Characterization and treatment proposals of shipboard slop wastewater contaminated by hydrocarbons

Shipboard slop wastewaters are produced by the activity of washing of oil tankers withseawater, and are characterized by high salinity and hydrocarbons. In this context, harbor authoritiesare forced to respect the international regulation IMO-MARPOL 73/78 and they must treat slopwastewater before discharging to the sea. This study compared data from three stand-alone treatmentsworking with the same real slop wastewater: (1) a chemical treatment of coagulation-flocculationwith aluminum sulphate as coagulant and an anionic flocculant (A57), (2) a physical treatmentof adsorption on granular activated carbon (GAC), (3) two biological treatments represented by amembrane bioreactor (MBR) and a moving bed biofilm reactor (MB-MBR). GAC treatment registeredthe highest removal efficiency of total petroleum hydrocarbons (ηTPH) next to 85%, since the activatedcarbon had excellent adsorption properties towards organic substances. The coagulation-flocculationtreatment reported the lowestηTPH≈57% due to the presence of emulsified hydrocarbons thatwere not affected by the coagulant and flocculant action, so remaining in liquid phase.ηTPH≈70%obtained with MB-MBR fed with 100% volume of slop, suggested biomass acclimation to salinityand hydrocarbons. Based on the results of each process, three main treatment chains are proposeddepending on the hydrocarbons load of the real slop wastewater.