Backwash water is an integral part of membrane treatment, normally making up between 2 and 10 % of the clean water production which constitutes a large volume on an industrial scale. To identify suitable treatment or disposal methods for backwash water, it is important to understand the characteristics of the backwash water and what contaminants it contains. In this study, the backwash water from an ultrafiltration membrane process for stormwater treatment was analysed. Concentrations of TSS and TOC were 2.4 and 24 times higher in the backwash water than the influent stormwater. The concentration of particulate and dissolved (<0.45µm) metals in the backwash water was high, for example, the average concentration of total Cu and Cr was 742 ± 215 and 737 ± 243 µg/L. In addition, the average concentration factors for Cu and Cr were 29 ± 9 and 41 ± 15.9. Methods such as coagulation, electrocoagulation and evaporation could be used to further treat backwash water. The residue fraction would contain high concentrations of metals that need to be disposed or could potentially be a good resource for metal recovery in the future.