OPTIMIZATION OF SOLIDIFICATION/STABILIZATION FOR PETROLEUM-BASED WASTE USING BLENDED CEMENT

Petroleum waste is categorized as scheduled waste, one of the hazardous wastes
that must be disposed at a licensed treatment plant. Refinery sludge produced in bulk
quantity requires substantial cost for treatment. Toxic substance in the waste can be
immobilized using stabilization and solidification method to reduce contaminant
solubility and leachability using Portland cement as a main binder. Solidified waste
with contaminants release in leachate below the standard levels can be disposed off onsite
or recovered with limited utilization for construction materials. The petroleum
sludge contained significant volatiles organics and oil and grease forming oily globules
in thick sludge. Portland cement mainly composed of tricalcium silicate and dicalcium
silicate. The cement to the sludge and water to cement ratios of 8 and 0.45 accordingly
was used as the design parameters to investigate the effect of cement replacement
materials at 5, I 0 and 15 % weight. The cement replacement materials are condensed
silica fume (CSF), fly ash (FA), activated carbon (A C), rice husk ash (RHA) and
metakaolin (MK). RHA was the best binder of all cement replacement materials with 5
% weight achieved optimum strength of 28.34 N/mm2
. Similarly, other binders'
strengths were optimized at 5 % weight. The increase in permeable porosity was in
tandem with the rise of cement to the sludge ratio, while a contradictory effect was
observed in the lower water to cement ratio. lsostrength peak was maximized at higher
water to cement ratio of 0.45 in tandems with porosity but reversing effect occurs at the
lower ratio. Prominent isostrength peak was observed with the inclusion of 5 % weight
of cement replacement material for all binders. Inclusion of 5 % weight CSF, FA and
MK in solidified sludge have resulted in the increased of micropore volume. Average
pore size was also increased with cement replacement materials except FA. Minimum
metals were leached out from of solidified sludge and solidified sludge with cement
replacement materials as determined by TCLP U.S. EPA SW-846 Method 1311