Treatment of Drip Dispersed Effluent in Imported Soils.

Three commercial establishments located on Table Rock Lake in southwest Missouri possessed failing onsite wastewater systems were renovated with various proprietary aeration treatment technologies followed by drip dispersal in imported soils. Imported soil, with narrow specification of soil properties, harvesting, transport, and placement at the site, was used for both the vertical separation and cover because of the lack of quality in-situ soil at the site. Two different soil treatment field monitoring collection methods were employed: a half-pipe lysimeter and a sheet lysimeter to provide collection of water in an integrative manner. Placement of drip dispersal tubing within the imported soil ranged from 3 to 22.5 cm between the drip tubing and lysimeter with 30 cm of soil cover. Plastic sheet lysimeters were preferred if lysimeters were installed during system installation. The wastewater volume design for the three systems was 7,267, 5,905, and 5,678 l/d with median BOD5 concentrations of 3,3, and 4 mg/L respectively, and median fecal coliform numbers of 81,186, and 153 colonies/100mL, respectively, for each system in the lysimeters within the imported soil. The median BOD5, ammonia and fecal coliform concentrations were below effluent discharge limits for mechanical surface discharging systems processing nitrification and disinfection unit processes.