Toxic Effect Of Azo Dyes On Nitrite-N Utilization By Nitrobacter

Abstract

The toxicity of five azo dyes (toxicants) on Nitrobacter was investigated. The index for toxicity was inhibition of rate of nitrite-N utilization. The rate of nitrite-N utilization decreased with increase in concentration of each toxicant at specific exposure time. However, stimulation of utilization was obtained at low concentrations and short exposure time for two of the dyes. This was attributed to hyperactivity. The median effective concentration₅₀ (EC₅₀) values increased with increase in exposure time for each toxicant. This was attributed to acclimatization and/or detoxification. Inhibition was attributed to any/or all of the following factors: molecular size, impurities in the toxicants and dye content.

KEY WORDS: Toxicity, Azo dyes, Nitrobacter, hyperactivity, acclimatization

Global Journal of Environmental Sciences Vol.4(1) 2005: 47-51