Abstract
Algeria’s pure reverse osmosis (RO) desalination systems face serious vulnerabilities: increasing turbidity events and frequent membrane replacements threaten operational stability, resulting in 1,680 hours of downtime annually across active plants. As the Mediterranean warms 20% faster than the global average, water security requires urgent innovation.
This article proposes a hybrid MED+RO technology (1/3 thermal + 2/3 membrane) to ensure operational resilience. If RO shuts down, MED continues independently at 33% capacity, guaranteeing minimum supply. Although hybrid systems require a 28% higher capital investment, break-even is reached in year 16 due to reduced membrane replacement costs.
Optimized pre-treatment with ultrafiltration (N+1 redundancy) and AI-enabled predictive maintenance lowers costs by 15-30%. Incorporating green hydrogen-powered turbines (GTH₂) reduces carbon emissions by 85-95%. Algeria’s abundant solar resources (2,000-2,500 kWh/m²/year) support cost-effective hydrogen electrolysis. This integrated strategy shifts water security from vulnerability to resilience.
The MENA Water Crisis and the Path to Resilience
The Middle East and North Africa (MENA) region is at a critical point in its water security journey. With an installed desalination capacity of 44 million m³ per day—making up nearly 48% of the world’s output—the region leads globally in desalination. However, beneath these impressive numbers lies a fragile situation: climate change, rising water demand, and aging infrastructure threaten the continued operation of desalination plants that millions depend on.
Algeria exemplifies this paradox. Once a water-rich nation, the country now faces a severe annual deficit of about 7 billion m³. By 2030, Algeria plans to increase its desalination capacity to 5.3 million cubic meters per day, which will cover over 55% of an estimated national drinking water demand of 9.6 million cubic meters daily. Currently, there are 18 large plants and 12 smaller facilities operating—all mostly relying on reverse osmosis (RO). Algeria has built its water security strategy around a single technological approach.
This dependency, although economically sensible in the short term, involves significant risks. Increasing turbidity events, frequent membrane replacements, and shutdowns averaging 1,680 hours annually across nine plants have revealed a core vulnerability: pure RO systems lack operational resilience against Mediterranean Sea degradation and climate variability.
The solution doesn’t lie in abandoning proven technologies but in rethinking how they work together. A hybrid desalination system—combining thermal multi-effect distillation (MED) and reverse osmosis with clean energy integration—provides a path to real water security.
The MENA region’s desalination leadership is undeniable but highly concentrated. Five countries—Saudi Arabia, the United Arab Emirates, Qatar, Kuwait, and Algeria—account for over 72% of regional production, representing more than 32% of global output. This concentration reflects both regional water stress and the capacity for technological adoption.
However, this concentration masks an operational fragility. The Mediterranean Sea is warming 20% faster than the global average, intensifying summer storms and extending marine heatwave seasons that now cover up to two-thirds of the basin. For desalination plants drawing raw seawater, these conditions create operational challenges that pure RO systems struggle to manage.
The critical parameters for RO viability, turbidity (NTU), the Silt Density Index (SDI), and organic load measurements (COD, BOD₅, TOC) become increasingly unstable. When turbidity exceeds 85 NTU during storm events, plants must shut down to prevent irreversible membrane damage. Algerian facilities experienced exactly this scenario, with multiple shutdowns lasting 20 to 70 days, reducing aggregate production capacity by roughly 10%.
These recurring stoppages directly threaten the reliability of the water supply. For a region where desalinated water is often the only reliable freshwater source, such interruptions transcend economic concerns; they represent genuine security risks.
The Hybrid Solution: Strategic Operational Independence
Addressing this vulnerability requires a fundamental rethinking of plant architecture. The hybrid MED (1/3) + RO (2/3) configuration offers a compelling alternative, particularly when coupled with appropriate energy sources and advanced automation.
The operational logic is simple: if the RO section shuts down due to high turbidity or membrane fouling, the MED section continues operating independently at 33% of total capacity. This guaranteed minimum production provides critical resilience. During the period of membrane replacement and cleaning (usually every 2-3 years), MED continues to supply essential water.
The economic case gets stronger over time. While hybrid systems need 28% more capital investment (CAPEX) than pure RO and have 18% higher total water costs (TWC) in the early years, the 25-year plant lifespan shows a different picture. Break-even occurs at 16 years, just as pure RO operating costs begin to rise again due to early membrane replacements.
