Method for predicting or controlling microbial status of a paper or board making process

A method for controlling microbial status of a paper or board making process or quality of the dry board or paper obtained from said process, the method comprising:

• a) measuring at multiple time points a surface level and duration of time in at least one pulp storage tower, broke storage tower, or broke pulper, and determining at the same time points at least one key performance index (KPI) of said process or of paper or board obtained from said process;
• b) defining, using a computing device a correlation between said measured surface levels and durations of time in the at least one pulp storage tower, broke storage tower, or broke pulper in relation to determined values of the at least one KPI of said process or of paper or board obtained from said process;
• c) from the correlation defining a surface level limit and defining a limit of duration of time during which the measured surface level exceeds the surface level limit wherein the at least one KPI value was within an acceptable range;
• d) continuously monitoring surface level information of at least one pulp storage tower, broke tower or broke pulper, using a computer controlled tower level sensor and providing the surface level information in real time to computer controlled timer programmed to turn on when the surface level information exceeds the surface level limit and reset itself when the surface level information drops below a lower predetermined level;
• f) wherein an increased risk of higher microbial activity is determined when time recorded by the timer is as long or longer than the limit of duration of time defined in step c), and then the surface level of at least one pulp storage tower, broke tower or broke pulper is decreased and/or a microbial control agent is added into the process in response to the increased risk of higher microbial activity.