International Journal of Scientific and Research Publications, Volume 6, Issue 7, July 2016 401 ISSN 2250-3153 www.ijsrp.org Efficiency assessment of an oil dispersant (Adt type 3) by Swirling flask test & Baffled flask test under laboratory condition M.V.K.S Wickramanayake, R. A. Maithreepala and H.B. Asanthi Department of Limnology and Water Technology, University of Ruhuna, Matara, Sri Lanka Abstract- This study was focused to assess efficiency and toxicity of an oil dispersant (Adt type 3) under the laboratory conditions. Swirling Flask Test (SFT) and Baffled Flask Test (BFT) were used for effectiveness assessments using Murban crude oil (density 0.837gcm -3 ) as the reference oil. The locally made baffled flask was used with 100μl of oil, 4μl of dispersant and120ml of filtered seawater at 1:25 dispersant to oil ratio. The SFT was followed using1:10 dispersant to oil ratio and the dispersant efficiency was expressed as a ratio between amount of oil initially added to test flask and amount of oil extracted to dichloromethane (DCM). Oil was extracted by using DCM and then the absorbance was measured at wavelengths of 300nm, 370nm and 400nm to determine the extracted oil amount. A marine fish, Neopamacentrus azysron(yellow tail damsel fish)was used as the target organism for the toxicity test which is common at shore areas as well live up to 20m depth. Seven glass tanks (44x29x31cm 3 ) were used as six replicates and one control tank and each tank was filled with 30L of filtered sea water. Median LC50 was calculated using Trimmed SPEARMAN- KARBER method, version 1.0.The efficiency of Adt concentrated type 3 oil dispersant was determined as 55.29±1.47%, and 16.08±1.19% under BFT and SFT respectively. The swirling flask test showed relatively low efficiency value than BFT and the value was lower than the USEPA recommended efficiency level of 45%. Percentage dispersant occurred due to natural dispensability of oil was obtained as 1.105 (mean of three control experiments). There was no significant difference of absorbance values among the replicates of each set up average values were taken for response factor. Water temperature, salinity, NH 3 , and pH did not show significant difference among the replicates of toxicity test. Dissolved Oxygen in the tanks reduced dramatically during first 3 hours and then it was constant. Acute toxicity level of Adt concentrate type 3 oil dispersant for Neopamacentrus azysronwas 746.16±3.56 ppm and it is moderately toxic under the laboratory conditions. Aggressive behavior and increase of breathing rate were observed in the toxicity test at the lethal concentrations. The present assessment explains that the Adt type 3 is low efficient and low toxic oil dispersant. Index Terms- BFT, efficiency, LC50, Oil dispersant, SFT, toxicity I. INTRODUCTION emediation method for oil spill is to be decided based on the characteristic features of the oil and sensitivity of nearby environment considering climatic variables [1]. has been reported that natural organic sorbents can adsorb 3 and 15 times their weight in oil, natural inorganic sorbents adsorb 4 to 20 times their weight in oil and synthetic sorbents can absorb up to 70 times their weight in oil. Even though, bio remediation techniques of bio augmentation or bio stimulation recommended as economically feasible methods use of chemical dispersant had been introduced to treat Torry canyon spill off Cornwall, England in 1967 and later chemical oil dispersants have been reformulated due to its successfulness of applications[2]. However, a review of ITPOFs database of past oil spills has been reported that, among the 258 of recorded marine incidents between 1995 and 2005 only 18% had been used chemical dispersants 4at the sea[3]. Dispersants are made of surfactants (surface active agents) dissolved in one or more solvents, composed with both lipophilic and hydrophilic groups in their chemical nature. The lipophilic end of the molecules is attached to the oil phase and the hydrophilic end extended into the water phase [4]. Surfactant creates interface stabilization and it prevents collision with adjacent droplets and reduce adherence to hydrophilic solid particles. Ultimate action of dispersant is making tiny oil particles and breaks the oil slick to small droplets. The behavior of a surfactant is strongly affected by the balance between the hydrophilic and lipophilic groups (HBL) in the molecule[5]. Dispersants are made by mixing different types of surfactants at different ratios as such modern dispersant formulations containing one or more nonionic surfactants (15 to 75 percent of the formulation), anionic surfactants (5 to 25 percent of formulation) and one or more solvents [5]. Effectiveness of dispersant is still remains as a major issue with chemical oil dispersants and many factors are influenced for dispersant effectiveness, including oil composition, sea energy, state of oil weathering, the type of dispersant used and the amount applied temperature, and salinity of water[6]. However, the major factor is considered as the composition of oil followed by sea energy and amount of dispersant added [7]. Rapid dispersion of dispersant-treated oil begins at a wind speed of approximately 7 knots with wave height of 0.3m. The formation of water-in-oil emulsion by wave action increases the viscosity of oil and thereby reduces the dispersant effectiveness [6]. Water chemistry is also important for oil dispersant efficiency and most R