On-line titration of non-ionic surfactants in wastewater treatment plants using a specific electrode.

Textile finishing industry wastewater often contains high concentrations of surfactants. Non-ionic surfactants like alcohol ethoxylates are among the most used surfactants and are discharged from batch-processes in widely varying concentrations. The anaerobic biomass and especially methanogenic microorganisms have been shown to be inhibited by surfactants. To protect these microorganisms from irreversible inhibition a measurement of the surfactant concentration is useful for the process control, but most analytical methods are too complicated and expensive for an on-line process control. It was shown that the titration of non-ionic surfactants is possible in the presence of biomass and in wastewater from textile wet processes using the Metrohm NIO-electrode. Titration and sampling were successfully performed with standard equipment. The software used for the process control of a lab-scale anaerobic treatment plant was also used to evaluate the obtained titration curves. This allowed performing the titrations without using a more expensive titrator.