Wastewater treatment using the soil profile for soil aquifer treatment has been practiced for over 100 years. Treatment levels of municipal wastewater prior to soil aquifer treatment (SAT) have included primary, secondary, disinfected secondary, disinfected tertiary, and advanced wastewater treatment. Performance in water quality improvement is dependent on soil type and depth, hydraulic loading rate, and degree of pretreatment. The effect on groundwater quality of different and increasingly higher pre-application treatment is compared for a number of land treatment systems.