Influence of nonionic surfactants and biocides on the anaerobic stages of paper mill waste water treatment plants

摘要

The majority of German paper mills utilize recovered paper as raw material. Recovered paper is known as perfect inoculum to process water cycles of paper production. To prevent microbial induced impacts on runability and paper quality a wide variety of nonionic surfactants and biocides is commonly used. Most additives have been specially developed and customized for application in these process water systems. However, only little information concerning the influences of those additives on anaerobic waste water treatment stages is known. Furthermore some observation in industrial use seemed to support the idea that nonionic surfactants affect the performance of anaerobic waste water plants. Aim of this work was to determine the impact of different additives (volume enhancers, biocides, deposit dispersants) on anaerobic digestion. Both batch and continuous trials were carried out. Batch trials took place in glass bottles (1 L) with a corresponding biogas measuring device on top. Continuous trials were carried out in UASB reactors (Plexiglas®, 30 L), that were fed in bypass to an industrial plant. Biogas production, COD degradation, acid concentration, pH-values and temperature were measured regularly. The batch tests showed that all studied additives only had very little influence on system stability and biogas production in intended concentrations. For very high concentrations some impacts on COD degradation and biogas production were detected. To cover long term effects of additive dosages into an anaerobic treatment stage the continuous trials were carried out. Comparison with a reference system did not show any negative influences of dosage in intended concentrations.