Abstract
Laboratory scale continuous-flow activated sludge reactors were operated using synthetic wastewater containing phenol as a toxic organics, m-aminobenzoic acid (m-ABA) as a refractory organics and inorganic nutrients to clarify the effects of powdered activated carbon (PAC) on removal of the toxic and refractory organics. The performance of the activated sludge system operated with the addition of PAC was compared with that of the system operated with the addition of bentonite (BEN), the system operated with the addition of raw material of PAC (NAC) having no ability to adsorb and the system of conventional activated sludge (AS).
Concentrations of DOC, phenol and m-ABA in the effluent of the reactor with PAC were much lower than those when other adsorbents were used. Especially, the m-ABA were not detected (< 0.2mg·l-1) in the effluent from the reactor with PAC, while those for BEN, NAC and AS were 80, 75 and 80 mg·l-1, respectively. Because contribution of adsorption of m-ABA on PAC to the removal of m-ABA was negligible, m-ABA was considered to be removed through biodegradation. Thus, biodegradation activity to phenol and m-ABA were much improved by the addition of PAC.
The microbial compositions in these systems were also determined by viable counts using nutrient broth medium, phenol-selective medium, and m-ABA-selective medium and by quinone profiles, respectively. As results, the microbial compositions in these systems were almost the same, irrespective of the difference in support media. Therefore, improvement of the biodegradation activity with the addition of PAC would be explained from the increase of individual bacterial activity due to the addition of PAC to activated sludge.
