Evaluating the Feasibility of Treated Urban Wastewater (Type II) Irrigation for Bioenergy Crop Production in the Far West Texas.

Water demands are increasing in the El Paso region, driven largely by rapid population and economic growth. Extending the use of existing water supplies is important for making the best use of available water resources and the economic and environmental well being of the region. At present, in El Paso alone, the total volume of treated municipal and industrial wastewater is about 65,000 acre-feet/year, of which only 8,700 acre-feet is being used as reclaimed water (TCEQ Type I quality) for industrial processes and irrigating urban landscapes. Rest is treated to meet Type II wastewater standards set by TCEQ, which may be suitable for agricultural irrigation. Some limited amount (about 2,000 acre-feet) of treated Type II wastewater is being released into Riverside canal to preserve Rio Bosque Wetlands. There is enormous potential for using this Type II treated wastewater for irrigating agricultural crops including bioenergy crops. Treated wastewater is a reliable source of irrigation and its availability increases with population and economic growth. Use of treated urban wastewater for meeting irrigation needs can extend the use of available freshwater for other beneficial purposes.  The major concern associated with treated wastewater irrigation is its salinity (EC ranges from 1.8 to 2.1 dS m^-1 and SAR ranges from 8 to 12). Irrigation with water having elevated salinity is possible on appropriate soils to produce crops tolerant to salinity. The U.S. Department of Energy has identified switchgrass (Panicum virgatum L.) as the most promising non-food bioenergy crop. The favorable attributes of switchgrass as a bioenergy crop include demonstrated long-term (>10 years) high biomass production capability across many environments, high net energy return, suitability for marginal land, low water and nutrients requirements, excellent compatibility with existing agricultural practices, positive effects on environment such as improved soil and water quality and its cover value for wildlife. Despite these potential advantages, hardly any information exists on switchgrass performance under irrigation with waters having elevated salinity such as treated wastewater in the arid southwest. Use of Type II wastewater to irrigate bioenergy crops in the southwest has several potential benefits such as extending the existing freshwater supplies, increased bioenergy feedstock production and improved farm income. The overall objective of this project is to evaluate feasibility of utilizing this treated Type II urban wastewater for irrigating bioenergy crops such as switchgrass and examine the effects on soil salinity through a long-term (3 years) greenhouse column study.