ORIGINAL PAPER Heterogeneity and spatial distribution of bacterial background contamination in pulp and process water of a paper mill K. Milferstedt • J. -J. Godon • R. Escudie ´ • S. Prasse • C. Neyret • N. Bernet Received: 31 May 2012 / Accepted: 29 August 2012 / Published online: 25 September 2012 Ó Society for Industrial Microbiology and Biotechnology 2012 Abstract Identifying the source and the distribution of bacterial contaminant communities in water circuits of industrial applications is critical even when the process may not show signs of acute biofouling. The endemic contamination of facilities can cause adverse effects on process runability but may be masked by the observed daily variability. The distribution of background commu- nities of bacterial contaminants may therefore be critical in the development of new site-specific antifouling strategies. In a paper mill as one example for a full-scale production process, bacterial contaminants in process water and pulp suspensions were mapped using molecular fingerprints at representative locations throughout the plant. These eco- logical data were analyzed in the process–engineering context of pulp and water flow in the facilities. Dispersal limits within the plant environment led to the presence of distinct groups of contaminant communities in the primary units of the plant, despite high flows of water and paper pulp between units. In the paper machine circuit, commu- nity profiles were more homogeneous than in the other primary units. The variability between sampled commu- nities in each primary unit was used to identify a possible point source of microbial contamination, in this case a storage silo for reused pulp. Part of the contamination problem in the paper mill is likely related to indirect effects of microbial activity under the local conditions in the silo rather than to the direct presence of accumulated microbial biomass. Keywords Bacterial community analysis Á Contamination Á Dispersal Á Storage silo Á Paper mill Introduction The discharge of used water from modern paper mills has continuously decreased over the last decades because of environmental concerns [1, 3]. In order to maintain the necessary flow rates of process water, water reuse has increased at the cost of spreading microbially contaminated process water throughout the facilities, leading to increased fouling of equipment and the deterioration of end products. Minimizing the contamination of production facilities has therefore been a major objective in papermaking. Also, manufacturers in the food, chemical, or oil industries pay substantial amounts of money for controlling biofouling and microbial contamination. In paper mills, these amounts are justified by achieving more stable operating conditions (e.g., pH and reduction–oxidation potential, dissolved organic carbon concentrations) while minimizing the use of additives (e.g., hydrogen peroxide, caustic soda). In modern paper mills, the continuous presence of a microbial contamination in the process water directly leads to visible slime formation on air-exposed surfaces receiv- ing aerosols and projections from the paper machine. Less visible but equally severe indirect effects are caused by the degradation of paper additives and the unfavorable alter- ation of pulp properties [3]. For example, released organic acids from fermentation reactions may dissolve the com- mon additive calcium carbonate and increase the ionic strength in the water phase. Among other problems, this K. Milferstedt (&) Á J.-J. Godon Á R. Escudie ´ Á N. Bernet INRA, UR0050, Laboratoire de Biotechnologie de l’Environnement, Avenue des Etangs, 11100 Narbonne, France e-mail: kim.milferstedt@supagro.inra.fr S. Prasse Á C. Neyret Centre Technique du Papier (CTP), Domaine Universitaire BP 251, 38044 Grenoble Cedex 9, France 123 J Ind Microbiol Biotechnol (2012) 39:1751–1759 DOI 10.1007/s10295-012-1196-8