For a facility processing over 300,000 m³/day, this results in significant operational savings. Pure RO systems have total water costs of $0.65-$0.95 per cubic meter, while hybrid systems range from $0.78-$1.18 per m³. Initially a disadvantage, but becoming more appealing as membrane replacement cycles shorten. MED’s operational stability at lower costs becomes the main economic argument in the plant’s second decade of operation.
Due to Repeated Stoppages, Urgent Action is Needed to Ensure the Safety of Drinking Water Supplies
Operating conditions are becoming more difficult to meet, especially due to climate change, which exerts strong pressure on the Mediterranean Sea and impacts both its physical features and water resource management in the region. Based on data from a 2020 study on desalination plant operations, the number of scheduled and unscheduled shutdowns is rising due to maintenance, leading to service interruptions lasting from 20 to 70 days.
For example, the nine operational desalination plants experienced about 1,680 hours of downtime in 2020. Shut-downs mainly occurred due to membrane cleaning and replacement, as well as turbidity exceeding the critical threshold of 85 NTU. This has led to a roughly 10% reduction in production capacity.
These recurring malfunctions directly threaten the reliability of the desalination system in certain regions, compromising water security and calling for an urgent review of the technology used to ensure a continuous supply and enhance the resilience of the drinking water production system.
The Hybrid MED (1/3) + RO (2/3) Plant: a Strategy for Operational Independence
To address water security issues, it is logical to suggest new solutions that enhance operational flexibility, such as a hybrid plant combining two complementary processes: the first, MED thermal (1/3), and the second, RO membrane (2/3).
If the RO section shuts down, the MED section can operate independently, with production dropping to 33% of its minimum capacity. All aspects of operational independence must be outlined during the initial design phase and explicitly incorporated into the piping and instrumentation diagram (P&ID).
The design must include isolation valves and bypasses on all common lines. A control system (DCS/SCADA) capable of managing both degraded modes. Concentrated discharge management adaptable to both configurations (variable flow to the sea discharge diffuser). Also, address other aspects related to the storage and distribution section’s capacity to compensate for the drop in production.
Table 1: Overall summary data for a desalination plant with an installed capacity of 300,000 m³/day (source: IDA and GWI).
|
Indicator |
Water Desalination Process
|
| Reverse Osmosis
(RO) |
Multi-Effect Distillation
(MED) |
Hybrid RO(2/3)+MED(1/3) |
| CAPEX Total (M. $) |
380-500 |
650-850 |
530-700 |
| CAPEX spécifique ($/m3/j) |
1270-1670 |
2170-2830 |
1766-2300 |
| OPEX($/m3) |
0.46-0.82 |
0.55-0.99 |
0.49-0.85 |
| LCOW ($/m3) |
0.50-0.80 |
0.75-1.15 |
0.63-0.99 |
| TWC ($/m3) |
0.65-0.95 |
0.90-1.35 |
0.78-1.18 |
| Specific energy consumption (kWh/m³)/(kWh/m³) équ. * |
3.5-4.5 |
6-9 |
4.5-6.4* |
| Quality of water produced /Total Dissolved Solids (TDS), (mg/L) |
200-500 |
<10 |
80-200 |
| Operational Resilience |
Average |
Average |
High |
The MED + RO hybrid plant, combined with a combined-cycle power plant (CCPP), is the best solution for high-capacity applications. It provides operational resilience, better water quality, and energy flexibility that pure RO cannot achieve on this scale.
To better understand the economic aspect, it helps to present a comparison using approximate orders of magnitude based on data from the desalination industry (IDA, GWI, SWCC) and World Bank figures on projects completed over the last decade.
It should be noted that these figures vary considerably depending on the site, country, local energy costs, specific configuration, and conditions. Although reverse osmosis is the least expensive process in terms of investment (CAPEX of 30 to 40%) and discounted water cost (LCOW less than $0.35/m³) compared to MED desalination, the hybrid system offers advantages in service continuity and is fully justified as an appealing alternative.
This is especially true when a cogeneration plant is close to the desalination plant site. In such cases, steam is almost free, which significantly reduces the MED’s OPEX, or when strict water-quality or operational-resilience standards are required by the specifications.
Although the hybrid process requires an additional initial investment of 28% compared to reverse osmosis, the total water cost (TWC) is also 18% higher during the first few years of operation.
