Response of low-strength phenol-acclimated activated sludge to shock loading of high phenol concentrations

Abstract

The objectives of this study were to: (i) evaluate the growth of low-strength phenol-acclimated activated sludge, (ii) investigate the degradation pathways and (iii) model the growth and biodegradation kinetics, all under the condition of increasingly higher phenol concentrations (step-up shock loading). With the use of activated sludge acclimated to phenol concentration of 140 mg·ℓ-1 (low-strength phenol-acclimated activated sludge), complete degradation of phenol with a COD removal efficiency of more than 95% was achieved up to 1 050 mg·ℓ-1 of initial phenol concentration. At low initial phenol concentrations, the experimental results were indicative of the meta-cleavage pathway for phenol degradation. When the initial phenol concentration was above 630 mg·ℓ-1, the degradation results were indicative of both meta- and ortho-cleavage pathways. The values of the Haldane kinetic parameters indicated a low degree of inhibition exerted by the presence of increasing phenol concentration. This was substantiated by the observation that the rate constant of phenol removal decreased by only 33% even though the initial phenol concentration was increased by 15 times from 70 to 1 050 mg·ℓ-1. Thus, the activated sludge acclimated to only 140 mg·ℓ-1 of phenol could successfully treat up to 1 050 mg·ℓ-1 of phenol without experiencing complete inhibition during the degradation process.