Is the Microfiltration Process Suitable as a Method of Removing Suspended Solids from Rainwater?

Abstract

Due to climate change and anthropogenic pressure, freshwater availability is declining in areas where it has not been noticeable so far. As a result, the demands for alternative sources of safe drinking water and effective methods of purification are growing. A solution worth considering is the treatment of rainwater by microfiltration. This study presents the results of selected analyses of rainwater runoff, collected from the roof surface of individual households equipped with the rainwater harvesting system. The method of rainwater management and research location (rural area) influenced the low content of suspended substances (TSS < 0.02 mg/L) and turbidity (< 4 NTU). Microfiltration allowed for the further removal of suspension particles with sizes larger than 0.45 μm and with efficiency greater than 60%. Granulometric analysis indicated that physical properties of suspended particles vary with the season and weather. During spring, particles with an average size of 500 μm predominated, while in autumn particles were much smaller (10 μm). However, Silt Density Index measurements confirmed that even a small amount of suspended solids can contribute to the fouling of membranes (SDI > 5). Therefore, rainwater cannot be purified by microfiltration without an appropriate pretreatment.