Search

Abstract: Innovation in the water sector is at play when addressing the global water security challenge. This paper highlights an emerging role for Quantitative Microbial Risk Assessment (QMRA) and health-based targets in the design and application of robust and flexible water quality regulation to protect public health. This role is especially critical as traditional supply sources are subject to increased contamination, and recycled wastewater and stormwater become a crucial contribution to integrated water supply strategies. Benefits and weaknesses of QMRA-based regulation are likely to be perceived differently by the multiple stakeholders involved. The goal of the current study is to evaluate the experience of QMRA-based regulation implementation in the Netherlands and Australia, and to draw some lessons learned for regulators, policy makers, the industry and scientists. Water experts from regulatory bodies, government, water utilities, and scientists were interviewed in both countries. This paper explores how QMRA-based regulation has helped decision-making in the Netherlands in drinking water safety management over the past decade. Implementation is more recent in Australia: an analysis of current institutional barriers to nationally harmonized implementation for water recycling regulation is presented. This in-depth retrospective analysis of experiences and perceptions highlights the benefits of QMRA-based regulation and the challenges of implementation. QMRA provides a better assessment of water safety than the absence of indicators. Setting a health target addresses the balance between investments and public safety, and helps understand risks from alternative water sources. Challenges lie in efficient monitoring, institutional support for utilities, interpretation of uncertainty by regulators, and risk communication to consumers. [Copyright &y& Elsevier]

Increasing demand for global food production is leading to greater use of irrigation to supplement rainfall and enable more intensive use of land. Minimizing adverse impacts of this intensification on surface water and groundwater resources is of critical importance for the achievement of sustainable land use. In this paper we examine the linkages between irrigation runoff and resulting changes in quality of receiving surface waters and groundwaters in Australia and New Zealand. Case studies are used to illustrate impacts under different irrigation techniques (notably flood and sprinkler systems) and land uses, particularly where irrigation has led to intensification of land use. For flood irrigation, changes in surface water contaminant concentrations are directly influenced by the amount of runoff, and the intensity and kind of land use. Mitigation for flood irrigation is best achieved by optimizing irrigation efficiency. For sprinkler irrigation, leaching to groundwater is the main transport path for contaminants, notably nitrate. Mitigation measures for sprinkler irrigation should take into account irrigation efficiency and the proximity of intensive land uses to sensitive waters. Relating contaminant concentrations in receiving groundwaters to their dominant causes is often complicated by uncertainty about the subsurface flow paths and the possible pollutant sources, viz. drainage from irrigated land. This highlights the need for identification of the patterns and dynamics of surface and subsurface waters to identify such sources of contaminants and minimize their impacts on the receiving environments. [ABSTRACT FROM AUTHOR]

Abstract: There is now evidence that naturally occurring acid–water is more abundant than previously thought and that it has been important in the geologic past. Understanding the processes leading to the formation of such systems is required to appreciate the role of acid systems in geologic processes and to develop indicators for recognizing the geologic/environmental importance of these systems in the past. This paper characterizes the hydrogeology, hydrogeochemistry, microbial biogeochemistry and landscape attributes of acid–groundwater surface water systems in Australia with an emphasis on a well studied playa-lake system, Lake Tyrrell, Murray Valley. A model for the origin of these acid brines is presented and the importance of acid-brine producing systems is speculated upon. Data include porewater and groundwater geochemical measurements (collected during a 10 day field campaign) and results from geochemical modeling and graphics (e.g., Piper diagrams and x–y plots of seawater evaporation trajectories). Key characteristics of the system are (1) aquifer materials have low acid buffering capacities, (2) saline groundwater flowing onto playa surfaces is an oxic, H2SO4 solution, (3) authigenic minerals include combinations of jarosite [KFe3(SO4)2(OH)6], alunite [KAl3(SO4)2(OH)6] and Fe oxides that can form as evaporite minerals, (4) a source for solutes can be marine aerosols and (5) the formation of ironstones. Groundwater acidification by various processes including sulfide oxidation and ferrolysis, and at many different times, are the unique aspects for evolution of these acid brines and they can be considered another end member of the Eugster–Jones–Hardie model for the evolution of brines in closed basins. Acid–hypersaline groundwater and playa systems such as Lake Tyrrell may be an example of expected changes in the hydrogeochemistry of terrestrial water during late-stage continental denudation under arid conditions. Historically these systems may have been integral to the formation of opal, bauxite, some low temperature ore deposits, of authigenic K-feldspars, and continental redbeds. Natural acid saline systems, such as those in Australia, may also be representative of acid saline systems on Mars. [Copyright &y& Elsevier]

The nature and magnitude of endemic waterborne disease are not well characterized in the United States. Epidemiologic studies of various designs can provide an estimate of the waterborne attributable risk along with other types of information. Community drinking water systems frequently improve their operations and may change drinking water treatment and their major source of water. In the United States, many of these treatment changes are the result of regulations promulgated under the Safe Drinking Water Act. A community-intervention study design takes advantage of these ‘natural’ experiments to assess changes in health risks. In this paper, we review the community-intervention studies that have assessed changes in waterborne gastroenteritis risks among immunocompetent populations in industrialized countries. Published results are available from two studies in Australia, one study in the United Kingdom, and one study in the United States. Preliminary results from two other US studies are also available. Although the current information is limited, the risks reported in these community-intervention studies can help inform the national estimate of endemic waterborne gastroenteritis. Information is provided about endemic waterborne risks for unfiltered surface water sources and a groundwater under the influence of surface water. Community-intervention studies with recommended study modifications should be conducted to better estimate the benefits associated with improved drinking water treatment. [ABSTRACT FROM AUTHOR]

