Showing papers in "Water Science & Technology: Water Supply in 2009"
TL;DR: The methodology used in the Barcelona network for distributing properly the sensors for a good discrimination in the leakage localisation process and the use of GA (Genetic Algorithms) has been proved adequate according to the formulation of the signatures in the sensitivity matrix.
Abstract: This paper proposes a leakage detection method based on detecting significant discrepancies between pressure measurements and their estimations obtained from the simulation of a calibrated water distribution network model. Every sensor in the network will allow to detect a discrepancy in pressure due to leakage depending on its location. Then, a set of well distributed pressure sensors will generate a leakage signature that allows leakage localisation. This paper presents the methodology used in the Barcelona network for distributing properly the sensors for a good discrimination in the leakage localisation process. The methodology for sensor placement uses the pressure sensitivity matrix to the leakage presence. This matrix is normalised and binarised in order to be used as a leakage signature matrix using the standard model based fault diagnosis approach. Sensors may be installed in any node and leakages are simulated as a constant demand that can appear in any node too. The problem of deciding which are the best localisations for a small number of sensors in order to detect and localise leakages is an inverse problem that should be solved using optimisation. The resulting optimisation problem is of discrete nature and very huge for a real network. This type of problem is, in general, hard to solve and very time consuming. The use of GA (Genetic Algorithms) has been proved adequate according to the formulation of the signatures in the sensitivity matrix.
97 citations
TL;DR: The MPC technique is used to generate flow control strategies from the sources to the consumer areas to meet future demands, optimizing performance indexes associated to operational goals such as economic cost, network safety volumes and flow control stability.
Abstract: This paper describes the application of model-based predictive control (MPC) techniques to the flow management in large-scale drinking water networks including a telemetry/telecontrol system. MPC technique is used to generate flow control strategies from the sources to the consumer areas to meet future demands, optimizing performance indexes associated to operational goals such as economic cost, network safety volumes and flow control stability. The designed management strategies are applied to a real case study based on a representative model of the drinking water network of Barcelona (Spain).
64 citations
TL;DR: In this paper, the overall environmental impacts were compared for water importation, reclamation and seawater desalination to address the water scarcity in areas where local supplies are not sufficient.
Abstract: The issues of water supply and management will become more and more critical as the global population increases. In order to meet future demands, water supply systems must be developed to maximize the use of locally available water. It is also important to minimize the impact of water system developments on the environment. In this study, the overall environmental impacts were compared for water importation, reclamation and seawater desalination to address the water scarcity in areas where local supplies are not sufficient. The city of Scottsdale, Arizona was chosen for this study. Life Cycle Assessment (LCA) was performed and it suggests that seawater desalination has the highest impact whereas reclamation shows a relatively lower impact. However, Importation and reclamation systems have comparable results for several damage categories. The impacts of facility operations are significantly higher than the construction phase even when the life-span of infrastructure reduces from 50 year to 10 year. Due to the high impacts associated with the energy use during plant operations, different energy mixes were analyzed for their capabilities to lower the environmental burden.
62 citations
TL;DR: In this paper, liquid chromatography with online organic carbon detection (LC-OCD) was used to characterize NOM in water samples from one of the two water treatment plants serving Amsterdam, The Netherlands.
Abstract: For drinking water treatment plants that do not use disinfectant residual in the distribution system, it is important to limit availability of easily biodegradable natural organic matter (NOM) fractions which could enhance bacterial regrowth in the distribution system. This can be achieved by optimising the removal of those fractions of interest during treatment; however, this requires a better understanding of the physical and chemical properties of these NOM components. Fluorescence excitation-emission matrix (EEM) and liquid chromatography with online organic carbon detection (LC-OCD) were used to characterize NOM in water samples from one of the two water treatment plants serving Amsterdam, The Netherlands. No disinfectant residual is applied in the distribution system. Fluorescence EEM and LC-OCD were used to track NOM fractions. Whereas fluorescence EEM shows the reduction of humic-like as well as protein-like fluorescence signatures, LC-OCD was able to quantify the changes in dissolved organic carbon (DOC) concentrations of five NOM fractions: humic substances, building blocks (hydrolysates of humics), biopolymers, low molecular weight acids and neutrals.
43 citations
TL;DR: In this paper, the authors proposed a velocity criterion to the conventional design criteria, which leads to a branched lay out of distribution networks, that perform better with respect to water quality, continuity of supply and investment costs.
