Phosphate treatment by onsite wastewater systems in nutrient-sensitive watersheds of North Carolina's Piedmont.


Journal Article

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.

Full Text

Duke Authors

Cited Authors

  • Humphrey, C; Serozi, B; Iverson, G; Jernigan, J; Pradhan, S; O'Driscoll, M; Bean, E

Published Date

  • October 2016

Published In

Volume / Issue

  • 74 / 7

Start / End Page

  • 1527 - 1538

PubMed ID

  • 27763333

Pubmed Central ID

  • 27763333

Electronic International Standard Serial Number (EISSN)

  • 1996-9732

International Standard Serial Number (ISSN)

  • 0273-1223

Digital Object Identifier (DOI)

  • 10.2166/wst.2016.355


  • eng