Water Science and Technology: Water Supply

The provision of high quality urban water services, the assets of which are often conceptualised as ‘blue infrastructure’, is essential for public health and quality of life in the cities. On the other hand, parks, recreation grounds, gardens, green roofs and in general ‘green infrastructure’, provide a range of (urban) ecosystem services (including quality of life and aesthetics) and could also be thought of as inter alia contributors to the mitigation of floods, droughts, noise, air pollution and urban heat island (UHI) effects, improvement of biodiversity, amenity values and human health. Currently, these ‘blue’ and ‘green’ assets/infrastructure are planned to operate as two separate systems despite the obvious interactions between them (for example, low runoff coefficient of green areas resulting in reduction of stormwater flows, and irrigation of green areas by potable water in increasing pressure on water supply systems). This study explores the prospects of a more integrated ‘blue-green’ approach – tested at the scale of a household. Specifically, UWOT (the Urban Water Optioneering Tool) was extended and used to assess the potential benefits of a scheme that employed locally treated greywater along with harvested rainwater for irrigating a green roof. The results of the simulations indicated that the blue-green approach combined the benefits of both ‘green’ and ‘blue’ technologies/services and at the same time minimised the disadvantages of each when installed separately.

An algorithm for the detection and location of sudden bursts in water distribution networks combining both continuous monitoring of pressure and hydraulic transient computation is presented. The approach is designed for medium and large bursts that are the result of the sudden rupture of the pipe wall or other physical element in the network and are accompanied by the transient pressure wave that propagates throughout the network. The burst-induced transient wave arrival times and magnitudes measured at two or more points are used to find the location of a burst. The wave arrival times and magnitudes are detected using the modified cumulative sum (CUSUM) change detection test. Results of validation on a real network show the potential of the proposed burst detection and location technique to be used in water distribution systems.

Antibiotics are deployed in large quantities both in human and in veterinary medicine. Studies show that antibiotic residues occur in the environment (e.g. soil and surface waters). In some cases they were also detected in ground and drinking water. However, the degree of groundwater pollution by antibiotic residues from livestock farming is unknown. Therefore, the federal environment agency (UBA) supported a project that aimed to investigate near-surface groundwater samples in regions of high livestock density and high risk of groundwater exposure to antibiotics. By applying worst case criteria on existing sampling sites of our groundwater monitoring grid (high amounts of manure on site, high precipitation, low adsorption capacity of soils, high nitrate concentrations in ground water, etc.) adequate sampling sites were identified as well as relevant antibiotics (amount of application, water solubility, biological stability, etc.) by a literature review and contacts to local veterinary authorities. In total, groundwater at 48 sampling sites was selected for analyses of 23 antibiotic substances. Out of the 23 antibiotics, only three sulfonamides could be detected and quantified. With regard to the 48 sampling sites, at 39 locations no veterinary antibiotics were detected. At seven locations sulfadimidine and/or sulfadiazine was detected at low concentrations (<0.012 μg/L). Only sulfamethoxazole was repeatedly detected above 0.1 μg/L at two sites. Results show that translocation of veterinary antibiotics into near-surface groundwater in most parts of Germany does not occur above detection limits. Under unfavourable conditions leaching does occur but well below the limit values for pesticides (0.1 μg/L/0.5 μg/L). However, under some extreme conditions (to be identified by further research work) one antibiotic was present in groundwater above the pesticides limit values.

Fouling and subsequent chemical cleaning are two important issues for sustainable operation of nanofiltration (NF) membranes in water quality control applications. Because fouling strongly depends on the feed water quality, especially the ionic composition, chemical cleaning solutions should be chosen to target the solution chemistry that is most responsible for the formation of a compact, high resistance fouling layer. In this study, the effect of solution chemistry on natural organic matter (NOM) fouling of two NF membranes with different surface properties was investigated. Compared to monovalent cations, divalent cations were found to greatly enhance NOM fouling by complexation. Moreover, calcium ions caused a much greater fouling rate than magnesium ions, presumably due to the intermolecular bridging formed among NOM molecules through the calcium ions. Various chemical cleaning solutions were evaluated for water flux recovery efficiency. Although both deionized water and dilute NaOH solution were found effective in cleaning membranes fouled in the absence of calcium ions, efficient chemical cleaning in presence of calcium was achieved only when the calcium ion bridging was eliminated. The cleaning efficiency was shown to be highly dependent on solution pH and the concentration of the chemical cleaning agent.

Organic micropollutants (OMPs) are detected in sources for drinking water and treatment possibilities are investigated. Innovative removal technologies are available such as membrane filtration and advanced oxidation, but also biological treatment should be considered. By combining an advanced oxidation process with managed aquifer recharge (MAR), two complementary processes are expected to provide a hybrid system for OMP removal, according to the multiple barrier approach. Laboratory scale batch reactor experiments were conducted to investigate the removal of dissolved organic carbon (DOC) and 14 different pharmaceutically active compounds (PhACs) from MAR influent water and water subjected to oxidation, under different process conditions. A DOC removal of 10% was found in water under oxic (aerobic) conditions for batch reactor experiments, a similar value for DOC removal was observed in the field. Batch reactor experiments for the removal of PhACs showed that the removal of pharmaceuticals ranged from negligible to more than 90%. Under oxic conditions, seven out of 14 pharmaceuticals were removed over 90% and 12 out of 14 pharmaceuticals were removed at more than 50% during 30 days of experiments. Under anoxic conditions, four out of 14 pharmaceuticals were removed over 90% and eight out of 14 pharmaceuticals were removed at more than 50% over 30 days' experiments. Carbamazepine and phenazone were persistent both under oxic and anoxic conditions. The PhACs removal efficiency with oxidized water was, for most compounds, comparable to the removal with MAR influent water.

