Investigation of the fouling behaviors correlating to water characteristics during the ultrafiltration with ozone treatment.

This study investigated the fouling behavior and mechanism of ozone treatment correlating to water characteristics for micro-polluted water during ultrafiltration (UF). The results indicated that pre-ozonation efficiently mitigated membrane fouling of natural organic matter (NOM). The higher ozone doses were, the more the performance transmembrane pressures (TMPs) decreased. Ozone mainly converted macro molecule organics into low molecule organics. Macro molecular biopolymers (BP) can be removed up to 35.5% with an ozone treatment of 9 mg/L, while low molecular weight building blocks of acids and humics (BB) and neutrals (LMWN) increased 7.25% and 14.62%, respectively, with an ozone treatment of 9 mg/L. Analysis of fluorescence excitation emission matrices (EEMs) coupled with parallel factor analysis (PARAFAC) indicated that ozone mainly removed soluble microbial organics and fulvic-like and humic-like organics but not tyrosine organics. Hydrophobic organics (HPO) were reduced with an increase of ozone doses, especially macro molecular BP and humic substances (HS), and the neutral hydrophilic fraction (N-HPI) was enhanced. Ozone treatment helped to reduce the interception of BP and HS in HPO and improved the interception of BP and HS in N-HPI, as well as BB and LMWN, in both fractions. Principal component analysis suggested that BP, as well as UV254, had high correlations with a membrane fouling index, which can be used as the fouling indicator during ozone treatment.

[Effects and Mechanism of the Combination of Ozone-PAC as a Pretreatment for the Reduction of Membrane Fouling].

The effects of ozone, powdered activated carbon (PAC), and their combination on controlling fouling and the removal of organic matter were investigated. The results showed that ozone mainly oxidized strong hydrophobic, high relative molecular mass (Mr) compounds and the high Mr was transferred to medium and small Mr hydrophilic fractions. Ozone could control fouling effectively, demonstrating that hydrophobic organic matter with higher Mr contributed to membrane fouling. PAC adsorbed organics with small Mr and alleviated membrane fouling, showing that organics with small Mr contributed also to membrane fouling. The ozone and PAC combination controlled membrane fouling and also enhanced the removal of organics, demonstrating the synergistic effect of such a combination.

[Effect of relative molecular mass distribution and hydrophilicity/ hydrophobicity of NOM on membrane fouling in MF-combined process].

This study investigated the reversible and irreversible foulants in a submerged microfiltration (MF) with pretreatments (coagulation/powdered activated carbon (PAC)/potassium permanganate) in a pilot scale treatment of water from Taihu Lake. The study focused on the effect of relative molecular mass (M(r)) distribution and hydrophilicity/hydrophobicity on membrane fouling using high performance size-exclusion chromatography (HPSEC) with UV and TOC detectors and three dimension fluorescence excitation-emission matrix (3DEEM). HPSEC analyses showed that pretreatments could almost completely remove the macro molecules (M(r) > 10 x 10(3)), but only eliminate part of medium (10 x 10(3)) > M(r) > 1 x 10(3)) and micro molecules (M(r) < 1 x 10(3)). A majority of medium and micro molecules were found in chemical cleaning solutions, indicating that medium and micro molecules were the main foulants that contributed to irreversible membrane fouling. In addition, it was also found that the content of strong hydrophobic acids (SHA) and neutral hydrophilic (Neut) fractions in chemical solutions were far higher than that of weakly hydrophobic acids (WHA) and charged hydrophilic (Char), which suggested that both organic fractions were responsible for irreversible fouling. 3DEEM fluorescence demonstrated that aromatic proteins and soluble microbial products were the main contributors to irreversible membrane fouling.