Paper machine for the production of paper containing waste paper and grass fibers

Paper machine for producing waste paper and paper containing grass fibers with: ?? a pulper for the introduction of waste paper and grass material as well as process water At least one support sieve onto which a mass with waste paper fibers provided by waste paper material introduced into the pulper and grass fibers provided by grass material introduced into the pulper can be applied with separation of any part of the process water in order to form a paper web， A process water return to return at least some of the process water for re-introduction into the pulper， A pH probe for recording a pH value of the process water， An addition device for adding probiotic bacteria into the process water， A metering device for metering a basic agent into the process water and A control system， the control system being set up， based on the measurement values ????of the pH probe recorded in the course of monitoring the pH value of the process water， the process water， which is originally obtained from fresh water， having a pH value in the range from 7.0 to 8.5， and to which a reduction in the formation of process-damaging microorganisms has been added probiotic bacteria， but not biocides， If the pH value measured with the pH sensor drops below a threshold value， the addition of the basic agent in increased doses is to be caused by the metering device in order to achieve a setting of the pH value of the process water to a target value and the pH value to keep at the target value， the threshold value of the pH being at least 0.2， in particular at least 0.3， greater than the target value.