All of the possible strategies to reduce water losses in piped distribution systems follow the law of diminishing returns: the higher the expenditure on water loss reduction, the lower the progressive return in terms of water saved. Therefore, water utilities need to estimate the economic level of water losses (ELWL) so that they can reduce their water loss to the level where the cost to reduce the water losses is equal to the value of the water saved. This paper aims to estimate the ELWL using four different methods: the total cost method, the marginal cost method, the cumulative cost–benefit method, and the component‐based methods. This analysis is based on data (2011– 2016) on the water utilities of the city of Malang (PDAM Kota Malang), Indonesia. It was found that the total cost and marginal cost methods gave almost similar results for ELWL. However, the total cost method is preferred to calculate ELWL because it is the most accurate, easier to apply, and does not need a long data series. In addition, the estimated ELWL for PDAM Kota Malang was 21.76%, which is 3.71% higher than the water loss level estimated in 2016, which means that their strategies to reduce water loss are not cost‐efficient. Moreover, the lack of data is a major challenge in the estimation of ELWL in Indonesia. This study emphasizes the importance of estimating the ELWL so that water utilities, especially in Indonesia, can evaluate their strategies in reducing water loss and improving their cost‐effectiveness.

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Intermittent supply is common worldwide. It triggers households with piped connection to adjust the supply scheme by the use of a water tank with a float valve (FV) at the entrance, which has a major influence on the water meter accuracy. This study investigated the impact of the water tank with a FV on the performance of water meters under intermittent and continuous supply conditions, using laboratory experiments, field measurements, and hydraulic modeling. Results revealed that the inflow rates into the water tank are consistently lower than the outflow rates of the tank. This will always be the case owing to the balancing mechanism of the tank. The flows that pass through the water meter represent the inflows into the tank. Therefore, higher metering errors and more apparent losses are expected for a combination of a water tank, FV, and continuous supply. Besides, different FV types have different hydraulic characteristics. Larger FVs with higher discharge rates tend to maintain the water level close to the full level in the tank and conferred longer periods of low flows, worse meter performance, and more apparent losses. For intermittent supply, results confirmed that higher intermittency levels lead to improved performance of water meters and reduce the apparent losses. This points to the complication in transformation from intermittent to continuous supply worldwide. In this case, water utilities should expect higher meter errors and more revenue losses unless the meter replacement policy recognises lower flows passing through the meter.

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Bank filtration (BF) has been used for many years as an economical technique for providing high-quality drinking water. However, under anaerobic conditions, the aquifer release of undesirable metal(loid)s, such as iron manganese, and arsenic, reduces the bank filtrate quality and thus restricts the application of this technique. This study investigates the impact of the organic-matter composition of source water on the mobilisation of Fe, Mn, and As during the anaerobic BF process. A laboratory-scale column study was conducted at a controlled-temperature (30 ± 2 °C) using different feed water sources. The organic matter characteristics of the feed water were elucidated using excitation-emission spectroscopy techniques integrated with parallel factor framework clustering analysis (PFFCA) model. The experiment was performed at redox conditions between 66 mv and −185 mv. Moreover, batch studies were implemented to study the effect of natural organic matter type (humic, fulvic and tyrosine) and concentration on the mobilisation of the selected metal(loids). The laboratory experiments demonstrated that the mobilisation of Fe, Mn and As during the BF are varied with the organic water concentration and composition of the source water. The fluorescence results revealed that terrestrial and condensed structure humic compounds are more capable to release Fe into the filtrate water. In contrast, Mn exhibited an equal tendency of mobilisation towards all the humic compounds regardless of its origin and structure. However, at a humic concentration higher than 5 mg-C/L, Mn showed more affinity towards lower molecular weight humic compounds. Arsenic was found to be the least impacted by the alteration in the source water organic matter composition; its mobilisation was highly correlated with iron releasing process. On the other hand, the biodegradable organic matter at high concentration (>10 mg-C/L) was found to be highly effective to turn the infiltration area into Fe-reducing environment and thereby elevating Fe and As concentrations in the pumped water. In conclusion, this study revealed that the DOM composition and concentration of the raw water could play an important role in the mobilisation of metal(loids) during the BF processes.

