Influence of particle size distribution on anaerobic degradation of phenol and analysis of methanogenic microbial community.

Sludge morphology considerably affects the mechanism underlying microbial anaerobic degradation of phenol. Here, we assessed the phenol degradation rate, specific methanogenic activity, electron transport activity, coenzyme F420 concentration, and microbial community structure of five phenol-degrading sludge of varying particle sizes (i.e., < 20, 20-50, 50-100, 100-200, and > 200 µm). The results indicated an increase in phenol degradation rate and microbial community structure that distinctly correlated with an increase in sludge particle size. Although the sludge with the smallest particle size (< 20 µm) showed the lowest phenol degradation rate (9.3 mg COD·gVSS-1 day-1), its methanogenic activity with propionic acid, butyric acid, and H2/CO2 as substrates was the best, and the concentration of coenzyme F420 was the highest. The small particle size sludge did not contain abundant syntrophic bacteria or hydrogenotrophic methanogens, but contained abundant acetoclastic methanogens. Moreover, the floc sizes of the different sludge varied in important phenol-degrading bacteria and archaea, which may dominate the synergistic mechanism. This study provides a new perspective on the role of sludge floc size on the anaerobic digestion of phenol.

Performance and recovery of a completely separated partial nitritation and anammox process treating phenol-containing wastewater.

Anammox process is considered as a promising technology for removing total nitrogen from low-strength ammonium and phenol-containing wastewater. However, it is still a challenge for the anammox process to treat high-strength ammonium and phenol-containing wastewater. A completely separated partial nitritation and anammox (CSPN/A) process was developed to remove total nitrogen from high-strength phenol-containing wastewater. About 92% of COD, 100% of phenol, and 82.4% of total nitrogen were successfully removed at a NH4+-N concentration of 200 mg L-1 with a phenol/NH4+-N mass ratio of 0.5 in the CSPN/A process. Furthermore, a shock loading of 300 mg phenol L-1 with a phenol/NH4+-N mass ratio of 1.5 led to a complete failure of partial nitritation, but the performance was rapidly recovered by the increase of NH4+-N concentration. Although the activities of ammonium-oxidizing bacteria and anammox bacteria were severely inhibited at a phenol/NH4+-N mass ratio of 1.5, the enrichment of efficient phenol degraders in the CSPN stage could strengthen the performance robustness of partial nitritation and anammox process. Therefore, this study presented a new insight on the feasibility of the anammox process for treating high-strength ammonium and phenol-containing wastewater.

Potential impact of methyl isobutyl ketone (MIBK) on phenols degradation in an UASB reactor and its degradation properties.

Methyl isobutyl ketone (MIBK) as a solvent is extensively used for the phenols extraction from the wastewater, so it is unavoidable to expose in the effluent due to the solubility and leakage problem. The present study evaluated the impact of MIBK on phenols degradation in an UASB reactor and analyzed its degradation properties. The results indicated that the continuous dosing (0.1gL-1) and impact (10gL-1) of MIBK had limited effect on phenols removal (1-2% reduction) in the UASB reactor, but the specific methanogenic activity (SMA) values of sludge decreased by 45-75% after MIBK exposure. Anaerobic degradation rate of MIBK fitted well to a pseudo-first-order kinetic equation with respect to the initial concentration of 35mgL-1 (k=0.0115h-1, R2=0.9664). Furthermore, the relative methane generation rate constants of MIBK were 0.00816, 0.00613, 0.00273, and 0.00207d-1 at the initial concentrations of 0.1, 0.5, 5, and 10gL-1, respectively. MIBK showed higher inhibitory effect on the methanogenesis than on phenols degradation. This study pointed out that the industrial installations should consider the influence of solvent on anaerobic treatment of phenolic wastewater.