Feasibility of treating emulsified oily and salty wastewaters through coagulation and bio-regenerated GAC filtration

In the present study, chemical oxygen demand (COD) removal by coagulation and packed-columns ofboth fresh and bioregenerated granular activated carbon (GAC) is reported as a feasible treatment forsaline and oily wastewaters (slops) generated from marine oil tankers cleaning. The use of Ferric chloride(FeCl3), Aluminium sulphate (Al2(SO4)3) and Polyaluminum chloride (Al2(OH3)Cl3) was evaluated in thepre-treatment by coagulation of a real slop, after a de-oiling phase in a tank skimmer Comparison ofcoagulation process indicated that Polyaluminum chloride and Aluminium sulphate operate equally well(20e30% of COD removal) when applied at their optimal dose (40 and 90 mg/l respectively) but the lattershould be preferred in order to significantly control the sludge production. The results from the columnfiltration tests indicated the feasibility of using the selected GAC (Filtrasorb 400 -Calgon Carbon Cor-poration) to achieve the respect of the discharge limits in the slops treatment with a carbon usage rate inthe range 0.1e0.3 kg/m3of treated effluent. Moreover, biological regeneration throughAlcalinovoraxborkumensisSK2 was proved to be a cost-effective procedure since the reuse of spent GAC through suchregeneration process for further treatment could still achieve approximately 90% of the initial sorptioncapacity, reducing then costs for the use of new sorbents and also the need for waste disposal.