Impacts of antimicrobial compounds in urban waterways receiving sewer overflows

Personal care products (PCPs) are a subset of emerging contaminants detected in waterways globally and include antimicrobial compounds, preservatives, organic UV-filters and industrial chemicals. These compounds are washed down household drains every day and can enter waterways via stormwater, sewer overflows and wastewater treatment plant effluents. There is growing concern about the effects of PCPs on aquatic ecosystems as many of these compounds impact microorganisms and are endocrine disruptors. Though research into the presence of PCPs is increasing, the majority of studies originate from Europe and North America and there is limited data on the presence and effects of PCPs in New Zealand waterways. The results from the work undertaken in this thesis will contribute to the development of any future regulations for PCPs in New Zealand. The occurrence of PCPs and effects on bacterial community structure were investigated over six months in two Christchurch urban streams previously impacted by sewer overflows: Dudley Creek Diversion and Cross Stream. The UV-filters benzophenone-3 and octyl-methoxycinnamate, and bisphenol A were frequently detected. Concentrations of UV-filters were lower during the winter months. Other detected compounds included methyl paraben, octylphenol, o-phenylphenol and triclosan. Compounds were detected in the low ng/L range in stream water and low ng/g range in sediment. As no sewer overflows occurred over the course of the study there were limited differences observed between upstream and downstream concentrations. Previous sewer overflows were likely to be the source of benzophenone-3 at Dudley Creek Diversion as downstream sediment concentrations were significantly higher than upstream. Triclosan was also detected in two sediment samples downstream at Dudley Creek Diversion in March and April but was not detected in any upstream samples. The sediment bacterial communities at Dudley Creek Diversion were significantly different at upstream and downstream sites of the overflow outfall indicating that contaminants derived from sewerage inputs may alter sediment bacterial community composition. Though concentrations were lower than those reported to have toxic effects in waterways, several compounds were identified using multivariate multiple regression with distance-based linear modelling as having an effect on the structure of bacterial communities including benzophenone-3, octyl-methoxycinnamate, triclosan and bisphenol A. The effect of the antimicrobial triclosan on the photosynthetic activity of the green alga Stigeoclonium sp. and cyanobacteria Phormidium autumnale was investigated. Stigeoclonium sp. was more sensitive to triclosan than Phormidium autumnale, the 96 hr EC50 values were 1.23 and 3.17 mg/L, respectively. Both organisms examined are commonly found in New Zealand rivers and these results provide new information on the effect of PCPs in New Zealand waterways