TOXICITY AND DEGRADABILITY OF NITROPHENOLS IN ANAEROBIC SYSTEMS

Nitrophenols are among the most important and versatile industrial org anic compounds and are widely used in the chemical industry and are li sted as priority pollutants by the U.S. EPA. The toxic effects and deg radability of three selected nitrophenols (2-nitrophenol, 4-nitropheno l and 2,4-dinitrophenol) in anaerobic acetate and propionate enrichmen t systems were studied using batch serum bottles. The toxicity to both propionate- and acetate-fed systems decreased in the following order: 2,4-dinitrophenol > 4-nitrophenol > 2-nitrophenol. An up-flow fixed f ilm, acetate-fed reactor was able to acclimate to 20 mg/L of 2- and 4- nitrophenol showing a 95% removal of each nitrophenol. The effect of b iomass was studied using serum bottles for anaerobic toxicity assays w ith the design volatile suspended solids (VSS) concentrations of 500, 1000, and 1500 mg/L. With higher VSS the toxic effects of nitrophenols on methanogenesis were less severe. Nitrophenols were more inhibitory to acetate utilization than propionate utilization. Under anaerobic c onditions, 2-nitrophenol and 2,4-dinitrophenol were transformed both a biotically and biotically to 2-aminophenol and 2-amino,4-nitrophenol, respectively. The presence of propionate in propionate enrichment cult ure enhanced the removal rates of all three nitrophenols studied.