I was wondering about the "Activated Sludge Troubleshooting Chart", which turns out not to be some McMurdo internal documentation, but a commercial product sold

I was wondering about the "Activated Sludge Troubleshooting Chart", which turns out not to be some McMurdo internal documentation, but a commercial product sold as a poster... for US$94.95! https://www.tetratech.com/en/markets/one-water/solutions/wastewater/wastewater-operations-posters/activated-sludge-troubleshooting-chart-2nd-edition https://www.tetratech.com/en/markets/one-water/solutions/was...