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The treatment of mine and Coal Seam Gas water using volcanic rocks

The treatment of mine and Coal Seam Gas water using volcanic rocks – Midell Water (www.midellwater.com.au) is a company that specialises in producing fit-for-purpose water treatment solutions for the mining industry.

The effective management of water in mines is essential. Mine water is both a resource and a regulated product that needs careful supervision. Midell Water can design, build, operate and maintain treatment systems for potable water, mine camp wastewater, stormwater, groundwater/ pit-water, and associated water from coal seam gas operations. These treatment chains are tailor-made for the specific mining requirement; as the water quality and volumes can change significantly between mines and over-time at the same mine. Midell Water has a range of treatment options specifically devised for the mining industry.

Water in the mining industry is not like municipal water; even those where the cities include significant commercial and industrial installations. The majority of water that requires treatment is typically linked to the mining process; such as pit-water or associated water. The water quality and the volume of mine water can be highly variable, depending on the aquifers at the site, rainfall patterns, and the type of mining being undertaken. The regulations covering the treatment, reuse, and release of this mine water varies from state-to-state, and can be altered in the short-term through specialised permits. The regulations covering the water quality parameters to be monitored differ between and within states, for example one mine may be required to report on arsenic and lead concentrations whereas a nearby similar mine may have to report on strontium and nickel. Treatment technologies developed to treat municipal water sometimes struggle to adapt to a mining environment and can have issues with cost effectiveness and water quality objectives. Midell Water has developed strategies to create economic and environmentally sustainable water treatment solutions for the mining industry.

An example of our approach can be in seen in the Coal Seam Gas Industry. The successful management of the associated water with CSG production has emerged as a major issue. Water and the CSG industry are continually raised by regulators, environmental lobby groups, the media, the community, and by CSG producers themselves. From a broad perspective concerns with associated water mainly involve fraccing chemicals, aquifer sustainability, and salinity. However, within the CSG industry, additional issues are apparent such as trace elements in aquifers, changing volumes of water, rapid evolution of regulations, and capital and operating expenditure.

CSG producers usually operate over a wide area; especially when compared to traditional ore or coal mining. The decentralised nature of CSG production with numerous wells/bores located in a basin adds complications to the management of the associated water. Not only does the associated water need to be transported to a treatment facility, but the quality of the water may be significantly different. Across a coal seam gas basin there is a generally a number of aquifers at different depths; the water quality between these basins may be quite dissimilar for a range of parameters. Different parts of the same aquifer may have fluctuating water quality due to changes in the hydrogeology across the water body. This can have a major impact on the types of water treatment required. For example if one part of the aquifer has a salinity of 2000 mg/L and another of 6000 mg/L is it better to treat this water together or separately? Conjointly if one part of the aquifer has relatively high levels of fluoride and boron, is it best to keep this associated water apart and treated with a specific treatment facility? Another issue that faces CSG producers is that they may have a treatment chain that is working well in one part of the aquifer; on what basis do they make the decision to replicate this treatment chain for all installations across the aquifer or decide to go for site specific treatment options?

The answer many consultants have devised for these questions has been reverse osmosis (RO). RO is a powerful treatment option with many advantages; however disadvantages also exist. Associated water treated by RO has a relatively high capital and operational cost, particularly in regards to energy consumption. The majority of RO membranes have been developed for the desalination of seawater and associated water can be quite dissimilar in regards to boron, bromide, and fluoride concentration. Other water quality parameters such as alkalinity and the sodium adsorption ratio (SAR) can also cause treatment difficulties for RO membranes. Associated water treated by RO units generally need to be chemically amended after post-treatment to reduce the SAR and make the water suitable for environmental reuse such as irrigation and river flow supplement. The chemical treatment is not only an additional cost but increases the salinity of the water. Midell Water has developed a range of treatment technologies specifically tailored to address the treatment requirements of different types of associated water.

Midell Water through a research relationship with Central Queensland University (www.cqu.edu.au) has developed a range of volcanic rock filter media that reduces SAR, salinity, heavy metals, and anions such as boron and fluoride. Additional research with other contact filter media such as granulated activated carbon and refinery by-products have produced filtration media blends with high adsorption capacities hydrocarbons, trace organics, and fraccing chemicals. Our research and development program is ongoing and we are continually developing new blends and treatment techniques for water quality parameters in the mining industry.

Our filtration media is used in conjunction with other water treatment techniques such as physical filtration, aeration (particularly ozone), and membrane filtration (micro, ultra, and RO) produces cost effective high quality water. Midell Water has designed treatment chains both with and without RO units; the water quality requirements make the decision rather than ideology. Separation at source where relatively good quality associated water is kept together and treated separately from the harshest associated water has cost effi ciencies and allows for shandying of the treated product.

A key component of any treatment chain design is the purpose to which the treated water will be used. The environmental and regulatory requirements are quite different for water that will be reused for aquifer recharge, irrigation, or placed into a freshwater stream that is used for potable purposes downstream. Midell Water has a relationship with Arris (www.arris.com.au); one of Australia’s most experienced recycled water reuse companies. Arris has a focus on the sustainable reuse of recycled water for agriculture with a strong history of successful community engagement and education. Perfect water without community acceptance is still associated water with a problem for the CSG industry. Midell Water and Arris can develop strategies to strengthen community engagement and acceptance for water reuse schemes.

The treatment chains developed by Midell Water can be either continuous flow or batching. The use of contact filter media in conjunction with a robust design means that highly variable flows can be treated. These treatment chains can be for small volumes to millions of litres per day. This is important in the CSG industry because the amount of water from the bores decreases over time. It is also important in the ore and coal mining industries because rainfall or mine expansion can alter the amount of groundwater and pit-water that requires treatment. Midell Water has filter media blends and treatment technologies for the management of wastewater from mining camps. The shift work involved with mining camps creates hydraulic surges at change-over and meal times that cause some technologies to struggle. Having filter media that can work in conjunction with benefi cial microorganisms to reduce nitrogen, phosphorus, and BOD concentrations helps ensure a consistent water quality that meets the regulatory guidelines. The treatment chains can be made so that they are transportable. This reduces construction time on the mine lease and enables the plant to be shifted if the requirements at the mine change.

Midell Water understands that mine water treatment is a specialised fi eld with specific water quality concerns and issues. Midell Water offers a range of treatment technologies and treatment chains that can be specifically tailored to address the water quality issues facing your mining activity. Because Midell Water has experience in the design, build, operation and maintenance of treatment plants we can offer a complete package to your water management requirements. Our operational knowledge provides us with continual updates on how to make our treatment plants robust and reliable. We have the skills required to work in regional and remote locations. Our partnerships with organisations in the research, education, agricultural, and community engagement sectors have ensured that we improve our outcomes for our clients. If you have mining water that needs treatment, especially if it’s difficult to treat, Midell Water has a solution for you.

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