Towards the circular economy — A pilot-scale membrane technology for the recovery of water and nutrients from secondary effluent

The concept of water reuse was proposed more than two decades ago in regions that suffered from water scarcity or relied on unpredictable water supplies. Since then, climate change, a rapidly growing global urban population, and environmental pollution have impacted sustainable water resources, driving a rise in demand for efficient wastewater reclamation technologies. According to the new Circular Economy Action Plan established by the EU, most activities that are undertaken as part of the wastewater treatment process should primarily concern the search for new technologies that use wastewater as a source of water and nutrients. This article proposes a new approach of secondary effluent (SE) management to recover the valuable components of wastewater for a variety of purposes, beginning with the water itself and followed by nutrients. With this objective in mind, we reclaimed SE in an integrated 3-stage pilot-scale membrane process (micro/ultrafiltration, nanofiltration and reverse osmosis). The effect of the process inlet pressure and flow configuration (cross-flow and dead-end filtration), as well as the type of membrane, on the efficiency of the process and water composition was investigated. In this study, microfiltration (MF), ultrafiltration (UF), and nanofiltration (NF) are not only pre-treatment processes reverse osmosis (RO) but also produce water for various purposes. This technology allowed the production of water for several types of applications. These uses include (a) industrial processes as a cooling medium, (b) urban non-potable applications (e.g., irrigation with reclaimed water and microelements), (c) potable water supplies, and (d) groundwater remediation. The classification of proper use was made based on standards, regulations, and the available literature. The conducted research demonstrated the versatility of the proposed technology with regard to water reclamation for various non-exclusive applications. Additionally, the cost-effectiveness of the implementation of the presented 3-stage-membrane technology was calculated.