A screening level fate model of organic contaminants from advanced water treatment in a potable water supply reservoir.

Augmentation of potable water sources by planned indirect potable reuse of wastewater is being widely considered to address growing water shortages. Environmental buffers such as lakes and dams may act as one of a series of barriers to potable water contamination stemming from micropollutants in wastewater. In South-East Queensland, Australia, current government policy is to begin indirect potable reuse of water from reverse osmosis equipped advanced water treatment plants (AWTPs) when the combined capacity of its major storages is at 40% capacity. A total of 15 organic contaminants including NDMA and bisphenol A have been publically reported as detected in recycled water from one of South-East Queensland's AWTPs, while another 98 chemicals were analysed for, but found to be below their detection limit. To assess the natural attenuation in Lake Wivenhoe, a Level III fugacity based evaluative fate model was constructed using the maximum concentrations of these contaminants detected as input data. A parallel aquivalence based model was constructed for those contaminants, such as dichloroacetic acid, dalapon and triclopyr, which are ionised in the environment of Lake Wivenhoe. A total of 247 organic chemicals of interest, including disinfection by-products, pesticides, pharmaceuticals and personal care products, xenoestrogens and industrial chemicals, were evaluated with the model to assess their potential for natural attenuation. Out of the 15 detected chemicals, trihalomethanes are expected to volatilise with concentrations in the outflow from the dam approximately 400 times lower than influent from the AWTPs. Transformation processes in water are likely to be more significant for NDMA and pharmaceuticals such as salicylic acid and paracetamol as well as for caffeine and the herbicides dalapon and triclopyr. For hydrophobic contaminants such as cholesterol and phenolic xenoestrogens such as 4-nonylphenol, 4-t-octylphenol and bisphenol A, equilibrium between water and sediments will not be attained and hence fate processes such as removal in outflow are predicted to become relatively important.

The occurrence of the herbicide dalapon (2,2-dichloropropionate) in potable water as a disinfection by-product.

Salts of 2,2-dichloropropionic acid, such as dalapon, are well known as herbicides and are regulated as such in potable water in Australia and elsewhere. It is also an identified disinfection by-product (DBP), but little is known about the compound's formation and typical levels from this source. This work presents results from a sampling campaign where 2,2-dichloropropionate was found at levels between 0.1 and 0.5 µg l(-1) in potable water samples from a major treatment plant in South East Queensland, Australia. However, levels were below the reporting limit (0.01 µg l(-1)) in the immediate source water for the plant. Also, temporal trends in 2,2-dichloropropionate observed in treated water during sampling mirrored those of trihalomethanes albeit at much lower concentrations, suggesting that the occurrence is due to in situ formation as a DBP. This could present a regulatory dilemma in some jurisdictions.

Ecotoxicities of polyquaterniums and their associated polyelectrolyte-surfactant aggregates (PSA) to Gambusia holbrooki.

The toxicity of 11 polyquaterniums used in cosmetic applications, and polydimethyldiallylammonium chloride (poly(DADMAC)) were studied for toxicity of the polyquaternium alone, and of a polyquaternium/anionic surfactant complex as occurs in some cosmetic formulations. The surfactant used in the study was sodium dodecyl sulfate (SDS), which is used in cosmetic formulations under its International Nomenclature of Cosmetic Ingredients (INCI) name Sodium Laurel Sulfate. In fish immobilization studies with Gambusia holbrooki, the EC(50) of the polyquaternium/surfactant complex was found to be the same as or similar to the EC(50) for the polyquaternium alone. The toxicity of the polyquaterniums investigated was similar to the published values for other cationic polyelectrolytes and cationic surfactants, in the range from < 1.0 to 10 mg/L, with the exception of low charge density cellulosic polyquaterniums. The anionic surfactant alone was not toxic to fish in the concentration range tested. Results thus showed the toxicity of the polyquaternium was not mitigated by the presence of the anionic surfactant.