What is Seawater Desalination

Global water resources are in limited supply now due to economic growth and dwindling freshwater supplies. Around 75,000,000 people use seawater desalination worldwide, and this figure is anticipated to continue rising as population growth depletes freshwater supplies.

Simultaneously, millions of people are migrating to coastal towns with limited freshwater supplies. As a result, coastal nations, therefore, are increasingly focusing on seawater desalination as a means of addressing water scarcity. North Africa and the Middle East, for example, account for over half of global saltwater desalination capacity.

Seawater accounts for over half of the saltwater sources that impact human intake worldwide. In the United States, for example, just 7% of desalination plants utilized brine in 2005. Certain water sources that must be desalted are categorized as saltwater, others as river water, and wastewater.

To cope with the crisis and contamination of water resources, it is critical to perform well in seawater desalination and to expedite the development of supporting facilities for saltwater desalination. As a result, the seawater desalination project is critical to resolving the freshwater issue.

It is for this reason, that NEWater Company, with over 20 years of technical research and experience in seawater desalination systems, among other water purification systems, seeks to provide a lasting solution to this problem.

This in return has placed us on top of the world map as leading manufacturers and suppliers of seawater desalination equipment. On the same note, we have built over 9,000 water technology system units for customers across the globe, where 2,000 of these are customized systems.

What is Seawater desalination:

Seawater desalination is the process of desalinating seawater to produce fresh water. It is an open-source incremental technique for utilizing water resources that may enhance the overall amount of fresh water and is unaffected by time, space, or climate.

There are over 20 different types of seawater desalination technologies in the world. These include reverse osmosis, multistage flash evaporation, electrodialysis, low multi-efficiency steam distillation, dew point evaporation, hydropower co-generation, hot film co-production, and seawater desalination technologies that use nuclear energy, solar energy, wind energy, and tidal energy, among others.

All these seawater desalination technologies use various pretreatment, and posttreatment processes some of which include, microfiltration, ultrafiltration, and nanofiltration.

Seawater desalination technology is divided into two main categories: membrane distillation and thermal. Low-temperature multi-effect distillation, multi-stage flash evaporation, and reverse osmosis membrane are the most common method.

i.Distillation:

Distillation is the process of heating seawater, vaporizing it, and condensing the steam into fresh water. Seawater desalination technology using the distillation method is the first to be put into industrial use, and it’s characterized by its applicability even in seawater environments with severe pollution and high levels of biological activity, as well as the high purity of the water produced. However, the desalination process consumes a lot of energy, increasing the initial investment cost significantly.

Figure 1 Distillation Process

ii. Reverse osmosis:

Reverse osmosis separates seawater from freshwater using a semipermeable membrane that permits the passage of solvents but not solutes. Also, it effectively removes inorganic salts, heavy metal ions, organic viruses, and bacteria from seawater and achieving seawater desalination.

Additionally, reverse osmosis is the most used seawater desalinating technology today. It is also the fastest-developing seawater desalination technology and has a broad range of applications due to its low investment, low energy consumption, short construction period, and small land occupation.

Reverse osmosis water flows are classified into two types: pure product water and brine with a high salt concentration.

Figure 2 Reverse Osmosis Water Flows

Distillation is a costly, complex, and energy-intensive process. In comparison, reverse osmosis membrane is more practical and cost-effective for seawater desalination.

Types of Different Reverse Osmosis Systems

To prepare deionized water, reverse osmosis water technology utilizes advanced reverse osmosis desalination technology, a purely physical process preparation technology.

Common reverse osmosis equipment displays include:

  • Large land seawater desalination plant
  • Portable seawater desalination device
  • Marine seawater desalination plant
  • Solar seawater desalination device

By desalinating seawater, reverse osmosis removes 99.5% of inorganic salts and contaminants such as heavy metal ions, organic matter, bacteria and germs, and other potentially hazardous components. This in return provides high-quality water that meets international drinking water standards.

Applicable Areas for Reverse Osmosis Seawater Desalination Systems.

Reverse osmosis equipment is highly automated, simple to operate, produces consistent effluent quality, and emits no pollutants. It’s widely used in various fields including; oil tankers, coastal development workboats, island enterprise hotels and resorts, fish processing factory villages, urban seaside construction sites, seaside villas, and so on.

Examples of Seawater desalination

i.Land Seawater desalination:

As science and technology develop continuously, environmental pollution is getting increasingly severe, water resources are facing more and more serious shortages and demand for seawater desalination technology with less energy consumption and greater efficiency is expanding. As a result, the large-scale use of land-based seawater desalination equipment is the primary development direction. At the moment, seawater desalination technology is the primary starting point to addressing this issue.

NEWater land seawater desalination equipment meets the highest technological level standards in the world and is highly regarded by various industries for its characteristics of high automation, precise control, low energy consumption, and wide application range.

