Capillary electrophoresis for continuous nitrogen quantification in wastewater treatment processes

A water quality analyzer based on the working principle of capillary electrophoresis (CE) was developed to determine ionic inorganic nitrogen compounds contained in wastewater samples. The instrument provides simultaneous quantification of anions and cations by superimposing hydrodynamic pumping with electrokinetic motion. It features a single separation capillary with contactless conductivity detection and a sequential injection manifold for fluid handling. Dynamic adaption of the system calibration was enabled by the use of a high precision pressure regulator to cover a wide measurement range showing low relative standard deviations (< 2 %) and high measurement accuracy comparable to conventional wastewater analyzers. The prototype is transportable, integrated in a 19 in. rack and connected to a membrane filter system developed for direct sample aspiration in the wastewater process. For operation on site, only a power supply and a network connection for remote control is necessary. Continuous operation was demonstrated over 24 h at the aeration tank of a pilot scale wastewater treatment plant at TU Wien and a good correlation with laboratory results was achieved. At this time, there is no device available, on the market, to analyze all nitrogen species in one assembly with limited hardware complexity and chemical demand. This entails a significant step forward towards automated water quality monitoring with respect to the implementation of new advanced wastewater treatment technologies.