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Mount Isa, Australia

Van Den Akker B.,Flinders University | Van Den Akker B.,University of New South Wales | Holmes M.,United Water International | Cromar N.,Flinders University | Fallowfield H.,Flinders University
Water Science and Technology | Year: 2010

The application of nitrifying trickling filters (NTFs) to potable water treatment is less well understood than their application to wastewater treatment, particularly regarding the effect of low ammonia substrate concentrations and organic carbon loading on filter performance. A large pilot-scale NTF was operated under conditions that simulated the raw water quality of poorly protected catchments typically found in SE Asia, with the objective of reducing the ammonia driven chlorine demand during disinfection. The efficacy of a high rate NTF to remove low concentrations of ammonia (0.5-5.0mgNH4-N L-1) in the presence of high organic carbon (1-12mg soluble biochemical oxygen demand (sBOD5) L -1) was investigated. Results demonstrated that 90 to 100% of nitrification was maintained only when the carbon load was less than 0.7 g sBOD5m-2 d-1 (<4mg sBOD5 L -1). Once the organic load was increased beyond 0.75 to 2.1 g sBOD5m-2 d-1 (4.5-12.1mgsBOD5 L -1), a linear decline in nitrification from 70 to 15% was observed within a timeframe of 8 to 10 d. The impact of high organic loads on the distribution of nitrification down the NTF was also investigated. Results confirmed that carbon loads greater than 0.95 g sBOD5m-2 d-1 (>5.5mg sBOD5 L-1), severely suppressed nitrification throughout the entire filter bed. © IWA publishing 2010. Source

Page D.,CSIRO | Page D.,Water for a Healthy Country National Research Flagship | Dillon P.,CSIRO | Dillon P.,Water for a Healthy Country National Research Flagship | And 10 more authors.
Journal of Environmental Quality | Year: 2010

The objective of the Parafield Aquifer Storage Transfer and Recovery research project in South Australia is to determine whether stormwater from an urban catchment that is treated in a constructed wetland and stored in an initially brackish aquifer before recovery can meet potable water standards. The water produced by the stormwater harvesting system, which included a constructed wetland, was found to be near potable quality. Parameters exceeding the drinking water guidelines before recharge included small numbers of fecal indicator bacteria and elevated iron concentrations and associated color. This is the first reported study of a managed aquifer recharge (MAR) scheme to be assessed following the Australian guidelines for MAR. A comprehensive staged approach to assess the risks to human health and the environment of this project has been undertaken, with 12 hazards being assessed. A quantitative microbial risk assessment undertaken on the water recovered from the aquifer indicated that the residual risks posed by the pathogenic hazards were acceptable if further supplementary treatment was included. Residual risks from organic chemicals were also assessed to be low based on an intensive monitoring program. Elevated iron concentrations in the recovered water exceeded the potable water guidelines. Iron concentrations increased after underground storage but would be acceptable after postrecovery aeration treatment. Arsenic concentrations in the recovered water continuously met the guideline concentrations acceptable for potable water supplies. However, the elevated concentration of arsenic in native groundwater and its presence in aquifer minerals suggest that the continuing acceptable residual risk from arsenic requires further evaluation. Copyright © 2010 by the American Society of Agronomy. Source

Van den Akker B.,Flinders University | Holmes M.,United Water International | Pearce P.,Thames Water Utilities | Cromar N.J.,Flinders University | Fallowfield H.J.,Flinders University
Water Research | Year: 2011

This study examined the composition and structure of nitrifying biofilms sampled from a high-rate nitrifying trickling filter which was designed to pre-treat raw surface water for potable supply. The filter was operated under a range of feed water ammonia and organic carbon concentrations that mimicked the raw water quality of poorly protected catchments. The biofilm structure was examined using a combination of fluorescence in situ hybridisation and scanning electron microscopy. Biopolymers (carbohydrate and protein) were also measured. When the filter was operated under low organic loads, nitrifiers were abundant, representing the majority of microorganisms present. Uniquely, the study identified not only Nitrospira but also the less common Nitrobacter. Small increases in organic carbon promoted the rapid growth of filamentous heterotrophs, as well as the production of large amounts of polysaccharide. Stratification of nitrifiers and heterotrophs, and high polysaccharide were observed at all filter bed depths, which coincided with the impediment of nitrification throughout most of the filter bed. Observations presented here specifically linked biofilm structure with filter functionality, physically validating previous empirical modelling hypotheses regarding competitive interactions between autotrophic and heterotrophic bacteria in biofilms. © 2011 Elsevier Ltd. Source

Van Den Akker B.,Flinders University | Van Den Akker B.,University of New South Wales | Holmes M.,United Water International | Short M.D.,University of New South Wales | And 2 more authors.
Water Science and Technology | Year: 2010

The interference of ammonia with the chlorination process is a problem for many reclaimed water treatment plant operators. This paper presents the findings from a series of pilot experiments that investigated the efficacy of high flow rate nitrifying trickling filters (NTFs) for the removal of low concentrations of ammonia (0.5-3.0mgNL-1) from reclaimed wastewater. Results showed that nitrification was impeded by a combination of high organic carbon loads and aquatic snails, which consumed much of the active biomass. With adequate snail control, nitrification rates (0.3-1.1 gNH4-Nm-2 d -1) equivalent to that of traditional wastewater NTFs were achieved, despite operating under comparably low ammonia feed concentrations and high hydraulic flow rates. © IWA Publishing 2010. Source

van den Akker B.,University of New South Wales | Beard H.,United Water International | Kaeding U.,United Water International | Giglio S.,South Australian Water Corporation | Short M.D.,University of New South Wales
Water Research | Year: 2010

This study investigated the nature of viscous sludge bulking within a molasses-fed integrated fixed-film activated sludge (IFAS) and conventional activated sludge (AS) plant by routinely measuring the total carbohydrate and protein fractions of the mixed liquor (ML). The impacts of sludge settleability and plant performance on the relative abundance of ammonia-oxidising bacteria (AOB) (Nitrosomonas oligotropha-cluster) were also investigated using quantitative polymerase chain reaction (qPCR). Results showed that sludge volume index (SVI) correlated positively with the amount of ML total carbohydrate in both the IFAS and traditional AS plants, highlighting the influential role that ML polysaccharide concentration plays on sludge settleability in these reactors. Results also revealed a negative relationship between the AOB/total Bacteria ratio and SVI, demonstrating that a poor settling sludge generally coincided with periods of relatively low AOB abundance. The existence of these relationships suggests that readily available organic carbon (molasses) was likely to have been present in excess in these systems. Our qPCR results also showed that concentrations of both AOB and total Bacteria genomic copies detected within the ML of the IFAS and conventional AS plants were remarkably similar. For the IFAS system, results showed that the ML supported an equivalent number of AOB (per gram of biomass) to that detected on the plastic IFAS media carriers, suggesting that the suspended biomass fraction plays an equally important role in the overall nitrification performance of these systems. Interestingly, large observed variations in AOB and AOB/total Bacteria ratio measured within both the ML and IFAS media carriers had no measurable impact on the apparent nitrification performance of these systems; indicating the presence of some excess or 'reserve' nitrifying capacity above that which is required for effective plant performance. Results presented here also constitute the first known side-by-side comparison of the distribution of AOB in IFAS and conventional racetrack-like AS plants at the full-scale level. © 2010 Elsevier Ltd. Source

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