Stability of mechanically and chemically dispersed oil: Effect of particle types on oil dispersion.

Abstract

Oil spill dispersant (OSD) application is one of the preferred cleanup options to cope with oil spills at sea. OSD, in principle, can enhance biodegradation of oil because of its effectiveness in producing relatively small droplets and dispersing them into the water column. Under turbulent conditions, suspended particulate matter (SPM) which are present naturally in the environment can interact with oil to form aggregates known as oil-SPM aggregates (OSA) which also enhances biodegradation of oil. Despite its high dispersion effectiveness, chemically dispersed oil (CDO) has a tendency to resurface with increasing time which decreases the biodegradation potential. Meanwhile, the presence of SPM prevents recoalescence of dispersed oil which can enhance stability of oil droplets. This study focused on the effects of SPM on the dispersion effectiveness and stability of mechanically dispersed oil (MDO) and CDO. Dispersion tests of MDO and CDO extended to 72h with and without SPM to see the initial effectiveness and the prolonged stability of dispersed oil. In the presence of SPM, the oil dispersed by MDO increased by 14.8-40.7%, while the resurfacing oil by CDO decreased by 8.7-19.4%. Regardless of SPM type, oil dispersion effectiveness and stability of MDO and CDO were significantly increased. Long-term stability test for 3months showed that stability of OSA increased as the particle size decreased and particle counts increased.