Evaluation of On-Site Wastewater Treatment Technology to Remove Estrogens, Nonylphenols
Authors:
- Ben Stanford, Ph. D. - Hazen and Sawyer
- Howard S. Weinberg - University of North Carolina
On-site wastewater treatment systems (i.e., septic systems) are used extensively throughout the United States and around the world. In the U.S., 35 of 50 states have greater than 25% of the population using septic treatment systems and nine eastern states including North Carolina have greater than 40% use.
During the 2003-2004 fiscal year, there were nearly 35,000 new permits issued for the installation and operation of on-site treatment systems in North Carolina alone. Traditional septic systems involve a collecting/settling tank leading to a drainfield installed in naturally occurring soils, whereas newer, larger systems may involve the use of prefilters, sand filters, wetlands, and other addons which primarily serve to remove nutrients from the system prior to discharge into the environment. In addition to typical percolation through soil, many states permit the discharge of septic system effluent directly into surface waters as long as fecal coliform and nutrient loading levels meet mandated limits.
With a wide variety of treatment options, discharge scenarios, soil types, and groundwater depth the question arises as to the ability of a given system to remove pollutants prior to reaching ground or surface waters. In properly functioning septic systems, groundwater contamination from viruses, bacteria, nutrients, and other organic wastewater pollutants has been well documented. Failing septic systems may further contribute to surface and groundwater pollution with raw effluent which may contain much higher levels of nutrients, pathogens, and organic micropollutants. Even systems which function well in early stages of operation may experience reduced capacity to treat wastewater over time with exposure to laundry detergents, eventually leading to increased infiltration of pollutants to groundwater or surface water. Potent micropollutants such as steroid estrogens and nonylphenols, which can impact microbial and aquatic macro-species at low concentrations, may also be of concern as they are released into the environment from septic systems…
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