Efficiency assessment of an oil dispersant (Adt type 3) by Swirling flask test & Baffled flask test under laboratory condition

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 (44x29x31cm3) 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, NH3, 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.