Santa Monica Achieves 90% Recovery with US’ First-Ever Municipal Flow Reversal RO Retrofit
The City of Santa Monica has completed the United States’ first full-scale municipal retrofit of its kind using Flow Reversal RO (FR-RO), successfully reaching a stable 90% recovery rate at the Arcadia Water Treatment Plant. This achievement is part of Santa Monica’s Sustainable Water Master Plan to reduce reliance on imported water and lower the long-term cost of water production through high-efficiency, high-recovery technologies.
FROM PILOT TO FULL-SCALE
The retrofit followed a rigorous pilot program that tested FR-RO under real-world conditions. The pilot, conducted in collaboration with the City of Santa Monica, demonstrated that FR-RO could maintain stable operation at 89–91% recovery over more than 100 days- even under challenging scaling conditions involving both silica and calcium carbonate. The system maintained extended cleaning intervals and demonstrated strong salt rejection, with permeate TDS consistently below 120 mg/L.
This performance led the City to select ROTEC’s FR-RO technology through a formal RFP process, following side-by-side testing with other high-recovery RO solutions.
INSIDE THE FULL-SCALE RETROFIT
The full-scale retrofit upgraded the plant’s conventional 3-stage RO system from a 39:19:9 to a 43:21:9 vessel configuration. Using ROTEC’s patented block rotation and flow reversal approach, the system distributes scaling stress evenly across membranes, allowing recovery to increase without aggressive chemical treatment.
Key implementation highlights:
- No added footprint-ROTEC was able to reuse existing skids and infrastructure.
- Operational flexibility – FR-RO is engineered to operate in conventional RO mode if needed.
- Reduced energy use- specific energy consumption dropped from 0.29 to 0.25 kWh/m³.
- Lower chemical costs- Significant annual savings from optimized antiscalant dosing.
Today, the Arcadia plant produces up to 10 MGD of potable water at high recovery, helping the city meet local demand while reducing operating costs and brine discharge. Despite the increase in recovery, the system continues to operate with low CIP frequency and consistent reliability.
By reducing production costs for imported water Santa Monica can now produces local water at roughly $1,000 per acre-foot, compared to about $1,400 per acre-foot for imported water, a difference that shows the economic and sustainability impact of high-recovery RO retrofits.