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Journal of Environmental Quality Abstract - Special Section: Microbial Transport and Fate in the Subsurface

Bacteria Transport in a Soil-Based Wastewater Treatment System under Simulated Operational and Climate Change Conditions

 

This article in JEQ

  1. Vol. 44 No. 5, p. 1459-1472
     
    Received: Dec 20, 2014
    Accepted: May 26, 2015
    Published: September 16, 2015


    * Corresponding author(s): boving@uri.edu
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doi:10.2134/jeq2014.12.0547
  1. Ivan Moralesa,
  2. José A. Amadorb and
  3. Thomas Boving *c
  1. a Dep. of Civil and Environmental Engineering, Univ. of Rhode Island, Kingston, RI 02881
    b Lab. of Soil Ecology and Microbiology, Univ. of Rhode Island, Kingston, RI 02881
    c Dep. of Civil and Environmental Engineering and Dep. of Geosciences, Univ. of Rhode Island, Kingston, RI 02881
Core Ideas:
  • Retention of E. coli was modeled in a conventional onsite wastewater treatment.
  • The model was run under varied operational and climate changing conditions.
  • Lower hydraulic loading rate values removed more E. coli due to unsaturated conditions.
  • Precipitation and warmer soil temperatures affect E. coli removal in the soil.
  • Higher soil temperatures increased E. coli die-off rates and system performance.

Abstract

Bacteria removal efficiencies in a conventional soil-based wastewater treatment system (OWTS) have been modeled to elucidate the fate and transport of E. coli bacteria under environmental and operational conditions that might be expected under changing climatic conditions. The HYDRUS 2D/3D software was used to model the impact of changing precipitation patterns, bacteria concentrations, hydraulic loading rates (HLRs), and higher subsurface temperatures at different depths and soil textures. Modeled effects of bacteria concentration shows that greater depth of treatment was required in coarser soils than in fine-textured ones to remove E. coli. The initial removal percentage was higher when HLR was lower, but it was greater when HLR was higher. When a biomat layer was included in the transport model, the performance of the system improved by up to 12.0%. Lower bacteria removal (<5%) was observed at all depths under the influence of precipitation rates ranging from 5 to 35 cm, and 35-cm rainfall combined with a 70% increase in HLR. Increased subsurface temperature (23°C) increased bacteria removal relative to a lower temperature range (5–20°C). Our results show that the model is able to effectively simulate bacteria removal and the effect of precipitation and temperature in different soil textures. It appears that the performance of OWTS may be impacted by changing climate.

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Copyright © 2015. . Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.