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COMMERCIAL WASTEWATER CHARACTERISTICS Primary wastewater constituents-of-concern found in septic tank effluent have influence over two important factors in the operation of an on-site, decentralized wastewater disposal system: Soil effluent acceptance rates and nitrate-nitrogen impact. The Biochemical Oxygen Demand(BOD) test is the most common test used in wastewater analysis,but can be unreliable for determining organic matter in water. BOD is the amount of oxygen, expressed as mg/L or ppm, that bacteria take from water when they oxidize organic matter. To determine BOD, oxygen the bacteria uses is calculated by comparing the amount left at the end of 5 days with the known amount at the beginning. Adsorption and volatilization, followed by microbial degradation are the primary processes for removal of soluble organics. Total Suspended Solids (TSS) is the material retained on a standard glass-fiber filter disk. Suspended solids can be categorized as volatile or fixed suspended solids. TSS can create and enhance biomat formation between the soil and effluent interface, thus restricting infiltration. The biomat, also referred to as a"clogging mat,"is a biological, slimy substance which forms on the soil-effluent interface over time. This mat is composed mostly of aerobic and anaerobic bacteria and bacterial products consisting of polyuronides and polysaccharides. The biomat does have one beneficial property: that is removing approximately 10%of the nitrogen from gravity flow disposal systems. It is unknown how much, if any, biomat material forms under pressurized filter bed systems. Consequently, this 10%nitrogen removal figure will not be used in the nitrate loading calculations on Page 12 to reduce the calculated nitrate loading. Total Nitrogen is the summation of ammonia-nitrogen(NH4) and organic nitrogen(proteins, amino acids, enzymes). Since the septic tank is predominately anaerobic, nitrogen cannot exist in its oxidized state as nitrate for any length of time in the septic effluent, and if it does, it is quickly reduced to NO or NOZ. If nitrate existed in the tank effluent, this would also be added to ammonium and organic nitrogen to arrive at Total Nitrogen. NLS§3.3. 1 To quantify the anticipated nitrogen concentration for use in the nitrate loading caic'ulations from the built-out Manteca RV Storage Park project, effluent sample test results were obtained from other comparable commercial facilities. These analytical test results(three total tests)were averaged to provide the concentrations found in Column 2, in Table 4 below. j In addition, septic tank effluent concentrations from various researchers that have been published in Small and Decentralized Wastewater Management Systems, by Crites and Tchobanoglous are found in Columns 3 and 4. These two columns illustrate the effect effluent filtration has on certain constituents of the effluent, particularly BOD and TSS. Column 5 illustrates septic tank effluent concentrations for the constituents listed that have been determined by the U.S.E.P.A. i 10 Chesney Consulting