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The effectiveness of bank filtration (BF) is highly dependent on the source water quality (e.g., organic matter composition, pH, and concentration of heavy metals (HMs)). In this study, the impact of dissolved organic matter (DOM) on the removal of selected metals (Cu, Zn, Pb, Se, and Ni) during BF was investigated. Column studies were conducted at 30 °C with feed water sources of different organic matter composition. Excitation–emission matrix fluorescence coupled with parallel factor analysis (PARAFAC–EEM) was used to characterise the organic composition of the feed waters. Moreover, another series of column studies was conducted to assess the impact of natural organic matter type (humic, protein) and concentration on the HMs removals. The experimental results revealed a high Pb(II) removal efficiency during filtration, which depends only slightly on the organic matter content of the feed water. In comparison, the removals of Cu, Zn and Ni ranged between 65 and 95 %; and relied significantly on the organic concentration and composition in the raw waters. Humic compounds (terrestrial or microbial) demonstrated adequate ability to reduce the removal efficiencies of these HMs during the infiltration. Conversely, biodegradable matter was found to be effective in enhancing the sorption of HMs onto the sand grains. The Se-removal was enhanced when the feed water contained a higher concentration of biodegradable matter. In general, it can be concluded that the organic composition of the source water affects profoundly the removal of HMs during the BF, and should be considered in the design of BF systems.

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Bank filtration (BF) is acknowledged as a sustainable and effective technique to provide drinking water of adequate quality; it has been known for a long time in Europe. However, this technique is site-specific and therefore its application in developing countries with different hydrologic and environment conditions remains limited. In this research, a 3-discipline study was performed to evaluate the feasibility of the application of this technique in Aswan City (Egypt). Firstly, a hydrological model was developed to identify key environmental factors that influence the effectiveness of BF, and to formulate plans for the design and management of the BF system. Secondly, water samples were collected for one year (January 2017 to December 2017) from the water sources and monitoring wells to characterize the bank-filtrate quality. Lastly, an economic study was conducted to compare the capital and operating costs of BF and the existing treatment techniques. The results demonstrated that there is high potential for application of BF under such hydrological and environmental conditions. However, there are some aspects that could restrict the BF efficacy and must therefore be considered during the design process. These include the following: (i) Over-pumping practices can reduce travel time, and thus decrease the efficiency of treatment; (ii) Locating the wells near the surface water systems (<50 m) decreases the travel time to the limit (<10 days), and thus could restrict the treatment capacity. In such case, a low pumping rate must be applied; (iii) the consequences of lowering the surface water level can be regulated through the continuous operation of the wells. Furthermore, laboratory analysis indicated that BF is capable of producing high quality drinking water. However, an increase in organic matter (i.e., humics) concentration was observed in the pumped water, which increases the risk of trihalomethanes being produced if post-chlorination is implemented. The economic study ultimately demonstrated that BF is an economic and sustainable technique for implementation in Aswan City to address the demand for potable water.

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Reducing all water loss components to zero is neither technically possible nor economically viable. The water loss components should be accurately assessed and prioritised for a reduction. This paper investigates all methods that break down the water losses in distribution networks into apparent and real losses. Their accuracies and uncertainties are discussed and applications to three case studies in developing countries are presented. The results show that different methods estimate the water loss components differently. Consequently, different reduction measures are planned and prioritised. Interestingly, the least accurate methods have a low level of uncertainty, but more realistic assumptions yield higher uncertainties. This suggests that the uncertainty analysis only assists in improving the outputs of each of the methods but does not demonstrate their accuracy. The cost of water loss varies depending on the used assessment method and the economic feasibility of the reduction measures is significantly influenced. The water loss components should therefore be assessed for the whole network using at least two methods to reasonably model and monitor the loss reduction in water distribution networks.

