Removal of soluble Cu and Pb by the automatic drip coffee brewing process: Application to risk assessment

Abstract

Three commercial brands of coffee were examined for sorption of Cu and Pb. We kept experimental conditions close to those in ordinary situations by using an automatic drip coffee maker. One‐liter increments of de‐ionized water spiked with increasing amounts of Cu and Pb were used to make pots of coffee. Influent (water) metal concentration was then compared with effluent (coffee) metal concentration. We kept influent metal concentrations in ranges that might be expected due to contamination from storage tanks and pipes in municipal water delivery systems (0.1 to 5.0 mg/L). The coffee brewing process removed 78 to 90% of both Cu and Pb from influent water. We ran experiments by varying coffee strength (function of bed depth) and varying brewed coffee volume (function of bed depth and water volume) . Most of the metal that goes through the coffee bed does so in the early stages of the brewing process before the coffee bed is wetted. The main factor influencing removal of soluble metal by coffee is contact time with the wetted coffee bed. Therefore, the strength and/or volume of coffee brewed play a critical role in metal removal. Preliminary work with steeping teabags in metal spiked water showed little to no reduction in the soluble Cu and Pb concentration. Results of this study are important for risk assessment model formulations. Daily human exposure to Cu and Pb from municipal water systems may be grossly overestimated if a large proportion of tapwater ingestion by an individual is filtered through coffee.