Effect of pre-coagulation on mitigating irreversible fouling during ultrafiltration of a surface water

Abstract

Membrane fouling can be divided into two types: reversible fouling and irreversible fouling. The former can be easily canceled by physical cleaning (e.g., backwashing) while the latter needs chemical cleaning to be mitigated. For more efficient use of membranes, the control of irreversible membrane fouling is of importance. In this study, the effectiveness of pre-coagulation/sedimentation on irreversible membrane fouling was investigated, based on the pilot-scale operation of the membrane unit installed at an existing water purification plant. The membrane employed was a low-pressure ultrafiltration (UF) membrane made of polysulfone and having a molecular weight cut-off of 750,000 daltons. Although pre-coagulation/ sedimentation significantly mitigated membrane fouling mainly through the reduction of reversible membrane fouling, the degree of irreversible fouling was not reduced by the pre-treatment. This was because the irreversible fouling observed during this study was mainly attributed to polysaccharides/protein like fractions of organic substances that cannot be efficiently removed by coagulation/sedimentation. Aluminium used as coagulant was thought to cause irreversible fouling to some extent but did not in the pilot operation, which could probable be explained by the fact that coagulation was conducted at relatively high pH (7.0) in this study.

Fluorescence analysis of NOM degradation by photocatalytic oxidation and its potential to mitigate membrane fouling in drinking water treatment

“…However, membrane fouling, primarily caused by natural organic matter (NOM), severely limits the efficient operation of large-scale industrial systems by increasing operational costs and hydraulic resistance (Peiris et al, 2008). Several pre-treatment methods have been implemented to mitigate membrane fouling in drinking water treatment including coagulation (Kimura et al, 2005), flocculation (Wang et al, 2013), oxidation (Mozia et al, 2006), and bio-filtration (Peldszus et al, 2012). Most of these methods transfer organic matter and pollutants from the aqueous phase to a solid phase necessitating subsequent treatment of the solid phase (Huck and Sozań ski, 2008;Liu et al, 2012).…”

Influence of floc structure on coagulation–microfiltration performance: Effect of Al speciation characteristics of PACls

“…Indeed, it is now very common to use coagulation as pretreatment of microfiltration (MF) and ultrafiltration (UF) to increase the removal of natural organic matter [1], improving membrane flux and even mitigate irreversible membrane fouling [2]. The hybrid coagulation-microfiltration process such as submerged membrane systems or direct membrane filtration processes which do not require to include settling processes are becoming more popular in the water industry [3].…”

Effect of coagulation mechanism on membrane permeability in coagulation-assisted microfiltration for spent filter backwash water recycling

“…Pikkarainen et al [39] found that pre-coagulation enhanced the DOC removal in upland surface water by more than 80% in a coagulation-assisted MF process. In our coagulation/dead-end MF process, on the other hand, the highest removal of DOC and UV 254 was 68% and 72%, respectively, which could be explained by the much lower SUVA value of the DOM [40]. As shown in Table 1, the SUVA value of SFBW was about 1.4 (less than 2), suggesting that the DOM in SFBW are low molecular weight and low hydrophobicity.…”