Optimization of Factors affecting Chemical Oxygen Demand Reduction from Palm Oil Mill Effluent using Anaerobic Digestion
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UNIVERSITI MALAYSIA SARAWAK
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This thesis was the outcome of a research conducted on chemical oxygen demand (COD) of palm oil mill effluent (POME) which focused on improving the performance of an anaerobic reactor. This study has addressed COD in POME as the problem to be solved and accordingly, this research was designed to reduce COD level in POME before POME it was discharged to the environment. The study aimed to optimize the factors that affect COD reduction from POME, and it was divided into three specific objectives: (1) determine the significant factors affecting COD reduction from POME, (2) determine the impact of manipulating variables on COD reduction from POME and (3) determine the optimum value of factors that contribute to COD reduction from POME. The novelty of this research was using C/N enriched inoculum from banana peel in a two-stage anaerobic reactor to determine its effects on COD reduction performance of POME A two-stage fermentation process and 350 L lab-scale reactors were used to treat POME. Five input factors were used which include pH, C/N, organic loading rate (OLR), hydraulic retention time (HRT), and sludge retention time (SRT). The Design Expert software was used for data analysis. The research findings found that the significant factors were pH, C/N, and OLR with p-values of 0.0001, 0.0227, and 0.0001 respectively. HRT and SRT also contributed to COD reduction although their contributions were not significant (p>0.05). The impact of these five factors was able to contribute up to 80% COD reduction and the lowest value of COD reduction contributed by these five factors is 57%. The findings in surface response diagrams revealed the optimum value of factors that affect COD reduction; 6.5 for pH, 26 for C/N, 8.5 kg/d.m3 for OLR, 7 days for HRT, 13 days for SRT, and 77% for COD reduction. The developed model was validated, and the results gave an average error within 6.72% and standard deviation error of 3.79%. In this study, banana peel which would normally be discarded upon consumption iv was used as inoculum to adjust the C/N to prepare substrate with POME. The findings demonstrated that the addition of banana peel achieved COD reduction up to 77%. Thus, this study justified that further research on POME should be done using different types of substrate and other contributing factors to achieve higher COD reduction from POME.