On-site sanitation systems such as septic tanks are widely used for treating domestic wastewater in urban and rural areas which lack sewage systems. However, a large portion of these systems do not properly treat human excreta. A main challenge to improve this is the absence of comprehensive data regarding the usage, emptying and maintenance. In this study, records of septic tank desludging frequency during 2009–2022 and the sewerage coverage updated to 2022 were used to investigate their spatial and temporal utilisation, and the persistence of septic tank usage in areas with sewer networks and uncover the current state of Faecal Sludge Management in Cuenca, Ecuador. The spatial behaviour revealed that OSSs are still in use besides the presence of a sewer network. In 2022, there were 109 septic tanks in urban areas with 14.7% in sectors with sewerage service. In rural areas, 469 septic tanks were recorded with 7.8% situated in areas with sewer networks. Although there is no specialised infrastructure in place for the treatment and disposal of faecal sludge, the city has effectively managed it with the existing sanitation facilities. This assessment contributes to the formulation of a secure framework for a safely managed sanitation.

  • Septic tanks are still in use in places where there is a sewage system (14.7% in urban areas and 7.8% in rural areas).

  • Urban districts, that are located close to the rural ones, have a septic tank/inhabitants ratio comparable to the rural districts.

  • A successful measure that promoted the end-user connection to the sewage system was the removal of the septic tank desludging subsidy.

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