Effluent standards to process train.
The GB 18918-2002 discharge limits, and the process combination that normally delivers each grade.
Basis
GB 18918-2002 Table 1 gives the discharge limits — national standard table values. The process combinations are common engineering practice and are not mandatory under the standard. The Middle East extended-aeration range is from the Saudi MEWA guide; the export route refers to EN 12566-3.
National limits, GB 18918-2002 Table 1 (daily average, mg/L)
Grade 1A is the strictest of the grades shown. Grade 3 limits are not yet available.
| Parameter | Grade 1A | Grade 1B | Grade 2 |
|---|---|---|---|
| COD | 50 | 60 | 100 |
| BOD₅ | 10 | 20 | 30 |
| SS | 10 | 20 | 30 |
| NH₃-N | 5 (8) | 8 (15) | 15 (30) |
| TN | 15 | 20 | — |
| TP | 0.5 | 1 | 3 |
For ammonia-N, the value outside the brackets applies when the water temperature is above 12 °C; the value inside the brackets applies at or below 12 °C. Grade 3 limits: [to be confirmed with factory].
Target to typical process train
| Target | Typical process train | Notes |
|---|---|---|
| Grade 2 / Grade 1B | A/O or A²/O + secondary clarifier + disinfection | Where only organics are controlled it can fall back to biological contact oxidation |
| Grade 1A | A²/O or MBBR + secondary clarifier + advanced treatment (coagulation sedimentation + deep-bed filter + disinfection); or MBR directly | MBR omits the secondary clarifier and takes less space, but energy use and membrane replacement cost more; at small flows it is often the better value |
| Reuse | MBR + disinfection; MBR + RO where a high degree of desalination is required | Water-quality limits also see GB/T 18920-2020 and GB 50335-2016 |
| Export, UK and EU | EN 12566-3 type test plus a local discharge permit | In the UK the discharge is also subject to the permit and to drainage-field conditions |
Process combinations are common engineering practice, not a mandatory requirement of the standard.
The target-country limits: who sets them, and where the original is
The GB 18918-2002 table above governs a plant discharging in China. A plant exported elsewhere is governed by the limits of the country it discharges in, and those limits are set by that country's environmental authority rather than by the equipment supplier. The three markets this site works in most are a good illustration of the method, because each one puts the authority in a different place.
- The Philippines: the limits come from the Department of Environment and Natural Resources (DENR) and its Environmental Management Bureau, which publishes the general effluent standards as a DENR Administrative Order. The permit is issued for the individual site by the DENR regional office, and a plant in the Laguna de Bay basin falls under the basin authority as well. Ask the authority for the Administrative Order in force and for the permit conditions for the site; both are public documents.
- Indonesia: national standards for a sector are set at ministry level by the Ministry of Environment and Forestry (KLHK) through a ministerial regulation, and provincial or district regulations may set stricter values for the same sector. That second layer is the one that catches an imported design out. The figures to design to are the ones in the local regulation that applies to the site, and for domestic wastewater the ministry regulation for domestic wastewater is the starting document.
- Saudi Arabia: the environmental regulator is the National Center for Environmental Compliance (NCEC), and older permits in the market were written against the Presidency of Meteorology and Environment (PME) environmental protection standards, which are still the reference many projects carry. Limits are stated for the discharge route — a receiving water body, a municipal sewer or land application — so the route has to be fixed before the limit is read. Reuse quality is a separate question from discharge quality.
- In all three, the document that governs the design is the permit for that site rather than the general standard. A permit may be stricter than the national figure where the receiving water is classified as sensitive or where the site discharges to a protected catchment, and it usually adds the sampling points, the parameters and the averaging period that a compliance test has to follow.
- The review method is the same everywhere: find out which authority issues the permit, obtain that authority's own published regulation rather than a summary table from a brochure, check what the receiving water is classified as, and confirm whether a second authority — a basin body, a province or a municipality — sets a tighter value. The design is then fixed against that document, and the general standard is only the fallback where the permit says nothing.
- We do not reproduce the limit tables of other countries here. Numbers change, and a table copied from a secondary source is the most common way a design is fixed against a limit that no longer applies. The current text of the regulation is the only reliable source, and it is normally downloadable from the authority itself.
How to use and notes
- The limits are national-standard table values. The process combinations are common engineering practice, not a mandatory requirement of the standard.
- Ammonia-N: read the bracket rule before comparing a design against the Grade 1A or Grade 1B limit, because the applicable number depends on water temperature.
- Grade 3 limits have not been obtained: [to be confirmed with factory].
- Middle East: Saudi MEWA mainly promotes extended aeration, with aeration time 18–36 h, MLSS 3,000–6,000 mg/L and sludge age 10–30 d.
- For reuse, the discharge standard alone is not enough; check GB/T 18920-2020 and GB 50335-2016 for the water-quality limits of the reuse application.
- Factory confirmation pending: the effluent grades covered by the product line and the process configuration for each, in particular the MBR and MBBR lines: [to be confirmed with factory].