Harnessing Soil's Capacity to Purify Contaminated Waterways
In the bucolic landscapes of Ohio, the importance of soil in wastewater treatment has long been recognised. The state's diverse soil resources, primarily used for agriculture, also play a crucial role in protecting the health of families, neighbours, and visitors, as well as the environment.
Fractured rock materials below soils, found mainly in eastern and southeastern Ohio, are not affected by glaciation. However, many of these tills are dense, resembling concrete, and have low capacity to move water or air. This can impede the movement of water away from the site and cause the formation of perched saturated conditions in the soil profile.
Naturally occurring soils have varying capacities to accomplish pollutant removal, with three properties being most important: unsaturated soil, deep enough soil, and permeable soil. Well-draining soils like loamy sand or sandy loam are preferred due to their better percolation and treatment capacities. Clay-heavy soils or high water table areas may require alternative systems or professional design considerations.
The ideal depth of soils for wastewater treatment absorption fields in Ohio requires at least 1 foot (12 inches) of suitable soil below the bottom of the absorption trench to ensure proper treatment and dispersal of effluent. The absorption trench bottom itself is typically designed with a minimum soil cover of about 6 inches above the trench aggregate.
When wastewater moves through soil to these porous materials, it often moves too quickly to provide treatment and can pollute nearby wells. For decades, households in rural areas were not held to a similar standard and were often able to dispose of wastewater without providing treatment. This oversight has led to sickness among rural neighbours due to waterborne diseases from contaminated wells.
In response, Ohio has set standards for soil suitability in septic system installation. The key soil horizon to consider for installation is the one extending to this depth below the trench bottom, which should have an acceptable percolation rate (not exceeding 90 minutes per inch for lots under three acres or 120 minutes per inch for larger lots) to be suitable for wastewater treatment systems.
However, in areas where saturation occurs, microorganisms rapidly deplete oxygen, and the resulting anaerobic conditions impede biological, chemical, and physical treatment of contaminants in wastewater. This is particularly true in areas with dense tills, where little effluent treatment occurs due to low permeability and limited biological activity.
Communities that provide sewage services for homes must treat wastewater to remove pollutants before discharging it into Ohio's environment. The goals in any sewage treatment system are to remove pollutants that cause disease and remove pollutants that kill fish and aquatic life. Unfortunately, Ohio has some of the most polluted swimming beaches in the nation.
As the state continues to grow and develop, it is essential to ensure that wastewater treatment systems are installed correctly and that the ideal soil depth is maintained to protect public health and the environment. By doing so, Ohio can continue to thrive while ensuring a clean and safe environment for all its residents.
[1] Ohio Department of Health. (n.d.). Septic Systems. Retrieved from https://www.odh.ohio.gov/wps/portal/gov/odh/know-our-programs/environmental-health/septic-systems
[2] Ohio Environmental Protection Agency. (n.d.). Septic Systems. Retrieved from https://epa.ohio.gov/wps/portal/gov/ohioepa/whatwedo/water/septic/septic-systems-homeowners
- The soil's ability to support agriculture, health-and-wellness, and environmental science is significant, as it functions in wastewater treatment and protects public health, in addition to its use in farming.
- Inadequate soil permeability, such as in dense tills, can hinder the movement of water and air, potentially causing perched saturated conditions and hindering the treatment and dispersal of wastewater effluent.
- Fitness-and-exercise enthusiasts, like those who swim in Ohio's polluted swimming beaches, may be exposed to pollutants that cause disease, emphasizing the importance of proper wastewater treatment and having suitable soil depth for wastewater treatment absorption fields.
