Biological trickling filters - New Zealand

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The Client
VWS UK is involved in a unique project in New Zealand for a new Wastewater treatment plant in Hastings.

The Client's Needs
In New Zealand the Maori people have a strong influence over any decision affecting the land. Maori are deeply offended by discharge of human wastes, particularly to natural waters and also land.Historically, in Maori settlements, human wastes were disposed of to land and Kaumatua (tribal elders) decided how many years needed to pass before Papatuanuku (primal father of the Maori) had transformed the wastes into non-human form.For wastewater treatment engineers this presents a significant challenge.

VWS Solution
In response to these cultural and environmental issues, VWS has designed and is building a low loaded biological trickling filter, which uses micro-organisms to convert solid and dissolved human and other organic wastes into carbon dioxide, water and excess cell (plant) biomass.

The new wastewater treatment system treats sewage to a high level, saves money and satisfies the unique cultural imperatives. The project was well managed from inception through to the consultation and consenting phases, producing an excellent cost-effective result.

This was a very innovative project taking account of the social and cultural issues and aspirations and wishes of the local Maori people with particular regard over the discharge of human wastes to the sea.The project also meets the need to reduce the carbon footprint by providing a solution that uses less energy and recycled media among other environmental benefits.

The Benefits
As an engineering project the Low Rate BTF process from VWS is an outstanding success in technological, sociological, political and economic terms. Technologically it has used an appropriate process which meets the required effluent quality, is sustainable and efficient with low energy consumption. Sociologically it has overcome the cultural objections so important to the Maori population. Politically it has utilised local resources in New Zealand. In purely economic terms the originally consented scheme including primary treatment would have cost the community an extra NZ$1m per year. The effluent quality is better, too. To treat the sewage to the same quality using a traditional configuration would have cost and extra NZ$2m per year.

So it really has been 'win-win all the way' - which was the phrase used by the judging panel when the plant won the Technology Innovation Category of the New Zealand Post Management Excellence Awards. The judges thought the project 'a very good example of the use of technology to find an effective response to particular issues facing the community, well managed from inception through to the consultation and consenting phases, producing an excellent cost-effective natural solution that treats sewage to a high level, saves money and answers cultural imperatives.'

The Hastings STWs is continuously monitored by HDC personnel who advise that the quality of the effluent produced in the biological trickling filters is excellent.

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