Integration of granular activated carbon (GAC) and gravity-driven membrane (GDM) reactor pretreatment for biofouling control in reverse osmosis (RO): Toward municipal wastewater reclamation and reuse

초록

This study evaluated the performance of a gravity-driven membrane (GDM) reactor integrated with granular activated carbon (GAC) as a pretreatment process for reverse osmosis (RO)-based reclamation and reuse of municipal wastewater secondary effluent, with a particular focus on mitigating RO biofouling. Incorporation of GAC significantly improved organic matter removal in the GDM reactor, achieving a 75.1% removal of total organic carbon (TOC), along with concurrent reductions in nitrate (25.4%) and total phosphorus (41.4%) relative to the influent, whereas the GDM-only pretreatment exhibited negligible removal. This improved pretreatment effectively mitigated downstream RO biofouling, resulting in a 21.1% lower increase in transmembrane pressure (TMP) and reduced polysaccharide (26.6%) and protein (21.3%) contents in the RO biofilm compared with the GDM-only pretreatment. To identify an effective operating strategy of the GAC-GDM reactor, the effects of variable hydrostatic head conditions during GDM operation were investigated. In the GAC-GDM reactor, operation with a stepwise increase in hydrostatic head resulted in stabilized flux 28.4-48.5% higher than that under the constant-head and decreasing-head conditions, respectively. An economic analysis indicated that the GACGDM pretreatment reduced the overall reclaimed water production cost by 12.5-14.0% reduction compared with the GDM-only pretreatment. Overall, these findings demonstrate the feasibility of the GAC-GDM reactor as an RO pretreatment for secondary effluent reclamation and reuse and highlight stepwise hydrostatic head operation as a practical strategy for further improving process performance and economics.

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