0011-9164/09/$– See front matter © 2009 Elsevier B.V. Desalination 239 (2009) 334–345 Chemical stability of inline blends of desalinated, surface and ground waters: the need for higher alkalinity values in desalinated water Ori Lahav a* , Elad Salomons b , Avi Ostfeld a a Faculty of Civil and Environmental Engineering, Technion–Israel Institute of Technology, Haifa 32000, Israel Tel. +972 (4) 829-2191; Fax: +972 (4) 822-8898; email: agori@tx.technion.ac.il b OptiWater, 6 Amikam Israel Street, Haifa 34385, Israel Received 11 May 2008; Accepted 20 July 2008 Abstract Blending desalinated water with surface and/or ground water may result in water that has a negative precipitation potential with respect to CaCO 3(s) , rendering it chemically unstable. In this paper a simulation tool for calculating the pH and calcium carbonate precipitation potential (CCPP) values at the nodes of a water distribution system is introduced. This computerized tool is then used to simulate the CCPP values that would develop in a schematic distribution system fed by three water sources (desalinated, surface and ground waters) under a simulative water consumption pattern. The simulation demonstrates, for a case study that is based on typical Israeli conditions, that an increase in the alkalinity value of the desalinated water from 50 to 100 mg/L as CaCO 3 results in a positive CCPP value at all times whereas at the low alkalinity value (which is the concentration which is currently supplied by the 100 million-m 3 /y and 30 million-m 3 /y Ashkelon and Palmachim plants in Israel) the CCPP values at the nodes are often negative as a result of blending the desalinated water with groundwater. The conclusion is that there is a need to increase the alkalinity value in desalinated waters. This request is augmented by additional arguments in support of this approach. The negative effect of high alkalinity values on copper-tubing corrosion rates is also noted. Keywords: Alkalinity; CCPP; Simulation tool; Distribution systems; Pipe corrosion 1. Introduction Desalinated water is providing an increasing portion of the total fresh water supply in a *Corresponding author. growing number of countries. The global desali- nation market is presently estimated at around 8 billion m 3 annually, and since global water consumption is predicted to double itself every 20 years, this number is expected to increase doi:10.1016/j.desal.2008.07.006 Published by