title: Nitrogen and carbon dynamics beneath on-site wastewater treatment systems in Pitt County, North Carolina.
abstract: On-site wastewater treatment systems (OWS) are a potentially significant non-point source of nutrients to groundwater and surface waters, and are extensively used in coastal North Carolina. The goal of this study was to determine the treatment efficiency of four OWS in reducing total dissolved nitrogen (TDN) and dissolved organic carbon (DOC) concentrations before discharge to groundwater and/or adjacent surface water. Piezometers were installed for groundwater sample collection and nutrient analysis at four separate residences that use OWS. Septic tank effluent, groundwater, and surface water samples (from an adjacent stream) were collected four times during 2012 for TDN and DOC analysis and pH, temperature, electrical conductivity, and dissolved oxygen measurements. Treatment efficiencies from the tank to the groundwater beneath the drainfields ranged from 33 to 95% for TDN and 45 to 82% for DOC, although dilution accounted for most of the concentration reductions. There was a significant positive correlation between nitrate concentration and separation distance from trench bottom to water table and a significant negative correlation between DOC concentration and separation distance. The TDN and DOC transport (>15 m) from two OWS with groundwater saturated drainfield trenches was significant.
authors.affiliation: Department of Health Education and Promotion, East Carolina University, Carol Belk Building, Greenville, NC 27858, USA.
authors.forename: Katie L
authors.initials: KL
authors.lastname: Del Rosario
authors.affiliation: Department of Health Education and Promotion, East Carolina University, 3408 Carol Belk Building, Greenville, NC 27858, USA E-mail: Humphreyc@ecu.edu.
authors.forename: Charles P
authors.initials: CP
authors.lastname: Humphrey
authors.affiliation: Department of Geological Sciences, East Carolina University, 101 Graham Building, Greenville, NC 27858, USA.
authors.forename: Siddhartha
authors.initials: S
authors.lastname: Mitra
authors.affiliation: Department of Geological Sciences, East Carolina University, 204 Graham Building, Greenville, NC 27858, USA.
authors.forename: Michael A
authors.initials: MA
authors.lastname: O'Driscoll
mesh_terms: D002244:Carbon / Q000032:analysis*; D060587:Groundwater / Q000032:analysis*; D009584:Nitrogen / Q000032:analysis*; D009657:North Carolina; D018505:Waste Management
chemical_list: D002244:Carbon; D009584:Nitrogen