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<br />were investigated with regard to (1) concentration versus time, <br /> <br />and (2) waste load versus time. <br /> <br />. <br /> <br />The first flush observance is a concentration of pollutants <br /> <br />effect. Both articles (McElroy and Bell, 1974 and DeFillipi and <br /> <br />. <br />Shih, 1971) presented plots of instantaneous mass loading (the <br /> <br />product of flow and concentration in Ib/day) of pollutants. The <br /> <br />maximum mass of pollutants per unit of time occurred at the flow <br /> <br />peak and not at the time of the first flush concentration. This <br /> <br />is shown in Figure 1. <br /> <br />Studies in San Francisco (Friedland, Shead and Ludwig, 1970) <br /> <br />and in England (Davidson and Gameson, 1967) have shown the pollu- <br /> <br />tional profile during the total runoff period of storms and have <br /> <br />identified the factors that cause variations in pollutional <br /> <br />strength as: the rainfall intensity, antecedent dry period and <br /> <br />the sewerage system configuration. <br /> <br />A few investigators have attempted to correlate the relation- <br /> <br />ship between the concentration of some parameters with the amount <br /> <br />of flow at sampling sites. No relation has been found between <br /> <br />parameters like BOD, Total N, Total P, and flow. However, for <br /> <br />suspended solids a correlation was found in a study in Stockholm, <br /> <br />Sweden (Soderlund and Lehtinen, 1972). Figure 2 shows a straight <br /> <br />line relationship with a correlation coefficient of 0.92. One <br /> <br />interesting observation they made was that the amount of pollutants <br /> <br />was linearly related to the rainfall intensity and independent of <br /> <br />the interval from the beginning of the downpour. <br /> <br />26 <br />