Comparative evaluation of the fate of disinfection byproducts at eight aquifer storage and recovery sites.

Despite the growth in aquifer storage and recovery (ASR) as a technique for the provision of potable water supplies, quantitative data on the fate of disinfection byproducts that may be present in the injected water remain rare. This study evaluates the data from eight ASR sites in Australia and the United States that cover a wide range of source water compositions, hydrogeological environments, and operating conditions. Rates of attenuation and formation of trihalomethanes (THMs) in groundwater were determined using analytical techniques that took dilution effects into account. Half-lives varied by more than 2 orders of magnitude (e.g., <1 to >120 days for total THMs) and were both compound- and site- specific. Chloroform was most persistent, and more highly brominated compounds tended to be less persistent, as has generally been found. For any particular THM compound, much of the variability could be explained by contrasts in geochemical conditions within the aquifer since microbial degradation is the primary mechanism for THM attenuation. As such, bounds on the half-life were defined according to the redox state of the groundwater. In situ formation of some THMs in the aquifer after injection was directly observed at a number of sites, and was predicted to have taken place at all sites. The variance in formation estimates was large between the different methods used. Formation may be more common than previously thought because of the low frequency of groundwater sampling after injection and concomitant attenuation and mixing.

Analysis of cyanobacterial-derived saxitoxins using high-performance ion exchange chromatography with chemical oxidation/fluorescence detection.

A single run HPLC method utilizing ion exchange as the separation mode with a novel mobile phase system coupled to chemical postcolumn oxidation and fluorescence detection has been developed and demonstrated to be applicable to the quantitative analysis of paralytic shellfish poisons (PSPs) produced by Australian cyanobacteria (Anabaena circinalis) and other cyanobacteria. Both the cyanobacterial matrix and natural water constituents did not significantly affect the performance of this method. The daily precision of this method was adequate for it to be considered as a routine analytical tool for direct PSP analysis (prePSP concentration is not required) of cyanobacterial extracts and water bodies containing PSPs (C1, C2, GTX2, GTX3, NEO, STX) in the low parts per billion concentration range (10-70 ppb).

Fate of disinfection by-products in groundwater during aquifer storage and recovery with reclaimed water.

Knowledge on the behaviour of disinfection by-products (DBPs) during aquifer storage and recovery (ASR) is limited even though this can be an important consideration where recovered waters are used for potable purposes. A reclaimed water ASR trial in an anoxic aquifer in South Australia has provided some of the first quantitative information at field-scale on the fate and transport of trihalomethanes (THMs) and haloacetic acids (HAAs). The results revealed that THM half-lives varied from <1 to 65 days, with persistence of chloroform being highest and bromoform lowest. HAA attenuation was rapid (<1 day). Rates of THM attenuation were shown to be highly dependent on the geochemical environment as evidenced by the 2-5 fold reduction in half-lives at the ASR well which became methanogenic during the storage phase of the trial, as compared to an observation well situated 4 m away, which remained nitrate-reducing. These findings agree with previous laboratory-based studies which also show persistence declining with increased bromination of THMs and reducing redox conditions. Modelling suggests that the chlorinated injectant has sufficient residual chlorine and natural organic matter for substantial increases in THMs to occur within the aquifer, however this is masked in some of the field observations due to concurrent attenuation, particularly for the more rapidly attenuated brominated compounds. The model is based on data taken from water distribution systems and may not be representative for ASR since bromide and ammonia concentrations in the injected water and the possible role of organic carbon in the aquifer were not taken into consideration. During the storage phase DBP formation potentials were reduced as a result of the removal of precursor material despite an increase in the THM formation potential per unit weight of total organic carbon. This suggests that water quality improvements with respect to THMs and HAAs can be achieved through ASR in anoxic aquifers.

Fate of disinfection by-products in groundwater during aquifer storage and recovery with reclaimed water.

