Treatment Performance and Long-Term Operation of a Decentralized Biofilter-Constructed Wetland System in Eswatini: Conditions for Sustaining Treatment Service

Sustaining the long-term operation of decentralized wastewater treatment facilities remains a challenge in resource-limited settings. This study evaluated an integrated biofilter-constructed wetland system installed at Eswatini Christian University in Mbabane, Eswatini, through a field monitoring campaign in 2015 and a qualitative operational follow-up in 2026. During the 2015 field campaign, the system reduced chemical oxygen demand, total nitrogen, and total phosphorus by 87.1%, 73.3%, and 79.0%, respectively. A 2026 follow-up documented continued use of one biofilter and the wetland, while other installed units were no longer operating. This follow-up provided the reported operational status but did not verify treatment performance after 2015. These findings highlight the need to distinguish continued operation from verified treatment performance when assessing the long-term sustainability of decentralized wastewater treatment. Based on this evidence, we propose a sustainability framework in which modular sustainable engineering, institutional and technical support, and financing act as practical enablers of long-term operation, while preventive public health and social welfare value provide the rationale for maintaining treatment service over time. The Eswatini case therefore supports a broader perspective in which decentralized wastewater systems are designed, financed, and monitored as environmental health infrastructure rather than one-time technology installations.