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.
Keywords: shochu distillery wastewater; Thermophilic up-flow anaerobic sludge blanket (UASB) reactor; alkalinity; multi-feed; pH.