Smith’s existing moving bed bioreactor.

Moving to sustainable water use at Smith’s Snackfoods in Queensland will not only slash water use and discharges but generate its own energy. Chris Hertle explains.

South-east Queensland is experiencing the worst drought in more than 100 years and the seventh consecutive year of below average rainfall. In response, the Queensland Water Commission has initiated a series of water conservation schemes, including water restrictions that started in May 2005 and development of the Water Efficiency Management Plan (WEMP) tool.

These efforts have brought into focus for both industry and the public the fact that water is a limited resource and that alternative supplies must be developed.

As part of these restrictions, all business and non-residential water users greater than 10ML/year in south-east Queensland have to develop a WEMP, which requires the business either to achieve a minimum reduction in water usage of 25 per cent by October (based on level 4, 5 and 6 water restrictions) or demonstrate world’s best practice.

The Smith’s Snackfood Company at Tingalpa has historically limited water use consistent with business financial and quality drivers, including minimisation of trade waste discharge costs, water purchase costs, operating labour costs and limiting risk to end product quality (read: consumer confidence).

It has cut on-site water consumption approximately 16 per cent from 2005 to 2006 by employing best practice water management. However, persisting drought conditions in the region and Smith’s own development plans have forced it to put a plan in place to ensure sustainable water supply into the future.

To this end, it regards water reuse as an excellent option to reduce potable water consumption and production of waste. Industrial water recycling, including within the food and beverage industry, demonstrates sustainability and provides a real edge on competitors.

Given these drivers, Smith’s engaged GHD to study the options to upgrade the secondary wastewater treatment plant and to integrate an advanced treatment plant to produce high quality water to be reused in the factory for non-product applications.

Water recycling options
Smith’s currently uses 0.8ML a day of potable water, but future planning indicates the site could potentially require up to 1.3ML per day. A range of options was considered to upgrade the secondary wastewater treatment plant, which consists of a moving bed biofilm reactor (MBBR) and dissolved air flotation (DAF). One of the primary goals was on-site process reuse.

Option one included the addition of induced air flotation (IAF) and a high rate Upflow Anaerobic Sludge Blanket reactor (IC reactor) into the wastewater treatment train. This would significantly reduce the organic load to the MBBR and improve final effluent quality. The treated effluent would then be directed to a tertiary treatment train of microfiltration (MF) and reverse osmosis (RO), producing recycled water of high quality.

A second option comprised the addition of an IAF unit, a membrane bioreactor (MBR) and associated sludge dewatering facilities. The effluent would again be passed to a tertiary RO plant to produce the final, high quality recycled water.

The last option involved the addition of a second stage MBBR, followed by a small MBR, with RO as the final stage.

Option one was the most favourable because it demonstrated a range of benefits, not least an expected reduction in potable water use of 70 per cent. The anaerobic treatment will reduce biological sludge and produce a high quality biogas that is expected to account for at least six per cent of the factory’s daily gas demand, cutting site energy use by 3,500kWh a day. It will have a small land footprint of 730m2 and a reduced environmental footprint.

The Recycled Water Plant (RWP), which is in the final stage of design and costing, will also reduce operating costs. The use of recycled water will cut potable water use in boilers, cooling towers, truck washing, the RWP itself and other applications.

The reduction in trade waste discharge is estimated to save about $270,000 per year in landfill and sewer costs. It will save another $90,000 a year on chemical operating costs and a similar sum in energy savings due to the methane generated.

General implications
Politically and strategically, this project demonstrates a practical and sustainable way forward, given the current climate in south-east Queensland.

Considering the uncertainty in water prices and energy costs, as well as the implementation of the proposed CO2 emissions trading scheme – Smith’s stands to benefit by creating offset credits – the payback period is acceptable, if difficult to pin down with precision. But the additional driver is strategic, securing supply in a time of drought and shoring up the capacity to expand.

Additionally, it should be mentioned that SEQ Water is supporting the project through its Business Water Efficiency Program with a subsidy of $2.7 million, up to approximately one-third of the capital costs.

With completion of the project, Smith’s parent company PepsiCo will not only be in a position to demonstrate industry best practice, relieving pressure from regulators, but it will reap the reputation rewards of moving towards sustainable management. The success of the project could lead to similar projects elsewhere in the food industry.

Chris Hertle is principal chemical engineer with GHD. Contact at (07) 3316 3710.