新規の多段型高温UASBリアクターによる高濃度脂質含有廃水の嫌気性処理特性

抄録

A novel multi-staged UASB (upflow anaerobic sludge blanket) reactor, which was originally developed by our research group, was applied to thermophilic treatment of a lipid-rich wastewater (dairy-milk). The reactor successfully reached a high COD loading of 35 kg COD/m³/d after 190 days operation, giving over 90% COD removal at a HRT of only 3.4 h for the influent 5000 mg COD/L, of which 50% is derived from lipid. This loading rate corresponds to two to three times as large as the maximum allowable loading rate of mesophilic conventional-type UASB reactor receiving the identical wastewater (our previousresult).
A severe deterioration of methane production occurred due to adsorption of LFA (long-chain fatty acids) to bacterial cell surfaces at the lower portion of sludge bed when the reactor temperature incidently dropped from 55°C to 45°C for a period of merely 12 hours. In order to clarify the mechanism of inhibitory effect of LFA adsorption, a separate vial-bottle activity test was conducted by using mesophilically-grown and thermophilically-grown granular sludge. Absorption of LFA caused more vital inhibition on the thermophilic sludge rather than the mesophilic sludge, due to cell lysis. Thermophilic acetate-utilizing methanogens were far more susceptible to LFA inhibition, compared with thermophilic hydrogen-utilizing methanogens.