60 g·l−1), T3 (0.80 g·l−1) and T4 (1.00 g·l−1), and each of these treatment concentrations was replicated three times for both toxicity exposures. The results clearly revealed that 96 h median lethal concentration (LC50) at treatments T4 (4.00), T3 (3.00), T2 (2.00) and T0 (0.00) g·l−1 gave an average mean value of 3.02 ± 0.02 g·l−1 with upper and lower limits of 6.28 and 1.42 g·l−1, respectively. The overall percentage mortality showed more than 71% of fish mortality at T4. Values for the 14 -day sub-acute exposures to ammonia concentrations of T4 (1.00), T3 (0.80), T2 (0.60) and control (0.00) g·l−1 were also obtained. Growth indices indicated significant decreases (P<0.05) in the total feed intake (TFI), specific growth rate (SGR), mean weight gain and food conversion ratio (FCR) compared with the control.

Study on the factors influencing air valve protection against water hammer with column separation and rejoinder

Abstract: Air valves are used to suppress negative water pressures in water transmission pipelines. They also play a key role during the water filling and drainage stages in pipeline systems. However, systematic guidelines for the selection of air valve parameters are lacking. In practical engineering applications, the selection is mainly based on personal experience. If the selected parameters are not appropriate, negative pressures can occur in a pipeline due to insufficient air inflow or destructive water hammer pressures with column separation and rejoinder, which are caused by rapid air discharge. Given the subjectivity of the selection of air valve parameters in engineering applications, this paper introduces the structure and working principle of two different types of air valves. Combined with engineering examples, the one-dimensional transient flow elastic model and the characteristic method are used to conduct numerical simulations in MATLAB to investigate the influences of the air valve type, the inlet and outlet orifice diameters, and the inflow and outflow discharge coefficients on protection against water hammer with column separation and rejoinder. The inflow and outflow coefficients of the anti-slam air valve have a slight influence on preventing water hammers with column separation and rejoinder. The research results provide a theoretical basis for the rational selection of air valves in practical engineering applications.

Hydraulic modeling approach for evaluating the performance of flow-starved water transmission networks

Abstract: The planning and design of water networks in water supply systems are primarily based on demand-driven modeling. The prevailing design provisions, such as minimum diameter, lead to oversizing of the water network, affecting operation. In upstream balancing reservoirs, outflow due to the water transmission network's excessive withdrawal capacity surpasses the available inflow causing flow starvation under intermittent water supply. This flow starvation causes partial flow in the downstream vicinity and forms a standing water column in the balancing reservoir's immediate downstream pipe. Traditional modeling approaches cannot simulate the piped network performance under this phenomenon due to their inability to model partial flow. Hence, a novel modeling approach is developed using a tank with an irregular cross-section, which integrates the hydraulic performance of the tank and the downstream pipe. Additionally, a reservoir and control valve represent the water withdrawal mechanism at the downstream reservoir. The proposed modeling approach simulates performance of a flow-starved water transmission network. A case study based on a real network is used to illustrate the robustness of the proposed approach. The developed modeling approach can serve as a management tool to devise operation schedules, helping better manage the operations of the water networks.

Study on water hammer protection of the siphon breaking structure in the water supply system

Abstract: An appropriate water hammer protective scheme is a significant concern in the operation of water supply projects. According to the special terrain in the water supply project, which forms a siphon breaking structure at the end of the pipeline, three protective schemes were proposed and compared: single vacuum breaking valve (VBV) scheme, VBV and air valve scheme, and VBV and one-way surge tower scheme. Based on the control standards of pipe pressure, three protective schemes were assessed in terms of suppressing the negative pressure caused by a pump trip accident. The results show that the siphon breaking structure with the VBV can achieve good effect protection only in a limited range of pipelines. In the VBV and air valve scheme, the pressure oscillations were obviously caused by repeated inlet and exhaust of the air valves. To avoid supplementing too much gas in the pipe by air valves, which will result in a gas column bridging phenomenon, the VBV and one-way surge tower scheme is proposed and can better meet the requirement of the pressure control standard.

