Aeration introduces a gas into a liquid. With fresh surface water this is usually atmospheric air. Poor water quality is often an indicator that the amount of dissolved oxygen in the water column, derived from atmospheric air, is insufficient to mitigate the negative effects on water quality of excess nutrients in the sediment floor of the pond, or in the water column. An aerator, or a surface-water aeration system, introduces concentrated oxygen to improve and maintain water quality by maintaining dissolved oxygen levels throughout the water column and at the sediment-water interface in particular.
Depending on the size of the water body and the specific characteristics of the water quality challenges, water scientists and managers choose different aeration systems. Types of surface water aeration systems include: bottom diffused aeration, sediment oxygenation, hypolimnetic aeration, nano-bubble generation and others.
For smaller, relatively shallow water bodies (less than 30 feet/10 meters deep), like ponds and dugouts, the most efficient and cost-effective method of aeration is usually bottom diffused aeration.
Beneath the Surface
Ponds and dugouts often stratify, with oxygen-saturated water being trapped at the surface and low or no oxygen conditions developing near the bottom. This can lead to poor degradation of organics and sludge accumulation; release of nutrients from the sediments, algae blooms, and pond turnovers resulting in fish kills.
Low dissolved oxygen levels are less common in newer ponds. But ponds will almost always develop stratification over time without implementing effective management strategies. It is far easier to maintain the water quality in a new pond and prevent nutrient accumulation, than it is to remediate an old one with significant organic nutrient accumulation.
A properly sized aeration system will draw anoxic water from the bottom and deliver it to the surface where it becomes saturated with oxygen before being circulated back to the bottom. This action effectively delivers oxygen to the sediments. The advantage of this aeration application is that a comparatively small compressor can fully saturate a water body with oxygen. It is both cost and energy-effective with the system ultimately acting as a high-efficiency water pump.
Sizing is very important to ensure proper circulation of the entire water column. Poor design with the wrong airflow, insufficient diffusers or poor diffuser spacing will cause poor mixing and the accumulation of nutrient-rich much in areas with little or no circulation.