Why Coastal Cities Are Facing Water Supply Challenges?
Coastal cities have highly concentrated ports, industrial parks, and population density, resulting in insufficient freshwater resources. Traditional municipal water supply has relied on rivers, reservoirs, and groundwater. However, climate change has led to unstable rainfall and prolonged drought cycles. Urbanization and industrialization have further increased water demand. Inter-regional water transfer is not only costly but also involves complex regional coordination projects.
Water resource issues also profoundly impact the industries of coastal cities. Without a stable water supply, project feasibility and investment returns become uncertain. Cities may be unable to attract investment or support the expansion of existing businesses, thus limiting urban development. Moreover, when a city’s main water supply comes from the same water source system, any problem in any link will directly threaten the operation of the coastal city, industrial production, and living conditions.
When traditional water sources can no longer reliably meet the needs of cities, where should we go next? One answer that is being seriously evaluated by more and more coastal cities is municipal seawater desalination.
Can Seawater Desalination Serve as a Municipal Water Supply?
When discussing municipal water supply plans, the first question that needs to be answered is “Is it feasible?” The feasibility assessment of water supply in coastal cities needs to be based on three dimensions: technological maturity, planarability, and operational stability.
Modern large-scale desalination RO technology is highly mature. Globally, several municipal seawater desalination plants with a daily output exceeding 500,000m3 are already operating stably. These projects are not short-term pilots but are integrated into their respective cities’ long-term water supply plans. Over the past decade, the international water industry has developed a mature framework for municipal seawater desalination projects, including feasibility studies, PPP models, and operation and maintenance standards.
Actual operational data shows that modern large-scale SWRO plants can achieve an average annual availability of over 95%, comparable to traditional water plants. During a drought, when reservoir water levels drop and river flows decrease, the water source for desalination plants will not be affected. This is precisely its core value as a drought-proof water source.
How a Municipal Desalination Plant Works?
A municipal seawater desalination plant can be simplified into three stages:
Intake and pretreatment
For municipal projects, intake and outfall design is a critical engineering milestone in the early planning stages. It relates to environmental impact, site selection, and long-term operation and maintenance costs. Seawater is introduced into the plant through near-shore pipelines.
The core task of pretreatment of the desalination system is to remove impurities such as silt, algae, and marine organisms to provide qualified feed water for the subsequent reverse osmosis membrane system.
RO system
Pretreated seawater is pumped into the RO membrane system under high pressure. The reverse osmosis membrane allows only water molecules to pass through. Salt and impurities are retained and discharged with the concentrated brine.
The core cost comes from energy consumption and the replacement and maintenance of membrane modules. The widespread adoption of energy recovery devices has reduced energy consumption in large-scale desalination plants by approximately 50%, a key technological driver of the continued decline in municipal desalination costs.
Post-treatment and distribution
After desalination, the mineral content and pH value of the water need to be adjusted to meet drinking water standards before it is connected to the city’s water supply network. This step determines whether the desalination plant can be integrated with the existing water system.
Cost Structure: CAPEX, OPEX, and Cost per m³
For any municipal infrastructure project, cost is never a single number, but a structure. Municipal seawater desalination requires knowing where the money is spent, the true cost per cubic meter of water, and whether the cost is predictable.
CAPEX
The CAPEX of a municipal desalination plant mainly includes: intake works, pretreatment systems, high-pressure pumps and energy recovery units, reverse osmosis membranes, post-treatment systems, and land and civil engineering works.
According to the GWI DesalData and the latest industry data, unit CAPEX decreases significantly with increasing scale. For every doubling of global cumulative desalination capacity, unit CAPEX decreases by approximately 15%. This is a direct reflection of technological maturity and economies of scale.
OPEX
The main components of OPEX include: energy consumption, membrane replacement and maintenance, chemical consumption, and labor and management. Energy consumption is the core variable in OPEX, accounting for approximately 40-60%, making it the largest single cost item.
Modern large-scale SWRO plants equipped with high-efficiency energy recovery devices have reduced energy consumption per ton of water to 3.0-4.0 kWh/m³, nearly half that of systems without energy recovery.
Levelized cost of water
After combining CAPEX and OPEX, according to the industry report published by William Blair in 2025, the levelized cost of water (LCOW) for municipal desalination is as follows:
| Scale | LCOW（USD/m3） |
| Mega-scale（>500,000m3/d） | $0.37-0.50 |
| Large-scale（100,000-500,000m3/d） | $0.50-0.80 |
| Medium-scale （10,000-100,000m3/d） | $0.80-1.00 |
| Small-scale （<10,000m3/d） | $0.90-1.50 |
Specific figures will vary depending on regional differences. For example, the corresponding SWRO project scale in Dubai’s Hassyan, with a scale of 120-180 MIGD, has already reached approximately $0.37-0.50/m³. This is the latest benchmark for the cost of large municipal seawater desalination projects worldwide.
