The adsorption of cyanobacterial hepatotoxins from water onto soil during batch experiments.

Public health concerns associated with cyanobacteria, both chronic and acute, arise from their ability to produce toxins. Rural communities within Australia and those in developing countries require an inexpensive and low-cost method for removing toxins from drinking water. A candidate technology is bank filtration. Adsorption of cyanobacterial hepatotoxins was measured in batch studies to determine the applicability of bank filtration as an efficient removal strategy. Five soils with different physicochemical properties were collected from regions around South Australia. The soils were mixed with either nodularin or microcystin-LR in distilled water and buffered solutions (pH 4.8, 6.9 and 9.1). Additionally, nodularin was mixed in unbuffered solutions (pH 4.8 and 8.9). The three soils with the high clay and/or organic carbon contents (Paringa A, McLaren Flat and Lakes Plains) had the higher nodularin adsorption coefficients, ranging from 0.2 to 16.59 L kg-1. Soil suspensions in acetate buffer (pH 4.8) generally produced significantly higher nodularin adsorption coefficients, when compared to the other buffer systems. The background interference from the ionic strength of the buffers, however, made interpretation of the effect of pH on toxin sorption difficult. Increases in solution ionic strength, from freshwater to seawater, resulted in corresponding increases in the nodularin adsorption coefficients for all sites, except the sandy Hallett Cove site. The implications for bank filtration are that higher water pH values and lower salinities will enhance the in situ mobility of the toxins, resulting in an increased distance of filtration through the river bank before toxin free water could be abstracted for human consumption.

Microbiological influences in 'blue water' copper corrosion.

AIMS: To investigate the influence of micro-organisms associated with copper corrosion on 'blue water' corrosion in drinking water. METHODS AND RESULTS: Laboratory rigs comprising of polycarbonate containers attached to annealed copper plumbing tubes were filled with Melbourne drinking water and sterilized by autoclaving. The copper tubes were inoculated with sterile or nonsterile extracts obtained from corroding copper and allowed to stand for 7 days. The extracts were drained and the tubes flushed and filled with sterile water from the rig. The water within the tubes was removed weekly for analysis and the tubes were refilled with freshly aerated water. The tube water sampled was analysed for pH, total copper and the presence of micro-organisms. Sterile rigs and rigs containing nonsterile water, both without tube inoculums, were used as controls. The results demonstrated that tubes inoculated with nonsterile corrosion extracts showed statistically higher copper release compared with the other rigs. Copper release as blue water was only observed after a lag period of 9 weeks. The internal surfaces of tubes releasing copper showed significant amounts of corrosion products and the presence of biofilm. Bacteria isolated from the corroding tubes included Acidovorax spp. and Sphingomonas sp. CONCLUSIONS: The results demonstrate a microbial role in blue water, as corrosion was induced in new copper tubes by exposure to nonsterile copper corrosion products. SIGNIFICANCE AND IMPACT OF THE STUDY: The potential for micro-organisms present in corrosion products to initiate blue water corrosion presents significant implications for the management of corrosion in distribution systems.

Biofilms and microbially influenced cuprosolvency in domestic copper plumbing systems.

AIMS: To survey biofilm accumulation within domestic copper plumbing pipes in South Australian drinking water distribution systems and examine its role in copper solvation (cuprosolvency). METHODS AND RESULTS: Cold water copper pipes were sampled from two different plumbing systems receiving filtered and unfiltered potable water respectively. Biomass was quantified by total organic carbon measurements and viable cell counts and microbial activity by respirometry. Biofilm accumulation was related to water chemistry within the systems, particularly nutrients, alkalinity and conductivity, as well as water turbulence. Laboratory coupon experiments were used to determine the effect of extracted biofilm on copper solvation. Biofilms were shown to be capable of both increasing and decreasing aqueous copper concentrations in comparison to sterile controls. CONCLUSIONS: The results suggest that water quality may influence the accumulation of biofilms in copper plumbing systems, as well as potential cuprosolvency activity. SIGNIFICANCE AND IMPACT OF THE STUDY: The presence of biofilms in copper plumbing systems and their ability to influence aqueous copper concentrations has implications for both public health and the management of distribution systems.

The influence of the chemical composition of drinking water on cuprosolvency by biofilm bacteria.

AIMS: This study investigated the influence of water chemistry on copper solvation (cuprosolvency) by pure culture biofilms of heterotrophic bacteria isolated from copper plumbing. METHODS AND RESULTS: Heterotrophic bacteria isolated from copper plumbing biofilms including Acidovorax delafieldii, Flavobacterium sp., Corynebacterium sp., Pseudomonas sp. and Stenotrophomonas maltophilia were used in laboratory coupon experiments to assess their potential for cuprosolvency. Sterile copper coupons were exposed to pure cultures of bacteria to allow biofilm formation and suspended in drinking waters with different chemical compositions. Sterile coupons not exposed to bacteria were used as controls. After 5 days of incubation, copper release and biofilm accumulation was quantified. The results demonstrated that cuprosolvency in the control experiments was influenced by water pH, total organic carbon (TOC) and conductivity. Cuprosolvency in the presence of biofilms correlated with the chemical composition of the water supplies particularly pH, Langeliers Index, chloride, alkalinity, TOC and soluble phosphate concentrations. CONCLUSIONS: The results suggest water quality may influence cuprosolvency by biofilms present within copper plumbing pipes. SIGNIFICANCE AND IMPACT OF THE STUDY: The potential for water chemistry to influence cuprosolvency by biofilms may contribute to the sporadic nature of copper corrosion problems in distribution systems.