Low strength graywater characterization and treatmentby direct membrane filtration Original Research Article

The potential of direct membrane filtration on either ultrafiltration (30,200 and 400 kDa MWCO) or nanofiltration (200 Da MWCO) membranes was studied as a method of treatment of low load graywater for on site reuse. The graywater collected from a sports centerʹs public showers and characterized for its chemical composition and physical properties fitted well to a low strength type (29.8 mg/l TSS and 170.3 mg/l as COD). Particle distribution analysis showed that colloidal size particles are the dominant fraction in terms of number distribution, while the much fewer, larger particles make up most of the particle volume (mean particle diameter0.1 μm). When treated by ultrafiltration, COD and turbidity concentration of permeates complied with established restrictions (45-70% and 92–97% reduction range, respectively), however BOD values were still above the requirements in all cases. Permeate produced by nanofiltration was of high quality with high rejection of soluble organic matter (>90%) and ionic species (50%). It can be concluded that direct dense-membrane filtration is a favorable candidate for efficient treatment of graywater for unrestricted reuse. MWCO optimization still needs to be done in order to achieve better economics at an acceptable quality of permeate produced.