The Smith's Snackfood Company is the largest snackfood manufacturer in Australia with operations in Adelaide, Brisbane and Perth. The Adelaide site processes potatoes and corn to produce a variety of products including brands such as Smithís Potato Chips, Ruffles, Lites, Doritos and Twisties.
The company's water use has increased by 19.5 percent since 1993, rising from 264 ML per annum (47 percent mains water and 53 percent bore water) to 315 ML per annum in 1997 (61 percent mains water and 39 percent bore water) without an increase in production.
A substantial volume of water is used to wash potatoes: the amount and type of soil on the potatoes governing the actual volume of water. The manufacturing process includes several washing stages to meet stringent quality requirements. If the soil is not removed in the initial stage by the rod washer, more water must be used in subsequent stages.
The effluent generated contained 10 percent solids and was directed to the wastewater treatment plant where solids were removed by sucker trucks at a cost of $130,000 per annum. The plant was often stopped when the build-up of solids caused flooding.
There was no routine monitoring of water use and of wastes generated.
Cleaner Production Initiative
A consultancy study into the environmental aspects of company operations was undertaken with the assistance of a $15,000 grant from the South Australian Environment Protection Agency under its Cleaner Industries Demonstration Scheme. The company also contributed to the project by providing $30,000 for equipment and $20,000 in kind for staff and analytical time.
The consultancy brought together staff from different levels of the organisation and involved them in the decision making process. This has led to greater questioning and understanding of the plant's operation and a smoother running plant.
Measures implemented initially focussed on equipment and process changes, installation of hydrocyclone technology to reduce water use and improve solid waste disposal, and staff training.
Hydrocyclones have been installed on both the potato and corn lines. The concentrated solid effluent streams from washing processes are directed to the hydrocyclones, where strong centrifugal forces separate the solids from the effluent. The underflow is collected in sludge bins, allowing separation of soil and the draining out of water. Cleaner water from the cyclones, containing minimal solids, is collected in a holding tank for recycling back into the system. A process flow diagram is set out below.
Water use, both from the mains and the bore, is now monitored daily. Water meters have been calibrated and installed at various locations within the plant to monitor the water used by individual production processes. The water meters are read on a daily basis by production crews. Water use is charted weekly and any rise that cannot be accounted for is investigated.