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Abstract: To investigate the efficiency of different methods on exopolymeric substance (EPS) extraction, mechanical and chemical treatments were applied on two activated sludges, regarding the yield of protein extraction as well as their compatibility with usual quantification methods. Mechanical disruption methods do not drastically affect protein measurements by both bicinchoninic acid (BCA) and modified Lowry methods. Chemical compounds such as cationic exchange resin and triton show high interference with modified Lowry method while the protein quantification by BCA method is not affected. In addition, inner sludge compounds were shown to interfere with both methods: BCA and modified Lowry measurement respectively overestimate and underestimate protein content. According to these data, BCA method was chosen in this study as the most appropriate protein quantification method in sludge extracts. Comparison of various extraction protocols, combining mechanical and/or chemical treatments, shows that efficiency can be increased by repeating the same method or by applying a prior mechanical treatment. Proteins are preferably extracted by triton treatments, indicating the importance of hydrophobic interactions linking proteins to the EPS matrix. The amount of extracted proteins reaches 182 and 148mgeq.BSAg−1 VSS using triton/triton and ultraturax/triton extractions, respectively. Protease activity/extracted protein ratios vary widely depending on extraction protocols. Protease seemed to be preferably extracted by ultrasound and triton treatments (150–220Umg−1 protein). This study underlines that the choice of a relevant coupled quantification/extraction method is of great importance for efficient EPS determination. [Copyright &y& Elsevier]

Abstract: The high water recycling ratio used in some industries can cause nutrients to accumulate in the system, leading to thick, rapidly growing biofilms inducing detrimental effects. Nowadays, chemical treatments are widely used but the increasingly restrictive environmental regulations induce the necessity to take the environmental aspect into account in the choice of a suitable treatment. With this in mind, this study analyses a method for controlling thick, dense biofilm development by applying synergistic actions having low environmental impact, i.e., an enzymatic and a mechanical (shear stress) treatment well suited to industrial water networks. For that purpose, biofilms were grown on plastic plates set in a Couette–Taylor reactor (CTR) that was inoculated using a “white water” sampled from a paper industry network. Development of the biofilms was controlled by applying a constant continuous feeding with a high COD/N ratio of 20, a well-defined shear stress and an external aeration, those conditions leading to a well-controlled G-value and a γ S/O2 value close to 1, and consequently, to the development of thick mainly aerobic heterotrophic biofilms representative of that encountered in high loaded industrial water networks. Optimal operating conditions for biofilm treatments were determined considering the penetration time for the enzymatic treatment taking into account both internal and external mass transport (using Biot number calculation). In addition, an optimal shear stress increment of 2.5Pa was selected in order to maximise biofilm detachment while avoiding compression phenomena due to the mechanical treatment. The combined treatment led to an increase of 80% in biofilm mass removal (COD) compared to the enzymatic treatment alone and removed a large part of the basal layer of the biofilm, 80% reduction being observed in the support coverage. [Copyright &y& Elsevier]