Simultaneous removal of phenol, ortho- and para-cresol by mixed anaerobic consortia

Two different anerobic consortia, one removing phenol and ortho- (o-) creso l and the other removing para(p-) cresol, were cultivated in serum bottles using whey as cosubstrate substitute for proteose peptone. Phenol and p-cre sol removal with the phenol-removing consortium were the same with 0.0125% (w/v) whey as with 0.05% proteose peptone. For the other consortium, 8 days were required to decrease the p-cresol concentration from 35 to 2 mg/L wit h 0.025% whey, while 35 days were required to achieve a similar removal wit h 0.5% proteose peptone. The two consortia were mixed and cultivated with 0 .025% whey. Phenolic compound removal with the mixed consortia was as good as that achieved by each of the two initial consortia against their respect ive substrates. This removal activity was maintained after several transfer s. In a continuous upflow fixed-film reactor, the mixed consortia removed o ver 98% of 150 mg/L of phenol and 35 mg/L of each o- and p-cresol in the in fluent at 29 degrees C, with 0.025% whey as cosubstrate. The hydraulic rete ntion time (HRT) was 0.25 day, corresponding to a phenolic compound volumic loading rate of 880 mg/(L of reactor x day). Once the continuous flow reac tor achieved constant phenolic compound removal, no intermediates were foun d in the effluent, while in serum bottles, m-toluic acid, an o-cresol inter mediate, accumulated. Measurements of the specific activity for the uptake of different substrates demonstrated the presence of all trophic groups inv olved in methanogenic fermentation. These activities were, in mg of substra te/(g of volatile suspended solids x day), as follows: 849 +/- 25 for the a cidogens; 554 +/- 15 for the acetogens; 934 +/- 37 for the aceticlastic met hanogens; and 135 +/- 15 for the hydrogenophilic methanogens. Electron micr ographs of the mixed consortia showed seven different morphological bacteri al types, including Methanotrix-like bacteria.