A comparison of treatment methods for palm oil mill effluent (POME) wastes

A study of the operational variables involved in the treatment of palm oil mill effluent (POME) was carried out. These included the acidic or alkaline nature of the POME discharged from the oil mills, the efficiency of the decay (or digestion) of the chemical oxygen demand (COD) contents of the POME, the economic benefits that could arise from the digested sludge and biogas and finally the net economic recovery abilities of the various treatment methods available. The chemical oxygen demand (COD) contents of the POME must be reduced to an acceptable level of 2000–3000 mg solids dm^?3 of sludge before the latter can be used as a fertiliser material. In 10 days of operational periods various anaerobic digestion treatment methods gave COD reduction efficiencies of 76–96%, the batch pond anaerobic digestion mode gave an efficiency of 76.5%, the continuous pond modes 92.5–95.5% and the tank digester 93.8%. In all anaerobic operations the optimal pH values of the POME media were in the range 7.1–7.6 and a ratio of the volatile acids to the total alkalinity of the media (VA/TA) of 0.3 or less was found to enhance the performance of these digesters. Economic analyses carried out on all modes of treatment gave the following economic recovery abilities: the decanter/drier system gave a break-even situation of 3 years, the tank digester system, 2 years, and the single stage anaerobic pond system, 6 years. The batch pond system appeared not to give a break-even situation. Of the treatment methods examined the decanter/drier and tank digester systems were concluded to be optimal.     

Effect of coagulation on palm oil mill effluent and subsequent treatment of coagulated sludge by anaerobic digestion

A new effluent treatment scheme is proposed for treating palm oil mill effluent based on coagulation and anaerobic digestion of coagulated sludge. The effectiveness of anionic (N9901) and cationic (N9907) polyelectrolytes manufactured by NALCO (Malaysia) was evaluated both as coagulant and coagulant aid. The results showed that the anionic and cationic polyelectrolytes were best suited as a coagulant aid, and the cationic polyelectrolyte showed better performance than the anionic polyelectrolyte. For an influent chemical oxygen demand (COD) concentration of 59 700 mg L^?1 at an alum dosage of 1700 mg L^?1, the residual COD, suspended solid removal, sludge volume and pH were found to be 39 665 mg L^?1, 87%, 260 mL L^?1 and 6.3, respectively. For the above influent COD and alum dosage with the addition of 2 mg L^?1 of cationic polyelectrolyte as coagulant aid, the results were 30 870 mg L^?1, 90%, 240 mL L^?1 and 6.2, respectively. The sludge resulting from the coagulation process using alum as coagulant and cationic polyelectrolyte as coagulant aid was tested for its digestibility in an anaerobic digester. The quantity of biogas generated per gram of volatile solids (VS) destroyed at a loading rate of 26.7 ± 0.5 and 35.2 ± 0.4 g VS L^?1 d^?1 was found to be 0.68 and 0.72 L g^?1 VS destroyed. The anaerobic biomass when subjected to varying alum dosage in the coagulated palm oil sludge did not exhibit inhibition as the digester performance was in conformity with the regular treatment process Copyright © 2006 Society of Chemical Industry