Posted by: Green Knight | April 2, 2013

Leachate vs. Sludge

Recently, a site in the St. Louis area has been generating some controversy, and rightly so. It’s an old solid-waste landfill that was, for a time, a repository for some low-level radioactive waste left over from the Manhattan project. The place has had several ownership changes over the years, as they tend to do. A suburface fire has been ongoing for a couple of years, also not uncommon. I’m just getting over a really nasty flu, or I’d type about 20 pages of info here, but for the moment, I just want to draw attention to how the media gets its terminology wrong, because they don’t know any better, and thus the public doesn’t either.

Channel 5 has been doing a good overall job of covering the situation, but they recently interchangeably used the terms “leachate” and “toxic sludge.” WRONG, not the same thing. That’s where my alarm bells go off.¬† Leachate is what leaches out of solid waste in a landfill over time: the liquids left in almost-empty spray cans, the stuff that degrades from putrescible kitchen-scraps, and everything in between. Leachate is a nasty, smelly, LIQUID.

Sludge, on the other hand, is what’s left over when you drain or strain the liquid out of municipal wastewater. Think of all the solids that go down your drains. Ick. The sludge is what’s left after they filter-press or drain or otherwise remove the liquids from that waste stream. Think of a handful of mud with two handfuls of coffee grounds in terms of consistency. You don’t get sludge out of a landfill, you get leachate. As a former instructor, I just hate it when people use the terminology incorrectly.

[There’s also sludge from industrial practices, notably electroplating. Now THAT’S some nasty stuff, all laced with toxic heavy metals and cyanides.]



  1. Awesome article, thank you! Did want to point out, though, that the “landfill that ‘WAS, FOR A TIME’, a repository for some low-level radioactive waste”, was not just ‘for a time’, but STILL IS a repository for radioactive waste…..

    • What I meant was that it only received the radwaste for a certain period of time. I didn’t mean to imply that it was some sort of temporary holding facility. That’s why it had to be either a short post or 20 pages. I’m still getting over this dratted flu.

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