Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 573, Issue -, Pages 278-289Publisher
ELSEVIER
DOI: 10.1016/j.scitotenv.2016.08.075
Keywords
Setback distances; Enteric viruses; Vadose zone; Water quality; Small biological wastewater treatment systems; Effluent land disposal
Categories
Funding
- Austrian Ministry of agriculture, forestry, environment and water resources
Ask authors/readers for more resources
Contamination of groundwater by pathogenic viruses from small biological wastewater treatment system discharges in remote areas is a major concern. To protect drinking water wells against virus contamination, safe setback distances are required between wastewater disposal fields and water supply wells. In this study, setback distances are calculated for alluvial sand and gravel aquifers for different vadose zone and aquifer thicknesses and horizontal groundwater gradients. This study applies to individual households and small settlements (1-20 persons) in decentralized locations without access to receiving surface waters but with the legal obligation of biological wastewater treatment. The calculations are based on Monte Carlo simulations using an analytical model that couples vertical unsaturated and horizontal saturated flow with virus transport. Hydraulic conductivities and water retention curves were selected from reported distribution functions depending on the type of subsurface media. The enteric virus concentration in effluent discharge was calculated based on reported ranges of enteric virus concentration in faeces, virus infectivity, suspension factor, and virus reduction by mechanical-biological wastewater treatment. To meet the risk target of <10(-4) infections/person/year, a 12 logo reduction was required, using a linear dose-response relationship for the total amount of enteric viruses, at very low exposure concentrations. The results of this study suggest that the horizontal setback distances vary widely ranging 39 to 144 m in sand aquifers, 66-289 m in gravel aquifers and 1-2.5 km in coarse gravel aquifers. It also varies for the same aquifers, dependingon the thickness of the vadose zones and the groundwater gradient. For vulnerable fast-flow alluvial aquifers like coarse gravels, the calculated setback distances were too large to achieve practically. Therefore, for this category of aquifer, a high level of treatment is recommended before the effluent is discharged to the ground surface: (C) 2016 The Authors. Published by Elsevier B.V.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available