Microbial degradation of BTEX compounds in groundwater after ozonation process

Abstract

BTEX (benzene, toluene, ethylbenzene, and xylene) compounds are common in a variety of water resources, including groundwater. However, the ongoing biodegradation processes are not sufficiently effective, and accumulation of these substances occurs. To enhance the biodegradability, ozonation can be used for transformation of these recalcitrant compounds to easily biodegradable organics. This paper is focused on expanding existing knowledge of degrading BTEX substances by ozonation process before biological degradation. Batch experiments were prepared from aquifer sediment with ozonated and non-ozonated groundwater contaminated by 10 mg dm−3 BTEX. The results showed that degradation efficiency of these compounds without previous ozonation was in the first 7 days 9.1% for benzene, 68.4% for toluene, 74.9% for p-xylene, and 89.4% for ethylbenzene. In this process, the complete degradation time for these substances was up to 7 days for ethylbenzene, and 14 days for toluene and p-xylene. Benzene was not degraded even after 21 days of the experiment. In comparison, the ozonation process increased the biological degradation efficiency when all these compounds were completely degraded within 7 days of the experiment. The total number of attached cells was on average 1.2 orders of magnitude higher than in the case of the non-ozonated BTEX samples.