Evaluation of a small calcification plant specialized for calcium dosing by pH requirements in small rivers

Summary

To reduce/eliminate mixing zone effects and ensure salmon production in Monebekken, a calcification plant was established in 2018 as a developing project. The aim of this is to be able to deliver stable pH for salmon with affordable solutions, thus creating a standard for how such facilities should be when establishing in other acidic side waterways with salmon. This report is an assessment of whether the goal has been achieved. The plant doses dry lime right into the river, and is richly equipped to produce correct doses. Active parameter data is logged, and relevant data is used in the reporting work. The dosing plant was constantly dosed far more than desirable, but also had many cases of lack of dosing that resulted in acidic river and unsuitable conditions, especially for salmon smolt. The cause was often both for late start and stop of dosing in connection with flooding. The plant is oversized in relation to the need for dosing in small and medium tributaries of salmon. Pulse dosing is used on the plant. Reduced dosing time between breaks can set the dosage capacity more in relation to the need. Alternative dosing technique should be considered. Any new management system should be programmed so that the process signal downstream dose can be placed near the plant to reduce the feedback time at low water flows. It is proposed that a multivariate PID regulation technique is proposed specifically designed for rapid response in case of unwanted condition development. When using such a system, the pH upstream system will be superfluous as a control parameter