Wednesday, November 4, 2009: 10:45 AM
Convention Center, Room 402, Fourth Floor
The use of soils for disposal of household wastewater in Northeast Ohio dates back prior to 1950. Very little was understood about the capacity of the soils to dissipate, much less treat the effluent to the point of suitable pathogen reduction to prevent pollution of either groundwater or surface water sources. Due to population density increases, greater emphasis is now needed for adequate treatment occur in these soils. Treatment of wastewater occurs only in soils which have sufficient oxygen to allow aerated respiration to occur. Soil saturated for extended periods that becomes depleted of oxygen in the critical depths cannot support the desired bacterial activity needed in the treatment of wastewater. Under anaerobic conditions, bacterial activity utilize energy (electrons) from iron and manganese, reducing these elements. For many northeastern Ohio soils, the resulting low chroma depletions and redox concentrations are the primary evidence that extended periods of reduction is occurring. Determining the depth of fluctuating soil water tables is critical for design parameters to be met. This is especially true if the A horizon is found to be saturated for extended periods. Many northeastern Ohio soils have evidence of oxidation and reduction, in the form of iron and manganese concretions and soft masses, that are masked by organic matter in the A horizon. As a result, many onsite systems fail because the evaluator does not see these concretions and subsequently the wrong kind of treatment systems are prescribed.