Abstract
Abstract A bioreactor system that consisted of Pseudomonas fluorescens cells immobilised in calcium-alginate beads was utilised to remediate endosulphan contaminated water and soil. A packed bed reactor system was designed for the bio-degradation of endosulphan in artificially spiked water samples (initial concentration of endosulphan: 350 µg/L). Reactor studies with cell-immobilised Ca-alginate beads were conducted after checking their efficiency through batch and column degradation studies. The results showed that the concentration of toxic isomers of endosulphan (endosulphan alpha and endosulphan beta) was below the limit in the bioreactor during the 7th day of the experiment. Experiments conducted with contaminated soil samples (initial concentration of endosulphan: 1,000 μg/kg) indicated that the toxic isomers of endosulphan degraded to below the detection limit within 10 days and monitoring of endosulphan residues on the 14th day revealed that almost complete degradation of metabolites of endosulphan had occurred. The bioreactor system designed can be scaled up for remediation of endosulphan in contaminated areas.
Highlights
The continuous unrestricted use of pesticides may cause harmful and unpredictable health impacts
This study shows the feasibility of using Ca-alginate immobilised cells of Pseudomonas fluorescens for the degradation of endosulphan in a packed bed bioreactor system
Approximately 100% removal of the toxic isomers of endosulphan in the bioreactor with cell-immobilised Ca-alginate beads during the 7th day of experiment (Figure 4). This rapid removal of endosulphan is mainly due to the presence of an increased cell concentration in the Ca-alginate beads, which is derived from the incorporation of 0.34 g wet cells
Summary
The continuous unrestricted use of pesticides may cause harmful and unpredictable health impacts. The persistence of organochlorine pesticides including endosulphan is a matter of concern due to its unexplored environmental impacts. Biological methods have been found to be more environmentally friendly, cost effective and socially acceptable (Harikumar et al 2012). Bioremediation helps to destroy toxic pollutants utilising natural biological activity. Bioreactor systems consist of mechanical vessels in which organisms are cultured in a controlled manner and materials are transformed by specific reactions. The design and conditions to be maintained in bioreactor systems are important to provide a higher degree of control over process upsets and contaminations, since the organisms are more sensitive and less stable than chemicals. Biological organisms can alter the biochemistry of the bioreaction which in turn can lead to the degradation of toxic pollutants. The major challenge in the development of a bioreactor system is minimising undesired activities and maintaining the desired
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