Some of NEWater’s land seawater desalination equipment advantage points include:

  1. NEWater land-based seawater desalination systems are equipped with technologically advanced energy recovery devices and advanced control technologies, ensuring that the equipment’s overall performance, quiet operation, energy consumption, and cost are among the best in the industry.
  2. The equipment system can be optimized based on the customer’s existing space and water production requirements.
  3. It perfectly realizes the unity of space application and technological rationality as a result of the successful application of modular systems.
  4. Provide comprehensive project services ranging from design to production to on-site installation and debugging.
  5. The entire set of NEWater land desalination equipment has mature technology, and it has a high intelligent function of man-machine dialogue with the help of a central monitoring and automatic control system.
  6. The efficient energy recovery device greatly reduces the loss of energy consumption, lowering the operation cost.

Land seawater desalination is primarily appropriate for islands, residents, and coastal water-deficient cities, and it’s used in islands, berths, fishing rafts, fishing boats, offshore operations, island domestic water, industrial, commercial, and residential ships.

Figure 3 Land Seawater desalination

ii.Marine seawater desalination:

The only complete solution to the draught onboard problem is to provide domestic and drinking water on board. Every day, people need a lot of freshwaters, but transporting that much water takes up a lot of space, and the amount consumed stays the same every day. Therefore, with the help of marine desalination equipment, this problem can be resolved completely.

The marine seawater desalination machine has been specifically designed for use on fishing boats. It is compact in size, light in weight, easy to install, and highly adaptable, allowing it to be installed in cramped cabins, docks, aisles, and other spaces.

The advantages of the NEWater marine reverse-osmosis seawater desalination device include the following: a compact and simple structure that conserves cabin space; There is no requirement for a ship’s heat source, no phase change, no scaling problem, and no effect on the ship’s main engine’s operation status;

The structure is modular, and the design scheme adapts to the cabin’s various conditions; Additionally, marine seawater equipment is simple to operate and maintain. Freshwater can be produced immediately as long as there is seawater and electricity (220-380-415V/50Hz/60Hz). The equipment has a high desalting rate, stable performance, safety, and reliability, a novel, and ingenious design avoids frequent cleaning and emits no pollution into the environment.

Marine seawater desalination Process flow:

Seawater pump in machine room → sterilization system → pipeline pressurization pump → bag filter → precision filter → ultrafiltration system → high-pressure pump reverse osmosis system → ultraviolet sterilizer → intermediate pressurization pump → primary filtration → secondary filtration → high- and low-pressure switch → high pressure pump → small reverse osmosis system → activated carbon filter → ultraviolet sterilizer → direct drinking water.

Main stages of desalination process:

  1. Pretreatment: In the machine room, a seawater pump, sterilization system, pipeline pressurization pump, and bag filter are arranged in accordance with the ship’s layout.
  2. Main part: precision filter, ultrafiltration, high-pressure pump, reverse osmosis system, and ultraviolet sterilizer, which are temporarily considered an integrated structure but can also be installed as separate parts if onboard space is limited.
  3. Direct drinking water: primary and secondary filtration, a high- and low-pressure switch, a high-pressure pump, a small reverse osmosis system, an activated carbon filter, and an ultraviolet sterilizer. The direct drinking water part can be hung on the wall, taking up approximately 600mm 500mm 400mm of space.

As direct drinking water, it must be safe for human consumption and free of odors. NEWater marine desalination equipment is filtered by activated carbon and sterilized by ultraviolet rays after reverse osmosis filtration, resulting in high-quality direct drinking water.

The resulting water, which is now free of additives meets the national drinking water quality standard (GB5749-85) and is safe for consumption.

On-board seawater desalination is simple and reliable, and the water yield is guaranteed.

Figure 4 Marine Seawater desalination

iii. Island desalination:

In light of the scarcity of fresh water and the inability of the urban tap water pipe network to reach coastal areas and islands, it is possible to desalinate seawater using seawater desalination equipment, solving the problem of residents’ drinking and production water.

Water and conventional power are in short supply on some small islands, and power is an important energy source for seawater desalination devices, which complicates seawater desalination projects on islands that are far from land.

NEWater reverse osmosis system combines renewable energy such as wind energy, solar energy, and wave energy with seawater desalination process to offer a lasting solution to the problem of water shortage in islands.

Coagulation filtration

Coagulation filtration reduces turbidity by removing colloid and suspended impurities from seawater. In reverse osmosis membrane separation engineering, the fouling index (FI) is usually used to measure, and the FI value of feed water entering reverse osmosis equipment must be less than 4.

Because of the high specific gravity of seawater, the high pH value, and the large seasonal variation in water temperature, FeCl3 is chosen as the coagulant in the system, which has the advantages of no temperature influence, a large and firm alum flower, and a fast-settling speed.

Removal of organic matter and odor in seawater

The surrounding environment has a considerable effect on the seawater surrounding the island, with the chemical oxygen demand (COD) of seawater ranging between 1.7 and 2.5 mg/L, particularly during the summer and autumn, when the seawater has a strong odor and a peculiar odor.

As a result, in addition to adding NaClO for oxidation, adding an activated carbon filter and selecting fruit granular activated carbon with high mechanical strength can effectively absorb organic matter and odor, improve the quality of reverse osmosis produced water, reduce pollution to the reverse osmosis membrane surface, and extend membrane service life.

