Roach were collected upstream and downstream from wastewater treatment plants and checked for gender. Researchers found significantly higher inter-sexed rates downstream from wastewater treatment plants. Researchers also looked at vitellogenin and found increased levels in fish downstream from wastewater treatment plants. The conclusion was that wastewater treatment plants are responsible for this occurrence. This is a specific example where wastewater treatment plants do seem to be disrupting the environment.
Municipal wastewater is composed of a variety of substances.
Domestic wastewater comes from residences and commercial facilities, institutional and recreational uses, industrial flows from bottling companies, pulp-paper mills, etc. There is also an unwanted infiltration inflow component in many sanitary flows, typically storm water that gets in through cross-connections between storm water systems and sanitary systems. There could also be groundwater leaking in through cracks in pipe joints and other defects. The domestic and industrial sources could potentially contribute a host of endocrine disrupting compounds. Certainly, wastewater receives alkylphenol and polyethoxylates, which eventually results in their degradation products.