Is this a worldwide pollution solution?

Macleay Island, one of the 365 islands in Moreton Bay, is cocooned in the calm waters of Redland Bay. The whole bay is classified as a Marine Park and conserves one of the largest concentrations of mangroves in the greater Brisbane area.

Historically fishers and farmers who sold their fish, oysters, fruit and small crops in Brisbane occupied the island. In more recent years, it has been extensively subdivided for permanent residential occupation and the population has expanded as new houses have been built. Macleay Island now has a population of about 3000 residents.

In 2003, a pilot-scale Biowater decentralised wastewater management system was implemented on the island.

Redland Water and Waste (the local authority for the Bay Island region), in cooperation with GHD and Biolytix Australasia, and with support from the Queensland government under the Advanced Wastewater Technology (AWWT) program, aimed to provide an economically viable and environmentally sustainable solution to meet the unique challenges of wastewater management in a sensitive island environment.

Under the pilot scheme, 20 island residences were fitted with Biolytix filters to treat their wastewater. Some houses in the scheme were also fitted with on-site subsurface irrigation and/or reticulation for in-house reuse (ie, toilet flushing).

The Biolytix filter is a passively aerated, biological peat filter, which also incorporates extensive vermicultural activity to accelerate the decomposition of biosolids and putrescible organic matter. These individual treatment units were connected together via a pressurised reticulation network to collect the secondary standard effluent to a central storage tank.

A nearby golf course makes use of the secondary effluent via a sub-surface irrigation network. All of the water and nutrients that are normally a problem for centralised sewerage have thus become a resource, with no health or environmental risks.

The Biolytix filtration system works by immediately separating solids from the water in raw sewage and other wastes, instead of letting them settle in a septic stage or pumping air into the material in the way that most conventional on-site systems operate. Worms and microorganisms then compost the waste and turn it into humus, which acts as an organic filter that turns the wastewater into water that is fit for irrigation purposes.

The effluent produced in the Macleay Island scheme is claimed to be better than that from a septic tank combined with a large sand filter. In detailed monitoring of the pilot scheme, the BOD5 and total suspended solids have been consistently better than 5 mg/L. There have been no operational problems or odour, even though half of the houses also discharge food waste through an Insinkerator into their on-site Biolytix systems.

The joining together of 20 Biolytix systems to form a Biowater network on Macleay Island has created a low-maintenance, small-diameter irrigation pipe network. This system has proven to be a viable alternative to more expensive, large-pipe sewerage systems. Independent studies by GHD engineers and the Cooperative Research Centre for Waste Management and Pollution Control have shown a Biowater network to be up to half the cost of sewerage infrastructure. The Biowater network optimises urban reuse without demanding large lot sizes or a 'third-pipe' system.

To date, Biolytix filtration and Biowater systems have been installed in New Zealand, Australia and South Africa in eco-resorts, hotels, a chicken processing factory, a chef's training school and five-star lodges, as well as households and golf courses.

With the trend in many developing countries and the United States towards smaller, decentralised sewerage systems, the Biolytix technology may provide a pollution solution that is suitable for adoption around the world.