Simulation of phosphate transport in sewage-contaminated groundwater, Cape Cod, Massachusetts

Applied Geochemistry



Sewage-contaminated groundwater currently discharges to Ashumet Pond, located on Cape Cod, Massachusetts. Phosphate concentrations as high as 60 μmol l−1 have been measured in groundwater entering Ashumet Pond, and there is concern that the rate of eutrophication could increase. Phosphate in the sewage plume is sorbed by aquifer sediment; the amount is a function of phosphate concentration and pH. A nonelectrostatic surface-complexation model coupled with a one-dimensional solute-transport code was used to simulate sorption and desorption of phosphate in laboratory column experiments. The model simulated sorption of phosphate reasonably well, although the slow rate of approach to complete breakthrough indicated a nonequilibrium process that was not accounted for in the solute-transport model. The rate of phosphate desorption in the column experiments was relatively slow. Phosphate could still be measured in effluent after 160 pore volumes of uncontaminated groundwater had been flushed through the columns. Desorption was partly a function of the slowly decreasing pH in the columns and could be modeled quantitatively. Disposal of sewage at this site is scheduled to stop in 1995; however, a large reservoir of sorbed phosphate exists on aquifer sediment upgradient from Ashumet Pond. Computer simulations predict that desorption of phosphate could result in contamination of Ashumet Pond for decades.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Simulation of phosphate transport in sewage-contaminated groundwater, Cape Cod, Massachusetts
Series title Applied Geochemistry
DOI 10.1016/0883-2927(95)00041-0
Volume 11
Issue 1-2
Year Published 1996
Language English
Publisher Elsevier
Contributing office(s) Toxic Substances Hydrology Program
Description 8 p.
First page 317
Last page 324
Google Analytic Metrics Metrics page