Evaluation of Corrosion and Precipitation Potential in Ardebil Drinking Water Distribution System by Using Langelier & Ryznar Indexes

Corrosion and sedimentation potential is one of the main factors in water quality control issues. Water tendency towards each of them, can be play very effective role in the transmission and distribution of drinking water in terms of economic and health aspects. The purpose of this study was evaluation of chemical quality, corrosive and sedimentation rate of drinking water in Ardabil water supply network and providing relevant solutions for probable problems. In a cross-sectional research conducted in autumn 2009, the city was divided into 12 blocks and water samples were taken in two instances (in the first half of October and the second half of December). Parameters of alkali, calcium hardness, electrical conductivity, temperature and pH were determined. Water samples were handled according to standard procedures, and corrosion and sedimentation potential were estimated using indicators Lanzhlyh (LSI) and Rayznr (RSI). The results of tests and calculations showed that the respective value for average of LSI index in the first and 2nd stage of water sampling was -0.23 and -0.46, and the average for RSI index in the first and 2nd stage of sampling was 7.98 and 8.24, respectively. Based on LSI index, drinking water in the water supply system has a tendency to corrosion in 9 and 12 stations in the first and second sampling campaigns, respectively; with the other stations tending to have sedimentation. However, according to RSI index six stations had tendency to corrosion and others was balanced in the first samples. For the second samples, ten stations tend to have corrosive property and the others had conditions of relative equilibrium. Based on the results obtained, water in Ardabil drinking water supply have slight tendency to corrosion and water quality must be controlled for the relevant parameters e.g. pH, alkali, and hardness. Application of corrosion-resistant pipes and materials should be considered in drinking water networks.