DAO 2016-08 Table 9 sets ordinary Class C effluent limits of BOD 50 mg/L, COD 100 mg/L and TSS 100 mg/L. DAO 2021-19 updates selected parameters and procedures; it does not replace those three limits with 30/90/60 mg/L. Choose the receiving water body's official classification, then read the applicable effluent standards and the facility's discharge permit before specifying treatment equipment.
Which table applies: water quality guidelines or effluent standards?
The DENR DAO 2016-08 original text separates water quality guidelines (WQG) for receiving waters from general effluent standards (GES) for discharges. An ambient-water monitoring value is not an interchangeable outlet specification. Freshwater classes AA, A, B, C and D also differ from marine/coastal classes SA, SB, SC and SD. There is no separate official category called “Class C coastal” in these tables.
Confirm the named receiving water body and its current official classification with the competent authority. Do not assume that every inland discharge is Class C, every coastal discharge is SC, or that Class AA can be treated as Class A. For a sewer connection, establish the receiving operator's acceptance and permitting requirements instead of copying a direct-discharge table. RA 9275, Section 14 makes the discharge permit the authorization that specifies allowed effluent quantity and quality, the compliance schedule and monitoring requirements.
DAO 2016-08 Table 9: BOD, COD and TSS by receiving-water class
The following is an extract of Table 9, printed page 20. All numerical values are in mg/L and are maximum allowable limits, not guaranteed equipment performance. The special strong-wastewater BOD route is discussed below.
| Receiving-water class | BOD | COD | TSS |
|---|---|---|---|
| AA / SA | NDA | NDA | NDA |
| A | 20 | 60 | 70 |
| B | 30 | 60 | 85 |
| C | 50 | 100 | 100 |
| D | 120 | 200 | 150 |
| SB | 30 | 60 | 70 |
| SC | 100 | 200 | 100 |
| SD | 150 | 300 | 150 |
NDA means No Discharge Allowed. The full Table 9 contains other parameters. For example, Class C pH is 6.0–9.5 and oil and grease is 5 mg/L. Temperature is expressed as a change relative to the background value: 3 °C for Class C, not a universal absolute limit of 35 °C. Read the footnotes and the complete permit parameter list.
What DAO 2021-19 actually changes
DAO 2021-19, Sections 3–4 and Tables 1–6, updates ammonia, boron, copper, fecal coliform, phosphate and sulfate. It also changes procedures for strong-wastewater BOD and requests to modify Significant Effluent Quality Parameters (SEQP). “Updated” does not mean that every numerical limit becomes lower.
| Class C parameter | DAO 2016-08 GES | DAO 2021-19 GES |
|---|---|---|
| Ammonia as NH3-N | 0.5 mg/L | 4 mg/L |
| Boron | 3 mg/L | 4 mg/L |
| Copper | 0.04 mg/L, dissolved copper | 1 mg/L, total copper |
| Fecal coliform | 400 MPN/100 mL | 400 MPN/100 mL |
| Phosphate | 1 mg/L, labelled phosphate | 4 mg/L, phosphate as phosphorus (total, reactive) |
| Sulfate | 550 mg/L | 550 mg/L |
Copper changes analytical basis from dissolved to total copper; do not compare those results as if they measured the same fraction. Preserve the specified phosphorus reporting basis as well. The WQG and GES columns in DAO 2021-19 serve different purposes: for example, its Class C ammonia WQG is 0.06 mg/L while the GES is 4 mg/L. Specify the correct column and laboratory basis in the monitoring plan.
When can the special strong-wastewater BOD standards be used?
DAO 2016-08 Table 10 provides a separate BOD route for strong wastewater. DAO 2021-19 Section 4.7 requires evidence that influent data from the last 12 months fall within the prescribed Table 10 ranges, with DENR-recognized laboratory results and a request submitted to the EMB Central Office. It only covers discharge to Class C, D, SC or SD waters. A high inlet BOD reading alone is not permission to choose a higher outlet limit; other parameters still need their applicable standards.
Turn the tables into a treatment purchase and acceptance plan
- Confirm the discharge route. Record the outfall, receiving authority, official water-body class and actual permit conditions. Obtain clarification for sewer acceptance, land application or reuse.
- Confirm the complete pollutant list. Start with DAO 2016-08 Table 8 for the relevant sector and check the actual process and permit. BOD, COD and TSS alone may omit nutrients, metals, salts or other significant pollutants.
- Characterize the duty. Measure average and peak flow and representative inlet quality across production and cleaning cycles. Agree sampling points, sample type, preservation, methods, frequency and laboratory with the authority and test plan. Do not replace effluent compliance checks with ambient-water annual averages.
- Test the proposed process. Evaluate DAF for the proposed solids/oil separation duty and MBR for the proposed biological treatment duty using actual wastewater. Neither product name establishes removal of every pollutant or guarantees a permit.
- Contract for measurable delivery. Give competing suppliers the same inlet range and outlet targets. Require treatment scope, operating conditions, residuals management, itemised installation and operating-cost inputs, and a site acceptance protocol covering all required parameters and a remedy for failed tests.
DAO 2021-19 Section 5 sets evidence requirements for an SEQP modification request. Its 20-working-day provision concerns that request after satisfactory completion of requirements; it is not a blanket discharge-permit renewal time. Confirm current application documents, fees and permit validity with the relevant office. For an equipment enquiry, attach the permit and laboratory report to the existing quotation form.
DAO comparison questions
Does DAO 2021-19 replace all of DAO 2016-08?
No. Read the selected amendments together with the unaffected provisions of DAO 2016-08. The ordinary Class C BOD/COD/TSS values above remain the Table 9 comparison basis; the strong-wastewater procedure is a separate conditional route.
Can I use the freshwater Class C table for a coastal outfall?
Only after the authority establishes the correct classification. Marine classes have their own rows; SC BOD and COD are 100 and 200 mg/L in Table 9, while freshwater C values are 50 and 100 mg/L.
Can a supplier promise compliance from one removal percentage?
No. Assess final concentrations and the full pollutant list at the agreed flow and inlet conditions, with representative sampling and laboratory testing. Set any additional design margin explicitly in the specification; do not label it a new statutory limit.
