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Drought conditions should magnify the effect of wastewater treatment plant (WWTP) effluent on river biogeochemistry. This study examined the impact of WWTP effluent on the Enoree River in the piedmont region of South Carolina during a period of significant drought. The Enoree River lacks impoundments, upstream agricultural runoff, and significant industrial point sources, so the single most important human influence on river chemistry is WWTP effluent. Water samples were collected from 28 locations on the Enoree River, 13 of its tributaries, and the effluent of four WWTPs. Effluent from the WWTP furthest upstream increased the salinity of the river and temporal variation and concentrations of most ions, especially nitrate, phosphate, sulfate, sodium, and chloride. The upstream WWTP set the downstream chemical composition of the river, with increasing proportions of chloride, sodium, and sulfate and decreasing proportions of dissolved silicon and bicarbonate. Downstream WWTPs had little or no impact on the chemical composition of the river. Mixing model results show that dilution was the dominant process of the downstream decrease in solute concentrations, but in-channel uptake mechanisms also contributed to declines in concentrations of nitrate, phosphate, and carbon dioxide. Despite dilution and uptake, the chemical signature of WWTP effluent was still evident 135 km downstream. These results lead to a better understanding of the effects of WWTP effluent on the biogeochemistry of rivers. [ABSTRACT FROM AUTHOR]

Summary: The concentration of bicarbonate, the dominant anion in river water, is typically calculated using measured alkalinity concentrations. Alkalinity concentrations also are necessary for analytical charge balance, carbonate speciation, and PCO2 calculations. Although the Gran titration is the standard method for measuring alkalinity, previous studies have varied in how water samples have been processed prior to analysis. The purpose of this study was to determine whether variation in filtering, refrigeration, and sample storage time leads to statistically significant differences in alkalinity concentrations in oxic, low-turbidity surface waters and groundwaters ranging from undersaturated to supersaturated with respect to calcite. Samples were collected from the Blue Ridge and Piedmont Provinces of northwestern South Carolina and the Valley and Ridge Province of eastern Tennessee. Each sample was analyzed using four processing treatments: filtered and refrigerated, filtered and unrefrigerated, unfiltered and refrigerated, and unfiltered and unrefrigerated (n =3 analyses per treatment combination). All replicates were analyzed within 24h using the Gran titration method. Samples then were reanalyzed after 17–194days of storage to determine if storage time affects alkalinity measurements. Overall, alkalinity concentrations ranged from 0.8 to 107mg/L CaCO3. Statistically significant differences among the treatments and significant interactions between filtration and refrigeration were limited. For samples in which treatment means differed significantly or in which interactions were significant, differences generally were less than 10% and probably of little biogeochemical importance. For all but one sample locality, storage time did not affect alkalinity. Our results show that for oxic waters that have low concentrations of DOC and reduced metals, filtration, refrigeration and storage time are unlikely to affect measured alkalinity concentrations. However, additional research is needed to determine the degree to which sample processing treatment is important to interpreting the alkalinity concentrations of DOC- and metal-rich samples. [Copyright &y& Elsevier]

Naturally high total dissolved solids and upstream agricultural runoff often mask the influence of urban land cover on stream chemistry and biology. We examined the influence of headwater urbanization on the water chemistry, microbiology, and fish communities of the Big Brushy Creek watershed, a 96 km2 drainage basin in the piedmont of South Carolina, USA. Concentrations of most major anions and cations (especially nitrate, sulfate, chloride, sodium, potassium, and calcium) were highest in the urban headwaters and decreased downstream. Generally, the highest concentrations of suspended coliform bacteria occurred in the urban headwaters. In contrast, stream habitat quality and the abundance, species richness, and species diversity of fishes did not differ significantly between urban and rural sites. Discharge of wastewater treatment plant effluent at one rural location caused an increase in concentrations of many solutes and possibly the abundance of benthic algae. We hypothesize that atmospheric dry deposition and domestic animal wastes are important sources of stream solutes and of coliform bacteria, respectively, in the urban headwaters. The lack of significant differences in fish abundance and diversity between urban and rural sites may indicate that urban development in the Big Brushy Creek watershed has not yet degraded habitat conditions greatly for stream fishes. Alternatively, agriculture or other land uses may have degraded stream habitat quality throughout the watershed prior to urbanization. [ABSTRACT FROM AUTHOR]