Wastewater quality and its reuse in agriculture in Saudi Arabia

"The water supply in Saudi Arabia, to meet the growing agricultural requirements, increased from 1.75 billion m3 in 1975 to 22.93 billion m3 in 1992. The total amount of wastewater available according to the references given is around 1.32 million m3/d. The total water salinity ranges between 1000–7273 mg L−1 in different areas. The quality of the wastewater ranges between low salinity-low sodium to very high salinity-very high sodium hazards which could create substantial soil and crop management problems when used for irrigation. Application of certain mathematical models has shown that the use of these wastewaters can affect the exchangeable-sodium-percentage (ESP) and soil salinity to create substantial soil and crop management problems. However, wastewater quality demands careful assessment if it were to be reused as a supplemental source of crop irrigation for agricultural expansion. Experiments have shown that use of wastewaters in Saudi Arabia as a supplemental irrigation has not only increased crop production, water use and nitrogen use efficiencies but also served as a source of plant nutrients. It was also found that the use of wastewater can save up to 50% application of inorganic nitrogen fertilizer if the wastewater contains 40 mg N L−1. The short- and long-term uses of different types of wastewaters for irrigation did not show any significant increase in the bioaccumulation of heavy metals in crops and soils. However, there exists much potential for reuse of wastewater in agriculture after appropriate treatment and by following certain management practices such as leaching requirements, proper crop selection, estimation of crop water requirements, adoption of improved irrigation methods and application of right amount of fertilizer."