The effects of lightweight macrocomposite on the treatment of palm oil mill effluent

Abstract

As agricultural industries are developing over the years, the discharged of untreated waste materials are also on the rise. Example includes the discharged of palm oil mill effluent (POME) from the palm oil mill industry. To mitigate this matter, final discharged of POME was treated using three types of macrocomposites coded MAC1, MAC2 and MAC3 developed in this study. MAC3 was developed consisting of 77% pumice rock as lightweight aggregates (5-10 mm size range), 10 % pumice powder, 20% cement, 2% zeolite (500-200 µm) and 1% activated carbon (AC). The efficiency of MAC3 for POME treatment was compared to other macrocomposites made at similar composition as MAC3 but without zeolite (MAC2) and without both zeolite and AC (MAC1). All macrocomposites were chemically tested for its durability, in acidic to alkaline conditions. Physical test conducted for its thermal property at 121 °C for 20 mins at 15 psi and deterioration test under running tap water for 14 days. All three macrocomposites were analyzed for their ability to reduce chemical oxygen demand (COD), color and ammoniacal nitrogen (NH3-N) in examine the applicability for POME bioremediation efficiency. The pH value following treatment were monitored too. Rate of COD removal was examined in another set of experiment, using adsorption kinetics and isotherm models. The biofilm developed on macrocomposites were calculated for its dry cell weight and examined its surface morphology using scanning electron microscopy (SEM). From the results, all macrocomposites demonstrated no change of the structures after exposed to both 1M of hydrochloric acid (HCl) and sodium hydroxide (NaOH). As for 5 M of HCl and NaOH, the macrocomposites were all disintegrated after a period of time, as the cement may lose its binding properties in high concentration of acidic and alkaline conditions. When treated with POME, MAC3 demonstrated highest POME removal compared to MAC2 and MAC 1 with color reduction data of 65.17±1.67% (3100 ADMI), COD removal (42.51±0.28% (741 mg/L) and NH3-N reduction (65.77±0.05% (38 mg/L) after 10 days incubation. Treatment with macrocomposites, however, indicated high alkalinity of the POME that was highly attributed to the alkali content of cement that was used up to 20% of total macrocomposite content. the isotherm analysis, MAC3 gave the maximum adsorption (qe) at 6.946x10-4 mg/g. Pseudo-first-order gave the best model equation for COD removal of POME and that the rate of adsorption is increased with MAC2>MAC3>MAC1. The color, COD and ammoniacal nitrogen reduction by macrocomposites is also suggested to be enhanced by the biofilm coated on the macrocomposites, indicated by cluster cells that deposited on the porous structure of macrocomposites in SEM. MAC3 contained the highest biofilm dry cell weight (3.14 ± 0.11 mg/g) than MAC2 and MAC1, in which suggested that the highest surface roughness produced a higher biofilm formation. In conclusion, MAC3 is promising to treat POME, however, further improvement is recommended to improve their performance in terms of reducing the pH value towards an environmentally friendly absorbent system.