Full Description

To comply with disinfection byproduct regulations, manyutilities have chosen to use chloramines rather than chlorine forresidual maintenance in drinking water distribution systems.However, the switch to chloramines may expose these systemsto another health risk, increased concentrations of lead. Thisstudy investigated total lead release in the presence of freechlorine and chloramine residuals in drinking waters producedfrom ground, surface, desalinated, and blended water sources.For both desalinated and blended finished waters, more totallead was released in the presence of chloramines than in thepresence of free chlorine.Little research has focused on the effect of oxidation-reductionpotentials on metal release. This work verified theoreticalpredictions from extensive field data that showed the chloramineredox potential was lower that the free chlorine redox potentialunder equivalent pipe and distribution system environments;however, the released lead in the lower redox potential chloramineenvironment was higher than in the lower redox potentialchlorine environment.The article relates redox potential to pH and the controllingsolid lead phase for lead release and demonstrates that theoreticalthermodynamic diagrams are practical tools for predictingrelease of lead (and perhaps other metals) in distribution systems.Utility managers who select chloramines for residual maintenancecan use this information to help avoid potential problems of violatingthe lead action level. Includes 39 references, tables, figures.

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Edition: Vol. 98 - No. 2 Published: 02/01/2006 Number of Pages: 11 File Size: 1 file , 520 KB