[France] French Béziers Wastewater Treatment Plant Pilots Intermittent Reverse Osmosis, Raising Reuse Recovery Rate to 95% and Cutting Energy Consumption by Up to 50%

The wastewater treatment plant in Béziers, a small city in southern France, is conducting a municipal wastewater reuse upgrade pilot, in collaboration between Salinity Solutions and Suez, with support from the French Agency for Ecological Transition (ADEME). The pilot adopts HyBatch batch Reverse Osmosis technology, using piston-driven pressure exchange to concentrate the feedwater through multiple cycles, and dynamically controlling pressure based on salinity, raising the recovery rate from approximately 85% for conventional Reverse Osmosis to 90%—95%, with energy consumption reduced by up to 50%. The pilot will continue until 2027年.

1. Where Conventional Reverse Osmosis Gets Stuck: The Awkward Fate of 15% of the Water

The mainstream technology for municipal wastewater reuse is Reverse Osmosis (RO). However, conventional RO systems achieve an average recovery rate of only about 85%—meaning that 15% of the water still becomes concentrate. Treating this concentrate is both troublesome and costly, making it a key constraint that prevents many wastewater reuse projects from further improving their economics.

More challenging is the associated chain reaction: high energy consumption, prone to membrane scaling, frequent chemical cleaning, and shortened membrane lifespan. Against the backdrop of ever-increasing pressure from water scarcity, wastewater reuse cannot stop at being merely "usable"—it must also be efficient, affordable, and scalable.

2. Two Key Changes in HyBatch

HyBatch takes a different approach, with changes focused on two points:

2.1 Variable Pressure Replaces Constant Pressure

Conventional RO applies constant pressure throughout the entire operation. HyBatch, however, dynamically controls pressure based on salinity levels: as the concentration process progresses and salinity rises, pressure is adjusted accordingly, avoiding the energy waste of applying maximum pressure throughout the entire process.

2.2 Piston-Driven Pressure Exchange and Cyclic Concentration

The technology relies on a piston-driven pressure exchange process, subjecting the feedwater to multiple cycles of treatment until the target recovery rate is reached. The pressure exchange device recovers energy from the concentrate side, further reducing the energy consumption per unit of produced water.

The combined effect of both is directly reflected in three indicators:

• Recovery rate—reaching 90%—95%, higher than the approximately 85% of conventional RO.
• Energy consumption—reduced by up to 50%.
• O&M—reduced scaling, lower chemical cleaning frequency, extended membrane lifespan, and simultaneous reduction in overall operating costs and environmental footprint.

3. Containerized Delivery: A Practical Solution for Retrofitting Old Plants

This technology was initially developed for lithium concentration applications. As water scarcity pressure intensifies in cities and industries, the two partners decided to adapt and scale it up for municipal wastewater treatment scenarios. Salinity Solutions and Suez began discussions as early as 2019年.

In terms of delivery format, the HyBatch system adopts a containerized, modular form, enabling rapid installation with minimal disruption to existing wastewater plant operations, and making future replication to other municipal facilities easier—this is particularly important for existing wastewater plants with limited land and no possibility of shutting down water supply.

The pilot is supported by the French Agency for Ecological Transition (ADEME) and is located at the Béziers wastewater treatment plant operated by Suez. HyBatch is operating in parallel with a conventional tertiary Reverse Osmosis unit that has been running since 2024年, which serves to establish a baseline. The pilot is expected to continue until 2027年, covering different seasons and various operating conditions to fully validate stability. The plant has currently been shortlisted for the Global Water Awards in the "Municipal Reuse Project of the Year" category.

4. Why a Few Percentage Points Are Worth Paying Attention To

From 85% to 95%, it appears to be just 10 percentage points, but the actual impact is multiplicative. Taking a project producing 1万 tons of reclaimed water per day as a rough calculation, raising the recovery rate from 85% to 95% increases the produced water volume by approximately 12% at the same intake volume, while reducing the concentrate volume requiring treatment by approximately two-thirds.

The reduction in concentrate volume brings triple cascading benefits: the scale of concentrate treatment facilities can be reduced, land acquisition requirements decrease, and the costs of external transport or evaporation for concentrate disposal are substantially cut. In industrial scenarios particularly sensitive to high-salinity wastewater, this could be the dividing line between project viability and failure.

5. Industry Observation: Beyond Efficiency, the "Refining" Trend in Wastewater Treatment Is Accelerating

The significance of the Béziers pilot goes beyond a single piece of new equipment—it reflects a global shift in water reuse technology from "large-scale construction" to "tapping unit efficiency potential":

• Return of batch/intermittent processes—In addition to HyBatch, the techno-economic advantages of Batch Reverse Osmosis (BRO) in distributed scenarios such as brackish water and oil and gas produced water are also being proven. Recent studies show that high-flux BRO can reduce the levelized cost of water by 0.07 USD/m³, increase the direct utilization rate of renewable energy by 40%, and reduce energy storage demand by 16 times.
• Energy consumption and chemical consumption become primary tender items—In the domestic MBR field, high-flux, low-energy, anti-fouling membrane modules are replacing traditional high-intensity aeration schemes; measured data from AI dynamic aeration control show that aeration energy consumption can be reduced by 18.22%, and membrane cleaning downtime can be reduced by 80%.
• Modularization becomes standard for overseas expansion—Containerized integrated units support plug-and-play, addressing the need for rapid deployment in remote areas and emergency scenarios, and are also one of the mainstream forms of overseas project delivery.

At the same time, the pull from domestic policy is equally clear. Shandong has specified that by 2030年, the province's urban Reclaimed Water utilization rate will reach 60%, and unconventional water utilization will reach 25亿 cubic meters or more; at the national level, total Reclaimed Water utilization has exceeded 256亿 cubic meters. The larger the reuse scale, the more valuable the marginal improvement in unit energy consumption and unit concentrate volume.

Industry analysis suggests that as Reclaimed Water moves from a supplementary water source to a conventional water source, the dimensions of competition in the industry are changing—in the past, it was about who had the larger scale; next, it will be about who can squeeze every ton of water cleaner and use it more economically.

TIANYI TECH Co., Ltd. (TIANYI LIMITED) is deeply engaged in the fields of wastewater treatment and Reclaimed Water Reuse, providing integrated overall solutions for Ultrafiltration, Reverse Osmosis, and special membrane process integration, concentrate reduction treatment, and smart operation around industrial and municipal Reclaimed Water Reuse scenarios. The company focuses on key operational indicators such as power consumption per ton of water, chemical consumption, and membrane lifespan, helping customers reduce the full life-cycle cost of reuse systems to a competitive range.

Source: Reports from Water Purification Technology and AQUATECH Water Technology Issue 2, 2026年, public interviews with Salinity Solutions and Suez, and publicly available information on pilots by the French Agency for Ecological Transition (ADEME).