Microbial community organization during anaerobic pulp and paper mill wastewater treatment

Abstract

Amplicon sequencing data and operating data from anaerobic wastewater treatment plants from three Canadian pulp and paper mills were used to explore the microbial community organization and identify relationships between organisms and operating conditions. These relationships were identified using Local Similarity Analysis (LSA). Each of the digesters contain two or three modules consisting of organisms that cover the entire anaerobic digestion process, i.e. hydrolysis, fermentation/acidogenesis, acetogenesis, and methanogenesis. These modules are functioning relatively independent from each other, and their relative abundance changes as a response to the varying operating conditions. The time delay between a change in digester operation and the change in the abundance of microorganisms was investigated using time-lagged operating parameters. Numerous correlations could only be identified by applying time lags at daily intervals. This time delay usually ranges between two to four days and is likely influenced by the growth rates of the anaerobic microorganisms and the hydraulic retention time of the digesters. The effects of single digester upset events on the change in microorganism abundance in the three mills were investigated. Plant shutdown periods and organic overload caused a drastic increase in the population of acetoclastic methanogens, acidogenic fermenters, and syntrophic acid degraders. As a response to impaired process conditions, the sameMethanothrixamplicon sequence variant (ASV) dominated methanogenesis in the digesters of all three mills. The common characteristics of the organisms represented by this ASV should be further investigated for their role in alleviating the impact of digester upset conditions.