Ultrafiltration with in-line coagulation (FeCl3) to enhance arsenic removal and improve drinking water quality: From bench to pilot-scale

Abstract

There is a growing interest in advanced technologies to guarantee drinking water safety in scenarios of increasingly polluted water sources. Based on that, this paper discusses the use of ultrafiltration membranes aided by in-line coagulation with FeCl3 (0.086 – 0.172 mg/L) to improve the resilience of drinking water treatment plants. The process was considered after the settling units and was first studied on a bench scale, later validated in a pilot plant that operated continuously for approximately 31 days. In experiments without an in-line dose of FeCl3, the average flux values corresponded to 189.9 ± 11.8 L/m2h, compared with 193.4 ± 5.3 L/m2h for experiments when the coagulant was considered. The flux decay was lower in experiments with an in-line dose of FeCl3 (J/J0 > 0.95) and analysis of particle sizes revealed that the average diameter increased from 24.1 to 29.2 µm after the coagulant was added. Consequences related to a greater particle size were a fouling layer more porous permeable, and with a lower hydraulic resistance. The additional coagulant dosage also acts on the residual natural organic matter, monitored by excitation-emission matrices. Furthermore, the results show that the concentrate recirculation to the beginning of the water treatment plant did not affect its overall performance. In fact, concentrate recycling would increase the recovery rate of ultrafiltration membranes and reduce losses during water treatment. Similar observations were obtained in pilot-scale operations, that validated the in-line dose on a more representative system that is closer to the full-scale treatment process.