In this study, the competitive mechanism of ammonia, iron and manganese for dissolved oxygen (DO) in a biofilter was investigated, and a new start-up method of a biofilter for ammonia, iron and manganese removal was approved, which can effectively shorten the start-up period from 3–4 months to 51 days. The results demonstrated that when DO was sufficient (about 8 mg · L−1), ammonia, iron and manganese could be completely removed. When DO decreased from 6.5 to 4 mg · L−1, the concentration of ammonia in the effluent increased accordingly, though iron and manganese were removed efficiently. When DO was as low as 3 mg · L−1, only iron was removed, whereas most of the ammonia and manganese still existed in the effluent. In addition, the oxidizing rates of the pollutants were not affected significantly with DO decrease. Turbidity removal in the biofilter was also investigated, and the results demonstrated that the turbidity decreased to less than 0.5 NTU at 0.4 m depth of the filter.

Sodium metabisulphite (SMBS) is the current standard preservation chemical used in RO plants during shut down. It is a cheap and efficient preservative, but its tendency to oxidize easily has several drawbacks. The use of a non-oxidizing biocide instead could solve some of the issues currently seen with the SMBS, but little has been reported about membrane compatibility and preservation efficiency in the long-term mode. Long-term membrane preservation trials have been executed with three different non-oxidizing biocides: DBNPA (2,2-dibromo-3-nitrilopropionamide), CMIT/MIT (5-chloro-2-methyl-4-isothiazolin-3-one (CMIT) and 2-methyl-4-isothiazolin-3-one (MIT), OIT (2-octyl-2H-isothiazol-3-one) as well as SMBS as the reference chemical. The suitability of these chemicals in this application was confirmed using both new Brackish Water Reverse Osmosis (BWRO) and used membranes with various membrane chemistries (Nanofiltration (NF), BWRO, Sea Water Reverse Osmosis (SWRO)). The preservation trial with new membranes confirmed the long-term stability of the product when stored in the biocide solution while the trial with used elements is closer to realistic plant conditions and validated the efficiency of the biocide against biofouling in the long-term. These results show that the biocides can be equivalent preservatives to SMBS and that the application is economically feasible. The used active concentrations for biocides are storage time and temperature dependent and this should be taken into account when first applying them in the field.

Cyanobacterial blooms in Thailand waters contain microcystin (MC) hepatotoxins that are a risk to animal and human health. The biodegradation of MCs is a safe and natural method of removal from water. The [Dha7] MC-LR was purified by chromatography, identified by liquid chromatography–tandem mass spectrometry (LC-MS) and used for examining the biodegradation of MCs. Analysis of MC levels revealed degradation of the [Dha7] MC-LR by the bacterium Novosphingobium sp. KKU15, with complete degradation occurring within 3 days under conditions in batches of a flask experiment. The ability of the bacterium to degrade the MCs through a slow sand filter was also investigated. Removal of the [Dha7] MC-LR by biological sand filtration was assessed using a polyvinyl chloride column experiment. In MC-dosed water, degradation of the MC was observed specifically in the inoculated samples (bacterial concentration of 1.6 × 107CFU/cm3 of sand), with complete degradation occurring within 7 days compared to the uninoculated controls. A polymerase chain reaction (PCR) specifically targeting the 16S rRNA gene of Novosphingobium sp. KKU15 was used to monitor the presence of the bacterium in the experimental trials. PCR products indicative of a bacterial population were observed at all of the sample sites in the column where the degradation of the MCs was observed, indicating that this bacterial isolate was active in the degradation of MCs.

As Pakistan is currently facing a severe shortage of irrigation water, this paper analyzes the determinants of water scarcity and its impact on the yield of cereal crops (wheat, maize and rice), household income, food security and poverty levels by employing the propensity-score-matching approach. This study is based on a comprehensive set of cross-sectional data collected from 950 farmers from all four major provinces in Pakistan. The empirical analysis indicated that farmers with a water-scarcity problem have lower yield and household income, and are food insecure. Poverty levels were higher: in the range of 7–12% for a household facing a water-scarcity problem. The policy implications of the study are that the public and private sector in Pakistan needs to invest in irrigation water management to maintain the productivity of cereal crops which is important for household food security and poverty reduction.

Activated alumina (AA) prepared from alum sludge (AS) was used in removal of fluoride from aqueous solutions. The capacity of AA in the adsorption of fluoride from water was found to be 17.75 mg/g. The maximum efficiency of fluoride adsorption was 96% at the optimum condition (C = 5 mg/L, pH = 7, t = 20 min and adsorbent dosage = 5 g/L). Based on the results, it can be concluded that conversion of AS to AA can be a method for recycling of AS. Also AA can be used for adsorption of fluoride from aqueous solutions. So AS as a substance harmful to the environment turns into AA as a usable material in water treatment.