Oxygen Levels and Common Water Quality Issues

Take a look at this blog for a brief overview on how oxygen levels have an impact on water quality.

Did you know that many water quality issues are driven by low oxygen levels, especially near the bottom of a lake or pond at the sediment-water interface? Common water quality issues related to oxygen levels are harmful algal blooms (HABs), excess ammonia, fecal coliforms, and stress on fish.

Oxygen management is one of the most common water quality restoration techniques used worldwide. This is because restoring deep water dissolved oxygen (DO) levels reduces internal nutrient loading from the release of phosphorus and ammonia from sediments and enhances a lake’s fishery while promoting a shift in the algal community to a more desirable one. As DO levels drop below 2 mg/L over the sediments, chemical reactions accelerate, causing iron and phosphorus in surficial sediments to mobilize to the overlying water column and accumulate in the hypolimnion. Sediment ammonification (release of ammonia, which is preferred by cyanobacteria) is also promoted when DO drops below 5 mg/L DO (Beutel 2001). The released phosphorus and ammonia (reduced form of nitrogen) can then be accessed by cyanobacteria, triggering a harmful algae bloom (HAB). In addition, the lack of oxygen in deep water is ecologically undesirable, limiting habitat for fish and other aquatic life (>5 mg/L DO 24-7 is the national US EPA minimum DO criteria for aquatic life). Therefore, adding enough oxygen to counter the oxygen demands is the most desirable approach to solving multiple problems.

While these numbers reflect a baseline of minimum DO levels, oxygen management strategies should be designed to meet the desired DO levels, not minimum DO levels. Managing to the minimum, one can expect minimum results. The desired DO levels for aquatic life (the level where no production and growth impairment occur across all life stages) is >8 mg/L for non-salmonid waters (warm-water fisheries) and >11 mg/L for salmonid waters (cold and cool-water fisheries) (USEPA 1986). The desired DO levels for aesthetics and water quality are between 15-25 mg/L right over the sediments. Keep in mind that DO levels should not exceed 25 mg/L to ensure oxidative stress does not occur (Colt 2006).

Oxygen Saturation Technology (OST^TM) is the next generation aeration system to improve lake/pond water quality. The patented design adds oxygen, which is generated onshore, to water being circulated at the lake or pond bottom, forming an oxygen blanket over the sediment, which in turn helps mitigate common water quality issues related to oxygen levels.

For more information on OST^TM or for a consultative meeting discussing your water quality issues and possible solutions, reach out to our team today.