Calculating water footprints requires assessment of the entire value chain
A water footprint is the amount of green, blue, and gray water required to produce a good or service or to keep an industry sector, company, or region running. Calculating water footprints has become an ever more important requirement of wise decision-making about water use.
To calculate a water footprint, you must consider more than the actual water contained in, for instance, a product. You must also consider the “virtual water” that it contains. A product is regarded as virtually containing all of the water used to produce it throughout the entire value chain. This “indirect water” is conceptually embedded in the product even if the finished product itself contains zero actual water. (Thus, “virtual water” is also called “embedded water.”)
The water footprint of paper products includes the water for the trees used to make the paper, the water used during logging and manufacturing, and the water used to assimilate the industrial wastewater produced by the manufacturing processes. It all adds up to an awful lot of virtual water associated with a product that contains no actual water.
There are three kinds of water footprint.
- The green water footprint is water in root zones that is the result of precipitation and that evaporates, is transpired, or is incorporated into plants.
- The blue water footprint is water from conventional water sources like surface water bodies or aquifers.
- The grey water footprint is the water required to dilute point and nonpoint sources of water pollution to meet a regulatory standard.
Reducing Water Footprints with Water and Wastewater Treatment
Many kinds of water treatment reduce grey water footprints at points of discharge: conventional activated sludge (CAS) and fixed-film (FF) processes, membrane bioreactors (MBRs), biological nutrient removal (BNR), and membrane processes like reverse osmosis (RO), microfiltration (MF), and dissolved air flotation (DAF).
In an industrial operation, treating water so that it can be used again reduces the amount of blue water drawn from surface and groundwater sources while permitting a high degree of quality control over process water and blowdown water. Generally, a thoughtful water management plan that reduces water footprints through treatment and reuse of water also lowers the cost of water, especially when there’s lots of competition for access to water in a region.
Desalination turns seawater into fresh water while reducing, perhaps even drastically, the amount of blue water taken from scarce natural sources. Desalination is even more cost-efficient when the water source is brackish, as is the case in many brackish aquifers that are still too often deemed unusable despite a marked decline in the costs of desalination.
For organizations in most sectors to undertake treatment of water and wastewater would entail a significant detour from their core missions. Fortunately, relatively new financing structures for delivering water infrastructure like public-private partnerships (P3s), build-own-operate, and build-own-operate-transfer address the problem by contractually bundling infrastructure development with long-term operations and maintenance.
These financing structures shift risk to the water company while enabling public and private concerns to exploit the expertise and resources of that specialized company. The benefits of the approach have led governments from the US to Asia to roll out new legal frameworks to standardize P3 projects and make them as easy as possible to adopt.
In an era when fresh water and the investment capital required to fund water infrastructure are both getting harder to find, the new financing models enable organizations to reduce the costs of their water footprints on a much larger scale. That is good news for their bottom lines and good news for the world’s freshwater resources.