WATER REUSE TECHNOLOGIES AVAILABLE TO INDUSTRY
We all recognize that water is essential to life for humans, animals, and plants. Yet, knowing this, we are faced with the harsh reality that 785 million people lack access to clean water.[1][2] That is one in ten people on the planet and more than 2 times the population of the United States. As industry looks to reduce impact on water quality and availability, it is important to have an awareness of how essential water is to the life of industries and to consider the options available to reduce industrial impact. The OECD Environmental Outlook to 2050 (OECD, 2012b) predicts that global water demand for manufacturing will increase by 400% from 2000 to 2050 which is much larger than any other sector.[3] Industries will be forced to implement water reclamation or wastewater reuse as a water-conservation approach. This might involve treatment and conversion of wastewater into either potable or non-potable water for different reuse purposes to reduce undue burdens on freshwater supplies. Many companies are already setting sustainability goals that look to reduce total water usage or increase their efficiency with respect to water usage by lowering their gallons/units of production.
Many technologies and opportunities for wastewater reuse and recycle are available today. In industry, specifically, they include process wastewater recycling, cooling tower blowdown, boiler blowdown, once through cooling water, ion exchange rinse waters, and collected rainwater. Depending on water quality requirements, space constraints, and budgetary considerations, these methods may be useful to consider:
Process Wastewater Recycling
With the proper purification equipment, process wastewaters can be reused for a variety of applications including washing, plating, rinsing, cooling, and boiler water make-up. Microfiltration techniques also substantially contribute to the recovery of water for industrial purposes. In the powder-coating industry, huge amounts of water are used in the finishing process. However, filtering with reverse osmosis and deionization can allow these companies to reclaim up to 90 percent or more of their post-process water and use it again.[4]
Cooling Tower Blowdown
Blowdown water from cooling towers is a large source of wastewaters from industrial processes. Besides minerals (TSS, TDS, Hardness and Alkalinity), the water might also contain bacteria and algae. Microfiltration, the physical separation of micron-sized particles and microorganisms through a microporous membrane, and Reverse Osmosis, the process to demineralize water or filter dissolved solids in water by applying pressure to force it through a semi-permeable membrane, are two technologies available for treatment prior to reuse.
Boiler Blowdown
Though it may be a difficult stream to treat there are technologies available for boiler blowdown water reuse. Zero liquid discharge technologies involve extensive treatment and volume reduction. Other options include reverse osmosis, filtration, softening, ion exchange, and pH adjustment.
Once-Through Cooling Water
Industrial processes and oftentimes powerplants will employ once-through cooling water processes, which have the negative impact of increasing the temperature of the surface water source. Industries could benefit from deciding to purify their once-through water for potable water use or redesign to an open recirculating system.
Ion Exchange Rinse Water Recycling
Many industrial processes use a city potable water source for rinsing of products followed by treatment and discharge to the sewer. This rinse water may be captured, sent into a prefiltration to remove any solids, and treated in an ion exchange process to produce deionized water. Using an ion exchange media or resin, negatively charged cation resin attracts positive ions or molecules from the water including sodium, calcium, magnesium, iron, and other metals releasing hydrogen ions (exchange) from the resin. Following the cation exchange, positively charged anion resin attracts negative ions including chlorides, sulfates, nitrates, carbon dioxide, and silica while releasing hydroxide ions. [5]
Rainwater Collection and Uses
Water quality and purification standards for specific industrial processes and volume requirements limit the uses for collected rainwater. However, harvested rainwater does provide an alternative source to facilities for landscape irrigation, wash applications, landscape pond/fountain filling, cooling tower make-up water, and sanitary water for toilets.
With all of these technologies and opportunities available today, the market for water recycle and reuse is certain to grow. Whether reducing costs and/or increasing sustainability, facilities can achieve their goals by evaluating their total water use at their facility on a regular basis. If you have not prepared a facility Water Balance analysis that shows the top 5-10 process contributing to water use and discharges from your facility, it may be a good practice to begin reviewing this data every couple of years. Stevens Environmental Consulting has experience helping clients prepare these analyses and identify potential sustainability goals or cost-savings projects to reduce overall water use.
Hunter Hill
Hunter@StevensEnvironmental.com
REFERENCES
[1] https://water.org/our-impact/water-crisis/global-water-crisis/
[2] https://www.worldvision.org/clean-water-news-stories/global-water-crisis-facts
[3) WWAP (United Nations World Water Assessment Programme). 2015. The United Nations World Water Development Report 2015: Water for a Sustainable World. Paris, UNESCO.
[4] https://wcponline.com/2020/12/15/the-potential-for-industrial-wastewater-reuse/
[5] https://waterinnovations.net/tag/ion-exchange-rinse-water-recycling/