Sludge sounds unattractive, and indeed usually is. Defined as, “a muddy or slushy mass, deposit, or sediment,” it’s the kind of thick, viscous goo you’ll find at the bottom of a pond. The thought of activating it conjurors up images of some science-fiction blob slithering through your town or city.
That’s actually not too far from reality. While it’s probably not in your neighborhood, activated sludge may well be just outside your city limits. The good news is that it’s far from harmful. In fact it’s positively beneficial as it forms an essential component of many large-scale wastewater treatment systems.