The effect of aromatic compounds on the work of activated sludge.

The resistance of bacteria occurring in activated sludge purifying refining-petrochemical wastewaters to phenol, cresol and pirocatechin as well as the possibility of the purification of synthetic wastewaters carrying high concentrations of these compounds by sludge composed of resistant strains was studied. The most toxic of the studied compounds was phenol. Six out of 29 strains were resistant to high concentration of phenol (1000 mg/l). Activated sludge synthesized from strains resistant to phenol, cresol and pyrocatechin was tolerant to high concentrations of these compounds. Worsening of the work of the sludge, expressed by decrease of GOD, was observed at the concentrations of phenol, cresol and pyrocatechin of 2000, 400 and 300 mg/l, respectively.