Seawater Desalination Plant Cost: How Much Does It Cost per Cubic Meter?

If you are researching seawater desalination plants, you have most likely already looked up “desalination plant costs” and “costs per m³ of desalinated water”. You may be confused by the cost figures for seawater desalination, with some projects quoted at $0.5 per ton of water and others at over $5.0. How much will your project actually cost?

This article will break down the cost structure, compare different options, and provide cost-reduction strategies. After reading this, you will know whether your project is worth investing in.

What Is the Cost per Cubic Meter of Desalinated Water?

Multiple factors influence the cost of seawater desalination and generally range from $0.5-$5.0/m³. Factors affecting the price difference include: project scale, raw water quality, energy options, technology selection, regional logistics, and whether you prioritize equipment costs or the total lifecycle cost. Generally speaking:

• Small projects (island communities, offshore facilities): $2-5/m³. Small-scale production is less economical, but still cheaper than bottled water or shipped fresh water.
• Medium projects (resorts, small towns): $1-3/m³. The price difference is mainly due to optimized energy consumption and pretreatment.
• Large projects (municipal water supply, industrial parks): $0.5-1.5/m³. It’s already cheaper than tap water in many areas.

CAPEX: Initial Investment of a Desalination Plant

The CAPEX of a seawater desalination project can be broken down into the following four items: equipment cost, installation, logistics, and infrastructure.

Equipment costs typically account for 40-50% of total CAPEX. It includes high-pressure pumps, SWRO membrane modules, energy recovery devices, pretreatment equipment, and instrumentation and control units. This is the part customers care about most, but the latter three are often where problems arise.

Installation accounts for 20-30%. This includes factory construction, pipeline laying, electrical wiring, and equipment installation. The more remote the project, the higher this expense.

Logistics account for 5-15%. The cost of moving equipment from the factory to the site may not seem high, but this expense needs to be considered in island projects and remote areas.

Infrastructure typically accounts for 10-20%. This includes seawater intake projects, brine discharge projects, power access, and water storage tanks. The cost of this area is often underestimated, especially for power access.

OPEX: Operating Cost Breakdown

In the long term, the total cost of a seawater desalination plant, CAPEX typically accounts for only 20-30%, while OPEX accounts for 70-80%. Neglecting OPEX could mean that the money you save on equipment might not even cover the first year’s electricity costs. An OPEX for a SWRO project typically consists of four accounts.

Energy

Energy consumption typically accounts for 40-60%, making it the largest expenditure. The essence of SWRO is to use a high-pressure pump to extract fresh water, and the high-pressure pump is the main energy consumer. 

Without energy recovery, SWRO consumes 4-6 kWh/m³. With an energy recovery system, this can be reduced to 2.5-3.5 kWh/m³. For diesel-powered power generation projects common on islands, this number would be even higher.

Chemicals

Chemical consumption can account for 10-20%. Seawater requires the addition of bactericides, coagulants, reducing agents, and other chemicals during pretreatment, and pH adjustment and chlorination are needed during post-treatment. 

Different raw water qualities require vastly different types and dosages of chemicals. Red tides require twice as much chlorine, and high-silica seawater requires a special scale inhibitor. These expenses may seem small, but they add up over the years.

Membrane replacement

The lifespan of a reverse osmosis membrane depends on the quality of the raw water, the effectiveness of pretreatment, and the level of operation and maintenance. The better the pretreatment, the longer the membrane life. 

The membrane replacement cost for a medium-sized project can range from $50,000 to $200,000. Although it’s not replaced annually, it’s a significant, recurring expense that must be factored into the lifecycle cost (LCC).

Labor

Labor and maintenance account for 5-15% of OPEX. This includes operator wages, regular inspections, equipment maintenance, and troubleshooting. The higher the degree of automation in a seawater desalination project, the lower the labor cost proportion. For small, island, off-grid projects, containerized or modular solutions can achieve semi-unmanned operation and generate greater returns.

