Contributions to enhancing the public health perspective on onsite wastewater management.

I ntroduction Onsite wastewater systems (onsite sys­ tems) treat and dispose of wastewater (effluent) near the point of generation (U.S. Environmental Protection Agency [U.S. EPA], 2002). Onsite systems are classified as septic or advanced systems. Septic systems may be conventional and enhanced treatment units or alternative onsite systems (New York State Department of Health, 2012; North Carolina Health and Human Services, 2013). Components of septic systems are the septic tank, distribution box, drain field, and soil. Wastewater flows by gravity or is pumped from the septic tank to the soil. Enhanced treatment units control the wastewater flow to the drain field, while oth­ ers may need an alternative drain field unit if the soil is unsuitable for effluent discharge or the water table is high. Wastewater treatment stages are defined as follows: • Primary treatment is the removal of solids (those that float and those that settle). • Secondary treatment is the removal of dis­ solved organic matter. • Tertiary treatment is the removal of nutrients (nitrogen and phosphorus compounds). Septic systems are designed to perform primary treatment (in the septic tank) and to some extent tertiary treatment (nitrate removal in suitable and aerated soils). Advanced onsite systems are designed to per­ form primary and secondary treatment. Most advanced onsite systems are small versions of conventional activated sludge systems that include an aerobic treatment unit. Currently, most of the onsite systems operating in the U.S. are conventional sep­ tic systems. The U.S. Environmental Protec­ tion Agency (U.S. EPA) estimates that 25% of American households have an onsite sys­ tem (U.S. EPA, 2013). Using the U.S. Census Bureau (2014) statistics for the period 2008– 2012, an estimated 75.18 million people use onsite systems in the U.S. (28,806,700 households with 2.61 persons per house­ hold). Assuming that each person produces 50–80 gallons of wastewater per day, daily effluent discharges from onsite systems range from 4,000 to 6,000 million gallons. Also, the estimated rate of malfunctioning onsite sys­ tems is 10%–20% each year (U.S. EPA, 2013). Therefore, the lack of data on the quality of effluents discharged to the environment cre­ ates a public health concern.