Bioaugmentation for oily waste remediation: Harm or benefit?

Abstract

© 2020 International Multidisciplinary Scientific Geoconference. All rights reserved. Recently, biostimulation has often been used to remediate oily wastes. The use of additional bioaugmentation to increase biostimulation efficiency is widely discussed in scientific and practical literature. In this study, three methods of bioremediation for oily waste containing 177.8 g kg-1 of hydrocarbons were used: the first one included biostimulation with 66.6 % compost (w/w) made from municipal waste, the second one combined biostimulation and one-time inoculation by hydrocarbon degrading strains, and the third one combined biostimulation and repeated inoculation by hydrocarbon degrading strains (2 strains belonging to the species Rhodococcus jialingiae, the others - Stenotrophomonas rhizophila and Pseudomonas gessardii). All three methods had the same efficiency in terms of TPH level declination and comparative efficiency in terms of phytotoxicity. It was found that hydrocarbon content decreased similarly in all three remediation mixtures, it fell twice during the first 63 days of investigation and then remained stable. Phytotoxicity after 150 days of investigation, expressed in GI, was equal to 104.7, 131.4 and 79.5 % in the first, second and third remediation mixtures, respectively. Bacterial as well as fungal counts were significantly higher in the first remediation mixture compared with the other two mixtures during the first 63 days of the experiment, while copy numbers of the alkB genes belonging to hydrocarbon degraders was significantly lower in this mixture. We suggest that inoculation inhibited the indigenous microbial community in the remediation mixture, but the consequent potential decrease in hydrocarbon decomposition rate was compensated by the high hydrocarbon degradation ability of the introduced strains. From a practical point of view, biostimulation without bioaugmentation may be recommended as the simplest of the methods checked.