Abstract
In the wood-free paper industry, whitewater is usually a mixture of additives for paper production. We are currently lacking an efficient, cost-effective purification technology for their removal. In closed whitewater cycles the additives accumulate, causing adverse production problems, such as the formation of slime and pitch. The aim of our study was to find an effective bio-based strategy for whitewater treatment using a selection of indigenous bacterial isolates. We first obtained a large collection of bacterial isolates and then tested them individually by simple plate and spectrophotometric methods for their ability to degrade the papermaking additives, i.e., carbohydrates, resin acids, alkyl ketene dimers, polyvinyl alcohol, latex, and azo and fluorescent dyes. We examined correlation between carbon source use, genera, and inoculum source of isolates using two multivariate methods: principal component analysis and FreeViz projection. Of the 318 bacterial isolates, we selected a consortium of four strains (Xanthomonadales bacterium sp. CST37-CF, Sphingomonas sp. BLA14-CF, Cellulosimicrobium sp. AKD4-BF and Aeromonas sp. RES19-BTP) that degrade the entire spectrum of tested additives by means of dissolved organic carbon measurements. A proof-of-concept study on a pilot scale was then performed by immobilizing the artificial consortium of the four strains and inserting them into a 33-liter, tubular flow-through reactor with a retention time of < 15 h. The consortium caused an 88% reduction in the COD of the whitewater, even after 21 days.
Highlights
The pulp and paper (P&P) industry is a major consumer and severe polluter of water resources
We prepared a whitewater treatment solution using an artificial consortium of preselected indigenous bacterial strains that efficiently degrade organic additives used in papermaking
We isolated a total of 318 bacterial strains from three inoculation sources, from which we successfully identified 95 by 16S 16S ribosomal ribonucleic acid (rRNA) gene sequencing
Summary
The pulp and paper (P&P) industry is a major consumer and severe polluter of water resources. With woodfree paper, the production demands call for large volumes of water per ton of wood-free paper (Hamm and Schabel, 2007; Suhr et al, 2015). The trend in the P&P industry to reduce water consumption by completely closing the process water (whitewater) cycles (Hubbe et al, 2016) has not been adopted by the majority of paper mills (Suhr et al, 2015), since the resulting accumulation of additives used in papermaking adversely affects the production process. To facilitate the closure of water cycles the whitewater can be treated to reduce the amount of accumulated organic matter and microbial growth (Hubbe et al, 2016). In the wood-free paper industry, whitewater might be easier to treat, because it lacks recalcitrant woody compounds like lignin.
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