Nutrients, Caffeine, DEET, Fecal Sterols, and Triclosan in the Blue River Basin, Metropolitan Kansas City, USA, 1998 to 2007

Surface-water samples collected from 1998 to 2007 in the largely urban Blue River Basin, metropolitan Kansas City, USA, were analyzed for more than 100 constituents including nutrients, selected pharmaceuticals, and personal care products. Water samples were collected over a range of hydrologic conditions in stream reaches that received either inputs of treated effluent, untreated combined sewer overflows, or combinations of both. For some persistent constituents detected in basin water samples, fitted linear regression load models were developed. Load estimation models for total nitrogen, total phosphorus, caffeine, the insect repellant DEET (n, n-diethyl-meta-toluamide), the fecal sterols cholesterol plus coprostanol, and the antimicrobial triclosan were utilized to evaluate the relative contributions of these compounds from different wastewater sources and factors that control their environmental distribution and occurrence. Model elements included concentration, flow, time, and in some cases, annual or seasonal terms.

Total nitrogen loads in the basin were approximately 10 times greater than the total phosphorus loads and about 1000 times greater than the caffeine, DEET, and triclosan loads. Cholesterol plus coprostanol loads were approximately 10 times greater than the caffeine, DEET, and triclosan loads. Loads in the effluent-dominated reaches were, on average, about 20 times greater than loads from reaches dominated by combined sewer overflows. Biogeochemical processes in bottom sediments reduced some constituent concentrations by approximately two-thirds during a 6 to 8-month period.

In effluent-dominated reaches, increased caffeine and cholesterol plus coprostanol contributions to streams occurred during the winter when colder temperatures may have reduced wastewater removal rates; constituent contribution declines coincided with increased summer temperatures. For stream reaches that received only combined sewer overflows, seasonal load patterns more closely followed seasonal precipitation patterns because overflows were controlled by rainfall events. One exception was DEET, for which June to August accounted for the largest percentage of seasonal contributions at all sites.