05Limits
What this record does not establish.
The saving is arithmetic on a reduced purchase rather than a measured outcome, and how the 54 per cent was arrived at is not shown — no carbon dose is published at either end. No treatment window is given beyond the annual figure, and nothing is recorded about what the influent did across it. Nothing was left untreated and the works is not named. Reducing a chemical you were buying is a real result; it is not the same thing as a reduction in the material itself.
Only the volatile organic fraction of a sludge responds to any of this. Grit, sand, silt, mineral precipitates and plastics remain at any dose, here and everywhere else.