Exploring the Impacts of Full-Scale Distribution System Orthophosphate Corrosion Control Implementation on the Microbial Ecology of Hydrologically Connected Urban Streams.

Many cities across the nation are plagued by lead contamination in drinking water. As such, many drinking water utilities have undertaken lead service line (LSL) replacement to prevent further lead contamination. However, given the urgency of lead mitigation, and the socioeconomic challenges associated with LSL replacement, cities have used phosphate-based corrosion inhibitors (i.e., orthophosphate) alongside LSL replacement. While necessary to ensure public health protection from lead contamination, the addition of orthophosphate into an aging and leaking drinking water system may increase the concentration of phosphate leaching into urban streams characterized by century-old failing water infrastructure. Such increases in phosphate availability may cascade into nutrient and microbial community composition shifts. The purpose of this study was to determine how this occurs and to understand whether full-scale distribution system orthophosphate addition impacts the microbial ecology of urban streams. Through monthly collection of water samples from five urban streams before and after orthophosphate addition, significant changes in microbial community composition (16S rRNA amplicon sequencing) and in the relative abundance of typical freshwater taxa were observed. In addition, key microbial phosphorus and nitrogen metabolism genes (e.g., two component regulatory systems) were predicted to change via BugBase. No significant differences in the absolute abundances of total bacteria, Cyanobacteria, and "Candidatus Accumulibacter" were observed. Overall, the findings from this study provide further evidence that urban streams are compromised by unintentional hydrologic connections with drinking water infrastructure. Moreover, our results suggest that infiltration of phosphate-based corrosion inhibitors can impact urban streams and have important, as-yet-overlooked impacts on urban stream microbial communities. IMPORTANCE Elevated lead levels in drinking water supplies are a public health risk. As such, it is imperative for cities to urgently address lead contamination from aging drinking water supplies by way of lead service line replacements and corrosion control methods. However, when applying corrosion control methods, it is also important to consider the chemical and microbiological effects that can occur in natural settings, given that our water infrastructure is aging and more prone to leaks and breaks. Here, we examine the impacts on the microbial ecology of five urban stream systems before and after full-scale distribution system orthophosphate addition. Overall, the results suggest that infiltration of corrosion inhibitors may impact microbial communities; however, future work should be done to ascertain the true impact to protect both public and environmental health.

Effects of Environmental Contamination and Acute Toxicity of N-Nitrate on Early Life Stages of Endemic Arboreal Frog, Polypedates cruciger (Blyth, 1852).

This study investigated the potential toxic effects of environmentally relevant nitrate concentrations on development, growth, and mortality of early life stages of common hour-glass tree frog, Polypedates cruciger. Tadpoles from hatchlings through pre-adult were exposed to environmentally relevant nitrate concentrations detected in Mirissa, Sri Lanka. Newly hatched, external gill stage, and internal gill stage tadpoles were exposed to potassium nitrate for bioassay tests. No behavioral changes or abnormalities were observed in control and nitrate-induced group. However, detected environmental nitrate concentration significantly increased (p < 0.05) the growth of the tadpoles up to 25 days old. Results revealed that newly hatched and external gill stage was more susceptible to the nitrate pollution than internal gill stage. The results suggest that environmentally relevant nitrate can cause mortality on the amphibian population in ecosystems associated with agro-pastoral activities through altering the growth and direct toxicological effects on the survivorship.

Artificial destratification effects on nitrogen and phosphorus dynamics in a eutrophic impoundment in the northern Great Plains.

To determine the influence of artificial destratification on nutrient variations in a small eutrophic impoundment, field monitoring and laboratory analyses were conducted in three consecutive summers (2010, 2011, and 2012). The impact of aeration among sampling locations and across the water column of nutrient concentrations, including total and dissolved inorganic nitrogen (N) and phosphorus (P) and water temperature and dissolved oxygen (DO) was evaluated under aerated and non-aerated conditions. Aeration eliminated thermal stratification and DO concentrations of bottom waters increased. Nutrients including soluble reactive phosphorus (SRP), total phosphorus (TP), and total nitrogen (TN) concentrations across the water column did not change significantly during aeration. Nevertheless, under aerated conditions, dissolved inorganic nutrients, TN, TP, and temperature were homogenously distributed throughout the water column as an effect of aeration. Results indicated that artificial destratification resuspended nutrients throughout the water column; however, it did not have a significant effect on nutrient concentrations in the water column, but SRP, TN, and TP concentrations did not reach to the recommended limit as needed by the North Dakota Department of Health requirements. Therefore, alternative aeration methods, for instance, hypolimnetic oxygenation or hypolimnetic aeration are recommended to control nutrient redistribution and/or further releases by existing aeration system.