Activation of Persulfate at Waste Heat Temperatures for Humic Acid Degradation

Humic acid (HA) as a major constituent of natural organic matter (NOM) in raw water presents major challenges to drinking water production including membrane fouling and serving as a precursor for the production of disinfection byproducts (DBPs). This study demonstrates the feasibility of HA degradation by heat-activated persulfate (PS) mainly at a waste heat temperature of 40 °C, but also at 60 and 90 °C in which ∼70% TOC loss was achieved within 168, 24, and 1 h, respectively. The use of waste heat for water treatment eliminates reliance on electricity, which is a requirement for conventional advanced oxidation processes. Heat-activated PS treatment of synthetic raw water at 40 °C was also shown to significantly reduce ultrafiltration membrane fouling. Low concentration of chloride (≤0.9 mM) accelerated PS degradation of HA, but the promotion was lost at higher concentration (≥9 mM). HA spiked into tap water was degraded by PS even at 25 °C, suggesting activation by trace minerals present within regulatory limits. Overall, the results of this study promise a sustainable and low-cost water treatment option.