Most of Ohio's soil natural resource is too shallow to use for wastewater treatment. For homes built in areas with these soils, septic system leach fields and mound systems will not work. If designed, constructed, and approved anyway, they will threaten public health and the environment. For these situations a separate wastewater treatment system must be constructed to remove ammonia, organic matter, suspended solids, bacteria, and viruses.
As noted with mound systems, sand does an excellent job of removing ammonia, organic matter, and suspended solids from wastewater. In areas with very shallow soils above a limiting condition, sealed basins or tanks of sand can be carefully constructed to accept septic tank effluent and partially treat the wastewater (Figure 8). Known as sand bioreactors, or sometimes called sand filters, these treatment systems can be constructed right on the lot. Bulletin 876, Sand Bioreactors for Wastewater Treatment in Ohio, gives all of the details to design and construct these sand treatment systems.
Sand, however, does a poor job of removing disease-causing organisms from wastewater. A separate disinfection unit is needed to remove bacteria and viruses from sand-filtered wastewater. Bulletin 876 also presents the options for disinfection.
Once treated and disinfected, wastewater must be released back into the environment. Remember, treated wastewater is not pure water, and will still contain low levels of water pollutants. The soil, once again, is a wonderful place to disperse the treated wastewater because the water pollutants of organic matter and ammonia are converted to useful constituents in soil.