Wastewater from domestic and industrial sources has the potential to provide both water and nutrients to support agriculture within close proximity to urban areas. Sixty percent of irrigated croplands across the globe are located within 20 kilometers of urban areas (Thebo et al., 2014). Due to its close proximity to consumers, urban agriculture is an important economic driver and also enhances food security. Direct wastewater reuse for agriculture is limited in the U.S., although it is commonly practiced worldwide, often at small scales and with minimal or no water treatment.
In arid and semi-arid areas, such as Nevada and the western U.S., conflicts often arise between competing environmental and agricultural water users during prolonged droughts and summer low-flow periods. Policies that support and facilitate the use of highly treated wastewater for irrigated agriculture may help alleviate conflicts over scarce resources (Blanco-Gutierrez et al., 2013).
The key constituents removed from treated wastewater are biochemical oxygen demand, total suspended solids, nitrogen, phosphorous, microorganisms (as bacterial indicators) and some inorganic/organic chemicals. Although regulations exist in Nevada and California, for wastewater reuse for irrigated agriculture, further treatments may be required to remove additional pollutants including emerging contaminants that are present in wastewater effluent. These include pharmaceuticals, personal care products, surfactants, flame retardants, plasticizers, pesticides and herbicides (Jelic et al., 2011). The extent to which some of these compounds may bioaccumulate or biomagnify through the food chain is unknown; therefore, potential exists for harmful effects to ecosystems or human beings even at low concentrations (nanogram or microgram per liter).
The Reclaiming Water for Urban Foodsheds research program addresses this knowledge gap by investigating the potential use of reclaimed water in urban irrigated agriculture and identifying any potential associated human health impacts and necessary mitigation measures. The resulting knowledge aims to support the adaptation of wastewater treatment systems to produce water suitable for irrigated agriculture.
Reclaimed water could provide a cost-effective and sustainable resource in the context of the food-energy-water nexus. Such knowledge will also enhance water sustainability in arid regions, such as the Truckee-Carson River System of northwestern Nevada, which includes the Truckee Meadows high-desert foodshed and surrounding agricultural communities.
The key research objectives of the Reclaiming Water for Urban Foodsheds program are to:
- Identify chemical contaminants in reclaimed water used for urban irrigated agriculture;
- Determine pathways of contaminant entrainment via water, soils and sediment into agricultural products (i.e., forage crop and animal production);
- Develop predictive models for the fate of trace organic chemicals during wastewater reuse and evaluate associated human health risks of identified contaminants at their respective concentrations; and
- Develop health risk mitigation strategies over the course of the agricultural production chain, particularly focusing on reclaimed water production for irrigation.