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r <br /> 1 <br /> F, <br /> C. WASTEWATER FLOW CALCULATIONS AND CHARACTERISTICS <br /> Domestic wastewater flows have been studied for decades with data published in the scientific <br /> literature, specifically Reference No. 15: Small and Decentralized Wastewater Management Systems. <br /> Wastewater flows are proposed to be managed by conventional on-site septic systems. The total daily <br /> water use is a combination of household and personal uses, as itemized below: <br /> F <br /> HOUSEHOLD PERSONAL USE <br /> 25F gal for laundry 2 gal for drinking and cooking <br /> 10 gal for dishwashing 3 gal for oral hygiene <br /> r 5 gal for misc. use 14 gal for bathing <br /> 16 gal for toilet flushing/sink washing <br /> FLOW RATE in gals/home/day= 40 gals/household/day+(35 gal/person/day x number of persons/home). Assuming <br /> i the average household within the project will have 4 persons per house (husband, wife and two <br /> children), the daily wastewater flow rate can be estimated at: <br /> 40 gals+ (35 gals x 4 people/home) = 180 gals/day for an average flow per resident of 45 gals. <br /> Although the residential structures must be built with water saving devises and fixtures, as a safety <br /> <. factor, the average flow per resident will be increased by 1.5x to 68 gals/resident/day. <br /> . The peaking factor for individual residences on septic tanks will vary with the day of-the week and <br /> usage. Peak hourly rates are normally associated with the discharge of clothes wash machines, <br /> dishwashers and shower/bath water. The ratio of the peak day to the average day can vary depending <br />€ upon the time of the year and usage, but is usually around 1.5. <br /> The characteristics or composition of septic tank effluent is dependent upon several parameters <br /> j because of idiosyncrasies within each household. Certain appurtenances change the characteristics of <br /> the wastewater effluent such as filter vaults within septic tanks and kitchen food-waste garbage <br /> disposals. In determining nitrogen concentrations of septic influent and effluent, per capita intake of <br /> nitrogen per day must be estimated. The average American consumes between 70 and 140 g of <br /> N/day. Since nitrogen comprises 16% of the weight of the average protein, 16% of 70 g N= 11 g <br /> N/capita/day and 16% of 140 g N =22 g N/capitalday. The average of these two values is 17 g <br /> N/capita/day of theoretical influent.. <br /> The concentration of nitrogen in septic system effluent is normally specified in the scientific literature <br /> as units of mg N/L. Unfortunately, these units superimpose wastewater flow variability onto nitrogen <br /> influent variability, thus creating even greater variability. One researcher, (Bauman), has averaged the <br /> means from 20 other studies to arrive at a concentration of 62 t 21 mg N/L in septic tank effluent. If <br /> the above figure for wastewater discharge is estimated at 68 gals/resident/day(257 liters) and using <br /> �- the figure of 17 g N/cap/day excreted= 17 g -257 L = 66 mg N/L/day estimated for the proposed <br /> project. This concentration will be the estimated nitrogen loading in the effluent discharged from the <br /> three proposed, and one existing residences for this project. <br /> F" F i <br /> F t <br /> 8 <br /> Chesney Consulting <br />