Wastewater reclamation is a promising solution to growing pressure on limited water resources. In this study we evaluated the efficiency of boron removal from effluent at a water resource recovery facility (WRRF) using a two-stage/two-pass RO membrane system. We propose using measurements of electrical conductivity (EC) as a proxy for boron concentration. We tested our approach to boron estimation and the proposed split partial second pass (SPSP) system at an established WRRF and a pilot plant we constructed at the same location. Results showed that boron in the effluent was directly related to the concentration of EC. The proposed regression equation (y = 4.959 × 10-5x + 0.138) represents a rule of thumb for wastewater plant operators. The proposed SPSP system was optimized through manipulation of operating conditions, achieving a promising total water recovery of 64% at maximum boron rejection (over 85% removal) in a manner that was both cost-effective and flexible. This study demonstrates that two-stage/two-pass split-partial permeate treatment with a high pH for boron removal offers a sustainable freshwater supply option suitable for use by the semiconductor industry.
Wastewater reuse presents a promising solution to the growing need for the sustainable use of available water resources. The reclamation of municipal sewage through reverse osmosis can be applied for diverse uses to alleviate chronic water scarcity. In this study, a pilot plant was fabricated to measure the efficiency and the costs that are associated with pretreatment by the fiber filtration and ultrafiltration of secondary effluent from a water resource recovery facility in Taiwan. The results of this dual-membrane process meet the quantity and quality standards for industrial reuse. The pretreatment produced feedwater with a silt density index (SDI15) lower than 4.1, and with average turbidity removal rates of 42.7% (fiber filtration) and 99.2% (ultrafiltration). Following reverse osmosis, a 97.9% rejection of the electrolyte conductivity was achieved in the reclaimed water. The fouling of the membranes was controlled through the application of intensive backwash, chemically enhanced backflushing, and cleaning in place. The proposed system improves the feasibility, reliability, and economy of the dual-membrane process as a tertiary treatment for safe water reuse, and it thereby demonstrates that this technology has reached maturity for the full-scale implementation of sustainable water reuse.
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