Evaluating dissolved air flotation for oil/water separation using a hybridized coagulant of ferric chloride and chitosan

Dissolved air flotation (DAF) is a separation technology widely used in the industry to reduce oil concentrations in wastewater. However, there are some issues with the existing DAF system, including high chemical cost, environmental pollution by chemical residual in the effluent, and generation of non-biodegradable sludge. In this study, an environmentally friendly and cost-effective DAF process was proposed and tested for separating emulsified oil from water. A hybrid coagulant/flocculant system with ferric chloride as a coagulant and chitosan as a bio-degradable flocculant was used to enhance the efficiency of oil/water separation. The findings of this study showed that the hybrid configuration led to (i) 37% reduction in chemical costs (ii) 90% reduction in the use of non-biodegradable ferric chloride and (iii) 50% reduction in flocculator footprint when compared to individual coagulants. This proposed dosing strategy also has a broader operating pH range between 5 and 9 and wider applicability for both fresh and high salinity water. The results from this study contribute to the wider, environment-friendly, and cost-effective application of air flotation for oil/water separation.