Aqualuz: a new solar disinfection device for treatment of cistern water

Abstract: We conducted field, laboratory and modeling studies to evaluate the efficiency of a new solar disinfection (SODIS) device called Aqualuz for the removal of Escherichia coli (EC) from cistern water in the Brazilian semiarid, for different solar exposure–water temperature conditions. The results indicated EC contamination (100–300 MPN/100 mL) in all tests performed. As compared to the literature, lower exposure times (2.5–4.0 h) and solar radiations (250–410 W/m²) were sufficient for EC elimination. Then, assuming the complete-mix approach and first-order kinetics, it was possible to adjust EC decay rate constants (k) considering three different models: constant k-value, k as a function of water temperature and a new formulation for k as a function of both solar radiation and water temperature. All models performed well with normalized root mean squared logarithmic error (NRMSLE) lower than 20%, but the best fitting was obtained with the new approach. A new relationship between solar radiation and water temperature was also obtained, which allowed model simulations of EC decay for 34 municipalities in the Brazilian northeast, resulting in a color map for the region depicting the exposure periods of 1.8–5.6 h for reaching a 3-log reduction.

A comparative study of the time of concentration methods for designing urban drainage infrastructure

Abstract: The time of concentration (ToC) is an important parameter in rainfall−runoff simulation for designing and evaluating an urban drainage system (UDS). There are several lumped and distributed methods available in the literature for estimating the ToC. However, these methods lead to significantly varied values. Therefore, it is imperative to choose an appropriate and best-suited method for estimating the ToC. This study analyses eight lumped approach-based and two distributed approach-based methods for estimating the ToC in an urban area of Gurugram, a satellite city in the National Capital Region (NCR) of Delhi in India. Considering the ToC obtained by the Natural Resource Conservation Service (NRCS) method as the ‘true’ value, the Carter method among lumped methods and the SWDM method between the distributed methods results in ToC values in agreement with the NRCS method. Furthermore, to study the impact of the underestimation or overestimation of ToC on drainage, the system is evaluated in terms of variation in flood volume, duration, peak discharge, and the time to peak for different ToC values. The simulations were carried out by setting the model in SWMM, and it was found that flood volume increases by 4.25 times and the duration increases by 7.25 times if the ToC is increased from 0.1 to 6.14 h. The results infer that ToC estimation methods significantly impact the design and performance of an urban drainage infrastructure.

Godunov-type solutions for free surface transient flow in pipeline incorporating unsteady friction

Abstract: A finite-volume second-order Godunov-type scheme (GTS) combining the unsteady friction model (UFM) is introduced to simulate free surface flow in pipelines. The exact solution to the Riemann problem calculates the mass and momentum fluxes while considering the Brunone unsteady friction factor. One simple boundary treatment with double virtual cells is proposed to ensure the whole computation domain with second-order accuracy. Results of various transient free-surface flows achieved by the proposed models are compared with exact solution, experimental data, the four-point implicit Preissmann scheme solution, as well as predictions by the classic Method of Characteristics (MOC). Results show that the proposed second-order GTS UFMs are accurate, efficient, and stable even for Courant numbers less than one and sparse grid. The four-point implicit Preissmann scheme may produce severe numerical attenuation in the case of large time steps and unsuitable weighting factors, while the MOC scheme may produce severe numerical attenuation in the case of a low Courant number and could not maintain mass conservation. The numerical simulations considering the unsteady friction factor are closer to the measured water depth variations. The effect of unsteady friction becomes more important as the initial water depth difference increases significantly.

Effects of boiling on iron particles in drinking water

Abstract: Discoloration events in drinking water distribution systems (DWDSs) caused by iron particles have occurred worldwide, and boiling has been applied in drinking water treatment households globally, but the effects of boiling on iron particles are not clear. Here, the effect of boiling on different kinds of iron particles (including loose deposits from the DWDS and their main components FeOOH, Fe2O3, and Fe3O4) was studied. At 10 mg/L, the turbidity values before/after boiling of Fe2O3, Fe3O4, and FeOOH were 134.00/121.00, 25.07/21.22, and 120.40/114.20 NTU, respectively. All the particles had a lower degree of crystallinity after boiling. After boiling, the number of particles in loose deposits increased and the particle size decreased, while iron oxides were on the contrary. Among the three iron oxides, the existence of Fe3O4 and Fe2O3 had different effects on disinfection by-products (DBPs) formation. The activity of microorganisms was the highest under particle concentration of 0.1 mg/L than other concentrations for all the particles, but the total microbiological risks were still very low after boiling. Thus, the boiling treatment would increase the turbidity and risks of the particles. As the particle concentration under low concentration is hard to be found, this risk is hard to be found.

