BIOREMEDIATION OF CRUDE OIL CONTAMINATED SOILS A Black Art or an Engineering Challenge? F. BENYAHIA  , M. ABDULKARIM, A. ZEKRI, O. CHAALAL and H. HASANAIN Department of Chemical and Petroleum Engineering, United Arab Emirates University, Al Ain, UAE A bioremediation of crude oil contaminated soils study was carried out in engineered laboratory biopile systems. In soil bioremediation, biopiles are ‘ex situ’ treatment systems that consist of excavated and aerated contaminated soils amended by addition of biological, mineral or organic material depending upon specific needs. When bac- teria are added to the contaminated soil undergoing biological treatment, the latter is referred to as a bioaugmented treatment system. Such soils are arranged above ground in a pile fashion and hence the term biopile. The study has shown virtually identical trends in respiration rates when indigenous and commercial added bacteria where employed. However, the bioaugmen- ted experiments yielded much greater respiration rates and lead to a reduction of 75% of the initial oil in just 118 days, compared to 1 year in similar studies in the literature. The benefits of engineered biopile systems include safe operations, facilitated material balance and process controllability. The benefits of bioaugmentation were clearly demonstrated and it was found that when no nutrients are added to the soil, bacteria tend to metabolize hydrocarbons into carbon dioxide and water rather than assimilate carbon in cell growth. Polyaromatics analysis of treated soil in this investigation pointed out that simpler and more bioavailable crude oil components were degraded first. A simple sigmoid model for the carbon dioxide generation was developed from the respiration data. Keywords: bioremediation; biopile system; contaminated soil; crude oil. INTRODUCTION Concern over soil contamination by crude oil or hydro- carbon products in general, is gathering momentum after a similar feeling has been around for a while on marine oil spills, which enjoy more media coverage because of the often spectacular visual effects images conveyed to people. There are similarities and differences between inland and offshore crude oil spills. Similarities include hazards to life in all its forms, contamination of valuable fresh water resources from aquifers or desalination plants and an uncertain long term environmental impact despite unsubstantiated claims that nature fully recovers in ‘a few years’. On the other hand, the differences concern mainly the behaviour of spilled oil, its interaction with the sur- rounding environment and the corresponding approach to remediation. In the case of soil contamination by hydrocarbon pro- ducts, there has been a great deal of work on biologically based treatment processes from several disciplines of the scientific community. This is not an odd phenomenon since environmental research concerns just as many disci- plines and more importantly attracts funding support from government and private sources. However, the diversity of backgrounds of the researchers created a collection of schools of thought as well as, sometimes convenient, basis for agreement or disagreement in interpretation of laboratory or field data on bioremediation. For people seriously engaged in large scale bioremediation of oil con- taminated soils, this situation leads to the legitimate ques- tion: is bioremediation of crude oil contaminated soils a black art or an engineering challenge? The following notes are extracts from relevant literature findings that cannot be considered as a comprehensive survey, for the sake of conciseness. Al-Daher et al. (1998) carried out what seemed to be a series of intermediate size (20 m 3 ) bioremediation tests on crude oil contaminated Kuwaiti soil by means of wind- row piles. Treated soils were initially referred to as lightly and heavily contaminated without providing a measure of hydrocarbon content that could easily be measured as TPH or equivalent TOC. The windrow piles employed were inoculated by sprinkling with solutions containing sewage sludge, mature compost and non-identified hetero- trophic bacteria isolated from contaminated soil and grown in the laboratory on hexadecane as the sole source of carbon. Whilst the study was found to be interesting,  Correspondence to: Dr F. Benyahia, Department of Chemical and Pet- roleum Engineering, United Arab Emirates University, PO Box 17555, Al Ain, UAE. E-mail: farid.benyahia@uaeu.ac.ae 364 0957–5820/05/$30.00+0.00 # 2005 Institution of Chemical Engineers www.icheme.org/journals Trans IChemE, Part B, July 2005 doi: 10.1205/psep.04388 Process Safety and Environmental Protection, 83(B4): 364–370