Whyalla Steel Mill Effluent Treatment
The scarcity of water is an intrinsic part of life in most of Australia. Better use and conservation of this vital resource will improve the quality of life for many Australians, especially those who live and work in the semi-arid region surrounding Whyalla in South Australia, where BHP Steel's Long Products Division (LPD) has been operating a steelworks since 1964.
Water is essential to the operations of a steelworks, being used for cooling, cleaning, lubrication and numerous other purposes. In Whyalla it is a scarce and expensive resource. BHP Steel was keen to reduce water consumption and was also aware of the need to efficiently treat waste effluent before it discharge.
Studies over a number of years looked into LPD's waste water discharges into the Spencer Gulf. The studies identified the effluent from coke ovens as a significant source of organic matter and ammonia. BHP Steel needed to reduce and/or eliminate these materials from its waste water prior to discharging it.
In Kickuth BioReactor systems (also known as reed beds), the effluent to be treated percolates through the soil and roots of a large bed of reeds and then drains through a pipe at the base of the bed. The function of the reeds is to pump oxygen into the soil through the roots. Near the roots, there is an aerobic (oxygen-containing) zone and further away, there is an anaerobic (oxygen-free) zone. Thus, within the soil, a range of processes exist that allow the transformation of environmentally undesirable components of waste water.
BHP commenced construction of the system in February 1993. This project is attracting considerable interest in Whyalla and other surrounding country towns. The Whyalla City Council is now also installing a wetland for stormwater. Regulatory authorities have taken a keen interest in the developments, recognising the significance of this trial for the use of reed bed technology for industrial chemical effluent treatment in Australia.
The advantages of the process include:
- improving the quality of LPD's fresh waste water discharges into the Spencer Gulf;
- recovery of a valuable resource of fresh water for recycling on the plant;
- improving the quality of reclaimed land that previously had no value in the coke ovens area, while improving the visual appearance of that part of the plant;
- reducing the impact of wind blown dust in an area with no vegetation; and
- providing a shield against the searing hot north winds during the summer months.
Cleaner Production Incentives
Alternatives to a reed bed system included a conventional biological treatment plant similar to that at BHP Steel's Port Kembla works in New South Wales. Such an approach had a capital cost of $12-14 million and involved greater operating costs. The projected cost of establishing a reed bed at Whyalla is $5 million. Reed beds only require electricity to carry the effluent to the system, after which nature looks after the rest through naturally occurring processes.
