Permeability and Leachability of Immobilized Petroleum Waste in Metakaolin Cement Binder

This research studies the waste management of petroleum sludge that was retrieved from the final decanter outlet of a petroleum refinery complex by the application of a technique known as Solidification and Stabilization (S/S). The S/S technique is a well-established waste disposal technique for hazardous wastes and the study focuses on the treatment of sludge waste using metakaolin. The effectiveness of the process is studied by chemical and physical methods, that is, through permeability, leachability and strength tests. The S/S technique applies a binder, commonly Ordinary Portland Cement, to immobilize and encapsulate the hydrocarbon waste to chemically stabilize it preventing from external chemical reaction with the environment. The purpose of this study is to investigate the factors affecting the strength of the solidified sludge waste and metakaolin cement binder using different mix ratios where the optimum ratio can lead to the strength improvement in waste-binder matrix. The objective is met by optimizing waste to cement and admixture ratio based on the unconfined compressive strength as the main judging criteria. The performance of the S/S is measured through leaching analysis to determine the lowest leachability of metals in the leachate through Toxicity Characteristic Leaching Procedure (TCLP), porosity and permeability properties of the stabilized waste with the unconfined compressive strength and its leaching behavior. It was found the presence of sludge and metakaolin showed that the highest cement to sludge ratio of 60 with highest amount of metakaolin of 15% produces the strongest cement matrix of strength of 85.75 MPa compared to the other lower cement to sludge ratio. Porosity was lowest at 12.09 when the C/Sd was at 40% and C/B at 5%, which however increases rapidly as C/B increases to 15%. A reversal was observed when C/Sd of 60 with increasing C/B ratio. The metals content in the leachate were relatively low and below the regulated metals content and in wastewater as outlined in EQA 1974. The optimum permeability for the solidified matrix of cement and metakaolin was the 15% metakaolin ratio with the aid of the FESEM EDX test method.