As a robust and cost-efficient solution for landfill leachate and other high-fouling industrial wastewater streams, ZwitterCo provided Serpol with long-term process reliability, regulatory compliance, and operational efficiency.
By Daan Vandeplassche
Serpol is a leading environmental services company in France with more than four decades of expertise in contaminated site remediation, effluent treatment, and sustainable waste management. With advanced in-house process development capabilities and a strong record of full-scale implementation, Serpol delivers technically robust solutions across a wide range of industrial and environmental applications.
Among its most complex and demanding operations is the treatment of landfill leachate, a highly variable wastewater stream containing elevated levels of organic compounds, nitrogen species, heavy metals, and inorganic salts. To meet strict discharge and reuse standards, Serpol applies membrane-based separation processes alongside biological and chemical treatment methods. In 2017, the municipality of Sytraival launched a design, build, and operate (DBO) tender aimed at reducing the cost of leachate treatment while also minimizing the consumption of potable water used for non-potable onsite tasks such as truck washing and dust control. Serpol was awarded the project with a membrane-centric treatment solution designed to address both treatment performance and water reuse.
The Challenge
The landfill leachate treated at the Sytraival site presents a complex and variable wastewater profile, containing elevated levels of organic compounds, nitrogen species, heavy metals, and inorganic salts. These constituents contribute to a combination of fouling mechanisms in reverse osmosis (RO) membranes, including organic adsorption, biofouling, colloidal deposition, and scaling. The result is a gradual decline in membrane performance, typically indicated by increased transmembrane pressure and reduced permeate production. Following the installation of a brackish water (BW) RO system, Serpol encountered significant operational challenges. Membranes required daily clean-in-place procedures using alternating alkaline and acidic formulations. Despite this routine, cleaning effectiveness declined over time, and membrane elements had to be replaced every two to three months. A membrane autopsy confirmed that organic fouling was the dominant issue.
To address the situation, Serpol trialed various solutions, including specialized cleaning agents and alternative membranes from different suppliers. None were able to provide sustained improvement in membrane performance or system stability. These issues led to elevated chemical consumption, increased operating costs, and frequent downtime. Serpol set out to identify a membrane solution that could maintain stable flux, resist fouling, extend membrane service life, and reduce the frequency and complexity of cleaning under real-world landfill leachate conditions.
The Solution
In early 2024, Serpol initiated membrane evaluation at its landfill leachate treatment facility in Sytraival to assess the performance of ZwitterCo Elevation BWRO membranes under standard site conditions and without modifying the existing system design or control strategy. One pressure vessel was retrofitted with ZwitterCo Elevation High Rejection BWRO membranes for side-by-side evaluation against incumbent elements under identical feed and hydraulic conditions. Operating pressures ranged from 250 to 365 psi (17 to 25 bars), feed temperature was maintained between 50掳F to 68掳F (10掳C to 20掳C), and inlet pH was adjusted to 6.5 using sulfuric acid. A recirculation loop maintained ~70 percent system recovery. All control strategies, alarm thresholds, and cleaning protocols were unchanged. Permeate rinse occurred every three to five hours based on flow thresholds, with CIP triggered by post-rinse osmotic pressure.
ZwitterCo Elevation BWRO membranes delivered stable flux and improved cleanability within the existing setup. Following performance validation, Serpol expanded ZwitterCo Elevation BWRO membranes across the entire system, achieving improved operational consistency without process modifications. Figure 1,聽 provides an overview of the treatment process including prefiltration and reverse osmosis.
The Results
The evaluation demonstrated a clear performance advantage for ZwitterCo Elevation BWRO membrane compared to a conventional BWRO element operating under identical landfill leachate conditions.
Normalized flux remained stable throughout the evaluation period for the ZwitterCo Elevation BWRO membrane, whereas the standard membrane exhibited a progressive decline in flux (see Figure 2). To quantify performance consistency statistically, the coefficient of variation (CV) was calculated for each dataset. ZwitterCo Elevation BWRO normalized flux exhibited a CV of 6.7 percent, while the standard BWRO membrane showed a CV exceeding 23 percent, indicating significantly greater variability and fouling progression in the conventional system.
