Water Recovery from Urban Wastewater for Irrigation using Ultrafiltration and Nanofiltration: Optimization and Performance

Abstract

The shortcomings of conventional processes for treating urban wastewater subjected to secondary treatment, in order to use this water for irrigation, are well known. Alternative advanced treatment techniques are required instead. This study aims to use single-stage ultrafiltration (UF) or nanofiltration (NF) membrane processes to produce irrigation water from biologically treated urban wastewater. For this purpose, the effects of four process variables (membrane type, cross flow velocity, temperature, and transmembrane pressure) on process performance parameters (permeate flux, concentrations/removal efficiencies of contaminants) are analyzed through Taguchi experiment design. Temperature and membrane type are found to have the biggest effect on UF, whereas the membrane type is the most significant variable for the NF. Moreover, the use of membrane permeate for landscaping and agricultural irrigation based on optimal conditions is assessed with reference to the criteria imposed by national regulation/international guidelines. Water in various quality categories is produced using different settings for 28 distinct specific parameters with reference to the membrane type, process performance, and the irrigation method. The results indicate that single-stage UF or NF membranes with high recovery rates can be used for wastewater subjected to secondary treatment, to recover irrigation water at low pressure and high water permeate flux.