Water-saving filter planned for aquatic centre

Gosford Council has agreed in principle to support a proposal to install a diatomaceous earth (DE) water filtration system in the Peninsula Regional Leisure Centre, despite being told that a sand filter would be less expensive.

The Council's Water and Sewer Fund is to support the initiative with a one-off capital grant of $100,000, recognising its significant savings in water use.

Diatomaceous earth filters operate differently to sand-based water filters as the fine particles are sucked onto a membrane, this allows for much smaller particles to be filtered, such as bacteria, which are common in children's swimming pools.

In both sand and diatomaceous systems the filters are cleansed by reversing the normal flow of water into the sewer system. This process is called "backwashing".

With sand filtration, more water is used, with the sand retained in the filter housing while being flushed.

With DE filtration, both the DE and the filtrate is washed to the sewer using much less water.

The filtration and water sterilisation technology to be incorporated in the Peninsula Regional Leisure Centre will be diatomaceous earth and ultraviolet light.

It has been selected for its efficacy in water treatment was supported as "consistent with the council's overall commitment to the principles of environmental sustainability".

Council had previously requested that the specialist aquatic consultants on the aquatic centre project, Geoff Ninnes, Fong and Partners Pty Ltd, assess the two options with a view to providing the most affordable solution.

The consultants estimated that the use of a DE filtration system over a sand based filtration system would cost an additional $100,000 in the construction process.

A DE system would also be more expensive in the ongoing running costs.

However, the use of a DE system would use only 15.7% of the amount of water used during the backwash process in a sand-based system.

The amount of water used in backwash process per annum is 826 cubic metres for diatomaceous earth and 5235 cubic metres in a sand-based system

The additional cost associated with the installation of a DE system is partially offset by the potential to reduce the size of the plant room required to house the equipment.

However, there are additional costs associated with operating the system which are estimated at $23,325 per annum.

The council agenda explained the more expensive decision stating: "Governments sometimes require their businesses to engage in activities that the business would not undertake on purely commercial grounds.

"These are called Community Service Obligations (CSOs).

"The provision of a subsidy to certain consumers to pay for some of their use of electricity is an example of a CSO.

"The Council of Australian Governments (CoAG) has stated that, for purposes of competitive neutrality, Governments are free to determine who should receive a CSO payment or subsidy, but that such payments or subsidies should be transparent, appropriately costed and directly funded by Government.

"It is appropriate therefore that as part of its service to the community, and as a recognition for employing water saving technology, Council's Water and Sewer Fund contribute to the additional cost of the water saving technology.

"The director of water and sewer has indicated that a one-off subsidy of $100,000 is appropriate in this instance.

"The policy objective is to encourage water use minimalisation strategies through technology.

"This contribution to a community project with significant economic and social benefits is within the power of Council to make.

"It is consistent with Council's statement of intent as contained in the Strategic Plan for 2002 to 2007 'to ensure development is compatible with, and protective of, the natural and existing built environment' and to be 'carried out on an ecologically sustainable basis'.

"On purely financial grounds, a sand-based filtration system would be recommended.

"It is proposed that an interpretive display be installed at the new Peninsula Regional Leisure Centre showing the technology that has been utilised and the benefits to the environment.

"This will ensure widespread recognition and a tangible example of Council's efforts to manage water resources responsibly and encourage others to do likewise."

Council agenda CS.034, April 22