The conductivity rejection profile in Figure 3,聽 illustrates consistent salt separation performance from both the ZwitterCo Elevation and standard RO membranes over the evaluation period. The ZwitterCo Elevation BWRO membrane exhibited a stable and repeatable rejection trend following a brief stabilization phase, maintaining high conductivity rejection across variable leachate conditions. This level of performance confirms that the membrane consistently achieved the site鈥檚 conductivity-based treatment objectives.
Analytical results illustrated below confirm that the ZwitterCo Elevation BWRO membrane delivers high rejection efficiency across critical leachate contaminants. Metals such as iron and manganese were removed to below detection limits, with rejections exceeding 97 percent and 98 percent, respectively. Phosphorus was effectively controlled with over 99.8 percent removal, contributing to a total metal rejection rate of approximately 94 percent. Organic compounds were also well retained: TOC was reduced by 94 percent, AOX by over 95 percent, COD by more than 99 percent, and BOD5 by over 94 percent, indicating strong barrier performance against both biodegradable and recalcitrant organics.
Nutrient rejection was similarly robust, with total nitrogen species reduced by ~93 percent, including ~95 percent removal of Kjeldahl nitrogen. These results demonstrate the membrane鈥檚 capability to produce high-quality permeate and manage the complex and variable composition of landfill leachate (see Figure 4).
The results in Table 1 demonstrate that the ZwitterCo Elevation BWRO membrane maintained both hydraulic stability and contaminant removal performance under challenging wastewater conditions without degradation or operational instability.
The Benefits
The performance evaluation of ZwitterCo Elevation High Rejection BWRO membrane against a conventional High Rejection BWRO membrane demonstrated significant advantages across all operational and financial performance indicators. Cleaning frequency was reduced from seven times to four times per week, with all cleanings performed using a caustic-only and acid + EDTA protocol. This simplification led to a measurable reduction in chemical usage and cost (see Table 2).
As illustrated in Figure 5,
ZwitterCo Elevation BWRO system reduced total cleaning-related operating costs by approximately 50 percent per m3 compared to a conventional High Rejection BWRO membrane. This reduction was enabled by a 57 percent per m3 decrease in chemical cost, a 43 percent per m3 reduction in cleaning-related water consumption, and the decrease in membrane replacement frequency. Downtime-related operating expenses were reduced by 43 percent per m3, driven by fewer cleaning events and improved membrane cleanability. The use of RO permeate for cleaning was significantly reduced, resulting in improved resource efficiency and reclaimed water value. The system operated with high process stability, maintaining consistent flux recovery and transmembrane pressure without signs of foaming, irreversible fouling, or progressive performance decay.
Cleaning triggers were predictable, and the membranes consistently returned to baseline performance with minimal operator intervention. Additionally, the treated permeate consistently met quality targets for onsite reuse in non-potable applications such as truck washing and dust suppression. The cost savings, operational consistency, and ease of use demonstrate the ability of ZwitterCo Elevation BWRO to address key challenges in landfill leachate treatment and deliver long-term value under demanding conditions.
Conclusion and Outlook
The evaluation at Serpol confirmed that ZwitterCo Elevation fouling-resistant BWRO membranes deliver stable performance and consistent contaminant rejection under the variable and challenging conditions of landfill leachate treatment. The membranes maintained hydraulic and separation stability throughout the trial, with no signs of irreversible fouling or performance degradation.
Compared to conventional High Rejection BWRO membranes, the ZwitterCo solution reduced cleaning frequency, eliminated the need for aggressive cleaning formulations, extended membrane service life, and lowered downtime-related operating expenses. These improvements resulted in an approximate 50 percent reduction in cleaning costs. Permeate consistently met internal reuse targets for non-potable applications such as truck washing and dust suppression. These results validate ZwitterCo Elevation BWRO as a technically robust and cost-efficient solution for landfill leachate and other high-fouling industrial wastewater streams. The performance achieved at Serpol supports long-term process reliability, regulatory compliance, and operational efficiency. | WA:
Daan Vandeplassche is Sales Engineer for ZwitterCo鈥檚 wastewater business, currently based out of London, UK, creating a gateway for ZwitterCo鈥檚 expansion into Europe. He is an Environmental Engineering graduate from Ghent University in Belgium. His eight-plus years of professional experience have primarily been in the sales of integrated, innovative wastewater solutions for the European, Middle East and African (EMEA) market. For more informatio, contact Christy Harner, VP of Marketing, at [email protected].