Mercury – Wastewater Treatment Options for a Capricious Element

Mercury is a persistent and capricious element that readily changes species in laboratory wastewater and process wastewater discharges. Although there is a movement toward mercuryfree chemicals and products, many older laboratory and research facilities are still dealing with unpredictable wastewater discharges of mercury from sediments that have historically accumulated in waste drains and piping. Options for addressing elevated mercury wastewater discharge concentrations are often limited to treatment or pipe rehabilitation/replacement. In most older laboratory buildings, pipe rehabilitation and/or replacement is typically cost prohibitive because the acid drains and piping are commonly above or below occupied research areas that cannot be disturbed or they are obstructed by other utilities as the result of generations of facility infrastructure upgrades. This paper provides a summary of options available for older research laboratories and institutions based on treatability and pilot testing experience using granular activated carbon (GAC), ion exchange (IX) and indexing belt filtration as a means to lower mercury levels below common local POTW effluent limits for mercury (1.0 part per billion). The three treatment technologies to be presented have each demonstrated varying levels of success in removing mercury from laboratory wastewater, depending on the nature of the wastewater stream. This paper will provide design issues to consider when evaluating treatment options and will emphasize the importance of treatability and pilot testing when considering each of the treatment technologies.