Bioenhancement of soil microorganisms in natural surfactant solutions .1. Aerobic

Natural surfactant solutions obtained from fruit pericarps of Sapindus mukorossi are very effective for flushing contaminants from soil columns. These solutions can solubilize significant quantities of hydrophobic organic compounds (HOCs) and are found to be comparable to commercial surfactants. The fate of surfactants left in the subsurface and the aqueous effluent generated during the remediation operations is crucial for the success of the soil flushing technology. In this study, bioenhancement of typical soil microorganisms in natural surfactant solutions is appraised under aerobic conditions. Natural surfactant solutions can readily serve as both carbon and energy sources and degrade considerably. The addition of nutrients to natural surfactant solutions increased the microbial growth significantly. Surfactant-bacterial cell interactions did not inhibit the growth of microorganisms in natural surfactant solutions as reported for some surfactants. Microbial growth increased significantly with the increase in surfactant concentration. The results of the study give a fair indication on the fate of residual surfactant in the subsurface.