Toxic Response of Nitrobacter to Orange II and Direct Blue 71

Abstract

Tolerance of Nitrobacter to Orange II (C.L. 15510) and Direct Blue 71 (C.I. 34140) dyes was determined by total viable count. There was decrease in percentage log survival with increase in concentration of the toxicants and increase in exposure time. Percentage survival at 20h was 84.50% and 75.50% at toxicants concentration of 100mgI-1 and 300mgI-1 respectively for orange II. The data obtained with direct Blue 71 for 20 were 88.96% and 83. 31% at 100mgI-1 and 300mgI-1 respectively. The LC50 for Orange II at various exposure times were 48h (139.86mgI-1) and 36h (352.79mgI-1). The LC50 was >1,000mgI-1 for exposure times of)-36h.The LC50 Direct Blue 71 were > 1000mgI-1 for all exposure times. The difference in toxicity of the two dyes was attributed to difference in dye content and molecular weight. (Journal of Applied Sciences & Environmental Management: 2002 6(1): 87-90)