AWWA ACE63021

Water utilities adjust water quality treatment procedures to minimize corrosion and to remain in compliance with local, state, and federal regulations. Some treatment changes though can adversely affect tubercle stability and cause red water and/or other related problems. Therefore, it is important for water quality managers and engineers to have a conceptual model in place to reasonably predict how such changes will impact the distribution system. Models require a comprehensive understanding of the relationships between corrosion of the iron pipe and the effects of the composition of the bulk waters on scale development and scale stability. Studies evaluating these parameters are based on the assumption that one or two tubercle types are representative of tuberculation in the given distribution system. This assumption though has been based on a limited number of real observations and needs to be further tested, so modeling predictions can be viewed with a high level of confidence. Therefore, the main objectives of this study were to perform a comprehensive assessment of the physio-chemical properties of three iron tubercles from a single pipe and assess their extent of variability. These results could be utilized to refine sampling strategies for assessing the effects of treatment changes on a distribution systems water quality. One 0.11 m long iron pipe segment was obtained from Utility X. Three tubercles were removed from the pipe and allowed to air dry for 72 hours to three months. No visable obvious alteration occurred to the samples during drying. The samples were then encased in Buehler Epo Thin® Low Viscosity Epoxy and then cut in half parallel to the length of the pipe with a band saw. One half of each sample was polished with fine grit sand paper and flushed with distilled deionized water. Subsamples were collected and ground with a mortar and pestle until they passed through a 200 mesh sieve. Includes 25 references.