Five Metro rivers declared ‘dead’

Five rivers in Metro Manila are now classified by the Department of Environment and Natural Resources (DENR) as biologically dead.

DENR Secretary Elisea Gozun said that based on the department’s 2003 Pollution Report, of the 94 Principal River Basins (PRBs) monitored for pollution activity nationwide, 15 were declared as biologically dead. Of the 15 rivers, five are in the metropolis and have failed the DENR’s standards for Class C water.

The DENR identified the dead Metro Manila rivers as the Marikina River, the San Juan River, the Navotas-Malabon-Tenejeros-Tullahan (NMTT) River, Parañaque River and the Pasig River.

Under DENR Administrative Order 34, Class C water refers to those rivers assessed to be safe for the propagation of aquatic fish such as tilapia and other aquatic resources, boating and other recreational use without human contact like swimming and for industrial use.

Gozun said the biochemical oxygen demand (BOD) for Class C water should not exceed seven miligrams per liter. BOD refers to the amount of oxygen that is consumed by micro-organisms present in wastewater when discharged into a body of water.

In addition, the dissolved oxygen (DO) present in Class C water should not be lower than five miligrams per liter to sustain aquatic life. According to the DENR, San Juan River has the highest BOD loading at 68 mg/l to a low of 54.8 mg/l against the DENR’s standard of 7 mg/l. Its average DO level was at 2.4 mg/l.

The Average DO level (ADL) of the Marikina River was pegged at 3.1 mg/l and its average BOD loading (ABL) was at 18.2 mg/l. The NMTT’s ADL was at 3.6 mg/l and its ABL was at 22.3 mg/l; Parañaque River registered a 2.5 mg/l ADL and a 42 mg/l ABL; and the Pasig River posted a 3.1 mg/l ADL and a 10.7 mg/l.

Aside from the five rivers in Metro Manila, the DENR also classified 10 rivers outside of the metropolis as biologically dead. These are the Bocaue and Meycauayan rivers in Central Luzon; the Imus, Ylang-Ylang and Mogpog rivers in Southern Tagalog; the Malaguit and Paniqui rivers in the Bicol region; the Balili River in the Cordillera Administrative Region (CAR); and two rivers in Central Visayas namely the Butuanon and Guadalupe rivers. – Mike Frialde