Document Type : Original Research Paper
Department of Civil and Environmental Engineering, Kagoshima National College of Technology, 1460-1 Shinko, Hayato-cho, Kirishima, Kagoshima, 899-5193, Japan
Department of Civil and Environmental Engineering, Tohoku University, 6-6-06 Aoba, Aramaki, Aoba ku, Sendai, Miyagi, 980-8579, Japan
Department of Civil and Environmental Engineering, Nagaoka University of Technology, 1603-1 Kamitomiokamachi, Nagaoka Niigata, 940-2188, Japan
Department of Social and Environmental Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashihiroshima, Hiroshima, 739- 8527, Japan
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.