BIOLOGICAL TREATMENT OF A LANDFILL LEACHATE CONTAINING PHENOXY HERBICIDES AND CHLOROPHENOLS

A biological treatment process has been developed for a landfill leachate containing phenoxyacetic acid herbicides and their associated chlorophenols. The mixed microbial population (Pseudomonas sp.) enriched from soil was capable of mineralising the key phenoxy components and has been found to be stable over 700 days in continuous culture, removing 99.5 % of phenoxies and 96.7 % of chlorophenols. Toxicity tests using D.magna and Microtox systems have shown a 90 % reduction in toxicity by biological treatment. A laboratory activated sludge system was developed resulting in complete degradation of the chlorophenols and phenoxies.