Key Factors That Affect Desalination Cost

Having understood the composition of CAPEX and OPEX, let’s now discuss the four most critical factors affecting the cost of seawater desalination.

Plant size

This is the single most influential factor. A key characteristic of seawater desalination plants is that their equipment costs do not increase linearly with capacity. 

The cost of building a desalination plant with a daily output of 1,000 tons will not be 10 times that of a plant with a daily output of 100 cubic meters. It may only be 5 to 6 times. This is because many costs, such as control systems and water intake works, are fixed. Amortized per ton of water, the larger the production volume, the lower the unit cost.

Specifically, small projects suffer from diseconomies of scale, with high equipment and labor costs per ton of water, typically opting for containerized solutions. Large-scale projects can employ multi-row designs and ERDs, thereby reducing the fixed cost per ton of water to an extremely low level.

The economies of scale of medium-sized projects are beginning to emerge, allowing for the configuration of ERD and automation systems, resulting in a significant decrease in unit energy consumption and labor costs. 

Energy source

Energy prices directly determine whether a project can be used. It’s not that desalination technology is expensive, but rather the cost of energy itself. If the electricity is supplied by the grid at a lower price, energy costs are controllable, making it the ideal choice. 

However, if diesel generators are used, the cost is at least 3-4 times higher. In recent years, the most noteworthy cost reduction path is the hybrid energy solution based on solar energy, whose total LCC is already lower than that of pure diesel solutions.

Feed water quality

Open sea areas have relatively stable water quality, low turbidity, and low pretreatment costs. Nearshore or tidal flat seawater is affected by tides and waves, leading to greater turbidity fluctuations and increased pretreatment costs. Bitter brine has lower pressure requirements, making it cheaper than seawater desalination.

In highly polluted or red tide-affected areas, algae can clog membranes, shortening their lifespan and increasing cleaning frequency, thus raising maintenance and replacement costs. It may even be necessary to add dissolved air flotation (DAF) or ultrafiltration (UF) as pretreatment, significantly increasing both CAPEX and OPEX.

System design

This is the area that truly tests a supplier’s expertise and is also the easiest to fall into traps. Insufficient pretreatment will cause OPEX to skyrocket; excessive pretreatment will result in excessive CAPEX. A good pretreatment design leaves just the right margin and is a customized solution based on the project’s water quality.

As mentioned earlier, ERD is the most influential technical decision affecting OPEX. For projects with a daily output of over 1000 tons, the increased CAPEX from adding ERD is usually recouped from electricity costs within 12-18 months, and the following ten years are pure profit.

Cost Comparison: Desalination vs Other Water Sources

Desalination vs water transport

This is the most common choice for islands, resorts, and coastal cities facing water scarcity. The cost of water transportation consists of: water source procurement cost, transportation cost, water storage facilities, evaporation, and leakage losses. Water transport prices fluctuate greatly, depending on distance and logistic conditions. 

Below is a brief comparison between water transport and desalination:

For long-term projects with daily water consumption exceeding 100 tons, desalination is almost always cheaper than water transport. Moreover, water transport prices rise annually, and fuel, ship charter, and labor costs are uncertain. Once the OPEX for desalination is locked in, it becomes increasingly competitive.

Desalination vs groundwater

This is a common comparison between inland projects and coastal well water projects. The cost of groundwater consists of: drilling costs, pump energy consumption, maintenance, and water treatment costs. Most groundwater, including deep, high-salinity groundwater, requires some level of treatment, or even RO treatment.

There is another easily overlooked issue: groundwater is not an unlimited supply. Over-extraction can lead to water table decline, water quality deterioration, and even land subsidence. 

In addition, the quality of seawater is relatively stable, while the quality of groundwater may vary with the seasons and the amount of water extracted. Not to mention, more and more countries and regions are now regulating groundwater extraction. Relying on groundwater is not a wise choice.

How to Reduce Cost per m³?

