Acute and sub-lethal toxicity of landfill leachate towards two aquatic macro-invertebrates: demonstrating the remediation potential of air stripping

A specific leachate that contained 1.036 mg l⁻¹ of 2-chlorobiphenyl was used in the study (255 mg l⁻¹ COD and 133 mg l⁻¹ BOD5). Bench scale (20 l) air stripping trials were used to simulate on a small-scale the treatment potential of this method. Air stripping effectively reduced the leachates COD concentration. Regardless of the volume of air supplied (1–5 l of air per minute) the leachates COD reached a < 50 mg l⁻¹ equilibrium after 96-h exposure, however, increasing the volume of air accelerated the process. In untreated leachate, the LC₅₀ for Asellus aquaticus was 57% v/v leachate in deionised water and 5% for Gammarus pulex (96-h, static LC₅₀ tests without nutrition and oxygen depleting conditions). After being exposed to air stripping, these values rose from 90% to below the LC₅₀ threshold for Asellus when 1–5 l of air per minute were applied and 30–90% for Gammarus. Furthermore, in sub-lethal concentrations of air stripped leachate (leachate that had been exposed to 5-l of air per minute for 96-h) the population dynamics of both test species remained unaltered.