Removal of antibiotic-resistant bacteria (ARBs) by ultrafiltration membranes for Nervión river water potabilization

Abstract

Ultrafiltration membranes associated with in-line coagulation and hydraulic flocculation were applied for antibiotic-resistant bacteria removal during Nervión river water potabilization. The study was conducted at pilot scale with an ultrafiltration module equipped with three hollow fibre polyvinylidenefluoride membranes (0.04 μm nominal pore size) with in-line precoagulation–flocculation. The system operated continuously with constant dose of 20 mg FeCl3/L and a stable production of 50 L/h (18.5 lmh), operating in vacuum. All physico-chemical water quality parameters analysed improved, but the yields were variable, highlighting the low capacity to remove organic matter, with a significant influence of influent concentration. A high capacity to retain bacteria was observed for ultrafiltration membranes with total absence of several faecal indicators in the effluent, but the presence of total aerobic bacteria and occasionally faecal coliform or even E. coli strains casts doubt on the microbiological quality of the treated water. Most of the isolated strains in effluent samples were antibiotic-resistant bacteria with a significant percentage of multi-antibiotic-resistant bacteria, which increase the one observed for the isolated strains from influent. Antibiotic-resistant bacteria to β-lactams, macrolide and the cotrimoxazole antibiotic groups were frequently detected in effluent samples.