Understanding Leading Practice in Water Management

This study was undertaken in the context of increased scrutiny over sustainability of the coal mining industry, particularly as it relates to water management. There are increasing expectations for a broader range of standards to be met; these standards are expressed by using the concept of leading practice, which outlines the best way of doing things for a given mine at a given time. As new challenges emerge and new solutions are developed, or better solutions are devised for existing issues, leading practice will evolve.

The aim of this project was to complement the results obtained as part of ACARP project C15001 by extending the database of site water use and determining and communicating how leading sites manage water. The objectives of the project were to:

· Extend the information base on leading practices to improve confidence that industry leaders have been identified;

· Explain leading practice indicators and communicate how they are being achieved; and

· Capture this knowledge in an on-line information system accessible to industry.

A total of 26 mines have been included from three regions: North Bowen Basin, South Bowen Basin and Hunter & Southern Coalfield. The project was organised in five main tasks: (1) site visits and analysis of water use in (2) dust suppression, (3) coal preparation, (4) underground mining and (5) compilation of all data in a knowledge system. In ACARP Project C15001, a structured approach to water management was designed and tested. This study uses this same framework, which has been modified to take into account some of the emerging requirements, such as the need to produce a water account.

The framework provides consistency in the way the key elements of an operation's water balance are described and water use is reported. The water management system is comprised of four functional elements:

(1) Inputs, representing the receipt of water to a site;

(2) Tasks, representing what a site does with its water: coal preparation and other industrial tasks, dust suppression, underground mining (if relevant) and discharge;

(3) Stores, the facilities on the site that hold and/or capture water and are used as temporary buffers between the inputs and the tasks;

(4) Outputs, representing the removal of water from the site. The discharge task is such that the input becomes an output. Discharge can thus be referred to as a task or an output, depending on the context of the analysis.

An extensive database describing water use in the industry was compiled and uploaded onto a water management information system (WaterMiner). A range of analyses and results were produced.

Another aspect of the study aimed to explain how leading practice values could be achieved. A more detailed analysis of each task's inputs and outputs was undertaken and it showed that:

By combining all results, it was concluded that leading sites are such that they:

· Manage their stores for the dual risk of running dry and discharging.

· Implement strategies for minimising losses from tasks and stores.

· Reuse water.

· Have low reliance on high quality sources, have high worked water availability and high reuse efficiency.

· Minimise the volume of water in tailings, and maximise the return of water from tailings. Ideally, the impact of thickening tailings on site energy consumption should be assessed.

· Minimise flow rates through unit operations (without impacting on plant yield and performance), particularly through flotation cells.

· If there is a business case to do so, expand effort in assessing and implementing a number of dust suppression strategies: route planning, optimising watering times and wetting rates, application of dust suppressants, increased attention to haul road maintenance and use of real-time monitoring system.

· Use worked water in underground mining if there is availability of supply and treatment requirements are addressed.

It is expected that the study's outcomes will facilitate improved communication between industry and stakeholders, as the industry has now improved its understanding, disclosure and reporting of water use. It has enabled the assessment of the coal mining industry's exposure to the operational risks laid out in the Leading Practice for Water Management Handbook (DRET, 2008). The study has also translated technical knowledge into actions that can be implemented, such as reducing water content in tailings and reviewing water storage capacity. From the detailed water balance analyses that were undertaken, specific recommendations could be made. They mainly addressed the requirements for reviewing storage capacity, catchment and drainage area, raw water orders and inputs into the tasks.

Finally, there clearly are many benefits arising from compiling all data in WaterMiner. These data should be based on sound monitoring and measurements and be updated regularly to ensure that the results that are being produced reflect site changes.