Knowledge on the behaviour of disinfection by-products (DBPs) during aquifer storage and recovery (ASR) is limited even though this can be an important consideration where recovered waters are used for potable purposes. A reclaimed water ASR trial in an anoxic aquifer in South Australia has provided some of the first quantitative information at field-scale on the fate and transport of trihalomethanes (THMs) and haloacetic acids (HAAs). The results revealed that THM half-lives varied from <1 to 65 days, with persistence of chloroform being highest and bromoform lowest. HAA attenuation was rapid (<1 day). Rates of THM attenuation were shown to be highly dependent on the geochemical environment as evidenced by the 2-5 fold reduction in half-lives at the ASR well which became methanogenic during the storage phase of the trial, as compared to an observation well situated 4 m away, which remained nitrate-reducing. These findings agree with previous laboratory-based studies which also show persistence declining with increased bromination of THMs and reducing redox conditions. Modelling suggests that the chlorinated injectant has sufficient residual chlorine and natural organic matter for substantial increases in THMs to occur within the aquifer, however this is masked in some of the field observations due to concurrent attenuation, particularly for the more rapidly attenuated brominated compounds. The model is based on data taken from water distribution systems and may not be representative for ASR since bromide and ammonia concentrations in the injected water and the possible role of organic carbon in the aquifer were not taken into consideration. During the storage phase DBP formation potentials were reduced as a result of the removal of precursor material despite an increase in the THM formation potential per unit weight of total organic carbon. This suggests that water quality improvements with respect to THMs and HAAs can be achieved through ASR in anoxic aquifers.

Bromide levels in natural waters: its relationship to levels of both chloride and total dissolved solids and the implications for water treatment.

South Australian freshwaters from a wide variety of environments were analysed for bromide and the results correlated with both chloride and total dissolved solids (TDS) concentrations. A linear relationship was obtained which allows chloride data to be successfully used to estimate bromide concentrations. Bromide displayed a slightly better correlation with TDS indicating that an improved estimate of bromide could be made by reference to TDS data which is more easily and commonly obtained, and generally available extensively as historical data. The bromide content in relation to its ratio with both chloride and TDS contents was around seventy percent of the corresponding ratios found in seawater, a finding reported in other published data. The ability to estimate bromide concentrations is a potentially useful tool in the drinking water industry as it enables the assessment of the extent of bromate formation (predicted through the use of mathematical models and other water quality data) which is an important factor when ozonation is being considered as a treatment option, particularly as many water industry regulatory bodies have imposed stringent limits on the levels of acceptable bromate.

Extraction of cyanobacterial endotoxin.

To simplify our efforts in acquiring toxicological information on endotoxins produced by cyanobacteria, a method development study was undertaken to identify relatively hazard-free and efficient procedures for their extraction. One article sourced and two novel methods were evaluated for their ability to extract lipopolysaccharides (LPSs) or endotoxins from cyanobacteria. The Limulus polyphemus amoebocyte lysate (LAL) assay was employed to compare the performance of a novel method utilizing a 1-butanol-water (HBW) solvent system to that of Westphal's (1965) phenol-water system (HPW) for the extraction of endotoxin from various cyanobacteria. The traditional HPW method extracted from 3- to 12-fold more endotoxin from six different cyanobacterial blooms and culture materials than did the novel HBW method. In direct contrast, the novel HBW method extracted ninefold more endotoxin from a non-microcystin producing Microcystis aeruginosa culture as compared to the HPW method. A solvent system utilizing N,N'-dimethylformamide-water (HDW) was compared to both the HPW and HBW methods for the extraction of endotoxin from natural samples of Anabaena circinalis, Microcystis flos-aquae, and a 1:1 mixture of Microcystis aeruginosa/Microcystisflos-aquae. The LAL activities of these extracts showed that the novel HDW method extracted two- and threefold more endotoxin from the Anabaena sample that did the HBW and HPW methods, respectively. The HDW method also extracted approximately 1.5-fold more endotoxin from the Microcystis flos-aquae sample as compared to both the HBW and HPW methods. On the other hand, the HBW method extracted 2- and 14-fold more endotoxin from the Microcystis flos-aquae/Microcystis aeruginosa mixture than did the HPW and HDW methods, respectively. Results of this study demonstrate that significant disparities exist between the physicochemical properties of the cell wall constituents not only of different cyanobacterial species but also of different strains of the same cyanobacterial species, as showing by the varying effectiveness of the solvent systems investigated. Therefore, a sole method cannot be regarded as universal and superior for the extraction of endotoxins from cyanobacteria. Nevertheless, the ability of the novel HBW and HDW methods to utilize easily handled organic solvents that are less hazardous than phenol render them attractive alternatives to the standard HPW method.