Escherichia coli Removal Efficacy of a Marshland Upwelling System

Abstract
The Marshland Upwelling System (MUS), a decentralized wastewater treatment strategy for coastal dwellings, was examined to assess its ability to remove Escherichia coli from raw sewage as a step towards total treatment. Wastewater was intermittently injected down a 4.6-m injection well into the surrounding salt marsh at 0.9, 1.9, and 3.8 lpm over the 13-month evaluation period. Optimal E. coli removal and hydraulic performance was achieved at the 1.9-lpm flow rate with influent concentrations of 260,000±370,000 E. coli/100 mL reduced to a mean effluent count of 0.4±10.6 E. coli/100 mL. Escherichia coli concentrations declined exponentially with only 0.9-m travel distance needed to reduce influent concentrations by 1 order of magnitude. Predicted surface concentrations were less than 1 E. coli/100 mL. The probability of effluent counts exceeding the U.S. Environmental Protection Agency standard of 126 E. coli/100 mL for recreational waters was 5.5×10-12%. Increasing flows to 3.8 lpm initiated localized hyd...