Soil hydraulic properties affected by various components of domestic wastewater

Hydraulic failure of a septic system may be attributed to the formation of a biomat in its trenches, but the chemical composition of wastewater may also significantly contribute to the failure of the system. The effects of various components of domestic wastewater on the hydraulic properties of three soils were studied. The soils were a sandy soil, the clayey Bt horizon of a soil, and a commonly occurring saprolite (C horizon) from North Carolina. Saturated hydraulic conductivity (K-sat) and infiltration rate (IR) of the soils and saprolite for tap water, simulated wastewaters from a washing machine, kitchen sink, bathroom sink and shower, and a car wash with a water softener were measured in situ for live consecutive days using three replications. The simulated wastewaters affected the K-sat and IR differently. Simulated wastewater from a laundry machine had the most deleterious impact on soil hydraulic properties. In some cases, application of a CaCl2 solution to the soil resulted in restoration of infiltration rate and hydraulic conductivity.