Singapore's seawater desalination solution

May 2010 Analytical Instrumentation & Environmental Monitoring

Singapore began tackling its drinking water supply problem a few years ago. The first large seawater desalination system ‘TUAS Desalination’ was designed and built by Hyflux. The system operates according to the reverse osmosis principle and produces more than 136 000 cubic metres of drinking water per day – enough to fill about 55 Olympic size swimming pools.

Technology and process

Seawater desalination runs in several process steps. The first of these is the drawing of the seawater and feeding into the system. This is followed by a multistage filtration, flotation and ventilation to remove suspended matter and undesirable substances dissolved in the water. The filtered water is conditioned with ferric chloride, sulphuric acid, hydrochloric acid, caustic soda and other additives for reverse osmosis and set to a specific pH. Without these important water treatment steps, the downstream osmosis diaphragms would become useless very quickly.

After conditioning of the water, it is fed to the osmosis diaphragm modules by high-pressure pumps. The systems have a modular structure so that the diaphragms can be backwashed at regular intervals. In a system with 10 modules, for example, one of them is always in backwash mode whilst the others produce drinking water. In the last part of the system, after the reverse osmosis, which supplies almost distilled water, the water is brought back up to drinking water quality mineral content. This is the final process step before the water is fed into the distribution pipes and sent on its way to the consumers.

The GEMÜ solution

GEMÜ supplied more than 760 valves in nominal sizes from DN 15 - 1400 for this project. To offer the customers a package solution, valves were also purchased from partner companies. The customer could therefore be offered everything from a single source.

Butterfly valves with the different disc materials in 1.4408, bronze or ECTFE coated are mainly used in the seawater inlet, in the filtration/flotation and in the supply (tanks and pump stations). The nominal sizes are between DN 65 – 1400 and the operating pressure is 2,5–18 bar depending on the process area. Positioning is via pneumatic and electric solutions as well as manual operation using hand levers and gears.

In water pre- and post-treatment, highly chemically resistant diaphragm valves made of PVC or PVDF are used for the chemical dosing processes. The nominal sizes are DN 15 - 40, operating at pressures from 3-5 bar. Float flowmeters of nominal sizes DN 20 – 40 are also installed. Chemical dosing is fully automatic so the valves are usually controlled pneumatically.

The high pressure and non-return valves on the pump stations in front of the osmosis modules are made of special materials such as Super Duplex A890. They are controlled pneumatically and equipped with intelligent positioners. The differential pressure in the start-up phase of a pump is up to 60 bar. The operating pressure is usually between 5–84 bars the valves are designed in DN 300 throughout.

For more information contact Keith Hedges, GEMÜ Africa, +27 (0)11 462 7795, [email protected], www.gemue.de

Further reading:

Ensuring occupational health and safety in mining
Analytical Instrumentation & Environmental Monitoring
Probe Integrated Mining Technologies (Probe IMT) has partnered with M3SH Technology to offer state-of-the-art environmental monitoring solutions that address these dual requirements.

Read more...

---

Sustainability of surface water
Endress+Hauser South Africa Analytical Instrumentation & Environmental Monitoring
The sustainability of surface water is critical for South Africa’s economic development, social well-being and environmental health. Endress+Hauser has a full range of liquid analysis sensors and transmitters to measure important parameters and has an excellent global track record in water and wastewater process plants and various surface and industrial water monitoring sites.

Read more...

---

Keeping an eye on invisible radiation
Omniflex Remote Monitoring Specialists Analytical Instrumentation & Environmental Monitoring
At its peak in 1994, the energy generation capacity of the UK’s nuclear power stations was 12,7 GW across 16 plants. In 2024, the capacity has fallen to around 5 GW, and the number of stations is down to nine. However, this is far from the end of the story as spent nuclear fuel remains radioactive for centuries, and requires rigorous safety processes to safeguard against leaks.

Read more...

---

Effective dust control in sugar processing
Analytical Instrumentation & Environmental Monitoring
BLT WORLD specialists work in conjunction with the global ScrapeTec team to offer dependable solutions for specific problems at the transfer points of conveyor systems in many industries where dust and material spillage are concerns, including the sugar sector.

Read more...

---

A benchmark for lubricant reliability in mining
Analytical Instrumentation & Environmental Monitoring
According to Craig FitzGerald from ISO-Reliability Partners, mines can save R500 000 or more on their yearly mill cleaning costs, while electricity consumption can be reduced by up to 12%, and lubricant consumption lowered up by up to 60% when using Bel-Ray Clear Gear lubricant.

Read more...

---

Safeguarding precision in industrial radiometric measurements
Mecosa Analytical Instrumentation & Environmental Monitoring
In the complex landscape of industrial plant operations, precision is paramount, especially when it comes to weld inspections to test for structural integrity of pipes. Berthold has the ideal answer to this challenge – X-Ray Interference Protection.

Read more...

---

New indoor air quality monitor
RS South Africa Analytical Instrumentation & Environmental Monitoring
RS South Africa has available a new indoor air quality (IAQ) monitor that provides continuous, easy-to-read, and accurate real-time monitoring of air quality in indoor environments.

Read more...

---

A quick guide to disinfection
Endress+Hauser South Africa Analytical Instrumentation & Environmental Monitoring
The distribution system in a drinking water network provides a reliable supply of high-quality water to consumers. Endress+Hauser’s range of robust, low-maintenance sensors are ideal for monitoring disinfectant levels in the water.

Read more...

---

Multi-parameter measuring system for water quality monitoring
KROHNE Analytical Instrumentation & Environmental Monitoring
Monitoring different parameters in water treatment processes can lead to a situation where different measuring points are scattered across the plant.

Read more...

---

Optimising energy consumption in the chemical industry
Anton Paar Analytical Instrumentation & Environmental Monitoring
To optimise energy consumption and save valuable resources on chemical process plants, operators have to continuously measure parameters such as concentration, raw density, sound velocity and refractive index. With Anton Paar’s wide product range, the process application team has many options for cutting-edge laboratory measurement technologies, and can develop tailor-made mathematical models for every application.

Read more...

---