Performance of Horizontal Roughing Filter for Colour Removal of Palm Oil Mill Effluent Using Natural Adsorbent

Palm oil wastewater treatment was investigated via a filtration process using raw and calcinated limestone. Column studies were conducted using different limestone sizes (4, 12, and 20 mm), calcination temperature (800 °C and 600 °C) and various filtration rates (20, 60, and 100 mL/min), and a comparison was made with raw limestone under similar conditions. The response surface methodology using central composite design was employed to optimize the process parameter. The experimental data was analyzed via the analysis of variance to identify the interaction between the parameters and the dependent parameter. The results showed that the colour removal increased with an increase in temperature (800 °C) for filtration rate of 20 mL/min, the retention time of 317 min and the smaller size (4 mm) of limestone, and decreased with an increase in the filtration rate and size of raw limestone. Based on the achieved results, the optimum condition for colour removal was at temperature 800 °C (61%), 600 °C (56%) and raw limestone (49%), respectively, with the same experimental setup (flow rate of 20 mL/min and limestone size of 4 mm). According to the statistical analysis, quadratic models demonstrated significant values (0.000) for the response (colour). Freundlich and Langmuir isotherms also provided good correlation coefficient for colour removal. The data conforms to the Langmuir isotherm with the best fit model (R2= 0.7).