Singapore's NEWater is produced from a multiple barrier treatment process. After passing through Amiad strainers, the feedwater goes through the first and second stages of NEWater treatment using microfiltration (MF) and reverse osmosis. Amiad's filters effectively remove the level of total suspended solid prior to the MF stage – where treated used water is passed through membranes to filter out and retain surface colloidal particles, disease causing bacteria, some viruses and protozoan cysts on the membrane.
Amiad ABF filters are heavy–duty strainers with a self–cleaning capability. Effective screening in the range 3500–200 μm is achieved. Amiad ABF filtration systems are fitted in parallel with three active units and a fourth in reserve, allowing for an uninterrupted treatment capacity in excess of 2000 m3/hour at Bedok (500 μm screening). The filters work by straining effluent through a cylindrical filter head from inside–to–out, the unit benefiting from a large screen area (6000–10000 cm2).
A filter cake forms on the inside of the head, and produces a pressure differential between the unit inlet and outlet. When this pressure differential reaches 0.5 bar the self–cleaning mechanism is triggered. Two stainless steel revolving brushes, powered by an electric motor, sweep the cylinder free of trapped cake and flush this via an exhaust from the cylinder head.
The self–cleaning operation takes approximately 15 seconds allowing uninterrupted operation of the filtration unit. Although the pressure–initiated self–cleaning trigger is reliably monitored by a pressure differential switch, the unit self–cleaning facility can alternatively be time–event triggered.
The flexibility of Amiad filter installations, combined with their robust construction and automated self cleaning proved attractive to the NEWater project plant designers, and their proven effectiveness has seen their introduction to all the NEWater factories in Singapore. www.amiad.com
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