Virus removal by unsaturated wastewater filtration: effects of biofilm accumulation and hydrophobicity

Abstract

Enhanced treatment of septic tank effluent can improve the hydraulic function and performance of infiltration systems and constructed wetlands. By intermittent spray application of septic tank effluent onto a coarse-grained filter media, an unsaturated flow regime beneficial for pathogen removal is created. A column filtration study showed an increase in PRD-1 removal by time of operation with corresponding biofilm accumulation in the filter material. The same increased removal was observed for 1 mum polystyrene beads, irrespective of their hydrophilic/hydrophobic surface properties. A control experiment with sorption of 1 mum hydrophobic and hydrophilic polystyrene beads to different glass surfaces with hydrophobic and hydrophilic properties indicate that mechanisms other than hydrophobic interactions may govern the rate of attachment to the filter media. For a given volumetric flow-rate in the columns, the presence of biofilm altered the hydrodynamic characteristics and this resulted in increased retention time and particle removal.

Review: Effects of Using Different Materials on Filtration Process of Wastewater

“…An increase in the elimination of bacteriophages with subsequent biofilm accumulation in the filter material by the time of operation was shown by a column filtration analysis. Regardless of their hydrophilic / hydrophobic surface properties, for 1 mm polystyrene beads, the same increased removal was observed [19].…”

Physicochemical regulation of biofilm formation

“…A recent study concluded that hydrophobic interactions may not be responsible for the attachment of bacteria to surfaces and the formation of biofilms. 36 Fluorinated surfaces represent a class of materials that oppose the hypothesis that bacteria preferentially adhere to hydrophobic substrates. The initial adhesion of bacteria to these surfaces and the maturation in biofilms is much lower compared to other commonly used surfaces in industrial applications (e.g., steel, glass, polypropylene).…”

Controlling the hydraulic resistance of membrane biofilms by engineering biofilm physical structure

“…Pore-blocking may arise from adsorption of low molecular weight natural organic matter or biofilm-by-products (e.g., surfactants, biomass associated products (BAP)) into the membrane's pores. The lesser contribution of R bp compared to R f in UF membranes treating surface water may arise from the biofilm layer functioning as a secondary filtration barrier which can help reduce membrane adsorption and pore-blockage during filtration of natural organic matter (NOM) of polymeric and LMW acid range, as indicated for removal of viral particles (Heistad et al, 2009). Filtration resistance is additionally postulated to arise from adsorption (R ad ) of NOM to the membrane surface, and is considered as a recalcitrant fouling layer persisting after hydraulic removal of a "gel layer".…”