Dynamics of drinking water biofilm in flow/non-flow conditions

Abstract

A B S T R A C TDrinking water biofilm formation on polyvinyl chloride (PVC), cross-linked polyethylene (PEX), high density polyethylene (HDPE) and polypropylene (PP) was followed in three different reactors operating under stagnant or continuous flow regimes. After one week, a quasi-steady state was achieved where biofilm total cell numbers per unit surface area were not affected by fluctuations in the concentration of suspended cells. Metabolically active cells in biofilms were around 17-35% of the total cells and 6-18% were able to form colony units in R 2 A medium. Microbiological analysis showed that the adhesion material and reactor design did not affect significantly the biofilm growth. However, operating under continuous flow (0.8-1.9 Pa) or stagnant water had a significant effect on biofilm formation: in stagnant waters, biofilm grew to a less extent. By applying mass balances and an asymptotic biofilm formation model to data from biofilms grown on PVC and HDPE surfaces under turbulent flow, specific growth rates of bacteria in the biofilm were found to be similar for both materials (around 0.15 day À1) and much lower than the specific growth rates of suspended bacteria (around 1.8 day À1 ).

Growth kinetics and chlorine resistance of heterotrophic bacteria isolated from young biofilms formed on a model drinking water distribution system

“…Predicting biofilm growth rates is of great interest, and we determined rates using TCC and HPC values and the method proposed by Manuel et al (2007). A biofilm model can be expressed by the following equation, which is based on the assumption that biofilm development reaches a steady state through a balance between growth and detachment (Manuel et al, 2007):…”

“…A biofilm model can be expressed by the following equation, which is based on the assumption that biofilm development reaches a steady state through a balance between growth and detachment (Manuel et al, 2007):…”

“…At steady state, the specific biofilm growth rate (μbiofilm) can be expressed as a function of the maximum biofilm density (Xbiofilm, max) and the biofilm production rate (P) (Manuel et al, 2007):…”

Preliminary surface topographical characteristics of biofilms attached on drip irrigation emitters using reclaimed water

“…Actually, biofilms exist on almost all of the solid surfaces exposed to water in the natural environment (White et al 1998;Dong et al 2002;Kang et al 2006;Dong et al 2004;Qin 2008), and microorganisms in the irrigation system can form biofilms. To date, the research on biofilms has been focused on sewage treatment, water supply/drainage, water environment self-purification and biological clogging of porous media (Bishop 2007;Simpson 2008;Gouidera et al 2009;Liu et al 2008;Manuel et al 2007). In contrast, the knowledge about biofilms in drip irrigation systems is much less.…”

“…In the natural environment, biofilms exist on almost all of the solid surfaces exposed to water (White et al 1998;Dong et al 2002Dong et al , 2004Kang et al 2006;Qin 2008) and thus have received close attention from researchers in the fields of sewage treatment (Bishop 2007;Simpson 2008) and water supply/drainage (Gouidera et al 2009;Liu et al 2008). To date, research on pipeline biofilms has been focused on the water supply pipeline (Gouidera et al 2009;Liu et al 2008;Manuel et al 2007), whereas the biofilms in irrigation systems have been rarely studied. Although knowledge about biofilms in reclaimed water drip irrigation systems is limited (Li et al 2012a, b), it has been found that biofilm formation was probably the basic cause of the emitter clogging.…”