The average number of such incidents in the United States in the period to was 25 per year. Most of these outbreaks were associated with obvious deficiencies in treatment or distribution systems. Remains of sanitary sewers are to be found in the ruins of the ancient cities of Crete and Assyria, Rome also had sewers, but they were primarily, drains to carry away storm water.
It was the practice to deposit all sorts of refuse in the streets, and accordingly the storm sewers also carried much organic matter at times. Sewerage was practically unknown during the Middle Ages, and construction of sewers was not resumed until modern times. At first, these were storm sewers not intended to carry domestic sewage. As late as , the discharge of household wastes into the sewers of London was forbidden. The water courses in or near towns apparently were used as convenient places of refuse disposal, for many Writers comment upon the offensive condition of the London brooks, with their burden of dead dogs and filthy of all sorts.
In the course of time it was recognized that sanitation would best be served by permitting the use of sewers to convey human excreta away from dwellings as promptly as possible, and the original storm drains became combined sewers which carried both stormwater runoff and the liquid wastes from occupied buildings. The development of water supplies, of course, played a large part in the greater use of plumbing Systems with water — flush toilets.
The commonly used vault toilets, which frequently overflowed and always Produced odours, were soon legislated out of existence in the larger cities in favour of the water — carried system. This improvement together with safer water supplies caused a sharp decline in the urban death rate. Providing sewers for the cities was not a complete solution of the problem of excreta disposal. The offensive and dangerous materials were discharged into the streams where they decomposed to cause discomfort and danger to rural populations or to cities located downstream.
Most cities, therefore, soon found it necessary to treat the sewage before releasing it. Even cities located along the ocean were in many cases obliged to protect bathing beaches or shellfish beds. Some, however, were able to discharge their sewage untreated into very large bodies of water or into streams that traversed relatively uninhabited regions.
Still others were indifferent to the need for sewage treatment and in the absence of laws or proper enforcement spoiled the beauty of streams, made them unusable for recreational purposes, and endangered lives.
A later development of this sanitary problem was the pollution of streams by industrial plants located not only in cities but in previously unspoiled rural sections. Streams have been spoiled for fishing, camping, and swimming by the putrescible and toxic wastes of industrial plants. Download Download PDF. Translate PDF. Step-by-step water and wastewater calculations-- updated for the latest methods and regulations Water and Wastewater Calculations Manual, Third Edition, provides basic principles, best practices, and detailed calculations for surface water, groundwater, drinking water treatment, and wastewater engineering.
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