Invisible Infrastructure: A Systematic Review of Wastewater Disposal and Treatment in the Philippines (1982–2026)

Wastewater disposal and treatment are critical, under-recognized components of public health and environmental protection in the Philippines. This systematic review synthesized evidence on wastewater system types, treatment technologies, assessment approaches, and population-level implications from January 1982 to 11 February 2026. Following PRISMA 2020, we searched Scopus, Web of Science, PubMed, ScienceDirect, Philippine E-Journals, and Google Scholar, plus 17 gray/institutional sources. From 717 records identified, 582 were screened and 120 full texts assessed; 57 sources (39 academic studies and 18 operational/regulatory documents) were included. Across four decades, wastewater management was constrained by fragmented governance, limited financing, weak local capacity, and low sewerage coverage, with most households relying on septic systems that often provide inadequate treatment. Evidence linked untreated or poorly treated wastewater to river and lake degradation, groundwater contamination, heavy metal bioaccumulation, eutrophication, and persistent chemical markers, while industrial case studies showed high removal efficiencies where compliant treatment was implemented. Decentralized and nature-based options (constructed wetlands, DHS, MSL, MBBR and hybrids) showed promising pollutant removal and community acceptability, and recent studies highlighted resource recovery and greenhouse-gas mitigation via sludge management. Overall, stronger coordination, investment, monitoring, septage management, and scalable decentralized solutions are essential for climate-aligned wastewater sustainability and public health protection.