AWWA MTC57577

For millennia, civilizations have had to deal with the impacts of irrigation, specifically importation of salt into agricultural areas with the irrigation water. Those civilizations that have done so successfully have survived. Those that haven't (the vast majority) have eventually failed as crop yields dropped and fertile land became desert. Every year, the southern San Joaquin Valley (one of the most productive agricultural areas in the world) imports about 1.5 million tons of dissolved salts with irrigation water. Until now, that salt has remained in place, since there is no method of removing the accumulating salts. In a few locations, groundwater salinity has risen as high as 100,000 mg/L. Recognizing that the salt buildup must eventually be addressed, the Buena Vista Water Storage District, in conjunction with the California Department of Water Resources, University of California at Los Angeles (UCLA), and Boyle Engineering, embarked upon a project to demonstrate the viability of desalting agricultural drainage waters, reclaiming a significant portion for irrigation or domestic use, and concentrating the salts to make them more amenable to disposal. This three year program (as presently structured) will be completed in the fall of 2002. There are many challenges facing agricultural drainage desalination, ranging from obtaining a consistent supply to dealing with the high biological activity of the water. The greatest challenge will be disposal of the concentrated salts. This paper describes the demonstration treatment plant and its three year operation. Operating data is given, specifically describing the fouling performance of the membrane system. An evaluation of water quality using various extraction methods is described, as well as the performance of the pretreatment filtration with these extraction methods. An evaluation of the potential requirements for desalination within the San Joaquin Valley is included.