A series of eight 31-litre, bench-scale, aerobic waste stabilization ponds were operated for 73 days to assess the potential performance of waste stabilization ponds in tropical Micronesia and to determine how elevated salinity levels affect pond kinetics. The outdoor reactors were loaded with screened raw domestic sewage and operated on a draw-and-fill basis. Salinity levels in the reactors varied from 600 to 36,000 mg/L, with detention times ranging from 6.2 to 15.5 days.

The mean influent values for biochemical oxygen demand (BOD₅) and suspended solids (SS) were 86.7 and 61.9 mg/L, respectively. The mean effluent values for the last 20 days of the experiment ranged from 2.3 to 11.2 mg/L BOD₅, and from 3.8 to 44.3 mg/L SS. Reactor 1, which contained no supplemental salt, consistently had the highest treatment efficiency. All of the reactors easily met the EPA secondary treatment standard of less than 30 mg/L BOD₅, but all the saline reactors had SS concentrations in excess of 30 mg/L. Effluent concentrations were high in the saline reactors due to the presence of large populations of algae. Suspended solids concentrations were very low in the freshwater reactor, presumably due to the presence of a large population of crustaceans, rotifers, insect larvae and other algal predators. These algal predators, or effluent polishers, never became well established in the saline reactors.

The results if this study show that waste stabilization ponds are an extremely viable waste treatment option in Micronesia. The ideal climatic conditions of the area minimize land requirements and make their use very cost effective.