Abstract: Resuspension of accumulated particles in residential networks is the main cause for customers to complain to the water company about the water quality. Preventing the particles from accumulating in these networks can be achieved by high velocities in pipes. Adding this velocity criterion to the conventional design criteria leads to a branched lay out of distribution networks, that perform better with respect to water quality, continuity of supply and investment costs. In close cooperation with fire brigades the conventional fire flow requirements were challenged. Based on modern building codes, it proved possible to reduce the capacity of fire-hydrants to 8.3 l/s (30 m 3 /h) in newly built areas. Six years after the introduction of the velocity criterion the characteristics of the newly laid networks have changed resulting in smaller diameter pipes and reduced length of networks. The amount of 100/110 mm pipes have dropped from 55% of the total length to 45% of total length. The total investment costs for new networks have dropped by 20% in the Netherlands.
41 citations
TL;DR: From a health perspective, drinking-water biofilms can thus act as a reservoir for P. aeruginosa and have to be considered as a source of contamination in water distribution systems.
Abstract: Seeding experiments in flow-through reactors were performed to investigate the incorporation of the opportunistic pathogen Pseudomonas aeruginosa into drinking-water biofilms on ethylene propylene diene monomer (EPDM) rubber as an example of an elastomeric material with a tendency to support biofilm formation. The continuous flow of tap water through the reactor resulted in the formation of biofilms which were in a quasi-stationary state after 14 days with average total cell counts of approximately 1.2 x 109 cells per cm2 and heterotrophic plate counts of about 1.0 x 108 colony-forming units (cfu) per cm2. After introduction of P. aeruginosa, these bacteria persisted in the drinking-water biofilms for at least 7 days and 5 weeks under stagnant and flow conditions, respectively. At the same time, P. aeruginosa was detected in the water phase, indicating detachment of cells from the biofilms. The extracellular polysaccharide alginate and cell-bound lectins LecA and LecB which are known to be involved in monospecies P. aeruginosa biofilm formation had no significant influence on the colonization of established drinking-water biofilms. From a health perspective, drinking-water biofilms can thus act as a reservoir for P. aeruginosa and have to be considered as a source of contamination in water distribution systems.
39 citations
TL;DR: In this paper, two regression-based models are employed, namely multiple and Poisson regression models, to predict failure frequency of watermains in the city of Sanandaj in Iran.
Abstract: An important concern for water utilities managers is the prediction of failure frequency of watermains. To provide insight, reliance can be structured based upon modeling of historical data. In this research two regression-based models are employed, namely multiple and Poisson regression models. The models are derived based on 10 years of historical data collected for the city of Sanandaj in Iran. Several tests to validate each of the models are described. The comparison of correlation coefficients for multiple and Poisson models, besides violating initial assumptions, show that multiple regression-based modeling is inadequate.
33 citations
TL;DR: In this paper, the Dutch multiple barrier approach was used for the removal of organic micropollutants in a drinking water system for The Hague and its surrounding areas, and the results showed that O3/H2O2 is a more energy efficient process compared to UV/H 2O2.
Abstract: Dunea, the drinking water company for The Hague and surroundings, has as objective the production of drinking water of impeccable quality, particularly with respect to organic micropollutants. As organic micropollutants are only a minor part of the total natural organic matter, a challenge is posed in targeting the removal of a very small, specific part of the DOC, without removing all of the natural organic matter. In addition, organic micropollutants encompass a broad range of physicochemical properties, which make their removal by a single treatment step impossible. Combining AOP with artificial recharge and recovery, two complementary processes are expected to provide a hybrid system for organic micropollutant removal, according to the Dutch multiple barrier approach. Pilot-scale experiments with O3 and different advanced oxidation processes (UV/H2O2, UV/O3 and O3/H2O2) were carried out in cooperation between Dunea and ITT Wedeco. The pilot installation had a capacity of about 0.5–2.0 m3/h, with a varying LP-UV-dose, ozone dose and peroxide dose. Atrazine, isoproturone, carbamazepine, diclofenac and ibuprofen are well removed by UV/H2O2 as well as by O3/H2O2. In general, O3/H2O2 is a more energy efficient process compared to UV/H2O2. MTBE is best removed by O3/H2O2, Amidotrizoic acid and iohexol are best removed by UV/H2O2.
29 citations
TL;DR: In this article, the authors investigate the mechanism, influence of operational conditions (e.g., filtration rate, manganese loading) and measures that enhance the removal capacity of the sand media.