Orange peel activated carbon produced from waste orange peels for adsorption of methyl red

Abstract: The existence of pollutants in the water is a very significant environmental problem that needs to be addressed. This work describes the development and testing of activated carbon made from orange peels, which is effective at removing methyl red (MR) from aqueous solutions, and thus provides a solution to this problem. Adsorbents made in the lab can be characterized by their bulk density, particle size, surface area, and proximate analysis. The surface area of the prepared adsorbent was 512.2 m2g−1. Standard procedures such as XRD, SEM, and FTIR analysis are also used to characterize prepared orange peel-activated carbon. Adsorbent dosage (0.25 to 1.25 g/L), MR concentration (100 to 400 mg/L), temperature (40 to 60 °C), contact time (10 to 60 minutes), and pH (3 to 11) were all examined in this experiment. At an amount of adsorbent of 1 g/L adsorbent, MR concentration of 100 mg/L, and a pH of 11, maximum adsorption has been observed. In order to analyze the results, adsorption models such as the Langmuir and Freundlich were applied. At 60 °C, the adsorption isotherm was found to fit the Langmuir model with 111.11 mg/g. The linear regression correlation coefficient, the R2 value is 0.999. Analytical results showed that MR could be effectively removed by using AC made from waste orange peels as an adsorbent.

Avoidance of operational sampling errors in drinking water analysis

Abstract: The internal audits carried out in the first half of 2019 in water laboratories as part of quality accreditation in accordance with ISO/IEC 17025:2017 showed a high frequency of adverse events in connection with sampling. These faults can be a consequence of a wide range of causes, and in some cases, the information about them can be insufficient or unclear. Considering that sampling has a major influence on the quality of the analytical results provided by water laboratories, this work presents a system for reporting and learning adverse events. Its aim is to record nonconformities, errors, and adverse events, making possible automatic data analysis aiming to ensure continuous improvement in operational sampling. The system is based on the Eindhoven Classification Model and enables automatic data analysis and reporting to identify the main causes of failure. Logic programming is used to represent knowledge and support the reasoning mechanisms to model the universe of discourse in scenarios of incomplete, contradicting, or even unknown information. In addition to suggesting solutions to the problem, the system provides formal evidence of the solutions presented, which will help to continuously improve drinking water quality and promote public health.

Limnoperna fortunei as an invasive biofouling bivalve species in freshwater: a review of its occurrence, biological traits, risks, and control strategies

Abstract: Concerns have been raised about the significant biofouling and environmental problems caused by the large numbers of Limnoperna fortunei clinging to water intake facilities. This review first provides a summary of the occurrence of L. fortunei in typical regions including China, South America, and Japan. Furthermore, this article provides a comprehensive overview of the biological traits, risks, and control of L. fortunei. Importantly, the planktonic larval stage is a critical period for the expansion of L. fortunei. Its biofouling process mainly relies on the adhesion of byssus to substrates. Various physical and chemical methods have been proposed and used to control L. fortunei. Among these methods, sodium hypochlorite has been shown to be effective in preventing the adhesion of L. fortunei by dissolving its byssus at much lower concentrations. Overall, effective and environmental-friendly antifouling strategies are still rare, particularly in drinking water treatment systems, and are encouraged to develop in future studies. This review not only provides a comprehensive understanding of L. fortunei but also helps to guide the prevention and control of L. fortunei.

Research on quantification method of water pollution ecological environment losses

Abstract: Economic and social development have worsened the situation of water pollution and even the ecological environment. It is helpful to quantify the water pollution ecological environment losses for decision-makers to formulate reasonable pollution control plans. However, the current quantitative analyses led by economic methods are not comprehensive and systematic. Therefore, based on the emergy theory and method system of eco-economics, this study analyzed the internal energy flow process of the water-polluted ecosystem, discussed the composition of water-polluted ecological environment loss, and proposed a quantitative model of water-polluted ecological environment loss based on the emergy analysis method. It can reasonably quantify the ecological environment loss caused by water pollution and provide a reference for optimizing regional industrial layout, scientifically formulating pollution control planning, and promoting the sustainable development of the ecosystem. Taking Kaifeng City in Henan Province as an example, the rationality of the model is verified. The results show that the annual average total energy value of water pollution ecological environment loss in Kaifeng City is 3.83 × 1020sej, equivalent to 145 million yuan (0.76) of Kaifeng's GDP in 2018.

