ABSTRACT
Modern conventional wastewater treatment plants already have incorporated or are in the process of incorporating biological nutrient removal (BNR) to remove nutrients, total nitrogen, and total phosphorus from the wastestream while it is being treated and before being outfalled to the receiving water body. Nitrogen and phosphorus are the primary causes of cultural eutrophication (i.e., nutrient enrichment due to human activities) in surface waters. The most recognizable manifestations of this eutrophication are algal blooms that occur during the summer. Chronic symptoms of overenrichment include low dissolved oxygen, fish kills, murky water, and depletion of desirable flora and fauna. In addition, the greater levels of algae and turbidity increase the need to chlorinate drinking water, which, in turn, leads to higher levels of disinfection byproducts that have been shown to increase the risk of cancer (USEPA, 2007c). Excessive amounts of nutrients can also stimulate the activity of microbes, such as Pfisteria, which may be harmful to human health (USEPA, 2007d).
