Reservoir Circulation Reduces Geosmin Production

Abstract

This article discusses an effort at Wake Forest Reservoir, North Carolina, to mitigate taste and odor issues caused by microorganisms. A new approach was used that consisted of releasing compressed air into the bottom of the reservoir through an air‐diffuser array. To study the link between water chemistry, stratification, and taste and odor production, limnocorrals – circular enclosures that isolate portions of the water column from the rest of the impoundment in which various treatments can be tested – were installed to test the potential effectiveness of artificial destratification and subsurface copper sulfate injection. Geosmin production was lower in the subsurface copper sulfate and aerated limnocorrals compared to the controls. Bolstered by reduced geosmin, manganese, and iron in the limnocorral treatments, the town of Wake Forest continued to apply copper sulfate to the surface waters of the impoundment and began to destratify the water column by centering a diffuser array on top of the deep basin. Information is presented from deep basin limnology studies that continued over a two year period, including the following: temperature variations; dissolved oxygen; copper sulfate application; and, taste‐ and odor‐producing microorganisms.