This past weekend the cub scouts toured the local waste-water treatment plant. I was surprised to learn that many of the processes they use these days are biological (biochemical) rather than chemical. As a taxpayer, I approve heartily: bacteria, protists, and rotifers do their work for practically nothing.
Another thing that surprised me was how little the place smelled. They’ve done wonders for managing the odor. Still, I don’t think this sign is really necessary: