116. It is important to remember that water resource management at the scale of a catchment should not only address managing the wet parts of the system (rivers, lakes and other wetlands) but also needs to incorporate the appropriate management of terrestrial ecosystems, since inappropriate activities in these systems can impact on water management. For example, in South Africa, afforestation of grasslands with commercial plantations of alien woody species has been shown to reduce surface runoff significantly. These plantations have also led to a draw-down in the groundwater table, resulting in peatlands drying out and becoming vulnerable to fire and causing the failure of shallow wells used by local communities. Conversely, in Australia, where woodlands have been removed and replaced with cereal crops, the groundwater table has subsequently risen leading to salinization of soilsandwater in the catchment.
Geochemical anomalies of fluorine (F), arsenic (As), mercury (Hg), cadmium (Cd) and chromium (Cr) in soils, sediments andwater may adversely impact human and animal health. These elements, if found in above average quantities against stipulated norms, may lead to different kinds of diseases which include the deformation of teeth and bones (dental and skeletal fluorosis), damaged central and peripheral nervous system, lung and bladder cancer, mesothelioma, among other deadly ailments. However, selenium (Se), besides causing juvenile cardiomyopathy and muscular abnormalities, it does present some desirable health benefits in various ways (anti-cancer, anti-aging, improved fertility, boosts immunity, among others). Other health benefits of these elements can be found in Finkleman (2006).
ratio of 11.5 and an organic matter (OM) content of 3.5%. A second soil was collected from an avocado (Persea americana) plantation that has been annually treated for 4 20 years with simazine (3.5 kg simazine ha 1 ), as a pre-emergent herbicide (AS soil). AS soil is a slightly acidic (pH 6.4) and loam soil with a nitrogen content of 2.0 g kg 1 soil, a C/N ratio of 12.8 and a higher OM content (8.5%). At the time of collection, residual simazine was not detected either in NS or in AS soil. For microcosms, each soil was homogeneously treated with commercial simazine to obtain different initial concentrations of 3.5 kg simazine ha 1 (10 mg kg 1 , low level), according to standard farming practices, and 35 kg simazine ha 1 (100 mg kg 1 , high level). Each microcosm contained 150 g of soil in a 500-mL sterile flask. Microcosms were bioaugmented by inoculating encapsulated strain MHP41 (0.5 g of alginate beads containing cells of strain MHP41 were added to 150 g soil to reach a final concentration of 1 10 8 cells g 1 dry soil) every 3–4 days. The soilsand the alginate beads were thoroughly mixed using a sterilized spatula. In order to reduce contamination risks due to manipulation, all flasks were covered with a polyethylene foil and sampled under aseptic conditions. Microcosms were incubated at room temperature for 28 days. In control microcosms, soil was inoculated with sterile alginate beads. All treatments were performed in triplicate. Soil moisture was periodically controlled using an infrared absorption mass balance (Sartorius MH30) and maintained by sprink- ling sterile water at 40–50% of the water-holding capacity. For microbial and chemical analysis, soil samples (50 g) were maintained at 4 1 C. For bacterial community analysis, soil samples (10 g) were collected in sterile tubes and kept frozen at 20 1 C. Statistical analysis was performed using two-way
In early 2008, a significant concern arose in relation to the Coorong and Lake Alexandrina and Albert Ramsar site (Coorong Ramsar site). The threat of most immediate concern is declining water levels and the resultant exposure of acid sulfate soils (ASS). The site is located at the mouth of the River Murray in the Murray-Darling Basin, which during the last seven years has experienced the second driest seven-year period on record and record low inflows. Emergency pumping of water from Lake Alexandrina to the smaller Lake Albert commenced in May 2008 and is currently preventing further exposure of ASS and the acidification of Lake Albert.
The sources of turbidity are diverse, and many of the constituent particles (e.g. clays, soilsand natural organic matter) are harmless. However, turbidity can also indicate the presence of hazardous chemical and microbial contaminants, and have significant implications for water quality (Table 2). The implications will vary depending on the characteristics of the turbidity. In addition, as indicated in Table 2, the point of detection is important in considering potential impacts. Elevated turbidity in source waters can signal pollution events in the catchment (e.g. heavy rain, spills or contamination of groundwater), and can challenge the effectiveness of coagulation and clarification, filtration and disinfection. Failure to meet turbidity targets for filtered water can indicate the possible presence of pathogens in drinking-water, and increased turbidity in distribution systems can represent detachment of biofilms and oxide scales or entry of external sources of contamination. Each source needs to be considered in context because the treatment and management implications will vary (Table 2).
