Its great to know that sensors from Proteus Instruments and wireless RTUs are hard at work in rivers and WWTWs in Northern Ireland providing real-time BOD, COD, coliform and water quality data. If you can measure it you can manage it...
https://www.theguardian.com/environment/2021/dec/15/7m-tonnes-of-raw-sewage-a-year-discharged-into-northern-irish-rivers21st Dec 2021