Interest in continuous monitoring has reached a new level as additional parameters are becoming more available for on-site analyses.&nbsp; One such area is that of trace metal analysis in process water.&nbsp; Trace levels of multiple metals can enter a water stream from a variety of locations and sources.&nbsp; Some may be brought in at the source while others may be introduced in the process itself.&nbsp; In either case, they must be considered regarding their potential impact downstream. The ability to detect the presence, as well as concentration levels of trace metals, can be critical especially when this water will be discharged into a regulated body of water.&nbsp;As process operations become tighter and environmental restrictions become more stringent, it is sometimes not enough to simply take random or even periodic grab samples to monitor concentrations of heavy metals.&nbsp; These contaminants can be detrimental in the steam cycle as well as in the incoming, cooling and wastewater streams of a facility.While trace amounts of some heavy metals are important for certain biological processes and for life, others pose a danger to humans, plant hardware and/or the environment.&nbsp; The presence of metals such as manganese, aluminum and iron can cause damage to both plant hardware and the environment.&nbsp; Others such as antimony, selenium and arsenic are highly toxic even at trace levels.&nbsp; As chromium, arsenic, cadmium, mercury, and lead have a strong affinity for sulfur, they can easily bind to enzymes in the human body which control the speed of metabolic reactions. Hexavalent chromium, manganese, cobalt and arsenic are&nbsp;carcinogens while antimony is a suspected carcinogen.&nbsp; Cadmium causes a&nbsp;degenerative bone disease. Mercury, lead and manganese damage the&nbsp;central nervous system.&nbsp; This list is not exhaustive, but an indication of some of the negative impacts that these metals can have even at very low levels.Permitted levels of discharge of these various metals into streams, river, lakes or other bodies of water can vary by industry and location.&nbsp; They are normally governed by a facility’s National Pollutant Discharge Elimination System (NPDES) permit.&nbsp; In general, antimony, arsenic, cadmium, chromium, copper, lead, mercury, nickel, selenium, silver, and zinc are among the metals regulated.&nbsp; Effluent limitations guidelines and standards are established by EPA for different non-municipal (i.e., industrial) categories.&nbsp;These guidelines are developed based on the degree of pollutant reduction attainable by an industrial category through the application of pollutant control technologies.&nbsp;It will not be part of the scope of this discussion to provide an overview of these methods.&nbsp; Instead, the intent here is to introduce some on-line techniques that can be used in monitoring trace level metals, though it is not implied that they are applicable for complying with NPDES permits or any EPA monitoring requirements.Multiple metals will be considered using two different monitoring techniques.&nbsp; One is an on-line colorimetric method with an option for digestion to allow determination of both dissolved and total concentrations.&nbsp; The other is stripping voltammetry which permits concentration of trace level metals followed by analysis.&nbsp; Some specific examples of these measurements in power facilities will be discussed.

Novel On-Line Methods for Monitoring Discharge of Trace Metals From a Power Generation Site

Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2021/volume/85109

ASME 2021 Power Conference (POWER2021)

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