TOXICITY OF PHENOL TOWARDS ANAEROBIC BIOGRANULES

Toxity of phenol towards upflow anaerobic sludge blanket (UASB) biogra nules treating wastewater containing different substrates was investig ated. Under shock-loading conditions, the specific methanogenic activi ty (SMA) of the biogranules decreased with the increase of phenol conc entration. The C-1.50 (i.e, the concentration at which bioactivity was 50% of the control) was 1750, 1000 and 1700 mg-phenol litre(-1) for a cetate-, propionate- and benzoate-degrading biogranules, respectively. Under continuous-loading conditions, however, phenol toxicity was not progressive. Instead, phenol had a threshold toxicity level for each type of biogranules: 1050-1600, >850 and 1100-1700 mg litre(-1) for be nzoate-, propionate- and acetate-degrading biogranules, respectively. Below these threshold levels, phenol was not inhibitive to the activit y of biogranules; but above them, the inhibition was nearly 100%. Phen ol toxicity was neither cumulative nor permanent. Once the phenol conc entration in wastewater was lowered to levels below the threshold, bio granules were able to gradually regain 100% of their activity. Lowerin g substrate concentration expedited the recovering process. (C) 1997 E lsevier Science Ltd.