Water Online

September 2015

Water Online the Magazine gives Water & Wastewater Engineers and end-users a venue to find project solutions and source valuable product information. We aim to educate the engineering and operations community on important issues and trends.

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Decentralized Wastewater Treatment Shines As Aquifer Recharge Solution Decentralized wastewater treatment systems have come a long way. Learn how new advancements have broadened their potential and may provide relief to fast-depleting groundwater resources. By Jessica L. Kautz P otable water sources are being exploited worldwide; water tables are dropping at drastic rates, causing wells to run dry, saltwater to intrude inland and leaving an increasing number of people without reliable sources of life-sustaining water. As populations continue to grow and shift, it is imperative for all aspects of the water cycle to be optimized for sustainability. Wastewater treatment creates a large impact on the water cycle, as large volumes of water are processed on a daily basis. The foremost goal of wastewater treatment has always been and continues to be the protection of public health. However, as the industry grows and the complexities of the challenges expand, it is important to consider that the method and level of treatment greatly impact environmental health and sustainability, as well as our potable water supplies. It is our respon- sibility as engineers, designers, and citizens to protect both public and environmental health. Models Of Wastewater Treatment Two general models are used in wastewater treatment — central- ized and decentralized wastewater treatment. Centralized wastewater treatment involves the collection of wastewater from a large area to one centralized location, where it is most commonly treated and released into local surface waters. Conversely, decentralized wastewater treatment provides treatment and disposal either directly on site or at a nearby location. Both methods can be designed to pro- vide equivalent levels of treatment and protection of public health. However, centralized and decen- tralized wastewater treatment systems vary greatly in regard to their impacts on environmental health and potable water supplies. Centralized treated effluent is usually released into flowing waterbodies (such as rivers or oceans); malfunctions in system performance therefore pose a significant risk to pub- lic health as they can flood surface waters with contaminants or hazard- ous chemicals. In addition, the clean water discharged from the facility is largely carried away from its original location before it filtrates into the soil, evaporates, or is removed for a down- stream potable water supply. Discharge thus provides limited groundwater recharge of the billions of gallons of treated effluent released daily. Centralized wastewater infrastructure also adds to groundwater depletion, as leaking pipes can cause groundwater to infiltrate into the pipes and be carried to the centralized facility. Decentralized systems, on the other hand, treat and filter effluent through the soil directly into the local aquifers. Once filtered through the natural soil into the aquifers, the clean water travels to surface waters or wells or estuaries, where it can be utilized by humans and natural ecosystems. In this way, decentralized wastewater treatment systems provide the most passive and environmentally sound form of aquifer recharge and wastewater recycling. Aquifer Recharge Using Decentralized Wastewater Treatment Aquifer recharge is a growing method of water table stabilization and water supply in the U.S. The U.S. EPA defines aquifer recharge as, "the enhancement of natural groundwater supplies using man-made convey- ances such as infiltration basins or injection wells." As currently defined by the EPA, aquifer recharge systems are typically used in areas with limited ground or surface water availability. 40 wateronline.com n Water Innovations Figure 1. Groundwater depletion in the continental U.S.

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