Characterization of natural organic matter in South African drinking water treatment plants: Towards integrating ceramic membrane filtration

Abstract

This work presents the first comprehensive investigation of natural organic matter (NOM) fraction removal using ceramic membranes in South Africa. The rate of removal of bulk NOM (measured as UV254 and DOC % removal), the biodegradable dissolved organic carbon (BDOC) fraction, polarity-based fractions, and fluorescent dissolved organic carbon (FDOM) fractions was investigated from water abstracted from drinking water treatment plants (WTPs) in South Africa.Further, mechanisms of ceramic membrane fouling by waters of South Africa were studied. Ceramic membranes removed more than 80% DOC from samples from coastal WTPs, whereas for inland plants, the removal was between 60% and 75% of DOC. FDOM was removed to at least 80% regardless of the site of the plant. The BDOC removal by the ceramic membranes was above 85%. The hydrophobic fraction was the most amenable to removal by ceramic membranes regardless of the site of sample abstraction (above 60% for all sites). The freshness index (β:α) correlated strongly to UV254 removal (R2 = 0.96), thus UV254 removal can serve as a proxy for the susceptibility to removal of such class of NOM by ceramic membranes. This investigation demonstrated that ceramic membranes could be a valuable technology if integrated into the existing WTPs.

Practitioner Points • The removal of bulk parameters by ceramic membrane was greater than unit conventional processes used in all the sampled water treatment plants. • The hydrophobic polarity-based fraction of NOM was the most amenable to removal by ceramic membranes regardless of the site of the WTP. • Polarity-based fractions, aromaticity, and initial DOC had a combined influence on the removal of organic matter by ceramic membranes as explained by principal component three.