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STATE WATER RESOURCES CONTROL BOARD _ 10 - ORDER 10 - ORDER WQ 2014-0153-DWQ GENERAL WASTE DISCHARGE REQUIREMENTS FOR SMALL DOMESTIC WASTEWATER TREATMENT SYSTEMS conditions, which are not favorable biological treatment conditions. This General Order includes effluent limits for nitrogen and BOD, and a process to determine how to apply the limits. Implementation of the process to determine the effluent limit that applies will result in the BPTC for the wastewater constituents. In addition, this General Order provides guidance on preparing a monitoring program that ensures the treatment is effective. Each of the wastewater constituents of concern are discussed below: a. Salinity is a measure of dissolved solids in water. Excessive salinity can reduce the beneficial uses of water. Salinity can be affected by the discharge of wastewater with elevated concentrations of TDS. TDS consists of both volatile (organic) and fixed (inorganic) fractions. In a well-operated land application system, volatile dissolved solids in percolate will be reduced to negligible concentrations. The best approach for addressing salinity is through source control activities. This General Order allows an Executive Officer to require participation in salt and nutrient management planning processes. b. Nitrogen is a nutrient normally present in domestic wastewater at a concentration that can degrade groundwater quality. The potential for degradation depends upon the wastewater treatment method and the environment into which the wastewater effluent is discharged. Nitrogen concentration reduction is not required in every situation, such as when wastewater treatment and application is performed in a way that is protective of the beneficial uses of water. When needed, nitrogen concentrations can be reduced in a number of ways, such as nitrification, denitrification, and/or crop uptake and removal. However, the General Order requires that the effluent limit for nitrogen be determined based on procedures in Attachment 1, which provides additional criteria to determine when and how much nitrogen control is required. Effluent limits are determined based on the threat to groundwater quality. If nitrogen control is needed, a minimum of 50-percent reduction is required. In cases where a higher threat to groundwater exists, a total nitrogen concentration limit of 10 mg/L is required. By imposing the total nitrogen limit of 10 mg/L, the wastewater derived nitrogen cannot exceed the maximum contaminant level (MCL) for groundwater. Because natural systems are rarely 100-percent efficient, the nitrogen concentration limit will be protective of the existing and/or potential beneficial use of groundwater. Effluent limitations for nitrogen are contained in this General Order. To ensure the nitrogen control is effective, the model Monitoring and Reporting Program (MRP) provided as Information Sheet Attachment C includes monitoring that can be implemented to verify compliance with effluent limits. c. Pathogens and other microorganisms are present in domestic wastewater. Wastewater treatment processes will reduce the concentration of pathogens but disinfection is required to significantly reduce their presence. Coliform bacteria are used as a surrogate (indicator) because they are excreted by warm-blooded animals, are present in high numbers, survive in the environment similar to September 23, 2014