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Water utilities should monitor their nonrevenue water (NRW) levels properly to manage water losses and sustain water services. However, monitoring NRW is problematic in an intermittent water supply regime. This is because more supplied water to users imposes higher volumes of NRW, and supplying significantly less water results in an unmet water demand but interestingly less NRW. This study investigates the influence of the amount of water supplied to a distribution system on the reported level of NRW. The volume and indicators of NRW all vary with variations in the system input volume (SIV). This is even more critical for monitoring NRWfor systems shifting from intermittent to continuous supply. To enable meaningful monitoring, the NRW volume should be normalised. Addressing that, this research proposes two normalisation approaches: regression analysis and average supply time adjustment. Analysis of the NRW performance indicators showed that regression analysis enables the monitoring of NRW and tracking its progression in an individual system only, but not for a comparison with other systems. For comparing (or benchmarking) a water system to other systems with different supply patterns, the average supply time adjustment should be used. However, this approach presents significant uncertainties when the average supply time is less than eight hours per day.@en

Riverbank filtration (RBF) represents a low-cost and sustainable alternative to advanced treatment technologies to pre-treat or remove several organic micropollutants (OMPs) from surface water. The objective of this research was to investigate the efficacy of biodegradation and adsorption processes in the removal of OMPs at high temperatures (20-30 ± 2 °C) during RBF. Laboratory-scale batch studies were conducted using silica sand at different temperatures (20, 25 and 30 °C) to study the removal of 19 OMPs (6 polyaromatic hydrocarbons (PAHs), 8 herbicides and 5 insecticides) from various water sources with different organic matter characteristics. Simazine, atrazine, metolachlor, and isoproturon exhibited partial persistent characters (16% < removal < 59%), which apparently decreased with increase in temperature. DDT, pyriproxyfen, pendimethalin, β-BHC, endosulfan sulfate and PAHs with high hydrophobicity (solubility in terms of logS < -4) tend to be well adsorbed onto sand grains (removal> 80%), regardless of temperature, redox conditions or type of organic carbon fraction fed to the batch reactors. These findings indicate that these hydrophobic compounds are effectively removed during RBF regardless of the environmental conditions. Hydrophilic compounds (molinate, dimethoate, and propanil) showed temperature-dependent characteristics for influent water with low organic matter; their attenuation increased at higher temperature (removal > 95%) due to the high microbial activity. This study revealed that temperature is an important parameter affecting the removal of OMPs with hydrophilic and low-hydrophobicity characters. However, temperature has less influence on the removal of highly hydrophobic OMPs during RBF process and thus should be considered during RBF system design.@en

Providing safe drinking water is a great challenge for both the developing and the developed world. Increasing demand and source water quality deterioration has led to the exploration of new technological innovations for better water management. Nanotechnology holds great promise in ensuring safe drinking water through designing innovative centralised and decentralised (household-level) water treatment systems. The paper provides an overview of recent advances in nanotechnologies for (household level) water treatment processes, such as its use as nanoadsorbents, photocatalysts, microbial disinfectants and in membranes. Extensive implementation of nanotechnology for water treatment would require overcoming the high cost of the nanomaterials by enabling their reuse and regeneration. This would also ensure minimising potential environmental exposure. Potential advances in nanotechnology must go hand in hand with environmental health to alleviate any undesirable consequences to humans.

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The study was designed to synthesize iron oxide/alumina nanocomposites and to investigate their application as an adsorbent to remove both fluoride and arsenic from aqueous solutions. The nanocomposites were extensively characterized by X-ray diffraction analysis, Brunauer–Emmett–Teller analysis, Fourier transform infrared spectroscopy and zeta potential analysis. The size and morphology of the particles were determined by scanning electron microscopy which revealed an average particle size of ~230 nm. The synthesized nanocomposites were stable for at least 4 h in static conditions as evidenced by particle size measurements. Batch sorption studies were carried out and sorption isotherms and reaction kinetics were analyzed. The nanocomposites followed the Langmuir isotherm model and fitted well with pseudo-second-order reaction for both As and F. The maximum sorption capacity of the nanocomposites for As(III), As(V) and F at pH 7 was 1,136 µg/g, 2,513 µg/g and 4 mg/g, respectively. The presence of F in the model water had a synergistic effect on As(III) and As(V) removal whereas the presence of As had no significant effect on F removal at pH 7. Furthermore, the nanocomposites demonstrated significant antibacterial activity at a concentration of 4 mg/mL with ~3 log reduction of Escherichia coli after 24 h. The results of the study showed that the synthesized nanocomposites can be a promising adsorbents for As and F removal in small-scale water systems.

