WCW26

Reverse osmosis and nanofiltration (RO/NF) is widely recognized as one of the most effective processes for removing problematic water constituents from drinking water. However, the non-selective nature of RO/NF membranes also strips beneficial ions and CO₂ buffering capacity, resulting in permeate with low pH, and indices inferring relatively unstable water in the distribution system.
To produce stable finished water, RO/NF post-treatment stabilization/remineralization is beneficial. Common industry approaches include bypass streams, chemical dosing, and calcite/limestone contactors, each presenting distinct trade-offs in capital investment, operational complexity, maintenance requirements, and long-term consumable costs.
This presentation compares these stabilization strategies using real-world performance data from multiple full-scale RO/NF facilities. Key metrics evaluated include achievable index and pH targets, alkalinity and hardness remineralization, chemical and consumable costs, and operator involvement over years of operation.
Findings highlight which approaches deliver the best balance of water quality, reliability, and cost for different plant sizes and source-water conditions, providing actionable guidance for designers and operators seeking to optimize RO/NF post-treatment systems.