| Summary: | When microfiltration (MF) and ultrafiltration (UF) membranes are applied for
drinking water treatment/wastewater reuse, membrane fouling is an evitable problem,
causing the loss of productivity over time. Polymeric membranes have been often
reported to experience rapid and/or problematical fouling, restraining sustainable
operation. Ceramic membranes can be effectively employed to treat impaired-quality
source waters due to their inherent robustness in terms of physical and chemical
stability. This research aimed to identify the effects of coagulation and/or ozonation
on ceramic membrane filtration for seawater and wastewater (WW) effluent. Two
different types of MF and UF ceramic membranes obtained by sintering (i.e., TAMI
made of TiO2+ZrO2) and anodic oxidation process (i.e., AAO made of Al2O3) were
employed for bench-scale tests.
Precoagulation was shown to play an important role in both enhancing membrane
filterability and natural organic matter (NOM) removal efficacy for treating a highorganic
surface water. The most critical factors were found to be pH and coagulant
dosage with the highest efficiency resulting under low pH and high coagulant dose.
Due to the ozone-resistance nature of the ceramic membranes, preozonation allowed
the ceramic membranes to be operated at higher flux, especially leading to significant
flux improvement when treating seawater in the presence of calcium and magnesium.
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Dissolved ozone in contact with the TAMI ceramic membrane surface accelerated the
formation of hydroxyl (˙OH) radicals in WW effluent treatment. Flux restoration of
both ceramic membranes, fouled with seawater and WW effluent, was efficiently
achieved by high backwash (BW) pressure and ozone in chemically enhanced
backwashing (CEB). Ceramic membranes exhibited a pH-dependent permeate flux
while filtering WW effluent, showing reduced fouling with increased pH. On the
other hand, for filtering seawater, differences in permeate flux between the two
membranes was observed under basic pH conditions, showing that the TAMI
membrane flux was stable regardless of changes in pH, while the AAO membrane
flux was significantly decreased as pH increased to 10.
Consequently, it is expected that ozone and/or coagulation prior to ceramic membrane
filtration can play a significant role in treating impaired-quality source waters (e.g.,
seawater and WW effluent), leading to maintaining sustainable membrane flux in
seawater pretreatment before reverse osmosis (RO) or water reuse applications.
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