Needle-type environmental microelectrode sensors for biofilm study in aqueous systems

The development of needle-type environmental microsensor techniques is a revolutionary advancement in the temporal and spatial measurement of both absolute levels and changes in chemical and biological species in engineered and natural aquatic systems. This advancement has utilized microscopic monitoring to contribute a greater understanding of biological mechanisms for decades. Biofilm plays a major role in many water reclamation and reuse technologies as well as bioremediation of contaminated soil. On the other hand, control of biofilm formation and growth in drinking water has been a great challenge. It is important to understand the dynamics of biofilm structure and function, reaction mechanisms, and related kinetics for better use or control of the biofilm for its appropriate purpose. A needle-type electrochemical microsensor represents one of the most prominent, novel methods for studying biofilms. Various kinetic parameters including net specific consumption and production rates can be estimated from the measured concentration profiles. This paper will demonstrate needle-type electrochemical microsensors, which are capable of probing the full depth of a biofilm, determining the profile of the relevant water quality parameters (e.g., monochloramine, free chlorine, phosphate, ammonia, dissolved oxygen, nitrate, nitrite, and pH) with high spatial and temporal resolution, and enabling calculations of the relative contribution of biofilm activity. Their applications to various biofilm systems from wastewater treatment processes to drinking water distribution systems will be addressed.