Towards the coordinated and fit-for-purpose deployment of Unmanned Aerial Systems (UASs) for flood risk management in England

Abstract: Preparedness for flood emergency response is crucial for effective flood management. The need for advanced flood decision support tools that aid flood management has been recognized by several authors. This work examines the variability that currently exists across England with regard to the Unmanned Aerial System (UAS) data collection and processing strategy in flood emergency events. Expert elicitation was carried out using a tailored questionnaire about UAS deployment in three flood emergency scenarios. The survey highlighted that reduced equipment assembly time, a national network of appropriately qualified UAS pilots and the effective UAS deployment when on-site, can reduce the response time to flood emergency. For improved comparability and reduced bias in data collection and interpretation, clear guidelines on which data products are most beneficial for particular purposes, processing time required, platform and sensor selection may also be necessary. We consider that releasing a comprehensive documentation pack, which includes guidelines, standards and protocols that detail the methods, tools, technology, quantity and quality of data, to UAS pilots on a flood emergency call, will enhance the timely response.

Uncertainty analysis of water quality in water distribution system

Abstract: Water quality simulation is affected by uncertain parameters such as pipe roughness coefficients, chlorine bulk decay coefficients, and chlorine wall decay coefficients, which are usually considered to be fuzzy variables. The minimum and maximum nodal chlorine concentrations and water ages at each α-cut level were obtained by the genetic algorithm (GA) based on EPANET hydraulic and water quality simulation toolkit. The fuzziness of nodal chlorine concentrations and water ages were measured using the fuzziness measure (FM) proposed in this paper. The method was applied to four networks to analyze the fuzziness of nodal chlorine concentrations and water ages. The results indicated that the distribution of nodal chlorine concentrations does not follow typical trapezoid distribution, while the distribution of nodal water ages follows typical trapezoid distribution. In addition, the chlorine concentration and water ages of nodes farther from the source are affected by uncertain parameters to a greater extent. The greater demands of nodes lead to less effects of uncertain parameters on chlorine concentration, and greater effects of uncertain parameters on water ages. This study would help in analyzing the fuzziness of hydraulic and water quality simulation results in WDS under uncertain conditions.

Willingness to pay for improved water supply service in coastal urban settings: evidence from Khulna, Bangladesh

Abstract: The provision of clean water and sanitation has been one of the challenging goals of the Sustainable Development Goals (SDGs) for developing countries like Bangladesh. The southern cities of the country confront the scarcity of fresh and improved water for drinking and sanitation. The study aims to investigate the demand for improved water service among city dwellers and the potential revenue for the water supply authority. The study surveyed 100 households in Khulna city by administering a simple random sampling method. The single-bounded dichotomous choice contingent valuation method revealed that years of schooling, household income, and excessive time in water collection positively affect willingness to pay (WTP) for improved water service. The households are willing to pay US$ 5.05 per month on average for enjoying improved water service, which in turn produces annual revenues of US$ 4.26 million, overriding the current level of revenue by 2.5 times. Additionally, the water supply authority is incurring around US$ 2.14 million of revenue loss annually which can be recovered by supplying improved water to the city households. This study suggests that the government may be able to address the fresh and improved water scarcity in the urban territory by capturing and utilizing the potential revenue efficiently through removing the structural barriers.

Isolation and evaluation of brackish diatoms for the photobiological treatment of reverse osmosis concentrate

Abstract: Recently, the use of brackish diatoms has been proposed to remove various inorganic constituents, such as dissolved silica, nutrients, calcium, and bicarbonate, to enhance the freshwater recovery in reverse osmosis (RO). In this study, nine strains of brackish diatoms isolated from water and sediment samples from several evaporation ponds in California and Arizona were examined for their ability to assimilate silica and remove other constituents from RO concentrate. In addition to two previously reported strains, namely Gedaniella flavovirens PEWL001 and Nitzschia communis PEWL002, several new isolates including Halamphora sydowii PEWL004, Nitzschia sp. PEWL008, and Halamphora sp. PEWL011 were found to remove more than 95% of silica, 95% of ammonia and orthophosphate, and more than 50% of calcium and carbonate within 6 days. Two additional G. flavovirens strains (Psetr3 and Psetr7) collected from a brackish lake in Aomori, Japan, also showed rapid dissolved silica uptake (32 mg L−1 day−1) comparable to the one isolated from an agricultural drainage water evaporation pond in the Central Valley, California. This study demonstrated that the brackish diatoms isolated from the evaporation ponds could be useful for the treatment of RO concentrate, which would possibly enable more sustainable desalination processes.

