Solar photo-Fenton coupled with kaolin-fly ash ceramic membrane system for removal of natural organic matter fractions in lake water

Coagulation/flocculation is often used to remove natural organic matter (NOM) in drinking water; however, this treatment method does not sufficiently remove NOM, especially the hydrophilic (HPI) fraction. A two-step treatment process involving solar photo-Fenton (pH 3; Fe(II) to H₂O₂ ratio of 1:5) and low-cost kaolin-fly ash ceramic microfiltration membrane was developed to treat lake water. The system achieved high removal of NOM fractions which were monitored through the analysis of dissolved organic carbon (DOC), UV₂₅₄, specific UV absorbance (SUVA), and fluorescence excitation-emission matrix (FEEM). Unlike conventional processes (coagulation/flocculation) which remove less than 40 % of HPI fraction, the proposed two-step treatment process removed up to 65 % DOC of the HPI constituent. The enhanced HPI fraction removal was attributed to the hydrophilic nature of the ceramic microfiltration membrane with a contact angle of 27.4 ± 4.6 °, and about 26 % porosity. A complementary effect was established between photo-Fenton and ceramic membrane filtration, resulting in enhanced removal of parent compounds and oxidation by-products identified using gas chromatography time of flight mass spectrometry (GC TOF-MS) screening method. The coupled treatment system demonstrated potential in NOM removal, especially the HPI fraction which is difficult to remove by conventional water treatment processes, and oxidation by-products thereby reducing the risk of disinfection by-products formation in water treatment.