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From the Executive Summary

Regional water systems utilize storage facilities to meet demand variations and pressure requirements of their systems. These storage facilities drain and fill in response to system water demands and water level control settings. Storage tanks are typically placed in strategic locations to maintain a consistent pressure in the distribution system. Storage facilities should be designed and operated such that the water is mixed to prevent stagnant water (old water that remains in the tank for an extended period). Stagnant water can lead to water quality issues, such as low disinfectant residuals, potential for microbial contamination, disinfectant by-product formation, and nitrification in chloraminated waters. Many tanks have been built without consideration of mixing. These tanks might have a single inlet/outlet, high height to diameter ratio, or have other design characteristics that do not promote mixing. Whether by design or not, tanks without artificial mixing depend upon movement of water during the filling process to mix the tank. A wide array of storage tank types and geometries are utilized in South Dakota’s regional rural water systems. Greater understanding of the relationships of these tank characteristics on stored water quality would enable water systems to optimize the design and operation of their tanks.

Objective of Study:
The objective of this study was to examine the impacts of tank design and operation on mixing and water quality in storage tanks in South Dakota’s regional rural water systems. This objective was met through a literature review, a survey of system characteristics and evaluation of water quality data obtained from several storage tanks.




South Dakota State University