Question & AnswerQ&A (DENR ADMINISTRATIVE ORDER NO. 34)
The primary objective is to maintain the quality of Philippine waters in a safe and satisfactory condition according to their best beneficial usages, ensuring suitability for designated uses through established water classifications and quality criteria.
Fresh surface waters are classified as Class AA, A, B, C, and D according to their beneficial uses such as public water supply (Class I and II), recreational waters, fishery waters, industrial water supply, agriculture, irrigation, and livestock watering.
Class AA is intended primarily for public water supply Class I, meaning waters from uninhabited and protected watersheds that require only approved disinfection to meet the National Standards for Drinking Water (NSDW).
Reclassification requires a petition with necessary supporting information, public notice and hearing, and affirmative findings by the DENR Regional Office that the reclassification establishes the most beneficial use, is in the public interest, and that the designated use is attainable considering environmental, technological, social, economic, and institutional factors.
Surface waters shall be free from domestic, industrial, agricultural or other man-induced non-thermal discharges that create nuisances, are acutely toxic, carcinogenic, mutagenic or teratogenic, or pose serious danger to public health, including thermal discharges that create nuisances or cause harm to aquatic life or interfere with beneficial uses.
Minimum water quality parameters considered include Dissolved Oxygen (DO), pH, Biochemical Oxygen Demand (BOD), and Total Coliform Organisms.
Class AA waters have a pH range of 6.5 to 8.5, minimum dissolved oxygen of 5.0 mg/L (70% saturation), and a 5-day BOD limit of 1 mg/L.
Coastal and marine waters are classified as Class SA, SB, SC, and SD based on beneficial uses such as areas for harvesting shellfish, tourist zones, coral reef parks, recreational water, fishery water, and industrial water supply.
The Azide Modification (Winkler Method) and Membrane Electrode (DO meter) are approved methods for analysis of dissolved oxygen.
For the nitrogen fertilizer industry: Chloride, Chromium, Dissolved Solids, Nitrate, Suspended Solids. For the phosphate fertilizer industry: pH, Phosphorus, Suspended Solids, Temperature, Cadmium, Arsenic.