Removal of COD from biodiesel wastewater using a hydrophobic polymer

Abstract

Biodiesel production is increasing internationally as an alternative fuel. This is due to the rapid depletion of non-renewable energy sources. Pure biodiesel product can be obtained by washing the product with hot water. This results in a huge quantity of wastewater that is unsafe for disposal in normal drainage systems. Treatment of this wastewater is thus important for reuse or safe disposal in the environment. There are a lot of existing treatment methods, but they are costly, produce large quantities of excessive sludge and are not economically feasible. Flocculation is widely used in water treatment as it is easy to use and affordable. Flocculants can be synthesized to treat the specific wastewater type focusing on the reduction of certain impurities. The reduction of Chemical Oxygen Demand (COD) in the biodiesel wastewater was investigated through jar-tests using hydrophobic, non-hydrophobic and a combination of hydrophobic and non-hydrophobic polymers that were synthesized. Almost 68% COD removal was obtained with the non-hydrophobic polymer and about 56% COD removal was obtained with the hydrophobic polymer. The non-hydrophobic polymer has a better removal efficiency, as the wastewater contains a large quantity of hydrophilic organic matters. Although the hydrophobic polymer also removes COD, it could be seen that the hydrophobic polymer attracted the unreacted oil in the biodiesel wastewater