Aqua Services & Engineering, a company of the global Veolia Water Solutions & Technologies operating in Namibia, has secured a contract to upgrade and refurbish a 400 m3/day seawater desalination plant in Walvis Bay. The project will help increase potable water supply for domestic use, and provide enough processed water to a Walvis Bay fish factory.
The source seawater's high organic content requires that ASE adopts an air flotation filtration system as a pre-treatment step to make it suitable for further treatment by reverse osmosis (RO) membranes. "Our engineers will introduce a vortex mixer to generate micro bubbles, which are fed into the flocculated raw seawater stream," says Christian StÃ¶ck, Managing Director at ASE. "This will help lighter organic particles float to the surface, and allow for heavier particles to settle."
These particles will then be filtered by a fine filtration bed where, unlike with an additional pumping step, minimal break-up of the flocculated particles will occur. This pre-treatment will ensure that the raw seawater, often affected by red tide and sulphur eruptions, meets the required pre-treatment standards.
To help the plant optimise its energy consumption, ASE will install an energy recovery system to better utilise the energy normally wasted in conventional reverse osmosis membrane systems. "This high-tech unit will help the plant reduce its reliance on municipal power sources by up to 42%," says StÃ¶ck.
The plant should be operational within five to six months, and will provide much needed relief to Walvis Bay, where periodic water scarcity has been a longstanding problem.
"Over the last 15 years, we have built up detailed knowledge of the Namibian coastal waters, and we have gained valuable experience from building and operating numerous seawater treatment plants. This will help ASE deliver the best possible solution to treat the often tricky Namibian seawater," concludes StÃ¶ck.