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A significant portion of the water supplied to people doesn't reach its valid users but instead leaks out of the distribution network, causing water wastage, revenue loss and contamination risks. This paper analyses the leakage rate, leakage components and leakage reduction potential. A minimum night flow (MNF) analysis was carried out on a district metered area (DMA) in an intermittent supply system in Zarqa, Jordan. Leakage was modelled and leakage reduction policies were analysed. Results show that MNF occurs at night or during day time depending on the water levels in customer tanks, implying that one-day MNF analysis cannot be carried out in intermittent supplies and the estimation of the legitimate consumption during MNF is more influential. The potential water savings of the different leakage reduction measures (pressure management; leakage detection; response time minimization) are separately analysed in the existing models in the literature, leading to significant overestimation of the total leakage reduction potential, while these measures are influencing each other. Pressure reduction lowers the failure frequencies but limits the potential of leakage detection surveys, as leaks will become harder to hear and detect. Investigating the inter-dependency relations of these measures is therefore essential for reasonable leakage reduction modelling and planning.

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Lately, due to overutilization of scarce natural resources such as water, tourist islands have been severely threatened. This is also the case in Santa Cruz Island, the main inhabited island of the Galápagos Archipelago. Therefore, a Multi-Criteria Decision Analysis (MCDA) was carried out with the aim of mitigating the future water crisis. The proposed solutions were evaluated in terms of environmental, technical, economic and social criteria. The results indicate that the ‘best’ alternative for municipality representatives is the option including desalination. However, for the other two groups of stakeholders, the chosen option was the one that combined all the proposed alternatives (greywater recycling, specific demand reduction and rainwater harvesting), except desalination. Conclusions show that for most stakeholders the environment is the most important criteria.

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Dissolved organic matter (DOM) in source water highly influences the removal of different contaminants and the dissolution of aquifer materials during bank filtration (BF). The fate of DOM during BF processes under arid climate conditions was analysed by conducting laboratory-scale batch and column studies under different environmental conditions with varying temperature (20-30 °C), redox, and feed water organic matter composition. The behaviour of the DOM fractions was monitored using various analytical techniques: fluorescence excitation-emission matrix spectroscopy coupled with parallel factor analysis (PARAFAC-EEM), and size exclusion liquid chromatography with organic carbon detection (LC-OCD). The results revealed that DOM attenuation is highly dependent (p < 0.05) on redox conditions and temperature, with higher removal at lower temperatures and oxic conditions. Biopolymers were the fraction most amenable to removal by biodegradation (> 80%) in oxic environments irrespective of temperature and feed water organic composition. This removal was 20-24% lower under sub-oxic conditions. In contrast, the removal of humic compounds exhibited a higher dependency on temperature. PARAFAC-EEM revealed that terrestrial humic components are the most temperature critical fractions during the BF processes as their sorption characteristics are negatively correlated with temperature. In general, it can be concluded that BF is capable of removing labile compounds under oxic conditions at all water temperatures; however, its efficiency is lower for humic compounds at higher temperatures.

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Santa Cruz Island (Galápagos Archipelago), like many other tourist islands, is currently experiencing an exponential increase in tourism and local population growth, jeopardizing current and future water supply. An accurate assessment of the future water supply/demand balance is crucial to capital investment for water infrastructure. This paper aims to present five intervention strategies, which are suggested to solve the future water crisis. The strategies combined include environmentally sustainable options such as rainwater harvesting, greywater recycling and water demand management, as well as desalination. These strategies were evaluated under four population growth scenarios (very fast, fast, moderate and slow growths) by using several Key Performance Indicators (KPI's) including water demand, leakage levels, total costs, energy consumption, rainwater delivered and greywater recycled. Moreover, it also aims to develop a methodology for similar islands, using the WaterMet² modelling approach, a tool for integrated of sustainable-based performance of urban water systems. The results obtained show that by 2044 only a small portion of the future water demand can be covered assuming business as usual. Therefore, desalination seems to be the most viable option in order to mitigate the lack of water at the end of the planning period considering the growth trends. However, strategies comprising more environmentally friendly alternatives may be sufficient, but only under slow population growth scenarios.

