The Implication of Total Petroleum Hydrocarbons in Oil Produced Water Discharged in Municipal Channels

Abstract

This paper discusses the results and observations of experiments that were performed to investigate the presence and implication of total petroleum hydrocarbons (TPH) in oil produced water (OPW) samples from an oil depot. An analytical method based on gas chromatography coupled to time-of-flight mass spectrometry (GC-TOF-MS) was developed for the determination of TPH. The effect of the extracting organic solvent was studied, and n-hexane was found to be the best extraction solvent as it resulted in 96.28% extraction efficiency. The TPH were determined in both influent and effluent samples. Various TPH fractions were identified including n-alkanes, branched alkanes, alkenes, etc. The TPH determination was investigated on a seasonal basis and the winter period (June-August) registered many compounds especially from the influent compartments than they were found in autumn. This suggests that the physical treatment employed by the oil depot does remove the TPH to a certain degree which is above the limit thresholds set by the regulatory authorities which is not satisfactory and thus the effluents need to be subjected to secondary treatment. The TPH analysis and identification results presented are mainly qualitative except for 1-chloro-octadecane, the surrogate standard. The TPH compounds were identified based on similarity indices to the databases.