Unlike clear and unproductive lakes, eutrophic lakes can emit a variety of noxious odors. Except when source water is high in organic matter (e.g., wastewater effluents and/or stormwater drainage), most odors are associated with blue-green algae blooms generated within the lake. In drinking water reservoirs, these algae are notorious for creating taste and odor problems associated with the release of 2-methylisoborneol (MIB), which gives a “musty” odor, and geosmin, which gives an “earthy” taste and odor. When blue-green algae die they either remain on the lake’s surface and along shores, or sink to the lake bottom. Those remaining on the surface create a foamy scum that produces truly eye-watering noxious odors. This surface scum should not be confused with filamentous algae that can form thick mats, particularly in small ponds, but do not create extraordinary odors. Algae that sink to the bottom deplete available dissolved oxygen (DO), enabling the formation of hydrogen sulfide (H2S) that produces a rotten egg odor when exposed to air. Thermal stratification during summer months, and under ice during the winter, allows H2S to accumulate in bottom waters that can create a significant odor event (and potential fish kill) with lake turnover in the fall and ice-out in the spring.

SolarBee’s long-distance circulation prevents noxious odors in several ways. First, the ability to control blue-green algae blooms eliminates the primary source of noxious odors in lakes. Second, hypolimnetic oxygenation keeps bottom waters sufficiently oxic so that H2S does not accumulate significantly in bottom waters. And third, odors from shallow ponds with wastewater inputs or highly sulfurous sediments can be prevented by a surface “odor cap” of oxygen-rich water to create a natural barrier to prevent H2S from escaping into the atmosphere. This same SolarBee application has proven very effective at odor capping wastewater effluent storage ponds.