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The study was designed to synthesize iron oxide nanoparticles and to investigate their application as a sorbent to remove fluoride and arsenic from contaminated water. The nanoparticles, synthesized by co-precipitation, were extensively characterized by X-ray diffraction analysis, Brunauer-EmmettTeller analysis and zeta potential analysis. The size and morphology of the particles were determined by scanning electron microscopy, which revealed an average particle size of ~130 nm. The synthesized nanoparticles were stable for at least 4 h in static conditions as evidenced by particle size measurements. Batch sorption studies were carried out, and sorption isotherms and reaction kinetics were analyzed. The iron oxide nanoparticles were not effective in fluoride removal at the pH and concentrations studied. They followed the Freundlich isotherm model and fitted well with pseudo-first-order reaction for As(III) and As(V) with R2 value of 0.93 and 0.98 at pH 7, respectively. The maximum sorption capacity of the nanoparticles for As(III) and As(V) at pH 7 were 909 and 3,333 µg/g, respectively. The results of the study showed that the synthesized nanoparticles can be promising adsorbents for As removal in small-scale water systems.@en

Tourism exerts a significant pressure on water resources in tropical islands and is the main reason for the increase in water demand. This paper analyzes and quantifies water demand in Santa Cruz, the most populated island of Galápagos Archipelago (Ecuador). The data for this study were collected from a survey of 374 households in the two main settlements, Puerto Ayora and Bellavista. Water supply from different sources was assessed and compared with domestic and tourist water use. The study revealed that the daily average water demand per capita differs 40% between the settlements, mainly resulting from a difference in water tariffs. The tourist sector was also confirmed as the major consumer, accounting for 55% of the total water demand. Lastly, implementation of proper water demand management measures is essential in order to develop consumers’ awareness and sustainable tourism.

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Intermittent water distribution systems are a stark reality in developing countries. Puerto Ayora, the centre of tourism of the Galápagos Archipelago, is not an exception, with its population and tourists suffering from scarce water resources. However, the extreme per capita consumptions, well above those in 24/7 supply situations in many other countries, contradict the (sense of) scarcity. In this study, 18 water meters were installed and a water-appliance diary was carried out in 15 randomly selected households in Puerto Ayora. The aim was to determine and analyse domestic water consumption, as well as the diurnal patterns, also by verifying per capita figures ranging from 40 to 380 litres per capita per day from a previous study. Also, the aim was to find a correlation between the consumption and schedules of distribution conducted by the municipality. The paper also elaborates on typical household appliances used, and gives an insight about a wide range of domestic demands in a predominantly water-scarce area. The conclusions indicate no influence of the specific intermittency patterns to the specific demand, but rather a wide range of different lifestyles, the possible presence of informal accommodations and excessive wastage.

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The study provides a comparative analysis of As (III), As (V) and F removal by iron oxide nanoparticles and iron oxide/alumina nanocomposites. The nanoparticles were characterized by particle size, zeta potential and Scanning Electron Microscopic analysis which showed spherical iron oxide nanoparticles around ~200 nm and nanocomposites around ~300 nm. Batch sorption studies carried out at varying initial concentrations of As and F revealed an enhanced F and As sorption capacity for the nanocomposites. The sorption isotherm showed that the data for As (III), As (V) and F fitted best to Freundlich isotherm for both the type of nanoparticles. The maximum sorption capacity of the iron oxide nanoparticles for As (III) and As (V) at pH 7 were 909 μg/g and 3333 μg/g while the comparative qm values for the nanocomposites were 1000 μg/g and 2500 μg/g respectively. The maximum F sorption capacity of iron oxide nanoparticles was 1.47 mg/g while it was 4.82 mg/g for the nanocomposites. The preliminary results of the study showed that the nanocomposites can be promising adsorbents for both As and F removal in small scale water systems.

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