Water is the most abundant compound in the universe and covers 71 percent of the earth’s surface. Yet society makes use of only a small percentage. Most of water on the earth by far is saline or seawater. Freshwater makes up only 2.5 percent of the total. Most freshwater is locked in glaciers, ice caps, and underground, with only about 1.3 percent of it available as surface water.
Industry competes with agricultural and municipalities for this precious resource. And businesses compete among themselves for its use. After all, it’s a limited resource, and consumption is bound to be driven by its relative scarcity.
Economic growth and development are going to lead to ever-higher stress on water supplies. Under a business-as-usual scenario, according to the 2030 Water Resources Group, “global [yearly] water requirements would grow from 4,500 billion cu m today (or 4,500 cu km) to 6,900 billion cu m” in 2030, a figure that is “a full 40 percent above current accessible, reliable supply.”
Three primary sectors account for water withdrawals, and the group projects that all three will increase their demand: Industrial use is projected to grow as a percentage of total withdrawals from 16 percent to 22 percent by 2030. While increasing its withdrawals by volume, agriculture is expected to decline from 71 percent to 65 percent of global withdrawals; domestic use from 14 percent to 12 percent of the total.
Water Stress and Manufacturing: We’re All in This Together
Neil Hawkins, vice president for sustainability at Dow Chemical Co., said in an interview that his company pays “a lot of attention to water-supply risk in terms of quality and quantity,” and that continued availability of water “both for today but also into the future is a strategic issue for Dow.” The chemical industry is water-intensive, as the manufacture of chemicals requires a lot of water for cooling, steam generation, cleaning, refining, and other processes.
Dow recognizes that it does not operate in a vacuum. To survive and thrive, the company depends on the communities where it operates, on the health of the larger economy, and on the beneficial resources and services it receives from the environment. Speaking about the company’s Texas Operations on the Brazos River, Hawkins said: “We’re very focused on reducing our demand on water and at the same time working upstream with the state on ways to improve the supply of water to everyone on the river as well. All of these water supply issues have to be approached through collaboration between companies, cities, governments, and farmers.”
“Zero discharge,” or zero liquid discharge, has become an important water management principle during the past two decades. While hard to achieve in an absolute sense, companies often employ it as a model, as a means for setting objectives for water and wastewater management. Gena Leathers, who leads corporate water strategy at Dow, explained that the zero-discharge model involves “bringing in technologies that allow you to capture, recycle and reuse water.” Hawkins added that “in general, you’ll see that the trends are more toward zero discharge and ever-tightening requirements on quality of discharge.” In fact, he said, “in a lot of places the water we discharge is cleaner than the water we take in.” In some markets where Dow operates, such as Saudi Arabia, said Hawkins, “you’re highly incentivized to keep that water and re-use it as much as you can. The more scarce the water, the more the economic incentive to go zero discharge.”
The concepts of water management, water footprint, and zero discharge — as well as the obvious economic value of reducing consumption of a costly resource — have led industrial firms to seek methods for intensive reuse and recycling of water.
Gary Howard, principal process engineer at construction and engineering firm Foster Wheeler, writes that at any industrial site “there are many operations and processes that require water,” and a good first step in minimizing waste is to “look at elimination or direct reuse of water as the first step.” Oil refineries, for example, can reuse stripped sour water in the desalters. A facility can get more use out of treated water by using it for “washing down dirty areas and for dust suppression in partially paved sites” or in cooling towers. In some cases, treated water can even be used for irrigation.
Treating Industrial Wastewater
Environmental regulations, as well as the desire to be good corporate citizens, have compelled industrial firms to improve the quality of their discharged water. While a smaller manufacturing concern might be able to discharge effluents into a local municipal wastewater plant, the greater number of medium-sized and larger facilities in developed lands operate their own on-site wastewater treatment plants.
Industrial wastewater treatment usually takes the form of an adaptation to the standard four-phase treatment process:
- Pretreatment or preliminary treatment uses screening and filtering to remove excess solids and other substances from wastewater. Manufacturing plants often use specialized filters and reverse osmosis technologies to remove toxic chemicals at this stage.
- Primary treatment allows suspended solids to settle to the bottom, where they can be removed as sludge.
- Secondary treatment removes organic matter using biological processes.
- Tertiary or advanced treatment polishes effluent before it is discharged into the environment. Some companies are starting to use constructed wetlands or other green infrastructure strategies for tertiary treatment.
This is the basic wastewater treatment model used in municipal systems. However, a manufacturing or industrial plant will generally need to adapt and expand upon this framework. Michelle Hamm, environmental manager for Monadnock Paper Mills in Bennington, N.H., explained the distinction: “For municipal plants, their largest issue is parasites, things like E. coli. But in industrial treatment systems, each waste stream is different, depending on the actual chemicals used in the facility.” Her company produces short paper fiber as a waste stream, resulting in a large volume of specialized sludge.
Manufacturers often produce multiple wastewater streams from different stages of their operations, and these streams have distinct contaminant profiles. Companies usually find it simpler, less expensive, and more effective to employ pretreatment of these individual streams before channeling them into the general wastewater treatment system. This keeps troublesome chemicals from mingling in the primary, secondary and tertiary stages, where they can cause major problems, even explosions and poisonous gases. Natural gas processing plants use special systems to remove oils, grease, solids, volatile organic compounds (VOCs), advanced metals, and other toxic substances from waste streams prior to any standard wastewater treatment.
Monadnock keeps toxic chemicals out of its waste stream by “eliminating hazardous materials in the facility itself,” avoiding contaminants on the front end, Hamm said. The sludge from Monadnock’s wastewater treatment plant is so clean that it is used for topsoil by local farms. “The sustainability of that byproduct is because hazardous materials don’t get introduced into the system in the first place,” she said.
How Will the Water Gap Be Closed?
Will the world be able to balance the supply and demand for freshwater? The 2030 Water Resources Group says that during the period from 1990 to 2004, the agricultural and industrial sectors each improved their water efficiencies by about 1 percent annually. That’s not enough, according to the group: “Were agriculture and industry to sustain this rate to 2030, improvements in water efficiency would address only 20 percent of the supply-demand gap, leaving a large deficit to be filled.” Increasing water supply by customary methods will only close another 20 percent of the gap.
Some countries and some industries are resorting to desalination to close the gap, but that is an expensive option. Expansion of surface-water supply requires accelerating the building of infrastructure, which is expensive also. The most affordable and effective way to close the gap would be through efficiency measures — if businesses, governments and communities can be convinced to move ahead with such measures as soon as possible.
“While the gap between supply and demand will be closed,” the 2030 Water Resources Group points out, “the question is how.”