Oxygenation and Mixing

See what bottom oxygenation does Successful treatment of water and wastewater is largely dependent on two critical items:

  1. Satisfying total oxygen demand
  2. Providing uniform mixing

Each wastewater constituent exerts a known oxygen demand on the water column. When oxygen demand surpasses available oxygen, treatment issues occur. Oxygen demand is typically greatest at the sludge-water interface where solids and sludge accumulate. In order to elevate dissolved oxygen levels, total oxygen demand must be met. BOD, TSS, and nitrogen compounds are the most common wastewater constituents.

Oxygen demand can be calculated by using the following formula:

Substance in mg/l x ADW flow x 8.34 x Oxygen Factor = Pounds of Oxygen Required

Oxygen Factors:

BOD = 1.4 pounds of oxygen per pound of BOD applied

TSS = 0.7 pounds of oxygen per pound of TSS applied

NH3 = 4.6 pounds of oxygen per pound of NH3 applied

Once oxygen demands are calculated, mixing requirements are determined by looking at the number of diffusers and their respective spacing. If diffuser spacing is too sparse or if mixing rates are too small, additional aeration is added to maintain proper oxygenation and mixing.