On 18 December 2008, the Supreme Court issued the Writ of Continuing Mandamus (G.R. Nos. 171947-48) and 13 mandamus agencies were directed to act for the clean-up, rehabilitation, and preservation of Manila Bay. As one of the mandamus agencies, MWSS is directed to install, operate and maintain adequate sewerage treatment facilities in strategic places under its jurisdiction and increase their capacities. Since its institution in 1971, the MWSS has been providing sewerage and sanitation services in its service area which includes the whole of Metro Manila and parts of Cavite and Rizal.

In addition, MWSS has been providing support to other mandamus agencies (e.g. DILG, DENR, etc.) in their respective programs related to the SC Continuing Mandamus. Last 17 December 2021 at the Manila Hotel, the MWSS, through the Water and Sewerage Management Department, has been recognized by the Department of Interior and Local Government (DILG) – National Capital Region (NCR) for its continued support to the 2021 Assessment of Local Government Units’ Compliance with the Manila Bay Clean-up, Rehabilitation, and Preservation Program (MBCRPP).

MWSS and its Concessionaires are committed to ensure that all sewerage and sanitation projects will be implemented and will continue to support the programs of various Government Agencies for the Clean-up, Rehabilitation, and Preservation of Manila Bay.