Phenol degradation in horizontal-flow anaerobic immobilized biomass (HAIB)reactor under mesophilic conditions

A bench-scale horizontal-flow anaerobic immobilized biomass (HAIB) reactor was assayed aiming to verify its potential use for phenol degradation. The HAIB reactor consisted of a bore-silicate tube (100 cm long; 5.04 cm diamet er) filled with polyurethane foam matrices containing immobilized anaerobic sludge. Before being subjected to phenol, the reactor was fed with synthet ic substrate at the influent chemical oxygen demand (COD) of 1,028 mg.l(-1) achieving 98% of COD removal efficiency. Thereafter, phenol as the sole ca rbon source was added under step-increasing concentrations from 50 to 1,200 mg.l(-1). Phenol degradation was evaluated by gas chromatographic analysis of influent and effluent samples. Process monitoring included determinatio ns of pH, volatile acids, alkalinity and COD. The HAIB reactor was operated at a constant hydraulic detention time (HDT) of 12 hours. After 33 days wi th 50 mg/l of phenol in the influent, the reactor achieved 98% of COD remov al efficiency. Successful phenol degradation (efficiency removal of 99%) oc curred for influent concentrations of 100, 300, 600, 900 and 1,200 mg.l(-1) after 143, 58, 47, 29 and 7 days, respectively. The predominance of Methan osaeta-like, rods and methanogenic cocci could be observed in all the opera ting conditions, besides the presence of phenol oxidizing microorganisms as irregular rods. The results indicate that phenol degradation at very high rates can be accomplished in HAIB reactors containing acclimatized biomass.