Trace organics in septic tank effluent

Abstract

This paper reviews the available information and presents the results of a study undertaken to estimate the presence and level of certain trace organics in wastewater samples collected from a septic tank in an individual household, from a lift station, and from a waste treatment lagoon near Regina, Canada. Out of 11 priority pollutants analyzed, 6 priority pollutants — chloroform, bromodichloromethane, toluene, benzene, methylene chloride and tetrachloroethylene — were detected in the samples. Benzene and bromodichloromethane were dominant. Methylene chloride and tetrachloroethylene could not be quantified at the low concentrations present. Chloroform was present in the lagoon effluent sample once at a concentration of 0.03 μg L⁻¹. Toluene was not present either in the septic tank effluent or in the lagoon effluent. Benzene was present in the septic tank effluent (max. value 450 μg L⁻¹) and in the lagoon effluent (max. value 120 μg L⁻¹). Bromodichloromethane was present in the septic tank effluent and lagoon effluent at concentrations lower than 1.10 μg L⁻¹. The trace organics in the septic tank effluent and lagoon effluent at these comparatively low concentrations may not pose any significant risk either to aquatic life or to public health, taking into account the attentuation capacity of the soil and the dilution usually available.