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ABBREVIATIONS
COD
chemical oxygen demand
PE
polyethylene
PVC
polyvinylchloride
Re
Reynolds number
TOC
total organic carbon
τ
shear stress [N m−2]
INTRODUCTION
Biofouling is encountered in most water systems and concerns microorganism accumulation and growth on wetted surfaces. It affects industrial equipment and leads to serious operational dysfunctions as well as significant treatment costs. Biofouling has been associated with performance losses (Flemming 2002), corrosion on steel surfaces (Videla & Characklis 1992), and potential pathogenic contamination (Lehtola et al. 2004). Physical and chemical cleaning is required to weaken and remove foulants (Nguyen et al. 2012). Within the context of wastewater reuse for industry (Mohsen & Jaber 2003) and agriculture (Qadir et al. 2010), numerous issues are linked to biofilm development. Biofouling has been specifically identified as an important cause of drip-irrigation system clogging when distributing wastewater (Tarchitzky et al. 2013; Gamri et al. 2014). Biofilm grows on emitters (Carpa & Scicolone 2004) and pipes (Li et al. 2012) and is generally associated with physical and chemical deposits (Adin & Sacks 1991). Previous studies have proved biofilm resistance to disinfection (De Beer et al. 1994). Biocides are more efficient against suspended microorganisms than against biofilms. Therefore, alternative measures should be explored in order to control biofilm growth.
Biofilm development is a complex phenomenon affected by several environmental conditions (Characklis 1981) (e.g., nutrient availability, temperature, surface roughness, and hydrodynamic conditions). The understanding of these parameters is crucial to develop anti-fouling strategies. Various studies have been carried out to investigate the impact of pipe materials on biofilm development in drinking water distribution systems (Schwartz et al. 1998; Niquette et al. 2000; Hallam et al. 2001; Van der Koiij et al. 2005). Bacterial adhesion is influenced by chemical properties on surfaces (Lehtola et al. 2004), roughness (Yu et al. 2010), and hydrophobicity (Hogt et al. 1983). Roughness is often amplified by metal surface corrosion (Beech & Sunner 2004), while non-corroded copper surfaces release substances which may inhibit bacteria attachment and slow down biofilm growth (Lehtola et al. 2004; Van der Koiij et al. 2005; Morvay et al. 2011).
Pipe material impacts on biofilm development have been analyzed by collecting samples from drinking water networks (Schwartz et al. 1998; Niquette et al. 2000) or by incubating pipe coupons in bacterial suspensions...