Water Case Studies - BlueScope Steel HSEC Report 2004

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Water Case Studies

New Zealand Steel Slag Filter Bed Improves Stormwater Discharge Quality

New Zealand Steel Slag Filter Bed Improves Stormwater
Discharge Quality

BlueScope Steel's plant at Glenbrook, south of Auckland, New Zealand is significantly improving the quality of stormwater that is discharged to the Waiuku Estuary.

The Glenbrook plant has continuously met stringent water quality standards and recently showed its commitment to the environment and sensitivity to local indigenous culture when working with representatives of the Huakina Development Trust (Tainui iwi).

The water from the Waiuku Estuary has special significance to local tribes. Water purity in the estuary is not only a matter of physical cleanliness but a spiritual and cultural concern. The iwi representatives asked the Company to explore the possibility of further treatment for stormwater discharging into the estuary. Passing the water through the land, before discharge to a natural water body was preferable from a cultural perspective.

Over half of the stormwater collected from the 150 hectare Glenbrook site flows to two large settling ponds, which are 15 cubic metres each and settle out the solids collected from around the plant, from roads, unsealed areas and stockpiles. The installation of a filtration bed at outfall of the settling ponds, to further treat a limited volume of waste water, was considered an economical system that met the needs of local tribes.

A filtration bed is a low cost, low technology treatment system that removes contaminants from water by filtration, settling, chemical precipitation and absorption. At the Glenbrook plant, the water is sprayed across a bed of fine slag, less than 3mm in thickness. It then drains through to a coarser slag layer below, travelling horizontally before exiting the filtration bed. It is also anticipated that planting in and around the filtration bed may further assist in the uptake of contaminants.

The filter bed was commissioned in May 2004 and early results show that approximately 80 per cent of the zinc and virtually all of the remaining suspended solids are removed. The water going in and out of the wetland is sampled daily and analysed for the full range of discharge water quality parameters as specified in the Company's discharge permit.

The installation of the filtration bed has shown very encouraging results, with an estimated 5.5 tonnes of suspended solids to be removed from the discharge water each year.

Every Drop Counts

All BlueScope Steel's Illawarra sites are participating in Sydney Water's Every Drop Counts Program, a water management initiative involving audits and improvement plans to reduce water usage.

The program is very much a partnership between BlueScope Steel and Sydney Water, where water usage is mapped and reduction opportunities identified.

Sydney Water has recognised the outstanding efforts of the Springhill plant, where a 40 per cent reduction in daily water consumption was achieved in 2002/2003.

Following the introduction of mandatory water restrictions in November 2003, the Springhill plant convened a drought committee, which aims to reduce the site's freshwater consumption by at least 15 per cent. Significant improvement opportunities have been identified and are currently being progressed. The program is bearing fruit, with Springhill achieving its lowest monthly domestic water use on record in August 2004 - 45 per cent lower than that for August 2003.

Planned installation of BlueScope Water rainwater tanks will see a further reduction in domestic consumption at Springhill and across our Illawarra operations.

Water Recycling at Western Port

BlueScope Steel's Western Port plant on the Mornington Peninsula has the capacity to process more than 1.4 million tonnes of steel each year and needs water for its manufacturing processes.

Two large stormwater lagoons capture all rainwater falling on the site for re-use in manufacturing operations. Under normal conditions, this provides 30 per cent of the water needed for recirculating cooling water systems at Western Port's Hot Strip Mill. Unfortunately, with the onset of drought, this water storage has dried up, forcing a reversion to reticulated water and redoubling of the plant's efforts to maximise water recycling.

Already, waste water discharged from the Western Port plant has been reduced by up to 40 per cent. Now, a more ambitious water saving program is planned as one part of a partnership with the EPA and the community to develop the next Environmental Improvement Plan for the plant for the period 2006-2011.

Many processes at Western Port are under review to achieve the plant's target of the lowest economically practical waste water discharge. Western Port is reviewing all manufacturing processes to set a benchmark for reduced water usage and increased recycling for the future. Waste water generators will also be examined for opportunities to reduce water wastage, by going back to the sources of usage.

The Western Port plant proposes to meet its target of reusing up to 80 per cent of waste water by taking advantage of the best available technology.

The largest user of fresh water at Western Port is the Cold Reduction Mill (where steel is rolled to its final thickness). In 2004 a Cyclovap - a unit that reclaims almost distilled quality water from dirty or oily water - is being installed. The Cyclovap removes contaminants so that treated water can be reused in the cold reduction process, reducing fresh water usage at the mill by 40 to 80 per cent.