The aim of this study is to contribute to the knowledge about 2-Chlorophenol (2CP) mineralization and methanization in batch culture. This work was focused on evaluating the effect of: (i) the use of sludge with different periods of previous contact to 2CP, (ii) the electron donor addition in stoichiometric relation with 2CP and (iii) the presence of different initial oxygen concentrations. When compared with the control, 50 and 80 days of previous contact to 2CP resulted in a lag phase reduction of 57% and an increase in 2CP specific consumption rate (q2CP) of 114%. These results were obtained with no addition of an external electron donor. When acetate was used as an electron donor its consumption resulted independently of 2CP consumption. No lag phase and increase of 46% in q2CP was observed when phenol was used as an electron donor. In the third part when sludge without previous contact to 2CP was used, it was found that consumption efficiency (E2CP) and q2CP values did not increase in the presence of different oxygen concentrations. However, at the highest oxygen concentration, CH4 yield (YCH4-C/2CP-C) and phenol yield (Yphenol-C/2CP-C) values decreased, while CO2 yield value (YCO2-C/2CP-C) increased with regard to the methanogenic control. The use of sludge previously exposed to both 2CP and O2 resulted in an increase in q2CP of 73%. However, among the different oxygen concentrations, no significant difference in E2CP or q2CP values was observed when compared to the control without oxygen. Therefore, previous contact to 2CP resulted in being a key factor for improving 2CP mineralization and methanization in batch culture.
Keywords: 2-Clorophenol (2-CP), electron donors, methanogenesis, sludge acclimation