Sustainability of Saline Water Management
Driven by increasing demand for freshwater supplies - against the pressures of climate change and increased pollution of water resources – significant progress has been made over the past two decades in developing sustainable water management strategies.
Whereas water scarcity has always existed, the need of water for people and industry alike is now growing at an alarming rate. A recent comment by an Oracle VP that “Water will be bigger than power is today” is a reflection of the situation.
Fortunately, technologies for desalination of sea water, brackish groundwater or any other saline water source do exist and are increasingly becoming cheaper because of technological and materials advances. By allowing access to a new water resource, these innovations are providing lifeblood of affordable freshwater supplies to communities in isolated arid regions. Industries have also turned to this technology, allowing the waste energy from their processes to be used as drivers of desalination units, thus significantly improving the efficiency of the treatment process and reducing the overall footprint (physical, economic, carbon). Investment in desalination projects that derive value-adding benefits, in the form of on-site energy generation or saleable byproducts has been particularly substantial in the recent years.
Desalination of seawater and inland brackish water therefore represents a real and viable option for securing potable water resources. However, as with other processes for volume reduction, desalination generates a higher salinity waste stream (commonly know as “brine”), which needs to be effectively managed, either by safe disposal or beneficial reuse.
Otherwise, it increases the water risk exposure in the desalination value chain. The risk profile is particularly pronounced in arid inland regions, where the conventional options for safe disposal of desalination brine are limited in scope and availability, compared to the brine from seawater desalination which may be discharged to sea. Cases already exist in the Southwest U.S., where lack of a cost effective and/or sustainable brine management solution has hindered the commercial development of inland desalination projects.
Brine as a Water Management Issue
As the corporations and governments around the world move from the measurement of carbon footprinting to water footprinting (Cleantech Group, 24 May 2010), the challenge of sustainable management of brine from desalination processes will become further highlighted as part of the measures needed for sustainable management of water – a critical resource at risk. This challenge is already evident in the case of Australian coal seam gas (CSG) industry, where desalination represents an essential component of the announced plans for the management of massive volumes of produced water that is expected from the proposed CSG to Liquified Natural Gas (LNG) development projects.
Apart from desalination, many other industries also produce saline waters. These include but are not limited to oil/gas, power production, mining and mineral processing, water recycling, food and beverage production and agricultural activities.
In cases where management of saline waters poses an important operational problem, thermo-mechanical equipment (brine concentrators and crystallisers) are applied for the reduction of brine volume. However, volume reduction processes produce a more highly concentrated brine stream with an organic and metal contaminant load that is often several fold higher than that of the feed brine. In many cases, the disposal options which were available for the feed brine are no longer available, unless pre-treatment is employed, a extra cost.
Challenge
Sustainable management of brine is a global challenge with an evolving demand. The challenge is particularly overwhelming in the case of large inland desalination and water recycling projects, where increasingly stringent regulatory regimes severely limit the use of evaporation ponds as a means for cheap volume reduction and landfill incurs significant cost and liabilities for the operators.
The Need
Whereas there is no silver bullet for all situations, a sustainable brine management solution needs to:
- Be cost effective.
- Maximise water recovery.
- Reduce the salt load of brine through recovery of useful byproducts.
- Minimise the need for evaporation ponds and landfill.
- Reduce the risks and liabilities for resource developers and/or users
