What if There is no Sanitary Sewer?
By Kris Barnswell, TMACOG Water Quality Planner
Like many of us, I have lived in areas where sanitary sewers are available and never have given much thought where the water goes after flushing a toilet, taking a shower, or washing dirty clothes. All the wastewater generated in my house goes to a sanitary sewer which ultimately flows into a publicly owned wastewater treatment plant. All I worry about is paying my utility bill. But, what happens to household wastewater in areas where sanitary sewers are not present and there is no wastewater treatment plant?
I spent a few afternoons with staff from the Toledo-Lucas County Health Department to gain a better understanding of how household or on-site sewage is treated in areas where no sanitary sewers are present. Registered Sanitarians Brandon Tester and Michael Butcher devote much of their time to inspecting and evaluating the performance of on-site sewage treatment systems to ensure they are functioning properly in compliance with state regulations. In general, there are two types of on-site treatment systems: septic systems and package plants.
Septic systems are generally used to treat household wastewater. Households that use septic systems are often rural areas, far from city sewer lines, or small communities that don’t own and operate a wastewater treatment plant.
Septic systems commonly include a tank where solids settle to the bottom (referred to as a septic tank) and a leach field where the liquid (or effluent) that flows out of the septic tank is distributed and filtered by the natural soil. Septic systems are very common in the eastern and western portions of Lucas County, with more than 12,000 systems across the entire county (see map below showing areas where sanitary sewers are present).
This map shows where municipalities manage sanitary sewers in Lucas County. The uncolored areas indicate there is no sanitary sewer available. These areas use home septic systems or package plants.
In general, septic systems have a site-specific design that takes into consideration the size of the home based on the number of bedrooms (and presumed number of people living in the house) and characteristics of the native soil. Based on these factors (and others such as depth to groundwater), the size of the septic tank and leach field are selected. For example, a home with one or two bedrooms is required to have a septic tank that stores 1,000 gallons, and a home with three bedrooms needs to have a septic tank that stores 1,500 gallons. The size of the leach field is calculated based on the flow of wastewater and permeability of the soil. This calculation usually results in a treatment area of several hundred square feet.
Mike Butcher inspects a leach field at a private residence using a probe to locate
the distribution tiles. Based on the color of the soil attached to the probe, Mike can
tell how the leach field is functioning.
Septic systems are also used to treat wastewater generated on commercial properties. These systems can be more complicated than a household system, which may be due to the greater volume of wastewater needed for treatment and the native soil conditions. However, the approach for treatment is similar: first settle out the solids then filter the effluent. The photo below shows a mounded septic system, which includes a septic tank, lift station that pumps effluent at a selected rate, and a leach field mound constructed of engineered sandy soil. A mound may be needed when the water table (or groundwater) has the potential to rise and be near the surface. Mound systems are common near lakes and other low-lying areas.
Mike Butcher explains how a mounded septic system works. The septic tank is located beneath the plastic lids, the lift station is in the center (white tower), and the mounded leach field is on the right.
Package plants are used on residential and commercial properties to treat wastewater that is generated at volumes exceeding 1,000 gallons per day. Package plants are a scaled down version of a wastewater treatment plant and include chambers for the settling of solids, aeration and treatment, clarification, and disinfection. They are prefabricated off-site, which simplifies their installation. The effluent of a package plant may flow into a leach field (just like a septic system), or discharge into a stream or storm sewer. Package plants that discharge into streams are regulated by the Ohio EPA under the National Pollutant Discharge Elimination System (NPDES) program and routinely monitored to ensure the effluent meets water quality standards.
Brandon Tester inspects a package plant.
For more information on septic systems and package plants, please visit the
Toledo-Lucas County Health Department website: at http://www.lucascountyhealth.com/sewage-treatment/.