Reduction of alkalinity supplementation for acid-based wastewater treatment using a thermophilic multi-feed upflow anaerobic sludge blanket reactor

Generally, Shochu distillery wastewater treatment is required the addition of alkalinity agents for an increase of pH in the UASB reactor. However, to reduce the cost of alkalinity supplementation, cost-effective reactor operation method has been desired. This study aimed to reduce the alkalinity supplementation for a thermophilic (55°C) multi-feed up-flow anaerobic sludge blanket (MF UASB) reactor for the low-cost treatment of the wastewater from the production of the Japanese distilled alcohol called shochu. Shochu distillery wastewater contains high concentrations of organics (46,500-57,600 mgCOD L^-1; COD: chemical oxygen demand) and volatile fatty acids (16,200-25,000 mgCOD L^-1), and low pH (4.1-4.5). With alkalinity supplementation of 0.045 mgCaCO₃ mgCOD^-1 using 24% NaOH, the MF UASB reactor achieved an 87 ± 2% COD removal rate with an organic loading rate of 24 kgCOD m^-3 day^-1 for 554 days reactor operation (hydraulic retention time of 10 h and influent concentration of 10,000 mgCOD L^-1). The organic removal rate decreased to 19 ± 3% in the MF UASB reactor when alkalinity supplementation was reduced to 0.015 mgCaCO₃·mgCOD^-1. In this study , the minimum alkalinity supplementation was 0.045 mgCaCO₃ mgCOD^-1 at an organic loading rate of 24 kgCOD m^-3 day^-1.