Assessment and Mitigation of Fecal Bacteria Exports from a Coastal North Carolina Watershed

Abstract

Urban runoff from the Boat House Creek watershed was suspected as a main delivery mechanism for fecal indicator bacteria (FIB) to the lower White Oak River Estuary in coastal North Carolina, but the dominant source of waste (animal or human) was unknown. Water samples from eight locations within the watershed were collected approximately monthly for two years for enumeration of Escherichia coli (E. coli), enterococci, physicochemical characterization, and microbial source tracking analyses. Concentrations and loadings of E. coli and enterococci were typically elevated during stormflow relative to baseflow conditions, and most samples (66% of enterococci and 75% of E. coli) exceeded the US EPA statistical threshold values. Concentrations of FIB were significantly higher during warm relative to colder months. Human sources of FIB were not observed in the samples, and FIB concentrations increased in locations with wider buffers, thus wildlife was the suspected main FIB source. Stormwater control measures including a rain garden, water control structures, swale modifications, and check dams were implemented to reduce runoff and FIB loadings to the estuary. Stormflow reductions of >5700 m3 year−1 are estimated from the installation of the practices. More work will be needed to improve/maintain water quality as watershed development continues.

Evaluation of Phosphate and E. coli Attenuation in a Natural Wetland Receiving Drainage from an Urbanized Catchment

“…Primers and probes for bacterial human indicator detection were BacHum Rev 5 ′ -CGCTACACCAC GAATTCCG-3 ′ , BacHum Fwd 5 ′ -CGCGGTAATACGGAGGATCC-3 ′ , BacHum LNA Probe 5 ′ -/56-FAM/AAGTTT+GC+GG+C+T+CAAC/3IABkFQ/-3 ′ (IDTDNA, Coralville, IA, USA). Similar protocols have been used in prior studies [21,22] to help identify bacteria sources. Stream samples from inlets 1 and 2 were collected during late summer (September) and early winter (December) of the project period.…”

“…However, prior research [61] has shown that check dams can reduce runoff volumes by 17% and increase hydraulic residence times by 29% or more. Other research [62] reported that implementation of check dams in drainageways helped to reduce the total volume and dynamic flows and the stormflow transport of pollutants, such as fecal indicator bacteria [21].…”

“…E. coli in surface waters may originate from many of the same sources as phosphorus including wastes from humans [17,18], pets [19], and wildlife [20]. Fecal bacteria can be delivered to surface waters via urban runoff that flushes waste deposited onto impervious surfaces [21], agricultural runoff from livestock waste deposited or applied to fields [22], discharges of municipal sewer effluent [23], and malfunctioning septic systems [17]. Reducing the delivery of E. coli from watersheds influenced by anthropogenic activities (e.g., agriculture, urbanization, wastewater discharges) to receiving waters is important for public and environmental health.…”