The cost range of seawater desalination is transparent and largely depends on the system design. Next, we will present four proven cost reduction paths, each corresponding to a specific cost item.

Energy recovery

To reduce energy expenditure, you can choose to install an energy recovery device. ERD recovers the residual energy from concentrated brine and reuses it to pressurize the feed water. The payback period is as short as 12 months, with savings of 30-50% on electricity bills. Except for extremely small projects, not adding an ERD sacrifices long-term costs for short-term capex reduction, which is not a wise choice.

Modular design

For projects with long timelines and complex on-site construction, pre-designed modular or containerized RO desalination systems can be selected. The equipment is assembled and tested in the factory and only requires on-site connection to water and electricity to operate.

It reduces CAPEX, shortens the water output cycle, and can be expanded simply by adding modules. Suitable for small projects, islands, remote areas, or emergency water supply. Same RO technology, faster delivery, and lower on-site costs.

Optimized pretreatment

To address the issues of frequent cleaning, shortened membrane life, and uncontrolled OPEX caused by membrane fouling, a customized pretreatment solution optimized based on the raw water quality can be selected. Proper preprocessing can reduce overall OPEX by 15-25%. 

For open marine areas, “media filtration + cartridge security filtration” is recommended. For nearshore or high-turbidity applications, “coagulation sedimentation + media filtration” is recommended. For areas experiencing red tides or algal blooms, “dissolved air flotation + ultrafiltration” is recommended.

Hybrid energy

For areas powered by diesel, a hybrid energy system combining photovoltaic and diesel power should be selected. During the day, solar power generates water, and excess electricity is stored in batteries. At night or on cloudy days, the electricity is replenished by batteries or diesel fuel. 

Because of the components such as solar panels, batteries, and inverters, the CAPEX of the hybrid energy solution is higher than that of a pure diesel solution. However, in regions with abundant sunshine, such as Africa, Southeast Asia, and the Middle East, the payback period is typically 3-6 years. Assuming a project lifespan of 20 years, the subsequent decade or so will be net savings.

Typical Cost by Application

Island

Typical cost range: $1.0-$3.0/m³. The core challenges of island projects are high logistics and energy costs, as well as difficulties with on-site service. 

Island projects typically choose containerized or skid-mounted equipment to reduce on-site installation and standard energy recovery systems to lower energy consumption. They also employ solar-powered hybrid solutions to reduce reliance on diesel fuel.

Offshore

Typical cost range: $0.5-$1.5/m³. Offshore scenarios are characterized by limited space and operational and maintenance challenges. 

Compact containerized RO systems designed specifically for these platforms are typically chosen, as their skid-mounted pretreatment effectively saves space, and corrosion-resistant materials and high automation reduce the difficulty of later maintenance.

Resort

Typical cost range: $0.7-$3.0/m³. Resorts are sensitive to upfront budgets and are increasingly emphasizing ESG, thus commanding a premium in terms of corporate image. They tend to favor modular systems and solar energy desalination solutions, while also incorporating remote monitoring and low-maintenance designs.

Emergency

Typical cost range: $3.0-$5.0/m³. Emergency projects have the highest unit cost because they are typically smaller in scale and powered by diesel. However, the cost is far lower than that of transporting bottled water, and the response time is far faster.

Conclusion 

The cost of seawater desalination depends on your project scale, energy solution, raw water quality, and application scenario. Although the cost is within an uncertain range, one thing is certain: it can be optimized. This optimization isn’t achieved by lowering supplier quotes, but by making the right design decisions.

Contact NEWater for cost optimization. We don’t aim for the lowest quote, but rather the lowest LCC. We can make you three promises:

• Modular/containerized: Reduces CAPEX and installation costs and enables rapid water output.
• Energy flexibility: solar/diesel/hybrid options to suit your project conditions.
• 10 years of experience: We have delivered high-quality services to clients across multiple regions worldwide, offering you customized solutions and quotations.