How to solve the problem of high-salt concentrated water treatment in reverse osmosis desalination plant?
Desalinated Water is one of the important sources of fresh water for coastal areas that lack fresh water, such as the Middle East, the coast of West Africa, the coast of East Africa and northern East Asia.
Why use seawater Reverse Osmosis desalination for seawater desalination?
As the main desalination technology used in seawater desalination, reverse osmosis desalination equipment is the most widely used technology among all seawater desalination equipment. This technology has been highly praised for its efficient desalination ability, and has played a very stable and effective role in actual application, allowing people in areas with severe water shortages to obtain high-quality fresh water resources!
Why are supporting high-salt water treatment solutions popular in the Middle East?
The average daily production capacity in the Middle East is about 50 million cubic meters per day (equivalent to more than 18 billion cubic meters per year), accounting for 50% of the world's total. 60% of the production capacity uses reverse osmosis technology, and the use of seawater desalination in other regions is far less than that in the Middle East. In recent years, the discharge of high-salt concentrated water produced by seawater desalination has become a marine environmental problem. The United Nations Environmental Protection Agency, the International Desalination Framework, and governments have warned against the discharge of high-salt water, and the World Bank has stopped lending to desalination projects without supporting high-salt water treatment. At present, various countries in the Middle East have issued various regulations to restrict the discharge of high-salt water, and at the same time, all newly launched seawater desalination projects are required to have supporting high-salt water treatment solutions. This shows that high-salt water wastewater has become a bottleneck problem in seawater desalination technology!
We will not discuss the high-salinity concentrated water of large-scale desalination projects. Today we will focus on the treatment of high-salinity concentrated water of small-scale desalination equipment (1000LPH~20000LPH).
As we all know, the high-salinity concentrated water after seawater desalination not only has a very high salt content, but also because chemical substances such as descaling agents are used in the desalination process, these chemicals will enter the high-salinity concentrated water.
How can we minimize the impact of these high-salinity concentrated water purification on the local marine environment when discharging it into the sea?
For small-scale desalination projects, the most economical and feasible method is dilution + sedimentation or the construction of artificial wetlands
(1)Dilution + Sedimentation of seawater reverse osmosis desalination
A：Dilution control
Water source selection:
Use low-salinity water sources (such as sewage treatment plant effluent, rainwater collection pool water) to dilute and reduce freshwater waste.
Ratio recommendation: Dilute the salinity of brine to less than 1.2 times that of natural seawater (such as original brine TDS 50,000 mg/L → ≤42,000 mg/L after mixing).
B：Dynamic mixing:
Use a pipeline mixer (static or mechanical) to ensure uniform mixing and avoid local salinity surges.
(2) Sedimentation enhancement of ro water desalination
Chemical sedimentation aids:
Add flocculants (such as PAC polyaluminium chloride) or lime (Ca(OH)₂) to promote co-precipitation of suspended solids and heavy metals.
Dosage: PAC is recommended to be 50-100 mg/L, and lime is adjusted according to calcium hardness (pH increased to 9-10).
Equipment recommendation:
Inclined plate sedimentation tank: small footprint, high efficiency, suitable for small projects (surface load 1-2 m³/m²·h).
Sludge treatment: Sedimented sludge can be dehydrated and landfilled (if heavy metals do not exceed the standard) or used for brick making (such as the UAE pilot project)
What are the application cases of reverse osmosis water desalination?
Case1: Maldives Resort Project
Flowchart:
Case2:Artificial wetland project
Process:
Plant selection: Suaeda salsa, Salicornia, which can absorb salt and serve as feed.
The above two methods are more suitable for areas with more precipitation. Rainwater can be used to directly dilute high-salinity concentrated water and reach a treatable salinity. The economic cost is low, easy to implement and simple to maintain, providing the possibility of sustainable development.
In addition to the above two methods, natural evaporation, electrochemical method, etc. can also be used. Today we focus on the above two methods, which are effective and feasible solutions for the treatment of high-salinity concentrated water in seawater desalination in South Asia and Southeast Asia.
Guangdong Xinjieyuan is committed to producing equipment for customers while also providing sustainable development solutions to reduce environmental risks and increase social value for our customers in future production and economic activities!
Contact us:
Name: Judy Chen
Position：sales manager
Company: Guangdong Xinjieyuan Environmental Protection Technology CO., Ltd
Email: xjy01@xjyept.com
Telephone: +8619867623549 (Wechat/Whatsapp)
Address: Room 101, Building 2, №2, West Wuheng Street, Xinqiao Tai'an Road, Dalong Street, Panyu District, Guangzhou
WhatsApp QR code:
WhatsApp QR code:
WeChat QR code:
