Application of membrane processes for expressway rainwater runoff treatment and reuse

In the presented study an application of membrane methods for treatment of rainwater runoff from expressway was examined. The possibility of reuse of obtained permeate was also analyzed. Ultrafiltration (UF), nanofiltration (NF), and reverse osmosis (RO) were employed to treat the rainwater that was taken from a rainwater reservoir on an expressway. The UF and NF process were carried out with activated carbon (AC) filter pretreatment. The effectiveness and efficiency of filtration processes were assessed by analyzing of permeate flux, electroconductivity concentrate factor, filtration time and removal rate for analyzed parameters. During rainwater treatment the most efficient method was AC-NF, where the average normalized flux value was 79% and was higher by 31% and 54% from RO and AC-UF, respectively. The highest efficiency in removing contaminants was achieved for AC-NF and RO. Average EC rejection rate was 99.6%, 42% and 2% respectively for RO, AC-NF, AC-UF. All methods had also good performance in bacteria removal (disinfection), although for microorganisms removal the efficiency over 90% was observed only for AC-NF and RO. The factor limiting the filtration process was membrane clogging, visible especially in AC-UF filtration. The results of the analysis of rainwater quality after using membrane processes indicate that permeate obtained from RO filtration could be used for economic purposes, such as flushing toilets, washing floors, and watering green areas.