Quality criteria for desalinated water and introduction of a novel, cost effective and advantageous post treatment process

In many places desalinated water is becoming a significant component of the overall water supply. Notwithstanding its superior quality, un-stabilized desalinated water may be corrosive to water distribution systems, and mixing such water with other water sources in the distribution system can result in corrosion of metallic constituents and in “red water” events. To date, no explicit quality criteria for desalinated water can be found in the literature. In this work, such criteria are discussed from various perspectives, including chemical stability, bio-stability, effect on wastewater treatment, water palatability, health and economic effects, and post-treatment engineering considerations. The first part of the work was carried out for the Committee for the Update of Water Quality Standards, appointed in 2005 by the Israeli Ministry of Health. As a result of the study, the following set of quality criteria was proposed and approved: Alkalinity > 80, 80 < [Ca2+] < 120, 3 < CCPP < 10 (all concentrations in mg/L as CaCO3), and pH < 8.5.The second part of the paper focuses on the implications of the new criteria on the post treatment process. A comparison between existing alternative post treatment processes is presented, and a novel, cost effective and unique post treatment process is introduced. The new process was developed not only to comply with the new criteria in a cost effective way, but also to result in a supply of Mg2+ ions, which are required in desalinated water for both health and agricultural reasons.