Use of Microelectrodes to Investigate the Effects of 2-chlorophenol on Microbial Activities in Biofilms

Abstract

In order to assess the applicability of using microelectrodes as a tool for inhibition tests, temporal and spatial inhibitory effects of 2-chlorophenol (2-CP) on O2 respiration and nitrification activities in municipal wastewater biofilms were investigated using microelectrodes for O2 and NH4+. The time-course microelectrode measurements demonstrated that 2-CP inhibited O2 respiration and nitrification activities within 6 to 18 min. The microbial activities were inhibited only in the upper 400 µm of the biofilms by 2-CP, and the bacteria present in the deeper parts of the biofilms were still active, probably due to limited penetration of 2-CP. These results could reasonably explain the difference in inhibitory ratios of the O2 respiration and nitrification activities in the biofilms. O2 respiration activity was incompletely inhibited, which was attributed to the presence of O2 respiration activities in the deeper parts of the biofilm. In contrast, nitrification activity was significantly inhibited because ammonia-oxidizing bacteria were present in the upper parts of the biofilm. These results indicate that the microelectrodes with a very quick response time and a high spatial resolution are useful tools to study temporal and spatial inhibitory effects of inhibitors on in situ microbial activities in biofilms