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Reclaimed Water Irrigation

Daria Giron, P.E., Project Manager, Leonard Rice Engineers, Inc., daria.giron@lrcwe.com

Figure 1. Daria Giron is a professional engineer and project manager at Leonard Rice Engineers. She lives with her family, including children Jaeda, Tevan, and Chloe, in the Denver area.

In our culture, we treat nearly 100 percent of the water used in all aspects of our residential lives to a water quality level suitable for drinking. Do we really need to use potable water to irrigate our lawns? Or our golf courses? Isn't that truly a waste of energy, time, materials, and an unnecessary production of treatment wastes? Or would a dual system (two pipelines, twice as much maintenance and operations, etc.) be more wasteful?

Two principles of green engineering that support the pursuit of rethinking our standard irrigation practices are: "It is better to prevent waste than to treat or clean up waste after it is formed", and "Design for unnecessary capacity should be considered a design flaw".

We don't drink the water used for irrigation, so why do we treat it as though we are going to? It seems to make sense to instead consider the possibility of parallel non-potable irrigation systems. Such systems have the potential to remove the peak irrigation demand from the existing municipal demand curve for a City. This in turn would decrease the required capacity in the water treatment plant (which is sized to meet peak demands), decrease the quantity of treatment chemicals produced and purchased, decrease the size of potable distribution mains, and decrease the quantity of treatment wastes that are produced - such as spent diatomaceous earth or brine waste streams.

Even greater benefits could be realized by implementing a reclaimed irrigation water system rather than only a non-potable system. With a reclaimed system, not only are there the above mentioned savings on the upfront water treatment side, but also the added benefit of reducing the quantity and concentration of nutrients being returned to the stream system. This is an often overlooked benefit to installing a reclaimed water irrigation system.

Consider for a minute the impact of irrigating one golf course with treated wastewater effluent (reclaimed water) in place of potable water. For example, a typical Denver area golf course has an average annual demand of 380 acre feet. Should this one golf course switch to reclaimed irrigation, approximately 125 Million gallons per year of nutrient loaded wastewater effluent could be kept out of our streams! With over 130 golf courses in the state, can you imagine the statewide impact on water quality if all our golf courses, parks, and larger irrigated acres were tied to a reclaimed system? And the reduced treatment costs for those municipalities downstream that have to treat their upstream neighbors' effluent in order to provide drinking water? The environmental benefit to our State's aquatic system, in addition to treatment costs that could potentially be saved, should encourage all of us to take another look at reclaimed irrigation.