Land Application of Saline Industrial Wastewater on a Chihuahuan Desert Upland

Abstract

Low-cost, sustainable wastewater treatment systems are needed for rapidly-growing communities of the southwestern United States. The objective of this study is to develop a practical management plan for land application of industrial wastewater on native Chihuahuan Desert vegetation. To assess environmental impact and create the management plan, wastewater effluent characteristics, soil physicochemical changes, and mineral uptake of the vegetation were monitored. The effluent was saline, ranging from 2500 to 6000 mg·L-1 of TDS and dominated by Na and Cl. Total N ranged from 10 to 40 mg·L-1. Soils sampled in Dec. 2002 (after 11 months and 64 cm of effluent irrigation) increased in salinity in the top 60 cm from 1.85 to 3.5 dS·m-1, and SAR in the top 30 cm was close to 15, but diminished with depth. Branch samples of the co-dominant perennial shrub vegetation members (Larrea tridentata and Prosopis glandulosa) harvested in July 2002 had elevated Na and Cl concentrations (0.4% to 2.1% of dry weight, respectively). By Oct. 2002, L. tridentata leaves contained comparable Na and Cl concentrations as those of P. glandulosa, yet removed 2 to three times more Na, Cl, and total N per branch, while maintaining their dry mass per branch. This raises the possibility of interspecific variation among the shrub species in salinity stress tolerance and capacity to remove wastewater contaminants. These data will aid in determining total vegetation removal of effluent components, preventing adverse environmental impact to the site, and developing a practical management plan suitable for small communities seeking cost-effective wastewater handling protocols.