Brackish / Sea Water Desalination
Case Study
For the past two decades, ROTEK has been supplying brackish water desalination systems to many countries. The most important feature of our brackish water RO systems is an automatic permeate flush with adjustable flush frequencies. This helps keep the system free from corrosion and membrane fouling, addressing the high levels of chloride and hardness in brackish water sources.
Efficient Desalination for Fresh Water Access
Desalination, or desalting, is a water treatment process that converts seawater or brackish water into potable water, providing a crucial supply for communities with limited access to fresh water.
The Reverse Osmosis (RO) System is currently the most common and economical method for desalinating water from brackish and seawater sources. Energy recovery devices (ERDs) are now widely used to reduce power consumption by 35-50% compared to systems without ERDs. However, the capital and operational costs remain relatively high compared to accessible freshwater sources.
Brackish water sources (with TDS ranging from 2,000-15,000 ppm) should be treated first before considering seawater desalination.
Why Is Permeate Flush So Important?
Prior to shutting down RO systems, a permeate water flush is recommended to prevent the precipitation of salts and organics on the membrane surface. Unfortunately, many RO systems do not incorporate a permeate flush and instead use a feedwater flush. This accelerates all forms of membrane fouling, including biofouling, colloidal fouling, scaling, and organic fouling.
The ROTEK patented C-5TM RO controller enables systems to perform automatic permeate flushes at the lowest possible cost.
CASE 1:
Island Resort Center - 6T/Hr Seawater Desalination RO System
Background and Challenges
Location: Island Resort Center
Environmental Constraints: No natural freshwater on the island; electricity supply relies entirely on high-cost diesel generators.
Smart Control & Durable Design
Utilizing an advanced OMRON PLC paired with an intuitive HMI (Human-Machine Interface), our system supports reliable remote monitoring. It offers effortless operation alongside exceptionally low maintenance costs.
Cavitation Protection Technology
Featuring our proprietary high-and-low pressure air relief valves, this system effectively prevents bubble implosion damage. By eliminating cavitation risks, we ensure maximum equipment lifespan and operational stability.
Multi-Stage Filtration Guard
From robust sand filtration and activated carbon to high-precision bag filters, our comprehensive pre-treatment process provides absolute protection for RO membranes against impurities and fouling.
Energy-Saving & Sustainable Desalination Solutions
This project goes far beyond standard water treatment engineering—it is a strategic "Energy-Saving & Revenue-Generating" solution specifically tailored for regions with high electricity costs. By implementing cutting-edge energy recovery technology, we transform seawater desalination from an expensive operational burden into a sustainable cornerstone for island development.
CASE 2:
Penghu Island Desalination Plant - 24 CMD Seawater Desalination Equipment
ROTEK has constructed a two-stage seawater desalination system for the four southern islands of Penghu (Dongji Island and Dongyuping Island) to improve the stable supply of drinking water for the outlying islands. The system is designed with a maximum seawater TDS of 42,000 mg/L, with an influent flow of 60 CMD. Through PASS 1 seawater RO and PASS 2 pure water RO, it produces 21 CMD of domestic water and 3 CMD of drinking water daily, meeting drinking water standards.
The system integrates a slow filter, bag filter, DANFOSS high-pressure pump, and energy-saving recovery device, saving approximately 32% of energy consumption and reducing diesel generator load. It balances stable water supply, energy efficiency, and marine environmental friendliness, serving as a model case for public water supply for outlying islands.
Energy Efficiency & Operational Features
Advanced Energy Recovery
By integrating the industry-leading DANFOSS-APM Energy Recovery Device (ERD), the overall system reduces total power consumption by approximately 32%.
High Performance & Stability
Achieves a salt rejection rate > 99%. The system guarantees stable, continuous freshwater production even under highly fluctuating feed water conditions with a TDS of 32,000 to 42,000 mg/L.
Eco-Friendly Operation
Engineered with low chemical consumption and minimal brine discharge, significantly reducing the environmental impact on marine ecosystems.
