3. the design criteria for oxidation ponds (also called facultative ponds, aerated facultative ponds) specified that (1) bod loading into the primary cell (or pond) shall not exceed 25 lbs bod/acre/day, (2) the minimum total water retention time, based on influent flow and all cells at water depth of 5 ft should not be less than 120 days., (3) the volume of winter storage between the water depths of 1.5 and 5 ft shall be sufficient so that no discharge is necessary for a four-month period, and (4) pond system should have at least two primary cells and one or more secondary cells. size the ponds for a community that generates 160,000 gpd wastewater with a bod of 220 mg/l. based on the climate of the area, the net water loss (evaporation plus seepage minus precipitation) during the storage months is 1.0 inch/month.