The two main rivers in the metropolis – Marikina River and Pasig River, have been
pronounced biologically dead. The Pasig River, once renowned for its pristine
waters and aquatic resources, is now one of the world’s most polluted river systems
with dissolved oxygen levels dropping to near zero for most of the year. Faecal
coliform levels exceed standards of the Department of Environment and Natural
Resources (DENR) and international standards by several orders of magnitude.
Findings of the DANIDA study confirm domestic wastewater as the primary source of
water pollution. (Pasig River BOD Load Assessment and Water Quality Projections Report, funded by DANIDA, by Carl Bro International, Danish Hydraulic Institute and
Institute for the Water Environment, 1999) According to the DENR, 75% of the
pollution loading into the Pasig River comes from domestic wastewater. Industrial
and commercial effluent contributes only 25% to the pollution of the Pasig River.
Given the amount of pollution contributed by domestic wastewater, the state of the
water resources in Metro Manila can be directly correlated to the dearth of
functioning sanitation systems and low sewerage coverage.