Remediation Treatments and Economic Assessment of Oil Residual Sludge from the Bottom of Tunisian Refinery Crude Oil Storage Tanks Olfa Ben Said, Rihab Belgacem, Boudour Ben Gaffar, Hamouda Beyrem, and James R Kahn Abstract The residual sludge from the bottom of refinery crude oil storage tanks causes major environmental and societal problems in Tunisia. Due to its high viscosity, it must be removed from the storage tanks in order to utilize the crude oil. However, its disposal in the environment leads to the infiltration of toxic metals into groundwater and eventual contamination of surface water bodies. The aim of this work was to characterize and treat sludge from Tunisian refinery by two different approaches (chemical and biological) and evaluate the economic ef ficiency of sludge remediation. Our results showed that both approaches are useful in terms of reducing the metal content of the sludge. However, the biological approach is more economically ef ficient and leads to better ecological outcomes. Keywords Sludge Á Petroleum Á Biological treatment Á Chemical treatment Á Metals 1 Introduction With the accelerated development of the industrial sector, humans are increasingly responsible for the pollution of the environment to such an extent that scientists are now labelling the current period as the Anthropocene [1]. The diversity, the scale and range of production of the industrial outputs have led to a considerable increase in the quantity of waste. Petroleum activity, in particular, produces an increasing amount of sludge in oil storage tanks which threatens the environment and human health by the infil- tration of toxic substances into the ground and consequently into the water table [2]. This situation poses a real ecological and social problem, due to the bad management of storage and disposal. The spread of untreated crude oil residual on agricultural land creates an economically and environmen- tally irreversible problem. The strong persistence of the metal contamination makes it environmentally irreversible, requiring hundreds of years for the metals to break down. The dispersal of the pollution makes the cost of post-spreading treatment too high to remediate [3]. Hence the economic and environmental need for adequate treatment of sludge before spreading or landfilling. In order to reduce the volumes of residues to be stored several treatment methods have been applied including chemical and physical treatment. The biological treatment alternative represents a reliable, low cost and environmentally friendly technology compared to the chemical and physical methods [4]. Sludge treatment is one of the most complicated pollution abatement processes with necessities and requirements of environ- mental and public health concerns. The economic magnitude of this problem is illustrated by the high cost of both investment and operation. The present work aimed to char- acterize the residual sludge from the bottom of an actual crude oil storage tank of the Tunisian refinery “la Société Tunisienne des Industries de Raf finage STIR”, to perform remediation treatments to reduce metal and to evaluate the sludge remediation economically. 2 Materials and Methods 2.1 Sludge Sampling, Characterization and Remediation Treatments STIR uses cylindrical tanks with floating covers to stabilize stored oil. The sludge sample was taken from the bottom of O. Ben Said (&) Á R. Belgacem Á B. Ben Gaffar Á H. Beyrem Bizerte Faculty of Sciences, Environment Biomonitoring Laboratory LBE, Bizerte, Tunisia e-mail: nourelimen@yahoo.fr J. R. Kahn Department of Economics, Washington and Lee University, Lexington, VA 24450, USA © Springer Nature Switzerland AG 2019 A. Kallel et al. (eds.), Recent Advances in Geo-Environmental Engineering, Geomechanics and Geotechnics, and Geohazards, Advances in Science, Technology & Innovation, https://doi.org/10.1007/978-3-030-01665-4_19 81