Fouling of low-pressure membranes during drinking water treatment: effect of NOM components and biofiltration pretreatment

Abstract

Fouling is a major challenge for low-pressure membrane drinking water treatment systems. Previous research has demonstrated that under the right conditions, biofiltration is an effective method to reduce fouling of low-pressure polymeric membranes. This study provides additional insight into the effect of biofiltration as a pretreatment for fouling reduction by using river water with different raw water quality characteristics than has been examined in previous studies. Two parallel pilot-scale dual media (sand/anthracite) biological filters were operated continuously over a period of 14 months. Liquid chromatography–organic carbon detection analysis confirmed that the parallel biofilters performed similarly with both averaging on 21% biopolymer removal. Raw and treated water biopolymer concentrations were correlated, with increased absolute removals occurring at higher raw water concentrations. Ultrafiltration (UF) membrane fouling experiments showed substantial improvement in performance following biofiltration pretreatment by reducing hydraulically irreversible and reversible fouling rates by 14–68% and 8–55%, respectively. The results also reaffirm the importance of biopolymers at concentrations as low as ∼0.1 mg/L on irreversible and reversible UF membrane fouling and a minimal impact of humic substances.

Full‐Scale Ozone–Biofiltration: Seasonally Related Effects on NOM Removal

“…It would therefore be expected that seasonal differences in biopolymer composition due to changes in relative loading from these sources could affect biodegradation rate. The reduced biopolymer removal observed through the biofilters at cold temperatures may be of concern to water treatment plants using biofiltration as a pretreatment to membranes, given that biopolymers have been shown to be a major constituent of low‐pressure membrane fouling (ElHadidy et al 2014, Rahman et al 2013, Tian et al 2013, Hallé et al 2009). However, the effect of this can be reduced by both a higher EBCT (Figure 4) and a lower raw water biopolymer concentration (Figure 1) at cold temperatures, as were observed in the current study.…”

“…These data can be used to understand how groups of compounds are affected by water treatment processes and to optimize treatment for specific purposes. For example, biopolymers have been shown to contribute to fouling of low‐pressure membranes (ElHadidy et al 2014, Rahman et al 2013, Tian et al 2013, Hallé et al 2009), and humic substances can act as precursors to DBPs (Wassink et al 2011).…”

The Minus Approach Can Redefine the Standard of Practice of Drinking Water Treatment

“…Pretreatment serves as an effective, and often necessary, strategy for combating fouling and extending the life span of membranes by reducing cleaning times, chemical demand, and energy requirements . Technologies associated with the Minus Approach are effective pretreatments. − …”

Optimization of air sparging and in-line coagulation for ultrafiltration fouling control

“…Hydraulically irreversible fouling which cannot be removed by physical cleaning is due to pore adsorption or pore blocking (Huang et al, 2007) by biopolymers and humic substances (Chen et 5 al., 2014;Rahman et al, 2014;Zularisam et al, 2006). The hydraulically irreversible foulants that can be removed by chemical cleaning are considered to be chemically reversible foulants.…”