Performance of Direct Biofiltration of Surface Water for Reduction of Biodegradable Organic Matter and Biofilm Formation Potential

Abstract

Direct biofiltration of surface water may be considered as pre-treatment for membrane filtration, in order to reduce fouling. The biofiltration process was investigated with regard to biodegradable organic matter and biofilm formation, covering the annual variations under moderately cold climate conditions. Granular activated carbon (GAC) and two types of crushed expanded clay (EC) were compared as filter media. To assess the biological properties of the biofilters, viable biomass and respiratory activity was examined. Biofiltration removed assimilable organic carbon (AOC) and biodegradable dissolved organic carbon (BDOC) by about 30% and also reduced the bacterial concentration in the water phase. Also, biofilm formation in the treated water was reduced by 80-90% during summer and winter conditions. The reductions in the investigated parameters were similar in the biofilters with GAC and EC. Likewise, a similar amount and development of biomass was found in the GAC and EC biofilters of comparable grain size with a pronounced stratification from top to bottom of the filter bed. The specific respiratory activity of the biofilter biomass was dependent on raw water temperature. Even though slight correlations between BDOC removal and temperature or respiratory activity were observed, AOC and BDOC removals were mainly dependent on the feed water concentrations of these compounds. The results indicate that direct biofiltration of surface water, by reducing AOC, BDOC and biofilm formation in the water, may be an advantageous pre-treatment for membrane filtration processes.

Study of Seawater Biofiltration by Measuring Adenosine Triphosphate (ATP) and Turbidity

“…These findings agree with the bacterial reductions found by Persson et al (2006), although we measured biological activity instead of the number of bacterial populations, and they are also in line with Meesters (2003), who found 30-to 40-fold lower ATP concentrations in biofiltered water than in feed water. Figure 3b shows the turbidity measured at the inlet and outlet streams of columns C-1 and C-2 in biofiltration processes Exp-1, Exp-2 and Exp-3 (see Table 5).…”

“…ozonation) to reduce ozonation by-products (Servais et al, 1994;Carlson and Amy, 1997;. Another purpose of biofiltration is consumption of the biodegradable fraction of natural organic matter (NOM) in order to prevent downstream operational problems such as regrowth in pipelines (Servais et al, 1994;Huck et al, 1994;Urfer et al, 1997;Persson et al, 2006;Emelko et al, 2006). Furthermore, good efficiency in turbidity removal can also be attributed to biofiltration since it can act as a conventional physical filter, which results in acceptable filtration performances (Wang et al, 1995;Urfer et al, 1997;Emelko et al, 2006).…”

“…Assuming that temperature is barely controlled in industrialized biofilters, the process variables in biofilters are commonly the empty bed contact time (EBCT), the hydraulic loading rate (HLR) and the intensity and frequency of the backwashings (BW) (Liu et al, 2001;Miltner et al, 1995;Urfer et al, 1997;Persson et al, 2006).…”

“…Biofiltration is used as a pretreatment process in membrane filtration (Persson et al, 2006;Chinu et al, 2009) and is installed downstream from advanced oxidation processes (e.g. ozonation) to reduce ozonation by-products (Servais et al, 1994;Carlson and Amy, 1997;.…”

Modeling the improvement of ultrafiltration membrane mass transfer when using biofiltration pretreatment in surface water applications

“…Azzeh et al (2015) and Sadreddini (2013) examined direct biofiltration of river water prior to UF membrane filtration and reported reductions in membrane resistance as compared to nonbiologically treated river water. In similar studies performed by Huang et al (2011), Persson et al (2006, and Velten et al (2011), biofiltration was found to effectively reduce turbidity, organic, and biological activity levels prior to UF membrane processes. UF operating parameters, including the membrane MTC, were not reported (Huang et al, 2011;Persson et al, 2006;and Velten et al, 2011).…”