The Big One That Did Not Get Away: Pilot Testing to Reach 12 µg TP/L in a Hatchery Effluent

In order to comply with the new ultra-low effluent phosphorus monthly limit of 12 µg/L, Powered Mill will, once completed, operate a state of the art water treatment plant with an upstream fish hatchery. Pilot testing completed earlier in 2022 included ultrafiltration with and without coagulant addition, ion exchange, and adsorption. The results showed that any individual technology was not capable of reliably meeting the phosphorus limit, but a combination of technology solutions could achieve the 12 µg/L limit. While the final selection is pending, the combination of ultrafiltration and downstream adsorption did meet the effluent limit while requiring minimal operator attention or chemicals; both of which are especially relevant in such a remote location. The pilot testing highlighted again the known challenges with measuring phosphorus at forensic levels. Split samples analyzed by different labs showed deviations as much as 100% between two results. This impacts both the evaluation of pilot results as well as future compliance monitoring and process control.