Plating operations are a huge headache. They have corrosive plating baths. They have to do some chemical processing on site to neutralize the corrosive chemicals and get them down to a neutral pH. Some years ago, a plating company in San Jose dumped a plating bath into the sewer system. This was so toxic that it killed the bacteria that reduce organic sludge at the sewerage plant. This knocked the whole plant offline…
Nuclear power plants have secondary and tertiary overflow reservoirs, intended to capture any uncontrolled dangerous outflow if things go wrong. I wonder if chemical plants have something similar, a way to contain an uncontrolled outflow of toxic stuff if the normal flow of neutralization fails. BTW this likely means quite a bit of land used up by such a reservoir which is ideally never needed, but must be present.
Wastewater plants have other ponds and tanks which are part of the process, and they're usually full, with liquid moving in and out, accompanied by stirring, air, and chemical injection. A big empty one is a backup system.
Real engineering.[1]
[1] https://www.epa.gov/sites/default/files/2014-09/documents/la...