Abstract: Most drinking water production plants use rapid sand filters for the removal of manganese from groundwater. The start-up of manganese removal on newly installed sand media is slow, taking several weeks till months. Reducing this period in order to prevent the loss of water during this phase has become an issue of concern. In this study pilot and bench scale experiments were conducted to investigate the mechanism, influence of operational conditions (e.g. filtration rate, manganese loading) and measures that enhance manganese removal capacity of the sand media. Other filter media were investigated with the objective of finding suitable substitutes for the sand. The development of the adsorptive/catalytic coating the sand media in a pilot plant was very slow, notwithstanding the relatively high pH of 8. Low manganese concentration and more frequent backwashing resulted in a longer start up period of the manganese removal. It can not be excluded, that nitrite has a negative effect as well. Measurements in the lab and bench scale tests show that the rate of adsorption/oxidation of manganese in the top layer of the filter bed is too low to explain the complete manganese removal in the filters. It is likely that the adsorptive catalyst in the top layer has partly been covered with ferric hydroxide. From the Freundlich's isotherms determined for 6 different filter media, a crushed medium consisting of mainly manganese dioxide and some silica, iron and aluminium (Aquamandix) followed by iron oxide coated sand, containing some manganese, demonstrated highest adsorption capacities at pHs 6 and 8. These materials can therefore be potential substitutes for sand in situations of slow start-up of manganese removal.
29 citations
TL;DR: In this paper, the effect of temperature on microbial and chemical decay coefficients is presented, and the results indicated that it is possible to express temperature dependence of both microbiological and chemical coefficients using the Arrhenius equation within the tested temperature range.
Abstract: Chloramine decays in distribution system due to wall and bulk water reactions. In bulk water, the decay could either be due to chemical or microbiological reactions. Without such distinction it is not possible to model chloramine decay in an actual distribution system since microbiological decay depends on different factors compared with chemical decay. The dependence of chloramine decay on chemical reactions is mostly understood. Although it is widely accepted that microbiological reactions could accelerate chloramine decay, quantification had not been possible until the microbiological decay factor method was proposed. In this paper, the effect of temperature on microbial and chemical decay coefficients is presented. This was done by following the procedure of the microbiological decay factor method but by varying the temperature of incubation between 18 and 30°C. The procedure was repeated for several samples. The results indicated that it is possible to express temperature dependence of both microbiological and chemical coefficients using the Arrhenius equation within the tested temperature range. Estimated E / R values were found to be 3,551±705 K−1 and 6,924±1,700 K−1 for chemical and microbiological decay rates respectively. Traditionally, it is believed that every 10°C rise would double the decay rate coefficients. However, the E / R value estimated in this study shows that a 16–17°C temperature rise is needed to double the chemical chloramine decay rate. A possible application to predict residuals in summer using winter water quality results is demonstrated. Results indicated that microbial decay factor method could help pre-warning water utilities of possible residual loss in summer. Traditional indicators could not offer such distinction.
28 citations
TL;DR: A specific mineral water off-odor, the so-called "sunlight" flavor produced after UV light exposure, was characterized by sensory analysis in different mineral water samples and ranked according to overall odor intensity.
Abstract: A specific mineral water off-odor, the so-called “sunlight” flavor produced after UV light exposure, was characterized by sensory analysis in different mineral water samples and ranked according to overall odor intensity. The odorants were isolated by means of solvent extraction and stir bar sorptive extraction (SBSE) techniques, respectively. Analyses were performed with two-dimensional (2D) high resolution gas chromatographic (HRGC) separation and parallel mass spectrometric (MS) and olfactometric (O) detection. Additionally, analyses of off-odor-free samples exposed to natural sunlight or to “artificial” UV radiation (replicating natural sunlight) were analyzed to assess off-odor compound formation. 14 common characteristic odorants in commercial off-odor and irradiated samples were identified. These were predominantly saturated and mono or di-unsaturated carbonyl compounds, with several substances exhibiting the characteristic fatty and plastic-like odor impressions. Eight of the compounds identified were detected for the first time as off-odor “sunlight” flavor contributors to mineral water and had amongst the highest flavor dilution (FD) factors in the extracted samples.
TL;DR: In this article, a combined PCOMF and TiO 2 photocatalytic oxidation was combined with microfiltration to remove humic acid (HA) in waters through investigating the flux performance, TOC, UV254 and UV436 removal efficiency, the fouled membrane surfaces by SEM.
Abstract: TiO 2 photocatalytic oxidation was combined with microfiltration (MF) (PCOMF) to remove humic acid (HA) in waters through investigating the flux performance, TOC, UV254 and UV436 removal efficiency, the fouled membrane surfaces by SEM. The results demonstrated that the combined PCOMF process showed a high removal efficiency of UV254 and UV436 of HA (close to 100%). The removal efficiency of TOC was about 84.34% indicating that most of HA was mineralized into water and carbon. The SEM images witnessed that the fouling on the membrane surfaces contaminated by PCO effluents after UV254 and UV365 light irradiation was mainly attributed to cake layer, which was reversible due to the increase of aggregated particles size consisting of HA and TiO 2 . Eventually, the combined PCOMF process displayed an improved effect on HA removal and fouling control to a certain level.