In the long term, the cost of desalination is on a significant downward trend. Technological advancements and the transition to green energy are the core drivers of this cost reduction.
Reliability and Water Security Benefits
The value of seawater desalination lies in fundamentally changing the water supply logic of cities, providing diversified water supply solutions. It boasts high reliability and excellent safety benefits, ensuring water security for coastal cities.
The core indicator for measuring the reliability of a water plant is availability, which is the percentage of actual operating time throughout the year. Modern large-scale SWRO plants typically achieve availability rates exceeding 95%, comparable to traditional water plants. This indicates that desalination plants are a primary water source that can operate stably year-round.
The water source for desalination plants is seawater, which is uninterrupted. This is the core value of a drought-proof water supply system. For coastal cities facing periodic droughts, this can ensure a stable water supply unaffected by climate change.
Water resource policies in many coastal cities are tightening. For industrial parks and large users relying on traditional water sources, the uncertainty of operating costs is increasing. Seawater desalination, where the main operating cost is electricity, provides a cost-predictable and independent water source solution, allowing industries to confidently expand.
Integration with Existing City Water Systems
Seawater desalination plants must be able to integrate seamlessly with existing urban water supply systems. Desalinated seawater is characterized by its high purity, but overly pure water may corrode pipelines. To solve this problem, post-mineralization treatment is needed to ensure that it can be safely and stably connected to the city’s water supply network.
The connection method can also be selected as needed. Currently, most coastal cities adopt a unified water supply system. Seawater desalination plants serve as a secondary water source, and the produced water, after mineralization treatment, is pumped into the city’s main water supply network. It is mixed with the effluent from surface water plants and groundwater plants to supply water for residential, commercial, and industrial use.
This eliminates the need for new dedicated pipelines, quickly achieving water source diversification. It is suitable for coastal cities with significant freshwater shortages and urban areas with well-established existing pipeline networks.
Differentiated water supply involves two independent pipe networks: one supplying high-quality drinking water and the other supplying non-drinking water. It is a more refined and efficient water resource allocation model. It is suitable for newly built industrial parks, large coastal new areas, and areas with a high concentration of water-intensive industries.
Point-to-point direct supply means directly connecting a seawater desalination plant to a specific industrial park. This is suitable for the independent implementation of large-scale industrial projects.
Regardless of the chosen method, the technical route for integrating desalinated seawater into urban water supply systems is standardized, regulated, and feasible.
Case Studies of Large-Scale SWRO Plants
Taweelah RO Desalination Plant
Located in Abu Dhabi, UAE, this project has a daily production capacity of approximately 900,000 tons of water, with an annual output of 324 million tons. It is the world’s largest and most technologically advanced seawater desalination project, meeting the annual water needs of nearly 2 million people and serving as the city’s primary water source.
The project integrates the most advanced desalination technologies from more than ten countries worldwide, achieving a globally leading desalination conversion rate.
This case demonstrates the technological maturity and large-scale feasibility of seawater desalination.
Alicante Ⅱ Seawater Desalination Plant
Located on the Mediterranean coast of Spain, this project has a daily production capacity of 65,000 cubic meters of water. Like many coastal areas, the plant was built to minimize the impact of water scarcity and drought on local communities.
More than 15 years after commissioning, the original membrane elements are still operating and performing excellently. Membrane durability means predictable replacement cycles and manageable long-term operating costs.
This case demonstrates the long-term reliability of seawater desalination. Furthermore, the Mediterranean climate, similar to that of some coastal cities in Southeast Asia or Africa, also demonstrates its resilience to drought.
Is It a Strategic Choice for Future Cities?
We have assessed the feasibility, cost, safety, and implementation pathways of municipal seawater desalination from a decision-making perspective. In conclusion, seawater desalination is a mature, stable, cost-controllable, and scalable municipal water supply solution, and a strategic option in a diversified water supply system.
NEWater specializes in municipal seawater desalination options, providing end-to-end services from feasibility studies to project delivery. If you are evaluating this solution, please contact us for a customized feasibility analysis tailored to your city or to learn more about our project operational experience.
Portable Desalination Unit
Skid-mounted Desalination Equipment
Containerized Desalination Plant
EN 
RU 
ES 
DE 
AR 
TH 
PT 
FR 
IT 
KO 
JA 