Reduction of Alkali Supplement in a Pilot-Scale Thermophilic Multi-Staged UASB Reactor Treating Alcohol Distillery Wastewater

One of the main disadvantages of anaerobic wastewater treatment at a low pH is the significant operational cost due to the addition of necessary alkali. To reduce alkali supplement and thus the cost, this study proposes a sequential multi-feed (SqMF) mode (distributed feeding) and effluent recycle (ER) mode. Experiments were conducted with a pilot-scale (2.5 m3) thermophilic (55°C) multi-staged up-flow anaerobic sludge blanket reactor. Alcohol distillery wastewater (shochu), a major source of industrial wastewater in Japan, was used for the study. The SqMF mode of operation (influent pH: 5.0; organic loading rate: 45 kgCOD/m3/day; HRT: 12 hours; influent COD concentration: 20,900 mgCOD/L) successfully reduced the alkali supplement (24% NaOH solution) requirement by 67.2% compared with the single-feed mode. For the ER mode operation (organic loading rate: 35 kgCOD/m3/day; HRT: 12 hours; influent COD concentration: 17,400 mgCOD/L), operation was possible without any alkali supplement since the system uses the alkalinity generated during microbial metabolism.