Electric current-driven technology aids water purification system
Electrically powered automobiles– among other electrically capable machines–have been trending over the past decade to combat air pollution and help slow the effects of global warming. Now, more environmentally responsible solutions to water treatment are being sought as global industries shift under pressure to abide by stricter regulations.
Droughts and climate change gradually have been depleting the globe’s natural water sources, with a number of countries seeing “Day Zero” in their line of vision. This has made water reuse and recycling more important than ever.
It also has pushed municipalities to become more aware of what is being discharged back into their local water sources. Wastewater with heavy amounts of salts require treatment and special permitting before it can safely flow back into these water sources.
The movement of more efficient, less environmentally impactful solutions to everyday tasks and responsibilities has become an immediate requirement, not a goal for the future.
New regulations and an awareness of the need for environmental responsibility have helped fuel the push for more innovative water treatment solutions in a variety of industries.
Certain water treatment technologies, such as electrodialysis reversal (EDR), ion exchange and membrane capacitive deionization, have rapidly gained acceptance in the once-conservative commercial and industrial water treatment market. They are paving the way for water consultants and distributors to add more sustainable options to their product catalogs.
Because of the extensive amount of water consumed on a regular basis, businesses are taking every opportunity to reduce the amount of water used and are looking for options that allow them to do that. One customer in particular was looking for an easy-to-use technology that required little maintenance and also could maintain a consistent quality output through any water quality spikes in turbidity. It decided to replace its current water treatment plan with a newer, less traditional option.
A Unilever margarine manufacturer located in Pratau, Germany, was using a large amount of water during its manufacturing process, which was increasing costs. Also, the plant is located in a part of Germany known for its extraordinarily high water costs, which added urgency for Unilever to find a water treatment solution for its cooling towers.
To treat its water, the site relied heavily on chemicals. This meant Unilever was paying to discharge its water to the municipality because the water needed extensive treatment before it could be reused or discharged. This solution was neither reliable nor sustainable, and was causing more problems in the long run.
The site evaluated various water treatment solutions to lower its water consumption and chemical usage, which included reverse osmosis (RO) and membrane capacitive deionization.
The Power of Electro-Deionization
Many industries have become more environmentally conscious, therefore, the search for an alternative to high-pressure, high-energy consuming water treatment technologies is well on its way.
Voltea’s membrane capacitive deionization (CapDI) removes total dissolved solids (TDS) from water sources with minimal pre-treatment requirements. It also eliminates dissolved salts and other minerals via direct current, or electro-deionization, where oppositely charged salt ions are attracted to electrodes, leaving pure water flowing out of the cells in a two-step process of purification and regeneration. When the ions are fully saturated, they flip polarity and the ions then are discharged.
One of the environmentally responsible features of this process is that soft salts never are added to the system to replace the hard salts that were removed. This allows the same salinity and mineral level that was in the original water source to be discharged without additional, higher salt levels. Traditional water softeners, where hard salts are replaced by soft salts, have been banned in some municipalities, especially those struck by drought where environmental concerns are a priority.
A Responsible Choice
Unilever required a solution that was fundamentally different. The company found a water treatment technology that would minimize chemical usage while reducing water consumption and costs. Ultimately, the manufacturer determined that RO was not an efficient water treatment solution for its needs for several reasons:
RO produces ultra-pure water as it removes all salt and TDS, which can have a negative effect on a cooling tower and steel pipes. In fact, it is common for water treated with RO to corrode steel pipes because the water can remove the iron from the pipes and neutralize itself.
Water with a low salt concentration is considered unbalanced and will naturally attempt to take in salts from other sources to balance itself out. This can corrode valuable equipment and causes structural damage to cooling operations.
A typical RO system will be accompanied by a remineralization bed to place the required amount of salts back into the water source where the majority of the natural salts have been removed. This piece of the process, unfortunately, causes issues within cooling towers as it produces a higher concentration of salt that is used within the cooling loop. When there is evaporation, that salt is left behind and causes unnecessary corrosion and scale, often leading to more water consumed.
A differentiating factor that led Unilever to rely on CapDI was its tunability. The system operator can set a desired TDS concentration of the output water required for the cooling tower or equipment based on the operation style or cycles of concentration necessary. The technology will do all the work, delivering consistent quality output even if there is variation in the incoming water source. The tunability feature removes unnecessary steps in the treatment process while eliminating a high concentration of salt in discharge water.
CapDI also offers real-time, remote monitoring and control capability to minimize user intervention and reduce maintenance.
Not all applications require the same removal rate, which eliminates any remineralization needed from using traditional desalination technologies,
such as RO.
Tuning the Technology
The margarine manufacturer had a cost-effective Industrial Series 2 (IS-2) system installed on location.
This system allows the original water source to be discharged without any additional salt levels, producing higher cycles of concentration and reducing overall water consumption.
In this situation, the CapDI system was set to reduce the incoming feed water TDS by 60%, enabling the customer to cycle up the cooling tower and realize savings in both fresh water usage, as well as wastewater production from blow down. Due to feeding the cooling tower with water of a higher quality, they were able to reduce their chemical usage.
It did not take long for Unilever to see results from the installation of the system. After six months of operation, the manufacturer saw more than $13,000 in savings, and after a year and a half, there were even more results, including a 78% reduction in chemical consumption, a 50% decrease of wastewater and a 26% reduction of fresh water consumption.
The graph above shows the consistent and substantial reduction in wastewater production and chemical and freshwater consumption. The average water recovery rate for this was approximately a consistent 82% over the data period.