Water is critical for all types of mining. Wastewater arising from mineral processing may contain a range of contaminants depending on the beneficiation process used, e.g. heavy metals, sediment, reagents, hydraulic oils used in the mining operation. Just like treatment strategies, mining wastewater can be highly variable. Treatment strategies generally include several different stages and technologies.
Water and wastewater treatment options may range from settlement in open ponds to constructed treatment plants depending upon the contamination present. Clarified water from ponds or from wastewater treatment can be reused within the mineral processing plant.
Depending on the desired final water quality, there might be required treatment technologies like reverse osmosis and other membrane filtration, ion exchange, electro-deionization, adsorption media.
Furthermore, in order to meet the terms and conditions of the government and ensure the highest quality of water discharged from mining sites, mining companies are now enforced to use mining wastewater treatment plants. Water used in mining applications is abided to go through treatment solutions before being released to the outer water bodies. It is employed for minimizing the possibility for water infectivity, as well as ensuring the quality water, and meeting up the government guidelines.
Read: Choosing the right plant maintenance strategy for your mining operation
The following are the different strategies of wastewater treatment:
Wastewater treatment for reuse
Not only are many productive mines around the world located in areas with stressed water supplies, but also, mining activity has contributed to the degradation of what little fresh water is available. In order to prevent further environmental contamination, mining companies can turn to advanced wastewater treatment solutions that produce water suitable for reuse.
Efficient wastewater treatment technologies can protect local freshwater sources by treating and reusing mining wastewater for landscaping, irrigation, dust control, and even drinking water. This reduces wastewater-disposal expenses and protects local water sources while meeting the most stringent standards.
Decentralized water and wastewater treatment
Connecting a remote mine to a central water and wastewater treatment plant via pipeline is expensive, time-consuming, and requires negotiation of complex right-of-way issues, so mining operations typically require decentralized treatment of water and wastewater. Decentralization, in a nutshell, means siting treatment near the water source, demand, or ideally both.
The benefits for decentralized water treatment technologies include: Lower capital costs, energy savings, lower carbon dioxide emissions, faster startup with containerized treatment and less maintenance.
Energy-Efficient wastewater treatment
Improving energy efficiency represents an opportunity to both lower operational costs and carbon footprint. Reducing energy consumption and increasing the efficiency of energy production are both required to have positive energy wastewater treatment plants. Measures to reach self-sufficient wastewater treatment plants include:
Process optimization: installing smart meters, developing control systems for the optimal operation of aeration systems and water pumps. EPRI has estimated that, in wastewater facilities, 10–20% energy savings can be reached through a better control and optimization of the process.
Enhanced biogas yield: currently, anaerobic digestion (AD) biogas can only provide around 50% of the total energy consumption. However, sludge pre-treatments can lead to an increase of the biomethane yield.
Efficient on-site combined power and heat (CHP) generation: the use of fuel cell systems can increase further the on-site electricity generation, which is key to self-sufficiency.
Co-digestion of sludge with food waste is also an interesting option to increase the overall biogas output.
