Biodegradation of Phenol with Wastewater as a Cosubstrate in Upflow Anaerobic Sludge Blanket

Anaerobic degradation of phenol mixed with a readily degradable synthetic wastewater (DSWW) as a cosubstrate was studied in a $12\mathrm{L}$ upflow anaerobic sludge blanket reactor at $30\pm 2°\mathrm{C}$ over a period of $632\text{days}$ . DSWW was prepared by diluting sugar cane based molasses. The biomass was acclimatized to high phenol concentration by gradually decreasing the DSWW chemical oxygen demand (COD) of $\mathrm{4,000}\mathrm{mg}∕\mathrm{L}$ . Feed made up of phenol COD and DSWW COD in the ratio of 7:3 (phenol $\text{concentration}=\mathrm{1,176}\mathrm{mg}∕\mathrm{L}$ ) was successfully treated at a hydraulic retention time (HRT) of $12\mathrm{h}$ and organic loading rate (OLR) of $8\mathrm{g}\mathrm{COD}∕\mathrm{L}\text{day}$ . Phenol removal ranged from 99.9 to 84% at phenol COD varying from 10 to 70% in the feed. During the entire operation, COD removal varied from about 74 to 91.3%. The influent COD was distributed into $\mathrm{C}{\mathrm{H}}_4–\mathrm{COD}$ $(\sim 72\%)$ , effluent COD $(\sim 17\%)$ , and sludge and unaccounted COD $(\sim 11\%)$ . The process failure occurred at 4:1 phenol COD: DSWW COD. Specific methanogenic activity of granular sludge exhibited uniform activity up to phenol COD of 70%. The performance of the reactor could not be maintained beyond 70% phenol COD even by reducing the sludge loading rate, increasing HRT, or decreasing OLR.