Recycling industrial saline wastewater for landscape irrigation in a desert urban area

With water conservation efforts accelerating in arid environments, industrial wastewater is considered a candidate for reuse. We investigated the possibility of using high-TDS (total dissolved solids) blowdown water from cooling towers to irrigate common landscape plants in a desert, urban environment. Nine species (three desert legume trees, three xeric-adapted shrubs and three groundcovers) were planted in a replicate block design on a 0.2 ha site. Each plant was irrigated according to water demand determined by the soil moisture deficit, with one of three water treatments: blowdown water (3.65 dS m−1, 2340 mg l−1), well water (0.52 dS m−1, 335 mg l−1) and a 1:1 blend (2.09 dS m−1, 1340 mg l−1). Water uptake, plant growth rates and soil salinity were monitored over a 27 month period. Irrigation rates were reduced for the final 12 months of the study to more closely match standard landscape practices. All plants grew well over the study and irrigation salinity did not have a significant effect (p>0.05) on growth or water use. Soil salinities were higher in basins irrigated with blowdown water compared to those irrigated with well water, but soil salinities did not increase significantly over time for any treatment. Soil solution salinities on the blowdown treatment were in the range of 6400–15,000 mg l−1, showing that these species have considerable tolerance. The overall feasibility of reusing industrial brines to irrigate urban landscapes is discussed in light of the results.