Membrane technology, i.e., ultrafiltration and nanofiltration, is growing in popularity, as it is a space efficient alternative for surface water treatment. Two types of hollow fiber membranes were tested in a fully equipped and automated pilot at a Swedish water treatment plant. Raw water was treated by a nanofilter and by coagulation before an ultrafilter. Operation parameters recorded during these trials have been the basis for cost estimations and assessments of environmental impact, comparing the two membrane modules to the existing conventional treatment. The membranes required lower chemical consumption, but led to increased costs from membrane modules and a higher energy demand. Compared to the existing treatment (0.33 €/m³), the operational costs were estimated to increase 6% for ultrafiltration and 30% for nanofiltration. Considering the low emissions from Nordic energy production, the membrane processes would lower the environmental impact, including factors such as climate and ecosystem health. Greenhouse gas emissions would decrease from 161 g CO₂-eq/m³ of the existing process, to 127 g CO₂-eq/m³ or 83 g CO₂-eq/m³ for ultrafiltration and nanofiltration, respectively. Lower chemical consumption and less pollution from the sludge leaving the water treatment plant lead to lower impacts on the environment.

Increasing trends of natural organic matter (NOM) in surface water in Nordic countries may cause future problems for drinking water producers. Emerging membrane technology, such as ultrafiltration (UF) and nanofiltration (NF), has the potential to produce safe drinking water of good quality from sources with high organic concentrations. In the present pilot study, surface water from three sources was treated by direct filtration on a hollow fiber ultrafilter (HFUF) and/or a hollow fiber nanofilter (HFNF). UV-absorbance (UVA) and total organic carbon showed a high percentage of NOM removal by HFUF/coagulation, with retentions of around 75% for UVA and 55% for the TOC. NOM removal was notably greater by HFNF; with 93% in UVA retention and 88% in TOC retention. Regrettably, the water treated with HFNF retained 20–35% of the desired hardness. HFUF achieved retention comparable to traditional flocculation and sedimentation steps, while HFNF achieved even better removal of NOM. Importantly, results indicate that a membrane process with only an additional polishing step would result in decreased concentrations of NOM in the drinking water, even with higher organic loads in the raw water.