TL;DR: In this article, the authors investigated the use of volcanic ash, pumice and Moringa oleifera (M. oleifa) for removal of natural organic matter (NOM) at Kampala and Masaka water treatment plants in Uganda.
Abstract: Volcanic ash, pumice and Moringa oleifera (M. oleifera) were investigated as indigenous materials for removal of natural organic matter (NOM) at Kampala and Masaka water treatment plants in Uganda. Coagulation and filtration experiments were done using raw water at Kampala (Ggaba) and Masaka (Boma) National Water & Sewerage Corporation water treatment plants. Assessment of the two plants was done and they were found to be faced with differing challenges given the nature of their raw water sources. Therefore, the study was conducted to seek appropriate treatment processes that suite the conditions at the respective plant and avoid or minimize formation of unwanted chlorination by-products. The results from the study indicated that there were both operational and design handicaps at the Ggaba treatment plant with a need to modify the filtration and clarification units. At Masaka, pre-chlorination led to increases in total trihalomethanes as high as 4000%. The characterization studies indicated the major fraction of NOM to be hydrophilic and there was no variation in the character of NOM along the unit treatment processes investigated. On the other hand experiments conducted at both the pilot and laboratory scale gave promising results. Simple horizontal flow roughing filter at Masaka gave rise to dissolved organic carbon (DOC) and ferrous iron removals of 27% and 89% respectively. With a combined use of pumice and hydrogen peroxide in the filter, DOC removals of up to 68% were achieved. The results from jar test experiments also indicated that use of alum with M. oleifera coagulant extracted with sodium chloride solution as coagulant aid is promising as a first stage in the treatment train for waters with a humic materials and high content of iron, typical of swamp water sources. Therefore the findings show that it is possible to avoid the formation of unwanted by-products by application of roughing filtration with hydrogen peroxide in place of the pre-chlorination process. Assessment of the characteristics of the volcanic ash showed that it meets the requirements for a filtration material; and results obtained from the pilot study showed that it was a suitable alternative material for use in a dual media filtration system. There was an increase in the filter run length of about two and half fold in the dual media filtration column compared to the mono medium column.
TL;DR: In this paper, the authors describe how the management of pressure can help reduce the leakage in the water distribution network, and the results indicate that the average reduction in pressure by 2.4 m can reduce leakage by 1 2.5% of the system inflow without compromising the level of service.
Abstract: Losses of water due to leakage occur in every distribution network, the only difference is in the amount of leakage. The leakage levels are relatively high in cities of developing Asian countries. Among the several factors, operating pressure is the most important affecting the leakage. This paper describes how the management of pressure can help reduce the leakage in the water distribution network. EPA N ET is used to develop the hydraulic model to analyse the effect of alternative pressure profiles on the leakage in a pilot area within the water distribution system of Bangkok. One of the alternatives is implemented in the field to verify the applicability of the model. Results indicate that the average reduction in pressure by 2.4 m can reduce the leakage by 1 2.5% of the system inflow without compromising the level of service.
TL;DR: In this article, the formation of DBPs in Nile River source water with a view toward optimizing conventional treatment, focusing on enhanced coagulation, to achieve reduction in DBP formation potential (FP) in a cost-effective scheme.
Abstract: Recent studies in communities in greater Cairo, Egypt have identified trihalomethanes (THMs) and haloacetic acids (HAAs) at levels that exceed regulatory limits depending upon the season The objective of this study was to better understand the formation of DBPs in Nile River source water with a view toward optimizing conventional treatment, focusing on enhanced coagulation, to achieve reduction in DBP formation potential (FP) in a cost-effective scheme To this end, characterisation of natural organic matter (NOM) in Nile raw water and after treatment by fractionating according to hydrophobic-hydrophilic properties was included in the analysis Seasonal variations in raw water quality were found to be important for achieving optimum reduction of turbidity and DBP formation In summer, alkalinity is lower; therefore, enhanced coagulation with 30 mg/L alum can be done at pH 6 without excessive additions of acid, and satisfactory reductions in turbidity and DBPs attained During the remainder of the year, high alkalinity results in enhanced coagulation at about pH 65 and notably lower reduction of NOM, THMFP, and HAAs versus summer conditions Supplementing enhanced coagulation with 10 mg/L PAC is highly recommended for these conditions as it improves removal of all DBP indicators The transphilic fraction was the main contributor to DBP formation and the primary fraction removed by enhanced coagulation for achieving gains in THMFP reduction
TL;DR: The NDMA formation potential of four commonly used amine-based cationic water treatment polymers was assessed in reactions with chlorine-based oxidants (free chlorine, monochloramine and chlorine dioxide) and nitrosifying agents (nitrite and nitrate).
