New insights into alkalinity regulation in microflocculation-ultrafiltration process: Synergistic mechanisms for scale inhibition, enhanced flocculation and mitigation of membrane fouling

Abstract

“Ancient Oriental Wisdom” refers to the fact that the Chinese traditional drink boiled water since ancient times, and boiling is the most common method of disinfection and water treatment in household, however, boiling may also generate scale which is harmful to human health. Surface water frequently suffers from issues such as scaling after boiling and natural organic matter (NOM). The microflocculation-ultrafiltration (MUF) process cannot inhibit scale, NOM removal requires improvement, and membrane fouling is still a major limiting factor in its application. The alkalinity regulated microflocculation-ultrafiltration (ARMUF) process can provide three effects simultaneously by regulating alkalinity: (i) significant scale inhibition and almost complete retention of beneficial Ca2+ and Mg2+ in the raw water; (ii) enhanced flocculation effect, increased NOM removal, forming a loose floc and larger floc size, which helps to mitigate membrane fouling; (iii) mitigation of membrane fouling, the ARMUF process showed the lowest total resistance, with significant recovery of membrane characteristics after chemical cleaning. Notably, the ARMUF process was used as the basis for the design and fabrication of a 150 tonnes/day device, demonstrating the engineering application potential of the ARMUF process and providing theoretical and data support for its promotion.