by Rachel, April 1, 1999
In the cities, cholera epidemics abated. However, cities drawing their drinking water downstream from sewage discharges began having outbreaks of typhoid. This engendered another debate: whether to treat sewage before dumping it into water bodies used for drinking, or whether to filter drinking water. Public health officials favored treating sewage before dumping it; sanitary engineers favored dumping sewage raw and filtering water before drinking. The engineers prevailed. As cities began to filter and disinfect their drinking water, typhoid abated.
Throughout the 20th century, the U.S. and Europe industrialized rapidly. Industry developed a huge demand for low-cost waste disposal, and sewers were the cheapest place to dump because the public was paying. As the pressure for greater waste disposal capacity increased, industrialized nations allocated vast sums of money to construct centralized sewer systems to serve the combined needs of homes and factories. As a result, the nutrients in excrement became mixed with industrial wastes, many of them toxic. So by the 1950s, essentially every body of water receiving piped wastes was badly polluted with a combination of excessive nutrients and toxicants. This led to a demand to treat wastes before dumping them into water. Thus began the "treatment" phase of the "get rid of it" approach to human waste.
As centralized sewer systems evolved, first came "primary treatment." This consists of mechanically screening out the dead cats and other "floatables." All other nutrients and toxic chemicals remain in the waste water that is discharged to a river or ocean. Next came "secondary treatment" which speeds up the biological decomposition of wastes by forcing oxygen into them, by promoting bacterial growth, and by other means. This is an energy-intensive process and therefore expensive. Unfortunately, it, too, leaves many of the nutrients and toxic chemicals in the discharge water. [The Congressional Research Service recently estimated that the federal government spent $69.5 billion on centralized sewage treatment plants, 1973-1999. Despite this huge expenditure, the Congressional Research Service said in 1999, "States report that municipal discharges are the second leading source of water quality impairment in all of the nation's waters (rivers and streams, lakes, and estuaries and coastal waters).