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INFORMATION SHEET FOR ORDER NO. -5- LINNE ESTATES,LLC LINNE ESTATES WASTEWATER TREATMENT SYSTEM SAN JOAQUIN COUNTY Treatment Technology and Control Selecting appropriate treatment and control technologies so that the soil underlying the disposal area can accept the residual waste constituent loading while preventing unacceptable levels of groundwater degradation is a critical aspect of land disposal system siting and design'. Given the character of municipal wastewater, secondary treatment technology is generally sufficient to control degradation of groundwater from decomposable organic constituents when there is sufficient separation between the base of the land discharge area and the water table. Adding disinfection significantly reduces populations of pathogenic organisms, and significant layers of fine-grained soils in the vadose zone can reduce them further by filtration. Neither organics nor total coliform organisms, the indicator parameter for pathogenic organisms, should be found in groundwater beneath a well-sited, well-designed, well- operated facility. Municipal wastewater typically contains nitrogen in concentrations greater than water quality objectives, which vary according to the form of nitrogen. Nitrogen concentrations can be controlled by an appropriate secondary treatment system to nitrify and denitrify the wastewater(e.g., oxidation ditch) or tertiary treatment for nitrogen reduction 2. Agronomic reuse of treated wastewater on harvested crops is an effective means to convert wastewater nitrogen into plant matter and nitrogen gas 3. The effectiveness of these approaches varies,but one or more of them should be able achieve nitrogen concentrations in groundwater well below the water quality objectives. The proposed interim groundwater limitations for nitrogen are based on the water quality objectives and on background water quality. Many waste constituents that are forms of salinity pass through conventional domestic wastewater treatment process unchanged except through evapoconcentration. Clay soils have a significant ability to assimilate some of the salinity through cation exchange, whereas sands and other soil types have relatively little4. However, in most cases, the combination of long term use of the dispersal area will ultimately overwhelm the natural attenuation capacity of the underlying soil. Therefore, effective control of long-term effects often relies upon effective source control and pretreatment measures. In the best of circumstances, long-term land discharge of treated municipal wastewater will degrade groundwater with salt (as measured by TDS and EC) and the individual components of salts (e.g., sodium, chloride). The proposed Order sets interim limits based on measured background water quality. A discharge of wastewater that overloads soils with nutrients and organics can result in anaerobic conditions in the soil profile, creation of organic acids, and a decrease in soil pH. Under these conditions, iron and manganese compounds in the soil can solubilize and leach into groundwater. Anaerobic conditions can also lead to the presence of ammonia in the groundwater. Such overloading is 1 USEPA Office of Research and Development,Manual of Wastewater Treatment and Disposal for Small Communities, EPA/625/R-92/006,Washington,D.C.(1992). 2 Metcalf,and Eddy,Inc.,Wastewater Engineering Treatment,Disposal and Reuse(3`d Ed.),McGraw-Hill,Inc.,New York, (1991). 3 Brown and Caldwell,Kennedy Jenks,Komex H2O Science,Manual of Good Practice for Land Application of Food Process/Rinse Water, California League of Food Processors, Sacramento(2003). Dragun,James,The Soil Chemistry of Hazardous Materials,Hazardous Materials Control Research Institute,Silver Spring MD,(1988).