Why Oxygenation?

Consequences of Eutrophication:

  • The bottom layers of the water body are generally depleted of oxygen and contain high concentrations of iron, manganese, ammonia, organic matter and in some cases, hydrogen sulphate. They are also characterised by high levels of turbidity.
  • The middle layers vary in terms of their chemical quality and combine the drawbacks of both surface and bottom waters.
  • The surface waters contain large concentrations of phytoplankton and other organic matter. They are highly turbid and their pH fluctuates (between 7 and 10) during the course of the day. They often contain toxic blue-green algae, flilamentous algae or nanoplankton.

Eutrophication thus pushes up investment and treatment plant operation costs (cost of reagents, activated carbon, ozonation, etc.) . increases water consumption (for filter washing, etc.) and creates taste and odour problems.

Benefits of Bottom-Layer Aeration

  • Substantial reductions in iron and manganese concentrations (which stay precipitated in the sediments).
  • Low or even zero ammonia concentrations.
  • Near-total eradication of phosphorus releases from the sediments.
  • Minimal blue-green algae growth, since these do not thrive in a precipitated environment.
  • Faster mineralisation of organic matter.
  • Lower turbidity
  • Year-round stability of raw water quality.
  • Reduction in reagent and filter wash water consumption (see table below).
  • Improved settling of sludges owing to the elimination of gas in these.
  • More effective chlorination.