Abstract: The NDMA formation potential (NDMA FP) of four commonly used amine-based cationic water treatment polymers was assessed in reactions with chlorine-based oxidants (free chlorine, monochloramine and chlorine dioxide) and nitrosifying agents (nitrite and nitrate). Relatively high dosages of polymers were directly exposed to oxidants for long reaction times in the FP tests to assess the potential to form NDMA and obtain mechanistic insight. Results show that the NDMA FP of the polymers generally follows the trend of aminomethylated polyacrylamide (Mannich polymer)>>poly(epichlorohydrin-dimethylamine) (polyamine) > poly(diallyldimethylammonium chloride) (polyDADMAC) > cationic polyacrylamide copolymer (cationic PAM). The high NDMA FP of Mannich polymer was largely due to the high amount of dimethylamine (DMA) residue in the polymer solution. For the other three polymers, the DMA concentration was increased after oxidation, indicating polymer degradation, and the trend of DMA increase agreed with that of NDMA FP. Among the oxidants, NDMA formation followed the order of monochloramine > free chlorine > chlorine dioxide, despite that the DMA release from the polymers caused by the oxidant followed the opposite order. At equal dosages, nitrite and nitrate generated NDMA from the polymers at levels comparable to those by free chlorine and chlorine dioxide; even so, the nitrosifying agents are unlikely to contribute significantly to NDMA formation due to expected lower concentrations in drinking water treatment systems. Jar tests followed by monochloramination of real water samples using conditions in line with those at potable water treatment plants generally showed relatively small contributions from polyamines and polyDADMACs to the overall NDMA formation.
TL;DR: In this article, the authors investigated the price and income elasticity of residential water demand in Poland and the determinants thereof, including both water tariffs and income levels, and found that the indicators of price elasticity are similar to those being known from the relevant surveys conducted in Western Europe.
Abstract: This paper analyzes residential water demand in Poland and the determinants thereof, including both water tariffs and income levels. Information on the price and income elasticities of residential water demand is crucial for effective management of water demand. We carried out this empirical analysis using several panel-data models. The analysis is based on data provided by the urban municipalities, in which the number of the end-users connected to water supply networks exceeded 50,000. We focused on the larger cities to obtain sample homogeneity in terms of the access to water supply and sewage collection systems, as well as the income structure. We found that the indicators of price elasticity of residential water demand in Poland are similar to those being known from the relevant surveys conducted in Western Europe. However, the income elasticity is smaller in absolute terms when compared to that in countries with more developed economies. Based on the results obtained, our prediction is that the decreasing trend of individual water consumption in Poland will slow down in the next few years. Our study is one of the first to investigate the price and income elasticities of water demand in Poland, and also one of the first such ones carried out for economies in transition.
TL;DR: In this article, a water resources system in the Bagmati River Basin (BRB) in Nepal from the perspective of both stress and adaptive capacity is analyzed based on evaluation of eleven indicators, eight parameters, two sub-indices and an index.
Abstract: It is widely accepted that water resources are vulnerable to socioeconomic development and environment change including climate change/variability. So, analyzing the type and extent of stresses (that render water a vulnerable resource) and the capacity of the system to adapt is necessary for integrated water resources management. This paper departs from the common notion that links vulnerability to water crisis, and analyzes a water resources system in the Bagmati River Basin (BRB) in Nepal from the perspective of both stress and adaptive capacity. The analysis is based on evaluation of eleven indicators, eight parameters, two sub-indices and an index. The situation analysis in basin and sub-watershed scale suggests considerable variation in parameter values and vulnerability index in different geographical (basin and sub-watershed) and spatial (three sub-watersheds) scales within the BRB, revealing the need for differential policy interventions based on scale. The northern sub-watershed in the BRB which has favourable climate for human settlement and cultivation, is more vulnerable than the southern sub-watershed. Relatively higher vulnerability in northern sub-watershed is due to high stress (related mainly to water scarcity) and low adaptive capacity (related mainly to low natural capacity). The comprehensive and easily interpretable finding is expected to help decision makers to reach sound solutions to reduce vulnerability of water resources system in the dynamic environment.
