Question

Assume a deep and fairly homogenous soil is going to be used to dispose of septic tank waste water that contains 10 mg/L of soluble phosphorus in the form of phosphate. An adsorption isotherm is measured for the soil, from which the total adsorption capacity of the soil is estimated to be 200 mg P/kg soil. The 600 Liters of wastewater that is generated each day is evenly disposed of over a 70 square meter area. Estimate the depth of phosphate movement in the soil after ten years, and make a decision whether the shallow well, located at a 10 meters depth at the edge of the disposal area, could become contaminated with phosphate. Assume that the bulk density of the soil is 1.5 kg/liter. Density, as always, is defined as mass per unit volume. If needed, you can assume that a 6-inch depth of soil, measured over a surface area, will weigh 2 million pounds. Please show all your calculations.

Answer 1