Click on “Download PDF” for the PDF version or on the title for the HTML version.

If you are not an ASABE member or if your employer has not arranged for access to the full-text, Click here for options.

The focus of the project is a slow rate wastewater treatment plant located in Michigan. The treatment plant wanted to expand to include a nearby communitys sanitary sewage effectively doubling the systems hydraulic load.

Evaluations concluded that the disposal systems soils had relatively low permeability values and was already operating near hydraulic capacity. Expanding to include more land for application was not feasible. Subsurface drainage was installed to increase the systems hydraulic capacity. Since the system was still maintaining adequate treatment, the subsurface drainage only needed to collect the additional wastewater volume generated by the systems expansion. Sections of the fields (subfields) were grouped based on available slope, hydraulic capacity, and depth to restricting layer (water table or less permeable strata). Different tile slopes and spacing were assigned for each field section. Tile spacing was determined with the Hooghoudt Equation.

The system is the first permitted for groundwater and surface water discharge in Michigan. The system is a balance between infiltration rate and nutrient uptake/adsorptive conditions. The effluent quality currently exceeds permit requirements by achieving an average removal efficiency of 60 percent for phosphorous and 81 percent for total nitrogen.