Factors regulating the density of bacteria in process waters of a paper mill

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Abstract
Variations in the numbers of total colonies of Klebsiella pneumoniae [a potential pathogen], Acinetobacter spp. and pseudomonads [potential slime formers] were investigated in process waters of a paper mill in southern Finland. Variations were related to independent parameters, i.e., temperature, pH, redox potential and production of offset paper, by using multiple regression analysis. Temperature was the most significant regressor variable and was negatively correlated with bacterial counts. It accounted for up to .apprx. 80% of the variance in bacterial counts in various parts of the process. The significance of temperature was due to its fluctuations in a critical range, above and below the maxima for bacterial growth. The pH level was also significant for total colony count and for K. pneumoniae. Redox potential and the production of offset paper were of significance for Acinetobacter spp. Washing the paper machine with water and lye decreased the numbers of bacteria in process waters.