ABSTRACT
Pressure-retarded osmosis (PRO) is one of the technologies to harvest osmotic energy through an osmotically-driven membrane process. Recent studies have found that the feed pair consisting of concentrated seawater brine from seawater reverse osmosis (SWRO) plants and discharged wastewater retentate (denoted as WWRe) from municipal wastewater plants could be applied in PRO processes. In addition to producing a higher energy output, it also lowers the energy consumption for SWRO, mitigates the environmental issues of brine disposal, reduces the water production cost, and produces a greener SWRO process. However, severe membrane fouling induced by WWRe has been found to occur inside the porous layer of PRO membrane during operations, which dramatically lowers the PRO membrane power density and shortens the membrane life. In order to control membrane fouling, the feed and draw solutions must be pretreated so that the foulants in those solutions can be removed. This chapter summarizes several commonly used pretreatment methods, such as membrane filtrations, chemical additives and coagulations, and their efficacies in detail.
