Enhanced in situ bioremediation of groundwater contaminated by petroleum hydrocarbons at the location of the Nitex textiles, Serbia

This study provides insight into the enhanced in situ bioremediation applied for remediation of groundwater contaminated by petroleum hydrocarbons. Activities prior to the application of this remediation approach included removal of the source of groundwater contamination—an underground storage tank and contaminated sediments—from the unsaturated zone. The hydraulic feasibility of this remediation approach was proved by hydraulic conductivity characterization of the site. Enhanced in situ bioremediation was performed by a combination of biostimulation and bioaugmentation within the closed bipolar system (one extraction and two injection wells). Biostimulation was conducted by addition of nutrients, and stimulation of oxidation processes by injection of H2O2, into the aquifer. Bioaugmentation/re-inoculation was achieved by injection of a zymogenous consortium of hydrocarbon degrading microorganisms isolated from the contaminated groundwater. The average extraction capacity was 0.5 l/s, with an average injection capacity of 0.25 l/s per well. The efficiency of the remediation approach was measured by changes in the content of total petroleum hydrocarbon (TPH), total chemoorganoheterotrophic (TC) and hydrocarbon degrading (HD) microorganisms. After biostimulation and bioaugmentation, the number of TC and HD microorganisms started to increase. This was followed by a decrease of TPH concentration in the groundwater from an initial 6.8–0.5 mg/l at the end of the bioremediation. The applied remediation approach was highly efficient and very effective in reducing TPH to acceptable levels. Together, these facts provide strong evidence of its potential for remediation of groundwater contaminated by petroleum hydrocarbons.