Characterization of oily sludge from a wastewater treatment plant flocculation-flotation unit in a petroleum refinery and its treatment implications

Abstract

Partly due to the complex and variable composition of oily sludge generated by the petroleum industry, cost-effective treatment and proper disposal pose considerable challenges worldwide. In this study, an extended component-based analysis of the oily sludge from a fl occulation-fl otation unit of a wastewater treatment system in a refi nery in Sweden was carried out over 1 year. The heterogeneity of the oily sludge is illustrated by the wide ranges of concentrations found for different chemical components, particularly metals. Among the petroleum hydrocarbons, the most abundant compounds were nonpolar aliphatic hydrocarbons (63.7 ± 16.7 g kg −1 ); from the benzene, toluene, ethylbenzene, and xylene group, xylenes (91-240 mg kg −1 ) were most abundant; and among polycyclic aromatic hydrocarbons, naphthalene (25.7 ± 21.4), fl uorene (27.25 ± 10.0), and phenanthrene (43.8 ± 18.4 mg kg −1 ) were most abundant (all results in terms of dry matter). Based on the EU guidelines and the mean concentration values for metals found in the oily sludge, e.g., Pb (135.4 ± 125.8), Cu (105.2 ± 79.1), Hg (42.8 ± 31.3), Ni (320 ± 267.4), and Zn (1321.7 ± 529.9 mg kg −1 ), disposal of oily sludge even in landfi lls for hazardous waste is not allowed. The organic content of the sludge can be reduced through biotreatment, but not the metal content. A multistep component-based treatment scheme is therefore needed.The oily sludge generated at fl occulation-fl otation units (FFU sludge) of wastewater treatment plants contains J Mater Cycles Waste Manag (2008) 10:79-86

Characterization of Petroleum Sludge from Refinery Industry Biological Wastewater Treatment Unit

“…Petroleum sludge is also generated from cleaning of oil storage tanks, from oil-water separators, from cleaning of processing equipment, and also from cleaning of oil-spill at both drilling and refining sites 11 . Petroleum sludge vary in composition depending on the origin and storage condition 12 . Generally, it contains about 10 -30 wt.% hydrocarbons, 5 -20 wt.% solids and 50 -85 wt.% water 13 .…”

Influence of ultrasonic waves on the removal of different oil components from oily sludge

“…[13,14] Different oil components have different wettability to solid particles. It is therefore easy to speculate that different oil components may exhibit different surface stripping efficiencies by ultrasonic washing, leading to differences in removal efficiencies for different components.…”

Development of novel oil recovery methods for petroleum refinery oily sludge treatment

“…The NSO fraction contains polar compounds such as naphthenic acids, mercaptans, thiophenes and pyridines (Kriipsalu et al, 2008). The nitrogen (N) content accounts for less than 3% in oily sludge, and most of them are contained in the distillate residue as part of asphalt and resin fraction.…”

“…The nitrogen (N) content accounts for less than 3% in oily sludge, and most of them are contained in the distillate residue as part of asphalt and resin fraction. The sulphur (S) content can be in the range of 0.3-10% whereas the oxygen (0) content is usually less than 4.8% (Kriipsalu et al, 2008).…”

“…The PHCs and other organic compounds in oily sludge can be generally classified into four fractions, including aliphatics, aromatics, nitrogen sulphur oxygen (NSO) containing compounds, and asphaltenes (Mrayyan and Battikhi, 2005;Reddy et al, 2011). The aliphatics and aromatic hydrocarbons usually account for up to 75% of PHCs in oily sludge , and their most common compounds include alkanes, cycloalkanes, benzene, toluene, xylenes, naphthalene, phenols and various polycyclic aromatic hydrocarbons (PAHs) (e.g., methylated derivatives of fluorine, phenanthrene, anthracene, chrysene, benzofluorene, and pyrene) (Kriipsalu et al, 2008).…”