Risk management during the Covid-19 crisis: business responses in the Polish water utilities

Abstract: Water utilities are an essential service that helps protect public health during crises. The Covid-19 pandemic revealed that crisis preparedness is a crucial capability that water utilities must possess. The purpose of this paper is to identify managerial actions and responses that were undertaken by water utility managers in order to reduce the risk related to the first economic lockdown caused by the unexpected Covid-19 crisis. As water utilities should learn from Covid-19 so as to strengthen their future risk preparedness, the paper offers some theoretical underpinnings on risk management. As a result of literature analysis, we focus on the risk management framework that distinguishes five types of risk. The survey was carried out among 116 waterworks in Poland in April 2020. The results indicate the importance of minimising liquidity risk and supply chain risk, which is relevant to the adopted theoretical framework. The findings also highlight the importance of a category that was not originally included in the research model – that is human resource risk, an area that requires managerial attention in the water utility sector. The results could also provide useful pointers for other water utilities, especially those operating in the same or similar legislative regime.

Enhanced removal of dissolved S2− from a river by the pump-and-treat ex-situ process with enriched consortium

Abstract: S2− is one of the common pollutants in heavily polluted rivers. A pump-and-treat ex-situ process with enriched consortium (PEPEC) was used to remove S2− in this study. The kinetic model of S2− removal was developed, and the inflow ratio of the PEPEC was analyzed according to the results of the kinetic models. The results showed that the S2− removal ratio could reach 97.5% 5 0.5%, when the inflow ratio was controlled at 2% for the PEPEC operation. Meanwhile, the removal efficiency and operation performance were assessed for both the simulating ex-situ and in-situ bench-scale tests. Compared with the in-situ processes, the PEPEC showed a stable operation performance during 120 h of bio-treatment, and the concentrations of S2−, COD, NH3-N and TP in the effluent reached approximately 0.5, 20, 0.5 and 0.5 mg/L, respectively. The time consumption (8 h for one batch) and consortium dosage (3 g for the whole operation) in the PEPEC were significantly less than those in the in-situ processes. The PEPEC presented some potential advantages for the bio-treatment of a heavily polluted river.

Analyzing the economic water loss level with a discrete stochastic optimization algorithm by considering budget constraints

Abstract: Water losses in water distribution systems (WDSs) cause inefficiency of water resources and increase operating costs. Water loss management (WLM) methods generally have high initial investment and operating costs. However, the budget planned within the scope of WLM in administrations is generally limited. Therefore, the most appropriate method should be determined by considering the budget conditions and cost–benefit analysis. The aim of this study is to propose a new economic water loss level (EWLL) model in WDSs with the different budget constraints of 5, 15 and 20% of the annual income. This EWLL model was developed by the discrete stochastic optimization algorithm. The EWLL and economically recoverable leakage volumes were determined by considering the budget constraints. Moreover, the most appropriate methods were determined to reach the EWLL values defined according to the budget constraints. The EWLL was calculated as 8.62% by the optimization model without budget constraints. Moreover, the EWLL values with budget constraints of 5, 15 and 20% of the annual income were determined as 56.82, 21.14 and 18.02%, respectively. This EWLL model will make a significant contribution to the annual planning in WLM depending on the budget constraints of the administrations.

Economic feasibility analysis of variable-speed pumps by simulating 15 multiple water distribution systems

Abstract: The UN Sustainability Goals address measures to reduce environmental pollution. Water distribution systems (WDSs) use electric energy, which pollutes the atmosphere through, at least partly, the burning of coal. This study simulates, through modeling, variable-speed pumps (VSPs) on 15 different real WDSs on the network solver EPANET and analyzes the payback period. An algorithm is introduced here to select the optimal pump speed pattern to save the most energy while satisfying the constrain of sufficient pressure at all times and all locations. It was found that five of the 15 systems operated unsuccessfully using a VSP, due to the VSP operating at lower speeds causing a lower pressure than normal, thereby causing the pressure to become negative. Additionally, a new chart that compares the payback period, project life, and energy costs between the base case and the VSP case was developed and different regions on the chart reflect different decision criteria.

