Intermittent osmotic relaxation: A strategy for organic fouling mitigation in a forward osmosis system treating landfill leachate

Abstract

In this study, the potential of osmotic backwashing was explored for the alleviation of the forward osmosis (FO) membrane fouling induced by landfill leachate. The normal osmotic backwashing employing NaCl as a draw solute resulted in an improved membrane flux (~ 4 LMH) and a reduction (45%) of the membrane resistance. We proposed an alternative way of osmotic backwashing based on the inherent osmotic potential of landfill leachate itself for the FO system. For the effort, intermittent osmotic relaxation (IOR) was newly introduced to the FO system to enhance the performance. This operation showed a comparable performance with fouling mitigation to the previous normal osmotic backwashing using NaCl as a draw solute. Under an optimized condition (4 h of filtration intervals and 20 min of backwashing time), the integration of the IOR with the FO system led to a 30% reduction in membrane resistance, a complete flux recovery, and 26% increment in the filtered volume. The IOR process does not require additional energy and/or chemical dosage. Therefore, it can be suggested as an innovative, practical, and energy-efficient osmotic backwashing strategy for a stable and the long-term operation of FO systems treating saline wastewater.