Isolation of potential total petroleum hydrocarbon degraders from river sediments

The terrestrial environment and its surrounding areas are vulnerable to contamination by hydrocarbon contaminants with more than half of the petroleum released into the waters is estimated to be adsorbed onto the suspended solids and settled as sediments. Bioremediation involves application of suitable biological substances such as microorganisms and plants to absorb and degrade chemical hazards into non-hazardous compounds. This study aims to isolate potential hydrocarbon degraders from weathered contaminated river sediments and the sediments were characterised physically and chemically. The sediments from Lutong River were categorised as neutral sandy loam with high moisture content at 47 %. The soil permeability was reduced to 0.01 – 0.002 cm/min due to the bonding of hydrocarbon compounds onto the soil particles. A very high amount of NPK nutrients were observed in the polluted soils with nitrogen 4584 ppm, followed by phosphorus 2650 ppm and potassium 1017 ppm. Heavy metal analysis showed low toxicity of metals in the river sediments which meet the environmental regulations. Ten bacterial isolates were successfully obtained from the sediments. There were four Gram-positive bacteria, namely isolates A(1), S3(1), 4(2) and 5(1). The rest of the isolates were found to be Gram-negative bacteria. Initial results of the petroleum degradation had shown the potential of indigenous bacteria isolates as petroleum degraders because they had successfully reduced 18 % of TPH in the soil within two weeks.