Aerobic treatment units (ATUs) serve as an alternative to traditional septic systems in many rural homes that lack access to municipal utilities. ATU effluent often flows directly into ditches that contain overgrown vegetation and rely on sunlight for disinfection. To date, it is unclear if effluent gets properly disinfected in these ditches, which is problematic since they often flow directly into major recreational water bodies. The goal of this work was to determine if ATUs negatively impact the environment by quantifying Escherichia coli and thermotolerant coliforms in: 1) ATU effluent, 2) Disposal ditches that received ATU effluent, and 3) Water collected upstream and downstream from ditches that transported effluent from ATUs into a local river. E. coli concentrations were high in effluent (1.8 x103 to 7.3 x 106 CFU/100 ml) and in most ditch samples (2.5 x 103 to 8.4 x 104 cfu/100 ml) collected near (less than 10 feet from) ATU effluent pipes. High concentrations of thermotolerant coliforms were also observed in effluent (3.1 x 103 to 5.4 x106 CFU/100 ml) and ditches (1.3 x 104 to greater than 1.5 x 106 cfu/100 ml). E. coli and thermotolerant coliforms were typically undetectable in the river before rain. After rain, the concentrations of E. coli and thermotolerant coliforms were higher at the downstream site (5.0 x 103 to 9.5 x 103 cfu/100 ml and 1.9 x 104 to 7.8 x 104 cfu/ml, respectively) relative to the upstream site (E. coli were undetectable and thermotolerant coliforms ranged from 9.8 x 103 to 1.8 x 104 cfu/100 ml). These results show that ATUs release high concentrations of fecal bacteria, which persist in disposal ditches and negatively impact a nearby river during rain events. These results also appear to provide some of the first evidence of negative environmental-related impacts associated with ATUs.
Deeb, Sarah; Souza da Costa, Tamylles; Eswani, Zahaan; and Struchtemeyer, Christopher
"Assessing the Environmental Impacts of Effluent from Aerobic Treatment Units,"
RURALS: Review of Undergraduate Research in Agricultural and Life Sciences: Vol. 13:
1, Article 1.
Available at: https://digitalcommons.unl.edu/rurals/vol13/iss1/1