The study evaluated how well ponds at a busy airport in Brazil treated wastewater over 16 years. The wastewater had similar quality to regular sewage, even with industrial waste like airplane toilets. The ponds were not overloaded and produced good quality water. A survey showed that after many years, only a small amount of sludge had built up in the ponds. The sludge accumulation rates were very low, showing that the ponds were working well to clean the water.