Kinetic and isotherm studies on the removal of reactive Red 2 from aqueous solutions using phosphoric acid activated carbon

Abstract: In the current study, an alternative precursor for the production of activated carbon (AC) is introduced using grape wood. The AC structures and functional groups were studied using a scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The efficiency of prepared AC has been investigated in the removal of Reactive Red 2 (RR2) from an aqueous solution. The effect of main variables, namely dye concentration (100–500 mg L−1), contact time (10–90 min), adsorbent dosage (0.25–12.25 g L−1), and initial pH (3–11) have been assessed on the adsorption process in order to find out the optimum conditions. Langmuir, Freundlich, and Temkin adsorption isotherm models were applied to describe the characteristics of adsorption behavior. Kinetic data were fitted to pseudo-first-order, pseudo-second-order, and intra-particle diffusion models. Based on the results, the highest removal efficiency (97.96%) of RR2 dye was obtained at an initial concentration of 100 mg L−1, adsorbent dose of 12.25 g, contact time of 90 min, and pH 3, which indicated a significant sorption efficiency. The rate of the adsorption fitted well to a pseudo-second-order kinetic model (R2 = 0.99). In addition, the Temkin adsorption isotherm model was found to fit the experimental data (R2 = 0.99).

Modeling the impact of a family structure on household water consumption

Abstract: Household water consumption plays an important role in addressing the problem of water shortage and achieving sustainable water development. To identify, assess, and analyze the impact of a family structure on household water consumption, this study develops a mathematical statistical method to conduct multi-scenario simulations of average annual household water consumption based on data from the 2016 China Family Panel Studies (CFPS). The Kolmogorov–Smirnov test and the two independent sample t-tests were used to obtain the distribution with the highest degree of fitting, and the probability distribution and expected value of average annual household water consumption were obtained from the distribution probability function. The results demonstrated that the Birnbaum–Saunders distribution was the optimal distribution; families comprising one and two generations were dominant in terms of water consumption; and the number of water-saving households was far less than that of households with high levels of water consumption. The findings of this study have valuable implications for water governance and policy optimization.

Factors affecting the seasonal succession of phytoplankton functional groups in a tropical floodplain reservoir in Vietnam

Abstract: Phytoplankton communities can be classified into different groups based on physiological, morphological, and ecological functions. In this study, the responses of phytoplankton functional groups (PFGs) to physicochemical variables and hydraulic regimes were investigated and used as ecological indicators in the Tri An Reservoir (TAR), a eutrophic tropical floodplain reservoir located in southern Vietnam. Altogether, 148 phytoplankton taxa were identified and assigned to 16 PFGs; the four predominant PFG groups were M (Microcystis spp.), MP (filamentous cyanobacteria: Oscillatoria spp., and some other diatoms: Gomphonema angustatum, Navicula sp.), J (green algae: Coelastrum spp., Cosmarium spp., Pediastrum spp., Scenedesmus spp., Staurastrum spp., Tetradesmus spp., Tetraëdron spp., and Xanthidium spp.), and P (Closterium spp., Aulacoseira granulata, Fragilaria spp., Pinnularia spp., and Desmidium baileyi). The average PFG biovolume ranged from 79.6 ± 20.2 to 230.1 ± 69.1 mg/L with M being the dominant group. The trophic state index (TSI) indicated that the water condition was light-eutrophic to hyper-eutrophic. It was found that the large water level fluctuation resulted in seasonal nutrient dynamics, with higher nutrient concentrations and higher turbidity during the low water level period and vice versa. The redundancy analysis (RDA) indicated that the nutrient concentrations, water level fluctuation, and mixing regimes were critical factors in the PFG selection in the TAR. Therefore, we assumed that water level fluctuation management coupled with biological competition have the potential to control toxic cyanobacteria in the TAR. In conclusion, the PFGs are suitable for examining the effects of environmental conditions on phytoplankton dynamics in tropical floodplain reservoirs, but their sensitivity to long-term changes in water quality and eutrophication requires further investigation.

Demystification of the true cost of water within industrial facilities

Abstract: The aim of this work is to provide the necessary steps to acquire the total cost of water at industrial facilities. Therefore, the research was developed in three parts: literature review to identify the available tools related to water management; a case study in the context of the dairy industry; and an analysis and discussion of results achieved. Water applications for process and utility end-users in the manufacturing context require pre- and post-treatment – these are interconnected assets that increase the cost of water, and introduce system inefficiencies, thus, they represent a challenge faced by companies and energy/utility managers. A meta-analysis approach was used to examine data from several independent studies of water management, in order to determine overall trends. The sources utilized during the study were water-related scientific publications, Master theses, books, companies, and standards’ websites. The results of the study highlight that auditing can be used to investigate water flows within productive processes entirely, as well as within individual process units and operations. The present study incorporates water-related thinking about supply and demand costs, opportunities, and strategies, promoting energy systems thinking and providing an internationally replicable solution to calculate the true cost of water.