TL;DR: It was concluded that MIEX ® Resin removes organics recalcitrant to coagulation from raw water and therefore increases DOC removal when both methods are combined.
Abstract: The aim of the research presented in this paper was to gain greater insight into the characteristics of NOM removed by MIEX ® Resin. Previous studies have shown that MIEX ® Resin increases the level of removable DOC when used in combination with coagulation, suggesting that these two processes target a different type of organics. Initially the characteristics of DOC in regenerant solutions from four different MIEX ® Resin treatment plants were analysed and compared to DOC in the respective raw water. Following this the raw water and the regenerant solutions were coagulated and the characteristics of the residual DOC analysed and compared to the regenerant solutions prior to coagulation. From the regenerant solutions it was seen that MIEX ® Resin targets DOC of increased UV 254 absorbance, increased charge density and of mid to low molecular weight (5 to 2 kDa). In terms of hydrophobicity no preference of MIEX ® Resin for a specific NOM type was seen. The presence of hydrophilic neutral acids in the regenerant solution was unexpected since the removal of only highly charged organic species was expected. Charge density measurements however revealed the presence of functional groups, allowing hydrophilic neutrals to be removed by anion exchange. Comparative coagulation of the raw water and regenerant solution showed that both a residual DOC of similar hydrophobicity in the sub 3 kDa area. Considering that this DOC fraction was present in the regenerant it was concluded that MIEX ® Resin removes organics recalcitrant to coagulation from raw water and therefore increases DOC removal when both methods are combined.
TL;DR: In this paper, a post-treatment process is proposed to supply water with alkalinity, Ca 2,+, and calcium carbonate precipitation potential values as required in the new criteria, along with the addition of a threshold Mg 2, +, concentration recently recommended by the WHO.
Abstract: The recent supply of large volumes of seawater desalinated water in Israel prompted both the development of new water quality standards and the development of a novel post treatment process, designed to comply with the new standards at a cost effective price. The new process is designed to supply water with alkalinity, Ca 2 + and calcium carbonate precipitation potential values as required in the new criteria, along with the addition of a threshold Mg 2 + concentration recently recommended by the WHO. The current paper describes the process in general, and focuses in particular on attaining these criteria while maintaining a low total hardness concentration (120 mg/L as CaCO 3 ). The process is based on dissolving calcite using H 2 SO 4 and replacing the excess calcium ions generated in this process by Mg 2 + ions (using a specific cation exchange resin—Amberlite) and by Na + (using a second cation exchange resin—chabazite, from the zeolite group). Once exhausted the resins are re-loaded with Mg 2 + and Na + by the brine generated in the RO process, thus no unwanted brines are generated. A case study is presented for which operational costs were approximated at 0.034 $US/m 3 product water.
TL;DR: Four case studies are presented with increasing level of detail, showing the type of information that is required for each of these levels and how each level informs risk management.
Abstract: System assessment is the part of the Water Safety Plan that evaluates whether a water supply system is capable of producing drinking water that meets the health-based targets. System assessment can be done at increasing level of detail, requiring more site specific information as the level of detail increases. Four case studies are presented with increasing level of detail, showing the type of information that is required for each of these levels and how each level informs risk management. The first case study shows how a system assessment can be performed without other site specific information than the type of source water and the type of treatment processes. The required data for the system assessment are collected from the large body of literature available. The second case study uses site specific microbial indicator data. The third study uses pathogen data and the fourth case study combines data on pathogens, microbial indicators and process parameters. The case studies show that the level of detail required largely depends on the risk management question.
TL;DR: In this paper, the authors proposed the fabrication of one-dimensional TiO 2 nanotubes through hydrothermal method, which showed excellent performance with complete photodegradation of humic acid (HA) in comparison with the 97.7% removal efficiency of P25.
Abstract: Heterogeneous photocatalysis is a promising technology in addressing the incapability of current water technology. In this present paper, we proposed the fabrication of one-dimensional TiO 2 nanotubes through hydrothermal method. Various techniques were used to characterize the nanotubes, i.e. FESEM, HRTEM, XRD and BET. Subsequently, the evaluation of photocatalytic oxidative (PCO) properties of TiO 2 nanotubes are compared with the commercial TiO 2 P25 (i.e. TiO 2 powder) in PCO batch reactor. The TiO 2 nanotubes show excellent performance with complete photodegradation of humic acid (HA) in comparison with the 97.7% removal efficiency of P25. The TiO 2 nanotubes are also tested in membrane filtration for verification of catalyst separation and recovery. The TiO 2 nanotubes were totally separated and recovered with membrane filtration. Lastly, its stability is tested in repeated reuse experiments. No catalyst deactivation is observed after five consecutive PCO experiments of newly added HA. Therefore, our novel nanostructured photoctalyst is an advancement in photocatalytic technology that has significant impact for current water technology.
