Water recovery from laundry wastewater by the cross flow microfiltration process: A strategy for water recycling in residential buildings

Abstract

In this work, domestic laundry wastewater was treated through a membrane process using a mixed cellulose ester (MCE) microfiltration membrane with 0.22 μm pore size. A cross flow filtration was used and the effect of operating parameters such as trans-membrane pressure (TMP) and feed flow rate on permeate flux and rejection characteristics have been studied. A detailed analysis of the membrane fouling and the formed resistances against permeation which caused flux decline including membrane, cake layer, reversible and irreversible resistances have been offered and the effect of trans-membrane pressure and flow rate on each of the mentioned resistances was examined. Finally, the removal efficiencies for BOD, COD, TSS and turbidity at different trans-membrane pressures and feed flow rates are determined. It was observed that an increase of TMP and feed flow rate has positive effects on the permeate flux and membrane rejection performance. Moreover, the overall resistance increases with an increase in TMP and decreases with an increase in feed flow rate. The highest removal efficiency for BOD, COD, TSS and turbidity was obtained as 93.9, 90.8 and 98.7 percent, respectively which was obtained at a TMP of 1 bar and feed flow rate of 44 L/h. Modeling of the microfiltration system by the Hermia models revealed that the cake formation model (CFM) has the best agreement with the experimental results and it could be concluded that the cake layer formation on the membrane surface is the main mechanism for membrane fouling and flux decline. The results of this study showed that the microfiltration is a reliable and simple operation for recycling and reuse of domestic laundry wastewater in mixture with fresh water for use in washing machines, toilets and irrigation.