Sammendrag
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
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