Security filtering

The high-pressure pump and energy recovery device are protected from damage by the security filtration system’s use of a 316L filter and 5μm filter element, which filters seawater before it enters the pump and blocks particulate impurities with a diameter larger than 5μm in the seawater.

High-Pressure Pump and Energy Recovery Device

The energy recovery devices and the high-pressure pump are critical pieces of equipment for reverse osmosis seawater desalination because they provide energy conversion and energy savings.

A single-stage centrifugal pump with a flow rate of 60m3/h and ahead of 640Psi is selected to meet the flow rate and pressure requirements of reverse osmosis seawater desalination. HTC-300 with hydraulic turbine structure is the energy recovery device, which can use the pressure of concentrated seawater discharged by reverse osmosis to increase the inlet water pressure of reverse osmosis by 30%, effectively reducing energy consumption.

Figure 5: High-pressure pump and Energy recovery system

Characteristics of Good Reverse Osmosis Seawater Desalination Equipment

Our seawater desalination equipment bears the following unique characteristics:

  • High-pressure pumps of superior quality with high efficiency, low energy consumption, low noise, and long service life.
  • Their reverse osmosis membranes are of superior quality, desalination rate of up to 99.8%, strong anti-pollution ability, and stable water quality.
  • Rack pipes and fittings are constructed of stainless steel and corrosion-resistant materials, ensuring the equipment’s durability and low maintenance costs.
  • Simple to operate and maintain, as long as electricity and seawater are available, concentrated water/freshwater can be supplied immediately upon initiating the connecting circuit.
  • The power supply has a wide operating voltage range of 220V to 440V/50 to 60Hz, allowing it to adapt to the domestic manufacturing environment.
  • Self-contained design that adheres to international quality standards.
  • The service life of 15-20 years; rigorous process design ensures a longer service life and lower maintenance costs.
  • Equipment combinations of various types are possible, including bracket type, skid type, container type, and plate type.

Parameter table of seawater desalination equipment

Parameter table of seawater desalination equipment

Parameter table of seawater desalination equipment with different specifications

Parameter table of seawater desalination equipment with different specifications

Advantages of Reverse Osmosis Seawater Desalination.

NEWater reverse osmosis seawater desalination systems are not only lauded across the world because of our highly rated expertise, but also for these various tangible benefits:

  1. A high rate of desalination, a high level of water treatment efficiency, and minimal environmental impact.
  2. The reverse osmosis technology for seawater desalination is mature, the project is stable and reliable, and the operation is straightforward. The technology for manufacturing reverse osmosis membrane materials is mature.
  3. Energy-efficient design: The prior art consumes between 1.8 and 4.5 degrees of electric energy per ton of water, thereby conserving energy and lowering the cost of water production.
  4. Reverse osmosis seawater desalination equipment is available in a variety of configurations to meet the varied water treatment requirements of users.
  5. The energy recovery equipment in a RO system enables the system’s feedwater flow to be reduced, the capacity of water diversion works and pretreatment equipment to be reduced, and the number of chemical agents to be reduced proportionately.
  6. The produced water complies with international drinking water standards, and the drinking water produced by reverse osmosis after seawater desalination is safe and reliable.
  7. Equipped with an advanced detection and monitoring system to ensure the system operates smoothly and produces high-quality water.

Figure 8: Reverse osmosis seawater desalination system

 

Cost of RO Seawater Desalination System in Comparison with Traditional Desalination Method.

  • Overall, reversed osmosis desalination costs include: construction costs of facilities, chemical use, energy use, replacement costs of membranes, fixed equipment depreciation, maintenance costs for equipment, human labor costs, and so on. Determining costs is heavily influenced by factors such as the size of the seawater desalination system, the local water quality, the demand for water production, the daily treatment water quantity, and the electricity and labor costs of where the system will be used.
  • Most importantly, reverse osmosis saves space and energy. It uses half the energy of electrodialysis and a tenth of the energy of distillation. Due to their high efficiency and long-life expectancy, this reduces their cost of ownership. A 10,000-ton-per-day ocean water desalination plant uses 0.05 Yuan per ton of water. The power per ton of water is 2.25 yuan. A new membrane costs 0.05 yuan per ton of water. 0.2 yuan per ton of water for wages and benefits. A ton of water is worth 0.12 yuan in depreciation. Equipment maintenance costs 0.04 yuan per ton of water used. Water is very cheap here; we charge less than 0.1 yuan per ton of it. For a general membrane desalination project, the cost of water production is 4.54 yuan per ton, with electricity and depreciation accounting for a large portion.
  • Other seawater desalination technologies have not progressed as quickly as this one has. The cost of the project and the cost of running it continues to fall. This is because, the main development trend is to reduce the reverse osmosis membrane’s operating pressure; increase the reverse osmosis system’s recuperation rate; develop cheap and efficient pretreatment technology; and improve antipollution capabilities.

If you’d like to learn more about desalination or need technical assistance, please don’t hesitate to contact us. If you’re looking for cost-effective design solutions, our professional design team is here to help you!

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