Research showing coffee grounds take lead and copper out of drinking water came around a few years ago (here’s a good summary at  This was one of those “I wish I’d thought of that” ideas for many of us who do water treatment…it’s such an obvious thing to look at, in hindsight.

The researchers published an article (abstract here) called “Removal of soluble Cu and Pb by the automatic drip coffee brewing process: Application to risk assessment,” which says

The coffee brewing process removed 78 to 90% of both Cu and Pb from influent water.

Preliminary work with steeping teabags in metal spiked water showed little to no reduction in the soluble Cu and Pb concentration.

The idea is that lead and copper associate with organic matter in the grounds as water flows through, and, to a large extent, are retained.  (Will that affect compost made from these grounds?  Probably not to a significant extent, in my opinion.)  The authors further make the interesting point that risk assessments for lead and copper may need to be revisited for people who drink a lot of coffee in lieu of water.

I’m wondering, though, if this research has been (I can’t find anywhere, so far), or ought to be, extended to look at regulated organic compounds that can be present in drinking water, such as various disinfection byproducts. Surely the heating process (volatilizing certain compounds), and/or mechanisms similar to the one described by the authors of this study, will also reduce concentrations of these compounds, as well.

One thing is for sure: lead and copper concentrations in water would be unaffected by instant coffee.