Effect of calcium chloride on abating inhibition due to volatile fatty acids during the start-up period in anaerobic digestion of municipal solid waste

Biomethanation of municipal solid waste (MSW) is a slow process and the yield of biogas is usually low. The present study was carried out to examine the effect of calcium chloride (CaCl₂) on anaerobic digestion of MSW. Three anaerobic digesters with different concentrations of CaCl₂ namely sample without additives (Control), sample with 2.5g/LCaCl₂ (R1) and sample with 5g/LCaCl₂ (R2) were studied separately and the significant results are presented. From the experimental results, it was observed that pH decreased with an increase in the dosage of CaCl_2. Total solids and volatile solids reduction percentage in digester R2 was considerably lower than Control and R1 digesters. The significant positive correlation with small increments in volatile solids and chemical oxygen demand (COD) reduction were observed with an increase in pH. The cumulative biogas production in all the three digesters (Control, R1 and R2) were observed to be 35.38, 46.46 and 37.56L, respectively. It was also observed that the volatile fatty acids (VFAs) removal efficiency in digester R1 was the best among all the three digesters. A comparison of the effluent characteristics revealed improvement in the overall performance of the digester R1 amended with 2.5g/LCaCl₂ over the other two digesters.