Addressing problems with gas supersaturation at drinking water utilities

Abstract

Gas bubbles forming during conventional water treatment can reduce operating efficiency. The most common problems caused by bubbles include floating floc during coagulation and sedimentation, air binding in media filters and upflow clarifiers, and erroneous particle counts or turbidity measurements. Gas bubbles form in areas that are supersaturated with dissolved gas with respect to the localized solution pressure. Measurements of dissolved gas through the facility and estimates of the localized pressure can identify problems, and bubble formation predictions should be routine before design of any new treatment plant. Although simple strategies often can be used to reduce the adverse effects of bubble formation, other cases may require additional treatment steps to alleviate dissolved‐gas supersaturation. The authors used case studies from several water utilities and laboratory studies to develop parameters that should be considered when designing a new treatment plant or modifying an existing facility to avoid problems associated with dissolved gas.