Studies of hydrogen and oxygen stable isotope ratios of water within plants and in soils have become an important tool in below- ground studies (Walker and Richardson 1991, Thorburn and Ehleringer 1995, Sternberg et al. 2002). Natural differences in the water isotopic signature along the soil profile and between soil and ground water can be used to indicate depth of acquisition of waterand other key soil resources. These studies have provided new information on competitive interactions andwater use patterns of plants in natural and agricultural conditions (Walker and Richardson 1991, Ehleringer and Dawson 1992, Ehleringer and Osmond 1999, Dawson et al. 2002). They have also revealed the sources of water utilized by different life forms in various environments (Dawson and Ehleringer 1991, Jackson et al. 1995, 1999, Meinzer et al. 1995, 1999, Pate and Dawson 1999, Stratton et al. 2000, Drake and Franks 2003), and the mechanisms involved in the control of water balance (Dawson 1993, Goldstein et al. 1996). Further application of these techniques have been conducted at sites where the depth of water uptake varies seasonally (Sternberg et al. 2002), and at very wet riparian tropical environments, where soil water partitioning among different life forms may occur only during the dry season (Drake and Franks 2003).
ABSTRACT: Concerns about land andwater use have led to research on perennial grasses as energy crops for marginal lands, including abandoned lands, low fertility soilsandwater-deficit areas. The potential of this type of crops should be assessed not only in terms of yield but also in terms of quality of the crop produce. The aim of this work was to investigate if water-deficit conditions affect the energy and compositional characteristics of giant reed when grown under a continental-Mediterranean climate. A two-year field experiment was designed with two sources of variation: water-deficit level (three levels or treatments) and biomass fraction (leaves, stalks), and thirteen variables (biomass properties). It was found that the differences between the studied water-deficit treatments were small for most variables; on the contrary, the differences between the properties of the leaf fraction and the stalk biomass were much higher and often statistically significant. Therefore, the biomass partitioning into leaves and stalks was revealed as the main factor influencing the quality of giant reed biomass.
Ion exchange is a treatment process in which a solid phase presaturant ion is exchanged for an unwanted ion in the untreated water. The process is used for water softening (removal of calcium and magnesium), removal of some radionuclides (e.g. radium and barium) and removal of various other contaminants (e.g. nitrate, arsenate, chromate, selenate and dissolved organic carbon). The effectiveness of the process depends on the background water quality, and the levels of other competing ions and total dissolved solids. Although some ion exchange systems can be effective for adsorbing viruses and bacteria (Semmens, 1977), such systems are not generally considered a microbial treatment barrier, because the organisms can be released from the resin by competing ions. Also, ion exchange resins may become colonized by bacteria, which can then contaminate treated effluents (Flemming, 1987; Parsons, 2000). Backflushing and other rinsing procedures, even regeneration, will not remove all of the attached microbes. Impregnation of the resin with silver suppresses bacterial growth initially, but eventually a silver-tolerant population develops. Disinfection of ion exchange resins using 0.01% peracetic acid (1 hour contact time) has been suggested (Flemming, 1987).
Changes in raw water quality can affect the efficiency of treatment processes. Depending on local and seasonal situations, each water treatment plant encounters different ranges of raw water quality. Data from 67 surface water treatment plants in the USA showed that the variation in particles greater than 3 µm in raw water followed a log-normal distribution pattern; particle concentrations ranged from 28/ml to 11 × 10 7 /ml, with a geometric mean of 22 800/ml (Arora et al., 1998). Factors influencing raw water quality are discussed in Chapter 6 (Section 6.2). A change of any water quality parameter in the source water may affect apparent treatment efficiency, as discussed in Section 5.3. For example, in their study of 67 surface water treatment plants in the USA, Arora et al. (1998) found that the removal efficiency (based on the difference in particle concentrations between raw and filtered waters) increased with increasing particle concentration in raw water. For raw water particle concentrations from 10 3 –25 × 10 3 /ml, the median removal efficiency was 2.08 logs; whereas, when concentrations increased to 10 6 –10 7 /ml, the median removal efficiency increased to 3.2 logs. The greater removal efficiency at higher particle concentrations was due primarily to more efficient clarification. This is to be expected because removal of particles by clarification depends significantly on aggregation efficiency, which is a second-order process with respect to particle concentration (i.e. a higher particle concentration means that particles will collide more frequently and thus be more likely to aggregate).
