The Chemical Contamination and Treatment of Wastewater and Sewage

Most municipalities treat the raw sewage collected from homes, buildings, and industries (including food processing plants) through a sanitary sewer system before the liquid residue is deposited into a nearby source of natural waters, whether a river, lake, or ocean. In contrast, since the rainwater and melted snow that drain from streets and other paved surfaces are usually not highly contaminated, they are often collected separately by storm sewers and deposited directly into a body of natural water. Unfortunately, in some municipalities, storm-driven overflow occurs in the sanitary sewer system and the overflow is combined with storm water and deposited, untreated, into waterways.

The main component of sewage—other than water—is organic matter of biological origin. It occurs mainly as particles—ranging from those of macroscopic size large enough to be trapped (together with such objets d'art as facial tissues, stones, socks, tree branches, condoms, and tampon applicators) by mesh screens to those which are microscopic in size and are suspended in the water as large colloids.

Continue reading here: Sewage Treatment

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