EFFECT OF ORGANIC LOAD AND ALKALINITY ON DAIRY WASTEWATER BIOMETHANATION

This study aimed to evaluate the effect of variations in organic load (hydraulic retention times - HRTs: from 2 to 0.5 day) and in alkalinity (NaHCO3 from 4,000 to 1,000 mg.L−1) on methane production. Biomass of sewage sludge was inoculated and stabilized on 1" polypropylene rings. The rings were immersed in the liquid phase (8.41 L) of an upflow anaerobic filter reactor (12.22 L). A solution of 5 g of whole milk powder per liter was used to simulate effluent from the dairy industry. Process effectiveness was measured by chemical oxygen demand reduction, biogas production, and biogas methane content. Biogas production started at a 2-day HRT and synthetic effluent alkalinization with 4,000 mg.L−1 NaHCO3. The best operation condition was at 1-day HRT and with the addition of 4,000 mg.L−1 NaHCO3. Biogas production reached 1.5 NL of biogas per L of reactor liquid phase, with 68% of methane and a concomitant reduction in COD of 57%.