[Study on 3-nitrophenol wastewater treatment in UASB]

Characteristics of anaerobic granules before and after acclimation, removal efficiencies of 3-nitrophenol (3-NP) and performance of 3-NP wastewater treatment were investigated in a lab-scale upflow anaerobic sludge bed (UASB). The results showed that granular sludge acclimatized to 3-NP rapidly during acclimation. Using SEM, the filamentous bacteria was the predominant bacteria on the surface of granules. Throughout the study of 3-NP wastewater anaerobic degradation, hydraulic retention time (HRT) and input COD concentration were kept constant as 26 h and 2 500 mg/L, respectively. While 3-NP concentrations increasing from 20 mg/L to 250 mg/L gradually, COD removal decreased from 95.2% to 85.1% and 3-NP removal efficiencies were always more than 99%. 3-AP was found to be the major intermediate during the degradation of 3-NP. Out of the total input of 3-NP concentration, on molar basis, about 58.7% - 111.9% of 3-NP was recovered in the form of 3-AP. With increasing 3-NP concentration, the variations of gas production were minimal. The minimum methane percentage was 65% and the maximum was 74%.