TL;DR: In this article, the mechanism of NOM removal by coagulation is investigated using coagulant polyaluminium chloride (PACl), compared with AlCl3, by using programmable jar test, photometric dispersion analyzer and ferron assaying.
Abstract: In this paper, the mechanism of NOM removal by coagulation is investigated using coagulant polyaluminium chloride (PACl), compared with AlCl3. The kinetics of Al ion hydrolysis, interaction of hydrolyzed species of Al and NOM, and hydraulic power condition in coagulation process are investigated by programmable jar test, photometric dispersion analyzer and ferron assaying. After the coagulant dosing, Al ion would hydrolyze very quickly, and then monomeric Al and small polymeric Al would further hydrolyze to form larger polymer and precipitate, based on pH condition, while the further hydrolyzed process is relative slow. Although complexation between NOM and Al appears to be several orders of magnitude slower than hydrolysis of monomeric forms of Al, it would be faster than further polymerization and precipitation of Al during aging. However the further polymerization of fresh Al would benefit to Al-NOM complex aggregation and settlement. Therefore, PACl, with stabile preformed polymer shows significantly different performance in NOM removal compared with AlCl3. Although the hydraulic power condition plays significant role in collision frequency and efficiency of particles removal, the process of the aggregation to form larger floc to settle down is relative slower than interaction of Al and NOM, and it is not very correlative to the performance of NOM removal if only it can provide enough mixture.
TL;DR: In this article, the performance of four different membranes, one made of polyvinylidenefluoride (PVDF), three polytetrafluoroethylene (PTFE) of different pore sizes, were assessed under different hot feed flow rates and inlet temperatures.
Abstract: Membrane distillation has been a known desalination process for many years, but its commercial implementation has been hampered by low water fluxes and the need for low cost heat sources. With greater emphasis being placed on energy efficiency, membrane distillation coupled with waste heat or solar heat sources to drive the process is being reconsidered. In particular, the use of membrane distillation to treat brine concentrates is receiving renewed attention, as it results in increased water recovery and lower brine discharges, and high salt concentrations do not increase the driving force requirements for membrane distillation. In this paper, four different membranes, one made of polyvinylidenefluoride (PVDF) and three made of polytetrafluoroethylene (PTFE) of different pore sizes, were assessed the performance in membrane distillation under different hot feed flow rates and inlet temperatures. The results show that the PTFE membranes had a much higher flux than that of PVDF at the same operational conditions, and PTFE membranes of large pore size produced higher flux than that of the small pore size. The results also showed that increasing the flow rate of the hot feed and its inlet temperature increased the flux, but the rates of increase decreased with increasing flow rate and inlet feed temperature.
Abstract: High quantum yield (1.4molEs ―1 ) of hydroxyl radicals (·OH) from photolysis of chlorine under typical disinfection conditions indicates the potential of UV/chlorine coexposure in serving as both disinfection and advanced oxidation processes (AOP). In this study, photolysis of chlorine and bromine was explored in buffer and simulated natural water solutions under low-pressure UV (LPUV) and medium-pressure UV (MPUV) lamps. At pH 6.5 and 8.5, the quantum yields of bromine photolysis were 3.8 and 0.6 for MPUV, and 4.4 and 0.8 for LPUV, respectively. At pH 6.5, the photolysis of bromine was faster than that of chlorine under either MPUV or LPUV source, while at a higher pH of 8.5, the contrary was found. For all conditions tested, the presence of bromide did not significantly change the observed photolysis rate of total free halogen during the UV/chlorine process in the presence or absence of natural organic matter. Upon UV irradiation, chlorine always produces higher ·OH concentration than bromine does. The presence of bromide results in considerable decrease of ·OH concentration at p H 6 . 5 , compared to that obtained from the UV/chlorine process in the absence of bromide.
TL;DR: In this paper, the authors presented a model of optimization to guarantee the delivery of enough water to populations, for each day, in order to achieve that, energy for pumping is needed, representing the main cost for the companies that operate the systems.
