The treated wastewater is applied evenly to a vegetated area on the residential lot. A means for preventing surface runoff of the sprayed effluent, and for diverting rainwater runoff away from the spray field area, is typically required for these systems. Current State of Texas rules for small residential scale spray irrigation systems with flows of 500 gallons per day or less require that inspections of the system be made by an authorized managing agent at least three times annually, with either chlorine residual or fecal coliform tested at each of those visits. Spray irrigation allows for the greatest amount of evaporation as compared with other on-site effluent disposal methods. Some volatilization of ammonia nitrogen is also usually achieved, which contributes to total nitrogen removal.
Moisture is removed by both evaporation and infiltration.
Many different types of pretreatment systems may be used to achieve a secondary quality of effluent prior to spray irrigation. Disinfection may be provided by chlorination, ultraviolet units or ozonation. The first documented system was installed in Europe over 400 years ago. During the past 20 years, the use of spray irrigation systems has become increasingly common for individual residences in various parts of the U.S. where conditions are not suitable for conventional subsurface disposal systems. Applications Spray irrigation systems are sometimes used for sites with conditions which are unsuitable for conventional absorption systems.