This paper presents a performance evaluation of facultative and maturation ponds in series treating wastewater from a large and intensively used international airport in Brazil, based on 16 years of regular monitoring. The wastewater from the airport showed similar or slightly lower concentrations compared to typical domestic sewage for most of the quality parameters. The contribution of effluents with possible industrial features (aircraft toilets and hangar effluent) did not seem to have adversely affected the characteristics of the influent in terms of aptitude to biological treatment. Overall, the ponds operated under very underloaded conditions (mean loading rate of 44 kg biochemical oxygen demand/ha.d in the facultative pond) and presented a satisfactory quality in terms of effluent concentrations for most parameters. A bathymetric survey of the ponds was done manually by a low-cost measurer constructed specifically for this purpose. After 27 years of operation, only 25% and 18% of the volumes of the facultative and maturation ponds were occupied by sludge. Specific sludge accumulation rates were 0.0071 m³/passenger.year for the facultative pond and 0.00017 m³/passenger.year for the maturation pond.