Analysis of the functional diversity of the microbial communities in a paper-mill water system

Abstract

Most microbiological studies of wastewater treatment systems rely on methods that are dependent on culturing. However, due to the limitation of conventional microbiological methods, alternative assays, such as the analysis of the functional diversity of the microbial communities using Biolog substrate utilisation profiles, have been proposed. The Biolog method was thus evaluated in a paper-mill water system. The influence of the production of various paper grades, biocide combinations and monthly maintenance shut-downs on the functional diversity of the microbial communities were determined using the Biolog technique. The communities in the planktonic as well as the sessile phases were analysed approximately every second week for a period of one year. The average well colour development (AWCD) technique was used to transform the data obtained from the Biolog plates prior to multivariate statistical analysis. Our results indicated that different microbial communities developed during the production of the different paper grades. A difference in substrate utilisation was evident after a single day of production of fluting or linerboard in the planktonic communities, while differences in the sessile communities only became significant after an extended period of production. The effect of the application of different biocides was more distinct in the planktonic than in the sessile populations. No clear trends concerning the influence of maintenance shut-downs and cleaning of machines could be observed in the sessile phase, while a shift in the microbial community could be observed in the planktonic phase. Biodiversity indices indicated that a high functional diversity existed in both the planktonic and sessile phases. It was concluded that the substrate utilisation profiles obtained with Biolog plates were a sensitive measure, which enabled the detecton of shifts in the microbial community function and possibly structure within the same water system.