Optimization of Biological pH Treatment for Acidic Palm Oil Mill Effluent

Palm oil mill effluent (POME) has been known as organic waste product from palm oil production which is featured by low pH of 3.5-4.5, high value of biological demand (BOD), chemical oxygen demand (COD) and suspended solids. It is mandatory for all palm oil mills to treat their wastewaters to an acceptable level before it is allowed to be discharged into the water courses. Biological treatment appears less cost than chemical and physical methods and have low environmental impact. The purpose of this study was to optimize the factors (temperature and agitation) which were influencing biological pH treatment of acidic POME. Acidic POME was collected from a nearby palm oil mill whereas soil mixed culture was obtained from soil near the plants root system. Soil mixed culture was acclimatized with POME as inoculum. Experimental design table was prepared based on Response Surface Method (RSM) and 13 experimental runs were conducted according to Center Composite Design (CCD) set up. The experimental results were optimized using Design Expert software (Version 6.0). The proposed model from the software showed proportional relationship between pH value and both studied factors. Temperature and agitation had individual significant influence on pH value. Based on the analysis, the suggested optimum conditions were at temperature of 32.50℃ and agitation speed of 125 rpm. The expected pH value at these conditions was at 8.03. Later, validation experiment was conducted at the suggested optimum conditions and the error between the actual and expected pH value was at 2.29%. Low errors from the validation experiments (