Industrial Bioremediation of Aquifer Sediment Contaminated with Hydrocarbons

Abstract

Pollution of groundwater reservoirs with petroleum hydrocarbons leads to measurable changes in the hydrochemistry of groundwater, mainly due to microbiolog ical activity. The aim of this chapter is to provide insight into research and in situ remediation activities for the removal of polluting petroleum hydrocarbons from polluted aquifer sediments, using the examples of the historically polluted kerosene loca tion in Vitanovac (central Serbia), as well as the example of two radial collection wells of the water supply system in New Belgrade. In Vitanovac, due to long - term hydrocarbon pollution and exposure to aerobic and anaerobic biodegradation mechanisms, the lowest concentrations of O 2 , NO 3 - , and SO 4 2 - (electron acceptors) and the highest concentrations of Mn and Fe (products of microbial metabolic activities) overlap. Terminal redox - accepting processes in groundwater varied from oxygen reduction to sulfate r eduction. Most anaerobic processes were registered in the piezometers closest to the pollution source, which was also confirmed by redox potential (Eh) measurements. High values of electrical conductivity and highest concentrations of TOC, SiO 2 and Al al so overlap in the pollution zone close to the pollution source. Analysis by scanning electron microscopy of quartz grains from the zone under the influence of biodegradation confirmed the occurrence of microscopic decomposition processes on mineral surface s. Taking into account all these factors, it can be assumed that the microbiological activity caused the increased decomposition of silicate minerals. At the Novi Beograd location, the most suitable method for remediation was in situ bioremediation because it is a clean, efficient and sustainable technology. Before starting the bioremediation process, it was necessary to isolate and grow the microorganisms present at the location of the pollution, so that they could later be used in the bioremediation proce ss. Samples before and after bioremediation were studied using GC and GC×GC – MS to determine how pollution concentrations changed over time. The spatio - temporal change of hydrocarbon content by depth within the zone of greatest pollution over time is shown. After 12 months of bioremediation, the hydrocarbon content in the samples decreased by 82.0%, and based on GC×GC - MS analysis, the order of decomposition of different hydrocarbon groups was as follows: steranes (99.6%), isoprenoids (98.4%), benzene derivat ives (98.4%), alkanes (97.2%), and terpenes (49.3%). The exponential decay model showed the highest rate of hydrocarbon decomposition at depths of 8 – 10 m, with an average decay constant of 0.227, independent of the initial hydrocarbon concentration.