Nutrient and Fecal Microbe Contamination in Tates Creek, Madison County, Kentucky
Tates Creek is a significant tributary to the Kentucky River that has shown high levels of microbial and nutrient pollution. We sampled the waters of Tates Creek comprehensively by occupying 25 stations along its 13-mile length, collecting stream water at the confluence of major tributaries from its headwaters to the Kentucky River. Samples were collected four times between May and August 2011 during dry periods as well as immediately after a rainfall event. We measured ammonium (NH4+), nitrate (NO3-) and phosphate (PO4-) concentrations using colorimetry. Microbial samples were measured for total coliform and Escherichia coli using IDEXX Colilert-18 media.
Background levels of NH4+, NO3- and PO4- are typically ~0.3 mg/L, 5 mg/L, and 1.0 mg/L, respectively. Background levels of nutrient concentrations generally increase during rainfall events, presumably because nutrients are flushed into the stream. Background counts of E. coli are typically ~100 cfu/mL but E. coli counts reached 1,000 – 2,419 cfu/mL immediately following rain events.
A sewage treatment plant exists approximately two miles from the headwaters and noticeably affects water quality. Nutrient concentration, especially NH4+ and PO4-, are markedly increased at the plant’s outflow. These nutrients then decrease steadily in concentration downstream to background levels. In contrast, fecal microbe counts are high upstream from the plant, but fall to near-zero levels at its outflow, and then increase anew downstream. The treatment plant went off line on 19 July 2011 and nutrient levels downstream immediately decreased whereas E. coli counts remained high upstream and downstream of the plant.
A companion study sampled stream biota before and after the plant shut down into 2012. This allows any changes in stream biota to be recognized and attributed to plant operations.