STUDIES ON MICROBIAL DEGRADATION OF OILY SLUDGE

Abstract

Oily sludge, comprising of hydrocarbons, sediments, heavy metals and water etc., gets accumulated over a period of time in storage tanks in refineries and poses several environmental and operational problems. Management of oily sludge remains an increasingly challenging task because the hydrocarbon fraction makes it highly recalcitrant and very difficult to treat, dispose and reutilize. In such a scenario, microbial degradation of petroleum hydrocarbons in oily sludge provides an effective and environmentally safe alternative for its treatment. In the present work, biodegradation potential of microbes in degrading soil sample contaminated with tank bottom sludge from Ankleshwar, Gujarat (India) is being investigated. On characterization of the sample, it was observed that it constituted of 50% petroleum hydrocarbons, of which 36% was the aliphatic fraction and 25% was the aromatic fraction. Enrichment technique was used to isolate oily sludge degrading bacteria from the contaminated soil samples. Among the eighteen bacterial strains isolated after enrichment, three isolates SV4 (Acinetobacter sp.), SV9 (Bacillus sp.) and SV17 (Pseudomonas sp.) were selected based on the criteria that they were able to display significant growth on crude oil, and individual hydrocarbons viz. n-Hexadecane, Pristane, Eicosane, Toluene, and Fluoranthene. The growth pattern indicated that optimal growth was achieved at a pH range of 7 to 8, temperature (30°C-35°C) and agitation rate of 120 rpm using 1% oily sludge.