Akira TOYAMA

Reduction of Alkalinity Supplementation on a Thermophilic UASB Reactor by a Multi-Feed Mode

Hideki HARADA, Akiyoshi OHASHI and Hiyoyuki IMACHI


An upflow anaerobic sludge blanket (UASB) process has been applied for the treatment of various wastewaters. However, because of a conventional UASB process is almost a single feed mode, the accumulation of VFA frequently occur at the inlet. Therefore, to maintain a neutral pH within the reactor, the addition of external alkalinity is necessary.

Since the wastewater is separated by a multi-feed mode along the reactor height, it is supposed that the multi-feed mode can reduce the effect of acidogenic reaction and the cost of additional alkaline chemical. In this study, the effect of alkalinity reduction on the multi-feed mode compared with the single feed mode was investigated.

Under the low alkalinity addition at the loading rate 50 kgCOD/m3 (10,000 mgCOD/L, HRT 4.8 h), the multi-feed mode could tolerate the additional alkalinity concentration 0.02-0.04 gCaCO3/gCOD, whereas the single feed mode made the process failure at alkalinity concentration 0.1 gCaCO3/gCOD. Consequently, the multi-feed mode reduced about 1/5 (0.02/0.1) of the additional alkaline chemical compared with the single feed mode.