1. The influence of hydraulic conditions on the spatial distribution of macroinvertebrate assemblages was investigated in three riffles in a perennial Australian river.2. Velocity, depth and variability of substrate roughness were measured at each of 56 macroinvertebrate sampling locations. Complex hydraulic variables (roughness Reynolds number, shear velocity, Froude number) were calculated from combinations of two or three of the directly measured variables. The biological significance of directly measured and complex hydraulic variables was determined by a combination of univariate and multivariate statistical procedures.3. Macroinvertebrate abundance, number of taxa and community composition were significantly different between the identified roughness Reynolds number, Froude number, velocity and shear velocity microhabitats throughout the studied riffles.4. Regression analysis showed macroinvertebrate abundance and number of taxa were negatively related to roughness Reynolds number, shear velocity, velocity and Froude number. Depth was negatively related to abundance. In general, the majority of the macroinvertebrate community preferred the areas of riffles with the lowest near-bed turbulence.5. Roughness Reynolds number explained more of the spatial variation in invertebrate abundance, number of taxa and community composition than the other hydraulic variables, either directly measured or calculated. Of the directly measured variables, velocity had the greatest explanatory power, which was marginally less than roughness Reynolds number and shear velocity.6. This study demonstrated that small-scale differences in hydraulic conditions created by combinations of velocity, depth and substrate roughness have an important role in the spatial distribution of macroinvertebrate assemblages in riffle habitats. [ABSTRACT FROM AUTHOR]

The Trooper Creek Formation is a mineralised submarine volcano-sedimentary sequence in the Cambro-Ordovician Seventy Mile Range Group, Queensland. Most of the Trooper Creek Formation accumulated in a below-storm-wave-base setting. However, microbialites and fossiliferous quartz–hematite ± magnetite lenses provide evidence for local shoaling to above fairweather wave-base (typically 5–15 m). The microbialites comprise biogenic (oncolites, stromatolites) and volcanogenic (pumice, shards, crystal fragments) components. Microstructural elements of the bioherms and biostromes include upwardly branching stromatolites, which suggest that photosynthetic microorganisms were important in constructing the microbialites. Because the microbialites are restricted to a thin stratigraphic interval in the Trooper Creek area, shallow-water environments are interpreted to have been spatially and temporarily restricted. The circumstances that led to local shoaling are recorded by the enclosing volcanic and sedimentary lithofacies. The microbialites are hosted by felsic syneruptive pumiceous turbidites and water-settled fall deposits generated by explosive eruptions. The microbialite host rocks overlie a thick association (≤300 m) of andesitic lithofacies that includes four main facies: coherent andesite and associated autoclastic breccia and peperite; graded andesitic scoria breccia (scoriaceous sediment gravity-flow deposits); fluidal clast-rich andesitic breccia (water-settled fall and sediment gravity-flow deposits); and cross-stratified andesitic sandstone and breccia (traction-current deposits). The latter three facies consist of poorly vesicular blocky fragments, scoriaceous clasts (10–90%), and up to 10% fluidally shaped clasts. The fluidal clasts are interpreted as volcanic bombs. Clast shapes and textures in the andesitic volcaniclastic facies association imply that fragmentation occurred through a combination of fire fountaining and Strombolian activity, and a large proportion of the pyroclasts disintegrated due to quenching and impacts. Rapid syneruptive, near-vent aggradation of bombs, scoria, and quench-fragmented clasts probably led to temporary shoaling, so that subsequent felsic volcaniclastic facies and microbialites were deposited in shallow water. When subsidence outpaced aggradation, the depositional setting at Trooper Creek returned to being relatively deep marine. [ABSTRACT FROM AUTHOR]

1. Interstitial bacterial abundance, production and ectoenzyme activity were investigated over an annual cycle in an Austrian river when infiltration of oligotrophic river water into a river-bank was artificially enhanced. These microbial parameters were related to porewater chemistry and the concentration of particulate (POC) and dissolved organic carbon (DOC). 2. Porewater chemistry reflected the hydrodynamic mixing of infiltrating river water with riparian groundwater. Seasonal fluctuations in the microbial parameters resulted mainly from changes in temperature and organic matter supply. Seasonal change in porewater chemistry in the river-bank was detectable laterally only within the first metre of the sediment and decreased rapidly with increasing distance from the sediment–water interface. 3. The DOC concentration decreased only slightly during lateral transport through the aquifer, while total organic carbon (TOC) concentration as well as abundance and activity of interstitial bacteria were reduced by up to one order of magnitude within the top metre of the sediment. Retention of incoming particulate matter structured the lateral distribution pattern of TOC concentration. The POC and not the DOC pool was the main source of carbon for interstitial bacteria and, therefore, the quality of POC determines the distribution of microbial metabolism within the riparian zone. [ABSTRACT FROM AUTHOR]