Bottles containing raw sewage final effluent and reclaimed water
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Aquifers to Store Reclaimed Water: Nature provides an elegant solution

The power of nature is amazing. The sun, wind, waves and bacteria that drive our world are incredible forces. Most of us love working on projects that find a way to use these simple, elegant forces to solve problems efficiently.

Nature’s power can also be used to convert wastewater to a valuable water supply. Instead of treating wastewater as a problem to be disposed of, it’s now possible to reclaim it as a resource. Because of advances in technology, wastewater can be treated to a high level at a reasonable cost to remove pathogens, nutrients and organic pollutants.

Reclaimed water can then be further treated using specially designed infiltration basins that percolate the water into aquifers. This process, called Soil Aquifer Treatment, works because the soil under an infiltration basin is essentially like a big biological reactor. The bacteria are hungry and want to use nutrients and organic pollutants as food and energy sources.

The communities in the South Puget Sound of western Washington have been engaged in a long-term project treating their wastewater so that it can be infiltrated to groundwater. This solves two problems: enhancing groundwater supply (which is locally used as a drinking water source) and reducing the nutrient load to Puget Sound.

The LOTT Clean Water Alliance (the regional wastewater utility in Thurston County, Washington) and HDR are conducting a multiyear study investigating the effectiveness of Soil Aquifer Treatment to recharge aquifers and preserve water quality. The study is specifically looking at the treatment effectiveness of a reclaimed water aquifer recharge facility that has been operating for approximately 10 years. This effort is referred to as the Reclaimed Water Infiltration Study.

This is one of the few studies being conducted for this application in a climate with a dry summer but a relatively wet and warm winter. Some of the project components include evaluating the types of chemicals that remain in reclaimed water after treatment (with a focus on nutrients, pharmaceuticals and personal care products) and their background concentrations in surface water and groundwater.

Monitoring wells, lysimeters and in-situ instrumentation are being installed to collect samples and monitor below-ground conditions to determine how water quality changes as reclaimed water moves through the unsaturated zone and into the aquifer and then down gradient. This information will be used to demonstrate the effects of reclaimed water infiltration on groundwater quality and to assist in the design of a larger scale aquifer recharge program that will help to reduce wastewater discharges to Puget Sound. If reclaimed water can be recharged into aquifers and still preserve groundwater quality, it provides a way to augment groundwater supply and convert a water resource management problem into a solution.

This applied research activity is a great example of the innovative and exciting work supported and encouraged by HDR’s Water Institute. More detail about the Reclaimed Water Infiltration Study can be found on LOTT’s website. Our scientists and engineers are also supporting reclaimed water aquifer recharge for a variety of other wastewater utilities, including the cities of Aurora, Billings, Lacey, and Tucson, the Santa Clara Valley Water District, and the Metropolitan Council’s Environmental Services Division (MCES) in Minneapolis, among others.

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Reclaimed Water Aquifer Recharge Replenishes Aquifers and Provides a Water Supply Source