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STAFF REPORT -5- <br /> PAT MITCHELL AND CALIFORNIA NATURAL PRODUCTS <br /> LATHROP,SAN JOAQUIN COUNTY <br /> available there are no alternative application areas to discharge the water to if a system upset <br /> occurs. <br /> CNP does not have the capability to store wastewater during periods of inclement weather. <br /> Pollution Abatement recommends storage of wastewater during times when it cannot be disposed. <br /> The tentative WDRs do not require construction of a wastewater storage pond,which would <br /> further limit the area available for application. Application of wastewater during rain events may <br /> result in standing water at the application area. By limiting the BOD loading rate, there is less <br /> potential for nuisance odors. <br /> Because of the recent optimization of the wastewater treatment equipment, BOD loading may not <br /> be a limiting parameter. Based on the concentrations of BOD in the applied wastewater the limits <br /> imposed by the WDRs can be met with careful application of wastewater. <br /> Nitrogen Loading Rate <br /> The Discharger states that the nitrogen limits presented in the WDRs are overly restrictive. The <br /> WDRs contain a Discharge Specification that restricts the total nitrogen loading rate to the <br /> agronomic rate, which is equal to the nitrogen requirements of the crop planted on the disposal <br /> field. Staff believes the restrictions are appropriate. This is a standard specification that has <br /> routinely been imposed on food processors, dairies, and other agricultural dischargers. The <br /> purpose of the specification is to ensure that the crop utilizes nitrogen to the maximum practical <br /> extent, thereby preventing groundwater quality degradation by nitrate. <br /> Nitrogen in food processing waste is typically present primarily in organic form. According to <br /> Irrigation with Reclaimed Municipal Wastewater, Fate of Wastewater Constituents in Soil and <br /> Groundwater, (Chapter 12 of Irrigation With Reclaimed Municipal Wastewater, A Guidance <br /> Manual, prepared by California State Water Resources Control Board,Report No. 84-1, 1984) <br /> organic nitrogen is mineralized to ammonium and then nitrified to form nitrate which is plant <br /> available. Mineralization requires aerobic conditions in the soil and sufficient bacteria. <br /> Mineralization does not occur at a constant rate because some forms of organic nitrogen <br /> mineralize less readily and tend to stay in organic form until the readily mineralized fraction has <br /> been fully utilized. Nitrification also requires adequate oxygen and bacteria to produce plant <br /> available nitrogen. <br /> For optimal plant uptake, the percolation rate must be slow enough to ensure that nitrogen <br /> (whether in organic or mineralized form) stays within the root zone to the maximum practical <br /> extent. According to Wastewater Management Systems, nitrogen can be stored in the soil, <br /> however, with continued application of wastewater, equilibrium is reached and net storage of <br /> nitrogen stops. Wastewater Management Systems states that it is most conservative to assume <br /> net storage will be zero. The WDRs are consistent with this conservative approach. <br /> Any nitrogen that percolates below the root zone can potentially degrade groundwater quality. <br /> However, under certain circumstances, nitrate can be denitrified to nitrogen gas, which resides <br />