Smith’s saves water waste

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The Smith’s Snackfood Company at Tingalpa in Queensland has reduced its water consumption by 16% through best practice water use on site.

For Smith’s, the drivers for limiting water use included cost reductions associated with minimising trade waste discharge; water purchase and operating labour costs; as well as limiting risk to end product quality.

However, persistent drought conditions in south east Queensland – now experiencing its worst drought in more than 100 years – have led to water restrictions that require all business and non-residential water users greater than 10ML per year to achieve a minimum reduction in water usage of 25% or demonstrate world’s best practice.

Smith’s has responded by engaging international professional service company GHD to conduct a study to consider various options related to upgrading its existing secondary wastewater treatment plant (WWTP), and to integrating an advanced treatment plant, to produce high quality water to be used within the factory for non-product applications.

The Company currently consumes 0.8ML per day of potable water. Future planning, however, indicates the site could potentially require up to 1.3ML per day. With on site process reuse as the primary objective of the treatment process, the following wastewater treatment train options were considered:

  • Option 1 included the addition of induced air floatation (IAF) and an upflow anaerobic sludge blanket (UASB) reactor into the existing secondary wastewater treatment train. This option would reduce the organic load to the existing moving bed biofilm reactor (MBBR) significantly, with a further significant improvement in final effluent quality. The effluent of the secondary WWTP would then be directed to a tertiary treatment train comprising ultra-filtration (UF) and reverse osmosis (RO) to produce recycled water of high quality;
  • Option 2 comprised the addition of an IAF unit, a membrane bioreactor (MBR) and associated sludge dewatering facilities. Finally the effluent would be directed to a tertiary RO plant to produce recycled water of high quality;
  • Option 3 involved the addition of a second stage MBBR followed by a small MBR. Finally the effluent of the secondary WWTP would be followed with a tertiary RO plant to produce recycled water of high quality.

The first option was considered the most favourable because it resulted in a 70% reduction in water use, as well as a reduction in biological sludge. It also meant Smith’s could utilise its existing secondary WWTP.

The use of recycled water results in two main cost reductions – a saving of potable water and a reduction in the trade waste discharge.

It is estimated that approximately $270,000 a year will be saved by the company in reduced trade waste charges. The recycled water plant (RWP) will save approximately $90,000 per annum on chemical operating costs, while the generated methane production will save approximately $90,000.

Implementation of the water recycling scheme will provide high quality water for reuse in non-contact areas in the plant, including potato supply, the primary effluent plant, hot clean in place water, cooling tower makeup and general wash down water.

Other benefits are a reduced environmental footprint and the production of high quality biogas for use in the plant (6% of the factory gas daily demand).

Considering the uncertainty in water price as well as the implementation of the proposed Carbon Pollution Reducation Scheme, the payback period of the proposed RWP becomes reasonable. Additionally, the project will be supported by a subsidy of approximately $2.7 million, through SEQ-Water’s Business Water Efficiency Program.

The project demonstrates a practical and sustainable way forward given the current climate in south east Queensland. It will not only position Smith’s to prove and demonstrate industry best practice, but will give the company an edge on its competitors when the project is implemented.

— Chris Hertle is the business leader for industrial water in Queensland at GHD.