title: Phosphate treatment by onsite wastewater systems in nutrient-sensitive watersheds of North Carolina's Piedmont.
abstract: The goal of this study was to gain a better understanding of the PO4-P treatment efficiency of onsite wastewater systems (OWS) installed in nutrient-sensitive watersheds of the North Carolina Piedmont. Four OWS including two conventional and two single-pass sand filter (SF) systems were evaluated at sites with clay-rich soils. Piezometers were installed near all of the OWS, and down-gradient from the conventional OWS for groundwater collection and characterization. Septic tanks, groundwater, SF effluent, and surface waters were sampled each season during 2015 (five times) and analyzed for PO4-P and Cl concentrations and for various environmental parameters. The conventional and SF OWS reduced PO4-P concentrations by an average of 99% and 90%, respectively, before discharge to surface waters. Mass-load reductions of PO4-P were also greater for the conventional OWS (mean 95%), relative to SF (83%) systems. The effluents discharged by SF OWS were influencing surface water quality. Additional treatment of the effluent from single-pass SF with reactive media is suggested, along with monitoring of the final effluent for PO4-P concentrations. This research provides important information that is absent from the published literature concerning PO4-P contributions to water resources from OWS in clay soils.
authors.affiliation: East Carolina University, Greenville, NC, USA E-mail: humphreyc@ecu.edu.
authors.forename: Charles
authors.initials: C
authors.lastname: Humphrey
authors.affiliation: Environmental Health Sciences Program, East Carolina University, Greenville, NC, USA.
authors.forename: Brent
authors.initials: B
authors.lastname: Serozi
authors.affiliation: Coastal Resources Management Program, East Carolina University, Greenville, NC, USA.
authors.forename: Guy
authors.initials: G
authors.lastname: Iverson
authors.affiliation: Environmental Health Sciences Program, East Carolina University, Greenville, NC, USA.
authors.forename: Jordan
authors.initials: J
authors.lastname: Jernigan
authors.affiliation: North Carolina Department of Health and Human Performance, Raleigh, NC, USA.
authors.forename: Sushama
authors.initials: S
authors.lastname: Pradhan
authors.affiliation: Department of Geological Sciences, East Carolina University, Greenville, NC, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: O'Driscoll
authors.affiliation: Department of Engineering and Institute for Coastal Science and Policy, East Carolina University, Greenville, NC, USA.
authors.forename: Eban
authors.initials: E
authors.lastname: Bean
mesh_terms: D002712:Chlorides / Q000737:chemistry; D005374:Filtration / Q000295:instrumentation* / Q000379:methods; D060587:Groundwater / Q000737:chemistry; D009657:North Carolina; D010710:Phosphates / Q000737:chemistry*; D012987:Soil / Q000737:chemistry; D062065:Wastewater / Q000737:chemistry*; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D014876:Water Pollution / Q000517:prevention & control; D060753:Water Quality
chemical_list: D002712:Chlorides; D010710:Phosphates; D012987:Soil; D062065:Wastewater; D014874:Water Pollutants, Chemical