Abstract: Water supply systems frequently present high-energy consumption, which correspond to the major expenses of these systems Energy costs are a function of real consumption and the daily energy tariff
This paper presents a model of optimization to guarantee the delivery of enough water to populations, for each day Although, in order to achieve that, energy for pumping is needed, representing the main cost for the companies that operate the systems The model, developed in MATLAB®, provides the best solution to take in each time step Simultaneously the population water consumption must be guaranteed, and the hydraulic system restrictions fulfilled The definition of optimal pumping schedules allows the reduction of operation and maintenance costs associated with pumping energy, as well as the increase of global hydraulic system efficiency The rules are subsequently introduced into a hydraulic simulator (EPANET), to verify the system behaviour along the simulation period In addiction, a water turbine is introduced in one of the system's branches The economical benefits from the generated energy from the water turbine can not be neglected and the wind complementary turbine for pumping supply provides also significant economical savings
TL;DR: In this article, the effect of acid treatment on porous carbon materials on their double layer capacitance and electrosorption of ions in capacitive deionization systems was reported.
Abstract: We report the effect of acid treatment on porous carbon materials on their double layer capacitance and electrosorption of ions in capacitive deionization systems. The as-received activated carbon cloth (ACC) had the capacitance value of 210 F/g and was markedly (∼175%) improved when treated with acid solution. Surface functional groups such as hydroxyl, quinines, lactones and ethers on carbon after modification were increased by 40% and 29% with HNO 3 and H 2 SO 4 respectively. In capacitive deionization test of NaCl solution, the ACC treated with HNO 3 had more than two times removal efficiency when charged with a 1.5 V current than the untreated one. This is attributed to activation and changes of surface functional groups when charged with a current.
TL;DR: In this article, a decision support tool for reservoir management which takes into account short-, mid-and long-term factors for water quality change is presented. But the tool is intended to simulate not only water quality, but also management impact on flood risk prevention and drinking water quality (treatment efficiency and costs).
Abstract: Reservoir water for drinking water production may undergo major short-term and long-term quality changes. These are results of natural processes in the water body and of the water's quality entering and leaving the reservoir. Long term quality changes are due to management of catchment areas, but also to a considerable extent by external impacts like climate change. Short term quality changes are impacted by extreme events like rain storms after drought periods, which might also be a result of climate change. Furthermore, short- and mid-term quality changes are impacted by reservoir management, which also influences the ecological state of rivers downstream the reservoir. The purpose of our work is to develop a decision support tool for reservoir management which takes into account short-, mid- and long-term factors for water quality change. With the tool it is intended to simulate not only water quality, but also management impact on flood risk prevention and drinking water quality (treatment efficiency and costs) and to assist decision making for reservoir management.
TL;DR: In this article, the degradation of geosmin and 2-methylisoborneol (MIB) was investigated using an immobilised TiO2 photoreactor, and the degradation rate was found to follow similar pseudo-first-order kinetics with reaction rate constants being approximately 0.025 min-1.
Abstract: Photocatalytic degradation of geosmin and 2-methylisoborneol (MIB), which are two taste and odour compounds commonly found in drinking water supply sources, was investigated using an immobilised TiO2 photoreactor. It was found that the degradation of geosmin and MIB followed similar pseudo-first-order kinetics with reaction rate constants being approximately 0.025 min-1 for typical geosmin and MIB concentrations of 250 and 500 ng/L. The normalised formal quantum efficiency was calculated to be in the range of 162–182 L/mol. Influence of additives (i.e. sodium bicarbonate and alcohols) on the degradation process was also investigated. It was found that there was a small reduction in the degradation rate constants of geosmin and MIB with increasing sodium bicarbonate concentration. At 50 mg/L sodium bicarbonate the degradation rate constants decreased by approximately 5%. Similarly, for methanol and ethanol concentrations up to 35 and 50 mg/L, respectively, these constants were found to also decrease. While addition of sodium bicarbonate and alcohols was seen to have relatively small negative effects on the photocatalytic degradation performance, the magnitude of their influence was consistent with the hypothesis that the degradation mechanism of geosmin and MIB was predominately that of attack involving HO∙ radicals.
TL;DR: In this article, a model based optimization of operation of a drinking water treatment plant by direct control of water quality objectives is discussed, which leads to less bromate formation at the same disinfection capacity.
Abstract: In general, the available control actions in drinking water treatment plants are not directly related to the process objectives for water quality. Model based optimization of operation of a drinking water treatment plant by direct control of water quality objectives is discussed. Plant control with PID controllers is embedded in the model of a drinking water treatment plant and the ozonation process in the plant is used as a case study. It is concluded that direct control of water quality objectives, e.g. Giardia inactivation for ozonation, can largely reduce uncertainty and variation in process performance and leads to improvements of drinking water quality. In the discussed case it led to less bromate formation at the same disinfection capacity. Embedded plant control with PID controllers in the model of drinking water treatment plants through the use of code for writing control functionality has a large potential for model based optimization of operation.