| Summary |
In the United States, nutrient and pharmaceutical loading into lakes, streams, and estuaries is a problem that has been recognized for decades and is of special concern for many North Carolina (NC) watersheds. Pharmaceuticals and personal care products (PPCPs) are used in households on a daily basis, and include prescription analgesics, antibiotics, and hormone regulators as well as over-the-counter medications, fragrances, and cleansers. Onsite wastewater treatment systems (OWTS) are a potential non-point source of nutrients, such as nitrogen and carbon, as well as PPCPs, and are extensively used in coastal NC. The goal of the present study was to determine the fate and transport of total dissolved nitrogen (TDN), dissolved organic carbon (DOC), and PPCPs from OWTS in the Tar-Pamlico river basin. Four residential OWTS, in Greenville, NC, were sampled to determine the flow path of TDN and DOC using hydrologic, physical, and chemical data, and determine the detection frequency of selected PPCPs. Specific site conditions influencing TDN, DOC, and PPCP concentrations were analyzed including: soil type, distances from the OWTS, wastewater loading rates, and various chemical properties such as pH, dissolved oxygen (DO), temperature, and electrical conductivity. Treatment efficiencies from the tank to the drainfield ranged from 32-95% for TDN and 45-82% for DOC. The PPCPs most commonly detected in groundwater beneath the OWTS drainfield, and down-gradient of the system included: DEET, ibuprofen, caffeine, and homosalate (a sunscreen agent), ranging in concentrations from 0.12 [mu]g L⁻¹ to 12.04 [mu]g L⁻¹ in the groundwater. The concentrations of PPCPs detected in this study were inversely correlated with distance from the tank ([rho]=-0.56; p-value= <0.0001). Findings from this study have implications for OWTS regulations in NC and could potentially be used to guide future nutrient and toxics-based water management strategies. |
