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<br />SECTION 2 <br /> <br />BACKGROUND AND LITERATURE REVIEW <br /> <br />I. Historical Review of Sewer Systems <br /> <br /> <br />The people of ancient Rome constructed large storm drains <br /> <br /> <br />to remove stormwater from the developed areas of their community. <br /> <br /> <br />Later, stormwater systems were developed in Europe and North <br /> <br /> <br />America. The early sewers were reserved for stormwater. Human <br /> <br /> <br />pollutants and solid wastes were not permitted in the flow. <br /> <br /> <br />When the industrial revolution occurred, people moved to city <br /> <br /> <br />environments and the problem of human waste disposal became more <br /> <br /> <br />significant. In 1815, the law was changed in London to allow <br /> <br /> <br />for the disposal of sanitary wastes in storm sewers. This was <br /> <br /> <br />the beginning of combined sewers. The trend continued in Boston <br /> <br /> <br />in 1853 and in Paris in 1880 (Metcalf & Eddy, 1928). Not until <br /> <br /> <br />the latter part of the nineteenth century was it recognized that <br /> <br /> <br />the problem merely had been removed from land to the waters. <br /> <br /> <br />Some cities initiated the practice of treating municipal sewage <br /> <br /> <br />before discharge. This practice usually started with those <br /> <br /> <br />cities located less favorably with respect to receiving waters. <br /> <br /> <br />Some interceptor sewer systems were then developed to <br /> <br /> <br />bring the dry-weather flow to locations for treatment. But <br /> <br /> <br />relief points had to be constructed to divide the large flows <br /> <br /> <br />during storms. The combined sewers at that time might carry 5 <br /> <br /> <br />to 50, or even more, times the dry-weather flow. A portion (up <br /> <br /> <br />to 3 times the dry-weather flow) was intercepted and about half <br /> <br />. <br /> <br />. <br /> <br />4 <br />