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Effects of Aeration on Water Quality from Septic System Leachfields
Author(s) -
Potts David A.,
Görres Josef H.,
Nicosia Erika L.,
Amador José A.
Publication year - 2004
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2004.1828
Subject(s) - lysimeter , aeration , septic tank , effluent , nitrate , environmental engineering , environmental science , environmental chemistry , zoology , chemistry , soil water , soil science , biology , organic chemistry
We conducted a pilot‐scale study at a research facility in southeastern Connecticut to assess the effects of leachfield aeration on removal of nutrients and pathogens from septic system effluent. Treatments consisted of lysimeters periodically aerated to maintain a headspace O 2 concentration of 0.209 mol mol −1 (AIR) or vented to an adjacent leachfield trench (LEACH) and were replicated three times. All lysimeters were dosed with effluent from a septic tank for 24 mo at a rate of 12 cm d −1 and subsequently for 2 mo at 4 cm d −1 LEACH lysimeters had developed a clogging mat, or biomat, 20 mo before the beginning of our study. The level of aeration in the AIR treatment was held constant regardless of loading rate. No conventional biomat developed in the AIR treatment, whereas a biomat was present in the LEACH lysimeters. The headspace of LEACH lysimeters was considerably depleted in O 2 and enriched in CH 4 , CO 2 , and H 2 S relative to AIR lysimeters. Drainage water from AIR lysimeters was saturated with O 2 and had significantly lower pH, five‐day biological oxygen demand (BOD 5 ), and ammonium, and higher levels of nitrate and sulfate than LEACH lysimeters regardless of dosing rate. By contrast, significantly lower levels of total N and fecal coliform bacteria were observed in AIR than in LEACH lysimeters only at the higher dosing rate. No significant differences in total P removal were observed. Our results suggest that aeration may improve the removal of nitrogen, BOD 5 , and fecal coliforms in leachfield soil, even in the absence of a biomat.