Abstract. The enormous problems caused by the scarcity of potable water and the transmission of waterborne diseases such as cholera, dracunculiasis, hepatitis, typhoid and filariasis in some parts of Nigeria have created a public health concern. Every day thousands of lives are lost due to contact with waterborne diseases. The insufficient medical resources available in developing countries are deployed towards the treatment of waterborne diseases that can easily be avoided if potable water can be made available. This study seeks to investigate the purification of four different water samples (namely water from flowing rivers, freshly dug well or groundwater, rainwater from the rooftops and heavily polluted dirty water) consumed by the people in the local community using a solar desalination method. A single basin solar still was constructed, and experimental studies were carried out to determine the influence of solar insolation and temperature variations on the yield of the distillate for both the passive and active solar stills tested. The quality of the distillate was tested by measuring the total dissolved solid (TDS) and electrical conductivity (EC) and later comparing it to the World Health Organization (WHO) standard for drinkable water. The values obtained after desalination fall within the acceptable/tolerable range for TDS and EC, in accordance with the WHO standard for drinkable water. This analysis provides an indigenous distillation method to enhance the production of drinkable water at a low cost.

Abstract. Many rural farming areas are located far from a reliable electricity supply; hence, obtaining a reliable source of water for crops and livestock can prove to be an expensive venture. A water pump operating on the water-hammer effect requires no external power source and can serve as an effective means of pumping water to a higher altitude once a reliable supply is available. A low-cost small water-hammer head pump was designed to operate on the water-hammer head effect created by the sudden stoppage of a flowing fluid. This design consisted of an inlet section followed by the pump body, a pressure section and an outlet. The experimental set-up for testing the water-hammer head pump was designed with a variable head input and an adjustable head output. For each test configuration, a total of 10 samples of pump supply water and pump exhausted water were collected. The water samples were collected for 30 s in each case. The results showed a non-linear variation of water flow with respect to pump outlet height. The pump was capable of delivering water to a maximum height of 8 to 10 times the height of the input head. The pump operated at average efficiencies of 26 %, 16 % and 6 % when the delivery height was 2, 4 and 6 times the input head height, respectively. There was a 5 % incremental decrease in pump efficiency as the delivery height increased in increments of the corresponding input head height.

Abstract. The increasing world population and growth of industrial development lead to growing water scarcity that, combined with deficient sanitation services, represents serious challenges, particularly in regions like sub-Saharan Africa. Water reclamation is a promising approach to reduce water scarcity, serving as a driving force for better sanitation services and protecting the environment by treating sewage and redistributing for the benefit of other water-dependent applications (e.g., industries). This paper aims to give an overview of the global trends on water reclamation, with a focus on industrial use, and to derive lessons for implementation of water reclamation projects in sub-Saharan Africa. Findings show that extensive experience exists in technology and management practices that can allow successful implementation of water reclamation projects in the region. Under the conditions of deficient sanitation services and low levels of technical expertise, the main challenge is to develop a framework that can facilitate the integration of social and technological methodologies and help in introducing water reclamation in water allocation planning, including the development of specific legislation for industrial water use and disposal.

Abstract. Nowadays, a settling tank's removal efficiency is one of the most crucial matters for all water or wastewater treatment plants (WTPs or WWTPs). The unit can affect WWTP performance and improve the provided effluent quality. In this paper, the geometrical aspects of a settling tank were numerically analyzed via tracer curves, the finite-volume method, and ANSYS CFX software in which the baffle depth and diameter of a settling tank were assessed. Firstly, a previous study was similarly remodeled to verify simulation results. The impact of tank depth variation was numerically assessed where the outcomes showed that a deeper tank could raise discharge time or the hydraulic retention time (HRT). Thus, extensive discharge time may result in less polluted effluent, degrading more solids. However, the tank should not be too deeply based on costs. Moreover, the differential effect of baffle height was analyzed and indicated that lower height is more useful for boosting the HRT. An investigation of tank diameter changes also revealed that wider diameters bring about a broader HRT.

Abstract. The design of a water network involves the selection of pipe diameters that satisfy pressure and flow requirements while considering cost. A variety of design approaches can be used to optimize for hydraulic performance or reduce costs. To help designers select an appropriate approach in the context of gravity-driven water networks (GDWNs), this work assesses three cost-minimization algorithms on six moderate-scale GDWN test cases. Two algorithms, a backtracking algorithm and a genetic algorithm, use a set of discrete pipe diameters, while a new calculus-based algorithm produces a continuous-diameter solution which is mapped onto a discrete-diameter set. The backtracking algorithm finds the global optimum for all but the largest of cases tested, for which its long runtime makes it an infeasible option. The calculus-based algorithm's discrete-diameter solution produced slightly higher-cost results but was more scalable to larger network cases. Furthermore, the new calculus-based algorithm's continuous-diameter and mapped solutions provided lower and upper bounds, respectively, on the discrete-diameter global optimum cost, where the mapped solutions were typically within one diameter size of the global optimum. The genetic algorithm produced solutions even closer to the global optimum with consistently short run times, although slightly higher solution costs were seen for the larger network cases tested. The results of this study highlight the advantages and weaknesses of each GDWN design method including closeness to the global optimum, the ability to prune the solution space of infeasible and suboptimal candidates without missing the global optimum, and algorithm run time. We also extend an existing closed-form model of Jones (2011) to include minor losses and a more comprehensive two-part cost model, which realistically applies to pipe sizes that span a broad range typical of GDWNs of interest in this work, and for smooth and commercial steel roughness values.

