Comparisons of NOM fouling and cleaning of ceramic and polymeric membranes during water treatment

This research examines the effect of various NOM fractions on ceramic and polymeric UF membranes performance in terms of fouling and cleaning. Fouling experiments were performed using five model solutions, humic acid, protein as bovine serum albumin (BSA), alginate with and without calcium, and a combined NOM mixture. Two chemical agents were selected: an oxidant (NaOCl) and caustic (NaOH). Fouling and cleaning behavior were assessed using the resistance in series (RIS) model, membrane permeability, carbon mass balance, and fluorescence excitation and emission matrix (FEEM) analysis. The results demonstrated that NOM fouling order of the ceramic UF was similar to polymeric UF with the following trend: NOM mixture ≈BSA > alginate ±Ca+2 > humic acid. However, the backwash efficiency was 1.5×–2× higher for the ceramic UF in comparison to the polymeric UF, indicating a much higher hydraulic reversibility for the ceramic UF. A carbon mass balance in compliment with FEEM plots determined that NOM removal by the ceramic UF was ≈ 10% higher than the polymeric UF. Chemical cleaning was found to be effective for both membrane types. Thus, it was not possible to conclude, that the ceramic membrane demonstrated an advantage for chemical cleaning under the conditions studied

Chemical cleaning of ceramic ultrafiltration membranes – Ozone versus conventional cleaning chemicals

This study investigates chemical cleaning mechanisms of a tubular ceramic UF membrane. The effect of cleaner type (ozone (O 3 ), sodium hypochlorite (NaOCl) and sodium hydroxide (NaOH)), clean in place (CIP) pH (11 vs. 12), and cleaning sequence on the removal of irreversible fouling of hydrophobic (humic acids) and hydrophilic (alginate with and without calcium (alginate + Ca +2 and alginate - Ca +2 , respectively)) NOM fractions were investigated. Results showed that different NOM types responded differently to chemical cleaning. Alginate-Ca +2 and humic acids were equivalently removed by NaOCl or NaOH whereas a lower cleaning efficiency of alginate + Ca +2 was observed. Increasing the pH of NaOCl and NaOH CIP increased the removal of the chemically reversible fouling index (UMFI cr ). The efficiency of NaOCl was always lower than that of NaOH at the same pH, which was attributed to surface tension (λ) differences in the CIP water and potential differences in cleaning mechanism. The ceramic UF CIP cleaning using O 3 (0.50 mg O 3 /mgC) for 1 h demonstrated higher cleaning efficiency for humic acids and alginate ± Ca +2 , (%UMFI cr > 98%), than NaOCl or NaOH alone (%UMFI cr >80%). The O 3 CIP was as effective as 4 h cleaning using a sequential NaOH/NaOCl or combined NaOCl + NaOH CIP