Dear Colleagues,

Reclaimed water (or reused wastewater) is municipal and industrial wastewater that has been treated and purified and that can be reused for a variety of purposes including urban, agricultural, landscaping, environmental, and replenishing of surface (rivers and lakes) and groundwaters (groundwater recharge). Water is the most important resource for the sustainable production of crops destined for human and animal consumption and is crucial for feeding and other basic needs of a growing global population. Around 97.5% of water on earth is saline, and 2.5% is freshwater. From this 2.5%,  around 69.5% is unavailable, and 30% is groundwater with lakes, rivers, and swamps, providing less than 0.4% freshwater. As groundwater is being heavily used to maintain irrigated agriculture as global temperatures rise, the effective use of our freshwater, its collection, treatment, and reuse are paramount to sustain food production and life on Earth. Ongoing rising temperatures lead to higher evapotranspiration and water consumption by crops, especially in semiarid regions during periods of drought. There is currently a pressing need to better manage freshwater and to expand the use of reclaimed water to ensure the long-term sustainability of irrigated agriculture.

Over 85% of the fresh and municipal waters used for urban (ca. 8%), industrial (ca. 12%), and agricultural (ca. 80%) needs are used only once and then discarded as waste. These wastewaters are valuable sources of alternative irrigation water, nutrients, and biosolids that can be reused to reduce our crop production footprint, to sustain food production, and to decrease the anthropogenic impact on our hydric resources. Although reclaimed municipal water use is high in Middle East and North African countries, this practice needs to spread globally. In the United States, California alone plans to increase the use of reclaimed water by nearly 500%—from 521 million m3 to over 3,083 million m3 per year by 2029 (Schwabe et al., 2020).

At a time when at least 20% of groundwater wells surveyed worldwide are at high risk of drying (Jasechko and Perrone, 2021), world temperatures have increased close to 1.0 °C, and 2020 was the second warmest year on record since the pre-industrial era from 1880 to 1900 (https://www.climate.gov/print/8430), governmental and non-governmental organization investments are urgently needed to support impactful research, education, and agreeable policies to guide the use and pricing of reclaimed wastewaters by urban, industrial, and agricultural sectors alike.

Although reclaimed water has so many angles, this issue will focus on original research on the  reuse of reclaimed municipal, agricultural, and animal-production-system wastewaters for the production of crops that are safe for human and animal consumption. This issue also welcomes work on economic aspects of comparing freshwater with treated wastewater to irrigate crops, landscape, and turfgrass, while saving freshwater resources for human consumption.

Dr. Jorge F.S. Ferreira
Guest Editor

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• municipal treated wastewater
• agriculture and aquaculture water reuse
• sustainable irrigated agriculture
• wastewater biosolids
• economics of wastewater treatment and agricultural reuse