Abstract. This paper discusses the development of an easy-to-use, all-in-one model for designing optimal water distribution networks. The model combines different optimization techniques into a single package in which a user can easily choose what optimizer to use and compare the results of different optimizers to gain confidence in the performances of the models. At present, three optimization techniques are included in the model: linear programming (LP), genetic algorithm (GA) and a heuristic one-by-one reduction method (OBORM) that was previously developed by the authors. The optimizers were tested on a number of benchmark problems and performed very well in terms of finding optimal or near-optimal solutions with a reasonable computation effort. The results indicate that the model effectively addresses the issues of complexity and limited performance trust associated with previous models and can thus be used for practical purposes.

Abstract. Experiments on photodegradation of Bisphenol A (BPA) were carried out in water samples by means photocatalytic and photo-oxidation methods in the presence of ZnO, TiO2 and SnO2 catalysts. The objective of this study was to develop an improved technique that can be used as a remediation procedure for a BPA-contaminated surface water and groundwater based on the UV solar radiation. The photodegradation of BPA in water performed under a low-intensity UV source mimics the UVC and UVA spectrum of solar radiation between 254 and 365 nm. The archived results reveal higher degradation rates observed in the presence of ZnO than with TiO2 and SnO2 catalysts during 20 h of irradiation. The intervention of the advanced photocatalytic oxidation (PCO) reduces the time of degradation to less than 1 h to reach a degradation rate of 90 % for BPA in water. The study proposes the use of ZnO as a competitor catalyst to the traditional TiO2, providing the most effective treatment of contaminated water with phenolic products.

Abstract. Household Water Treatment and safe Storage (HWTS) systems aim to provide safe drinking water in an affordable manner to users where safe piped water supply is either not feasible or not reliable. In this study the effectiveness, economic parameters and costs of three selected HWTS systems were identified. The selected systems are SODIS, ceramic filter and biosand filter. These options were selected based on their accessibility, affordability and available scientific data. Data was obtained through peer-reviewed literature, reports, web-pages and informal sources. The findings show a wide dispersion for log removal of effectiveness of the HWTS systems. For bacteria (E. coli), log removals of 1–9 (SODIS), 0.5–7.2 (ceramic) and 0–3 (biosand) were reported. In the case of viruses (mostly echovirus and bacteriophages), log removals of 0–4.3 (SODIS), 0.09–2.4 (ceramic) and 0–7 (biosand) were found. The dispersions of log removals for both bacteria and viruses range from non-protective to highly protective according to WHO performance targets. The reported costs of HWTS systems show a wide range as well. The price per cubic meter water is found to be EUR 0–8 (SODIS), EUR 0.37–6.4 (ceramic) and EUR 0.08–12.3 (biosand). The retail prices found are: negligible (SODIS), USD 1.9–30 (ceramic) and USD 7–100 (biosand). No relationship was observed between removal efficiency and economics of the three systems.

Abstract. Recently, rainwater composition affected by atmospheric pollutants has been the topic of intense study in East Asia because of its adverse environmental and human health effects. In the present study, the chemical composition and organic compounds of rainwater were investigated from June to December 2012 at Gwangju in Korea. The aim of this study is to determine the seasonal variation of rainwater chemical composition and to identify possible sources of inorganic and organic compounds. The volume-weighted mean of pH ranged from 3.83 to 8.90 with an average of 5.78. Of rainwater samples, 50 % had pH values below 5.6. The volume-weighted mean concentration (VWMC) of major ions followed the order Cl− > SO42− > NH4+ > Na+ > NO3− > Ca2+ > Mg2+ > K+. The VWMC of trace metals decreased in the order Zn > Al > Fe > Mn > Pb > Cu > Ni > Cd > Cr. The VWMCs of major ions and trace metals were higher in winter than in summer. The high enrichment factors indicate that Zn, Pb, Cu, and Cd originated predominantly from anthropogenic sources. Factor analysis (principal component analysis) indicates the influence of anthropogenic pollutants, sea salt, and crustal materials on the chemical compositions of rainwater. Benzoic acids, 1H-isoindole-1,3(2H)-dione, phthalic anhydride, benzene, acetic acids, 1,2-benzenedicarboxylic acids, benzonitrile, acetaldehyde, and acetamide were the most prominent pyrolysis fragments for rainwater organic compounds identified by pyrolysis gas chromatography/mass spectrometry (Py-GC/MS). The results indicate that anthropogenic sources are the most important factors affecting the organic composition of rainwater in an urban area.

Abstract. Advanced oxidation with O3 / H2O2 (peroxone) was conducted on pilot plant scale on pre-treated Meuse river water to investigate the conversion of organic micropollutants (OMPs) and the formation of bromate. Fourteen selected model compounds were dosed to the pre-treated river water on a regular basis to assess the efficiency of the peroxone process and to establish the influence of the water matrix. The ozone dose was the main factor in the conversion of the model compounds, however, the ozone dose was limited because of bromate formation. The hydrogen peroxide dosage had only a minor effect on the conversion, but it limited the bromate formation effectively. In terms of limited chemical consumption, maximal conversion and to comply the strict Dutch drinking water act for bromate of 1 μg L−1, a practical peroxone setting was 6 mg L−1 hydrogen peroxide and 1.5 mg L−1 ozone. During the investigation period, the average conversion of the model compounds was 78.9 %. The conversion of OMPs was higher at higher water temperatures and lower concentrations of DOC and bicarbonate. The bromate formation also was higher at higher water temperature and lower bicarbonate concentration and proportional with the bromide concentration, above a threshold of about 32 μg L−1 bromide. The peroxone process can be controlled on basis of the (derived) parameters water temperature, bicarbonate and DOC.