Grundfos to treat Singapore's wastewater

Pump manufacturer Grundfos has been awarded a S$1.4 million R&D grant by the Singapore Environment and Water Industry Programme Office (EWI) to develop a novel wastewater filtration technology that can significantly reduce capital investment and operational costs for wastewater treatment.

The project will be led by the Grundfos Water Innovation Centre in Singapore, headed by Dr Gao Xin, with support from Nanyang Technological University’s Nanyang Environment & Water Research Institute (NEWRI). It will focus on the industrial treatment of wastewater using a cake filter made from activated sludge - the ‘active ingredient’ of a biological wastewater treatment plant. The sludge contains a suspension of bacteria that feed on wastewater impurities, thereby cleaning it.

The cake filtration technology utilises the physico-chemical properties of this material to construct good filters on simple supports. Unlike conventional technologies such as ultrafiltration, which require a lot of energy and maintenance during operation, the cake filtration technology requires very little energy as it can operate under the low water pressure generated by gravity.

The method can be outlined in four steps:

1. The cake filter is formed by collecting the activated sludge on a porous support frame.
2. The cake filter is treated to deliver hydraulic properties and remove impurities so as to meet the required effluent-discharge standards.
3. After treatment, the cake filter is now ready to be used to filter secondary effluents from wastewater treatment plants.
4. A backwash will easily remove the used filter to make way for a new cake.

The cake filtration is said to produce superior filtrate quality (compared to traditional techniques) which can be safely discharged into the sea. The effluent discharge standard is comparable to that of membrane filtration while halving the cost of effluent polishing, which is the removal of impurities from secondary effluent. There is further potential to treat the filtrate and recycle it for irrigation or industrial uses.

The technology is expected to fit in with a broad range of solutions for water treatment, wastewater discharge and recycling, with the R&D enabling the development of a suite of wastewater treatment solutions. As explained by Lars Enevoldsen, group vice president of Grundfos Global Research and Technology, “The cake filtration project relies strongly on precise and controlled pumping of water and sludge, and will offer a good study platform on the optimisation of cost and energy use in pumping operations.”

Upon successful proof of concept, the grant will fund a pilot demonstration of the technology.