These figures might seem intimidating, but the analysis conclusion is quite different. Over a 25-year span, which is the typical lifespan of a desalination plant, the break-even point actually happens at 16 years. This is when reverse osmosis operating costs start to rise due to premature membrane replacements caused by more frequent cleaning and replacement every 2 to 3 years, which are well below the service intervals recommended by the manufacturer. Meanwhile, the MED thermal process offers much greater operational stability at a much lower cost.
Figure 1: Comparative overview of operational costs (OPEX) for desalination, by item, for RO, MED, and Hybrid processes.
Optimizing Pre-treatment to sustain Reverse Osmosis (RO) Efficiency
If the reverse osmosis membrane process remains effective, given technical and economic feasibility, alternative solutions, such as water intakes or anti-clogging treatments, can be explored. The water intake should have two independent supply pipes to facilitate maintenance without halting production.
The screen room must be equipped with double filter drums with a bypass to protect the membranes, which are the most sensitive and costly part of the desalination plant. Inadequate pre-treatment can lead to reduced permeate flow, increased differential pressure, irreversible membrane damage, and frequent, costly chemical in-place cleaning (CIP).
The water intake must have two separate supply pipes to enable maintenance without disrupting production. The screen room should be fitted with double filter drums with a bypass. The goal is to protect the membranes, which are the most delicate and costly part of the desalination plant. Inadequate pretreatment can cause a decrease in permeate flow, an increase in differential pressure, irreversible membrane damage, and frequent, expensive chemical cleaning (CIP, Cleaning in Place).
The UF pretreatment should be sized with a redundancy margin of 20–25% (N+1 or N+2 equipment redundancy for larger trains) to handle spikes in quality degradation without disrupting production. The management of UF membrane washing should be integrated into the distributed control system (DCS), with automatic adjustments of the frequency based on real-time quality data (turbidity, online SDI).
The combination of optimized water intake, ultrafiltration (UF) as the core of the pretreatment process, and targeted chemical inhibitors provides the best balance of performance, reliability, and cost over the lifetime of the installation.
Figure 2: Example diagram of the suggested pre-treatment based on raw water quality
AI: The Key to Optimization and Predictive Maintenance of Osmotic Membranes
For regions that lack alternative drinking water sources during extended outages of more than four days, and to ensure continuous service, the hybrid MED (1/3) plus RO (2/3) desalination process offers a solution that guarantees water availability regardless of climatic conditions.
Advances in artificial intelligence (AI) can be used to optimize and maintain membranes and distillers, extending their service life and reducing outages. The results of a prediction system that automatically alerts to the time remaining before CIP, integrated into the plant’s SCADA control system, enable predictive maintenance and can lower membrane-related costs by 15 to 30%, depending on fouling levels and raw water quality.
Monitoring and predicting fault detection in pumping systems or secondary circuits can be achieved by integrating IoT data and analyzing it with AI algorithms. This enhances the reliability, safety, and lifespan of installations while reducing the costs and risks associated with unexpected breakdowns.
Energy Synergy and Optimisation of Cogeneration or Through the Use of Clean Energy Sources
Furthermore, it is crucial to maximize the use of water and electricity generated by cogeneration, utilizing residual heat to power the multi-effect distillation (MED) process while providing the electrical energy needed for the reverse osmosis (RO) membrane process.
Integrating renewable energy (RE) is considered a key strategy for reducing CO₂ emissions by 20% and the carbon footprint by approximately 40%. This option may be advantageous and promising in the future, as it converts hydrogen into electrical energy by intelligent adaptation of existing gas turbines (GTH₂ / Gas Turbine Hydrogen) to burn hydrogen instead of natural gas.
References
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[2] Advanced Programme for IDA World Congress, 2019. Filtration + Separation [online]. Vol. 56, No. 5, pp. 6 6. DOI 10.1016/S0015-1882(20)30126-9[online]. [Accessed 1 February 2026].
[3] WORLD BANK, 2019. The Role of Desalination in an Increasingly Water-Scarce World [online]. World Bank, Washington, DC. [Accessed 16 February 2026].
[4] ØSTERGAARD, Poul Alberg, DUIC, Neven, NOOROLLAHI, Younes, and KALOGIROU, Soteris, 2020. Latest progress in Sustainable Development using renewable energy technology. Renewable Energy [online]. December 2020. Vol. 162, pp. 1554–1562. DOI 10.1016/j.renene.2020.09.124. [Accessed 16 February, 2026].