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Fundamental to the quality of the treated water is the proper operation and maintenance of the pipe system. The WHO publication Safe piped water: Managing microbial water quality in piped distribution systems (Ainsworth, 2004) provides comprehensive guidance on the management of distribution system operation and maintenance. It includes guidance on development of a monitoring program for water quality and other parameters, such as pressure in the distribution system. Control measures include using a more stable secondary disinfecting chemical than is used in primary treatment (e.g. chloramines instead of free chlorine), reducing the time that water spends in the system (e.g. avoiding stagnation in storage tanks and looping dead-end sections), replacing pipes, flushing and relining, and maintaining positive pressure in the distribution system.
The performance of a treatment unit can affect the efficiency of downstream treatment units. For example, the presence of suspended solids increases the resistance of most microbes to disinfection (LeChevallier, Evans & Seidler, 1981). Therefore, a failure in the removal efficiency of turbidity or particles by granular filtration processes can decrease the inactivation efficiency of disinfection processes. Similarly, clarification affects filter performance. Clarification removes suspended solids, thus reducing the solid loading to the filters and improving filter performance. If an incorrect dose of coagulant is used and floc is carried over from a sedimentation tank, head loss develops more rapidly, shortening the filter run.
Owens JH et al. (1999). In vitro excystation and infectivity in mice and cell culture to assess chlorine dioxide inactivation of Cryptosporidium oocycsts. Proceedings of the American Water Works Association Water Quality Technology Conference, Tampa, FL, 31 October – 3 November. Denver, CO, American Water Works Association.
difference in composition as the authors measured at w= 0.22. Most values are in agreement with our uncertainties. There are other few viscosity measurements in the literature for the systems studied in this paper but they were measured at different compositions and it is not possible to compare the data.
There are a number of potential problems with pretreatment oxidation. Variable source water conditions mean that variable or high levels of oxidant may be needed. This may lead to overdosing of pre-oxidants, which can result in “pink coloured” water when potassium permanganate is misapplied. Also, the process can produce oxidation by-products such as trihalomethanes (THMs), haloacetic acids and bromate. For example, in using chlorine as a pretreatment oxidant, chlorinated by-products can form rapidly. This often limits the application of chlorine to a later stage of the treatment process, when precursor material has been removed. A further problem is that oxidants can lyse algal cells, releasing liver or nerve toxins, or creating objectionable tastes or odours. (Yoo et al., 1995b; Chorus & Bartram, 1999).
To be removed, a particle must not only come into contact with a media grain, but must also attach to it. Not all contacts between particles and media lead to attachment; an attachment efficiency (α) is used to represent the fraction of successful contact. The value of α varies from one (all contact results in attachment) to zero (no contact results in attachment). In drinking-water treatment, chemical coagulation pretreatment promotes attachment efficiency, with optimized coagulation conditions increasing the value of α . A predictive equation for removal efficiency can be derived from single collector efficiency, attachment efficiency and the total number of media collectors.
29 No information about soil texture and soil depth was obtained from the Venezuelan part of the basin, thus an extrapolation of the S max values was undertaken. This was done using GIS editing tools, where horizontal strips were generated for the no information area using known S max values near the border Colombia/Venezuela. Visually, the S max extrapolation values for the upper basin area (southeast) match with the pattern of the Colombian side. For the middle basin area the urban district of Cucuta in the Colombian side has a S max equal to 0. This is why it seems that the pattern of S max in the Venezuelan side in the middle basin area does not match with the Colombian side. Even though, there are urban areas in the Venezuelan middle part of the basin there are assumed to be smaller than in the Colombian side. In conclusion, the extrapolated S max values for the middle basin area generate a large area with high S max values (between 200 mm and 300 mm). In a water balance perspective, it means that there is more water storage potential and the monthly discharge in the rivers can be lower, thus a safe condition for a surface water supply reliability analysis required in this thesis.
The most effective means of consistently ensuring the safety of a drinking-water supply is through the use of a comprehensive risk assessment and risk management approach that encompasses all steps in water supply from attachment to consumer .In this guidelines, such approaches are called water safety plans (WSPs) .(WHO Guidelines for Drinking Water Quality. 3rd Edition, 2004)
addressing issues of strategic scientific and technical direction for the Convention, acting as a response mechanism to give scientific and technical advice to the Convention on emerging issues, with an overall aim of achieving a balance between these proactive guidance and reactive advice functions.