A method is disclosed for producing paper containing waste paper fibers and grass fibers. In a pulper, waste paper material and grass material and process water are introduced. A mass with waste paper fibers provided by the waste paper material introduced into the pulper and with grass fibers provided by the grass material introduced into the pulper is applied to at least one carrier screen with separation of at least part of the process water in order to form a paper web. In any case, part of the process water is fed back into the pulper for reintroduction. The process water is originally obtained from fresh water, which has a pH value in the range from 7.0 to 8.5. Probiotic bacteria, but not biocides, are added to the process water to reduce the formation of process-damaging microorganisms. The pH value of the process water is monitored, and if the pH value is detected to fall below a threshold value, an increased dose of a basic agent is added in order to adjust the pH value of the process water to a target value and to increase the pH value to keep the target value. The threshold value of the pH value is at least 0.2, in particular at least 0.3, greater than the target value.
展开▼
