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<br />analyses and estimation of loads. Comparing the two, one can <br /> <br /> <br />readily see that the solids parameters are larger for the <br /> <br /> <br />separate storm sewer in terms of pounds/acre. <br /> <br /> <br />The study made in Trondheim, Norway (Ka11eberg and Malme, <br /> <br /> <br />1974) has also considered mass loadings, and besides reporting <br /> <br /> <br />their own findings in area yield rates (kg/ha/yr), they have <br /> <br /> <br />also tabulated values from other studies for both combined and <br /> <br /> <br />separate sewer systems. <br /> <br /> <br />Loehr (1974) has published a listing of concentration and <br /> <br /> <br />mass loadings based on reported studies and made an analysis of <br /> <br /> <br />the impact of many of the non-point sources. <br /> <br />F. Pollution from Combined Sewers <br /> <br /> <br />Many of the older, larger cities in the U.S. have areas <br /> <br /> <br />where combined sanitary storm sewers are used. The systems are <br /> <br /> <br />designed so that total flow during dry weather will receive <br /> <br /> <br />wastewater treatment. During large storms, the extra flow of <br /> <br /> <br />water goes to the receiving stream without treatment. The <br /> <br /> <br />untreated portion of the flow is termed stormwater overflows. <br /> <br /> <br />The impact of stormwater overflows has been researched more <br /> <br /> <br />extensively than that of separate storm sewers. Although the <br /> <br /> <br />emphasis of this study was with separate systems, a brief review <br /> <br /> <br />of overflow quality is included for comparative purposes. <br /> <br /> <br />An EPA (1974) review of data from several investigations <br /> <br /> <br />and comparisons of the quality of combined sewage for various <br /> <br /> <br />cities has been made. Table 22 is a comparison of results for <br /> <br />4~ <br /> <br />. <br />