Dr. Alan Rimer (PhD, DEE, P.E.). With a varied, 46-year career in environmental engineering, Dr. Rimer has been involved with planning and design for a variety of water reuse, water resources, wastewater treatment, solid waste management and environmental management projects for local, state and the federal governments, as well as a wide variety of industries, across the United States, Asia, Europe and South America. He recently retired from Black & Veatch and joined with a friend to start a consulting firm where he will continue his reuse work.The following is a guest post by Project WET Foundation Board of Directors member
We all generally understand the hydrologic cycle: It rains, the runoff flows to the sea or replenishes groundwater, evaporates and the cycle begins again. But there is something new in this cycle that is becoming increasingly important as climate change, localized drought and other factors reduce our confidence that we will always have potable water where and when we want it—water reuse. Water reuse is the reclamation of wastewater by advanced treatment that permits its use for a variety of purposes. On the one hand, it can be used for basic crop or landscape irrigation and on the other end to additional and very sophisticated wastewater treatment providing for its use as a water supply resource through a process called direct potable reuse (DPR).
Utilities in many parts of the country are now considering water reuse as part of their water supply portfolio for many reasons. As communities grow, many are finding that managing their water resources (water availability), competition for the use (e.g. agriculture, domestic and industrial use) and evolving regulations are making it difficult to assure adequate water for their customers. The five year drought in California is a good example of a “perfect storm” in which the needs of utilities to supply adequate potable water to their customers and the provision of water for agriculture collide. We are all beginning to see the interrelated nature of water supply and treatment, wastewater collection and treatment and stormwater management and their intersection. While good planning can resolve some of these issues, there is only so much water available for allocation, so water reuse becomes an important management tool to meet water resource needs.
Just what is water reuse? In the west it is known as water recycling, but in most other locations it is understood to mean water reclamation. Conceptually, water reuse is the reclamation of a “used” water (wastewater or stormwater) to a state that will permit some form of beneficial reuse. It can take many different forms. It can be a suitably treated wastewater that is used for irrigation purposes or it can be very highly treated wastewater that ultimately becomes a source water for a potable water treatment plant (DPR.) Generally, the utility producing the reclaimed water is the wastewater utility. They can derive income from this new source of water by selling a resource they used to discharge directly to a water body. This view of deriving income from an otherwise wasted resource is shaping the way utilities actually evaluate projects and incorporate water reuse into their water supply portfolio.
Why do citizens and utilities care? Traditionally, California, Florida, Texas and Arizona have been the major states where we have seen the most implementation of water reuse projects. This is primarily because of their need for a better utilization of their water resources due to increasing demand and dwindling water resources. The new frontier includes states where water resources are presumed to be plentiful. These range from such diverse states as North Carolina to Minnesota. The pressure for reuse comes from demand for more water for cooling purposes in large urban areas. Such cooling water does not have to be treated to potable standards (North Carolina). Or water reuse may be driven by the need to alleviate pressure on the drawdown of groundwater tables caused by the high demand for industrial use (Minnesota).
In the end, the drivers for water reuse vary and are significantly impacted by location and climate. In California, the “produce basket” of the United States, the availability of water to provide the abundance of food available is significantly impacted when water resources are constrained. What is more important and who gets to decide—water to provide for all of the citizens of California, or water for the produce that feeds the nation? In the end, water reclamation can supplement the water resources available to the utilities serving the citizens of California for a variety of non-potable uses. It also means that the farmers can adopt more efficient irrigation practices. Therefore, with a shrinking water resource “pot” due to climate change and other factors, both parties can supply their growing needs.
Water reuse will play an increasingly important role in the water portfolio adopted by utilities and the agricultural community in the decades ahead. Educating the public about its importance and reliability will be an important challenge.