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TABLE 8 - CONTINUED WASTEWATER FLOW AVERAGE DAILY FLOW VOLUMES DETERMINATION METHOD (gallons per day) St. Bernard's Current Water Consumption History 1,980 gpd St. Bernard's Extrapolated Future Water Consumption 2,475 gpd Average of All Wastewater Flow Determination Methods 2,996 gpd Primary Wastewater Constituents Primary wastewater constituents-of-concern found in septic tank effluent have influence over two important factors in the operation of an on-site 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 the 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 pH of a solution is a measure of the hydrogen ion concentration(acidity). Optimum range for nitrification is between 6.5 and 8.2. Because nitrification consumes approximately 7.1 mg of alkalinity for every mg. of ammonium-nitrogen oxidized, in low alkalinity wastewater there is a possibility that nitrification will lower the pH to inhibitory levels. Total Alkalinity is a measure of the capacity of the effluent or water to neutralize acids without a significant change in pH. It is usually associated with the presence of carbonate/bicarbonate and/or hydroxyl radicals in the water. Total Nitrogen is the summation of ammonia-nitrogen (NH4) and organic nitrogen(proteins, amino acids, enzymes). Since the septic tank is predominately anaerobic, virtually no nitrate exists in the effluent. If nitrate existed in septic tank effluent,this would also be added to arrive at Total Nitrogen. Typically, 70-90% of the total nitrogen in septic tank effluent is in the form of ammonium, while 10 to 30%is in the organic form. These percentages are reflected in the results of the effluent chemistry, as illustrated in Tables 10 and 11. Page -14- Chesney Consulting