High-COD wastewater (2,000–20,000+ mg/L) is common in food and beverage, dairy, brewery, pulp and paper, and petrochemical industries. MBBR treats these concentrated streams effectively through staged reactor configurations, robust biofilm that tolerates organic surges, and high oxygen-transfer aeration systems.
Design approach for high COD
- Multi-stage reactors: 2–3 MBBR stages in series. The first stage operates as a roughing reactor at high loading; subsequent stages polish to target quality.
- Equalization: High-COD streams often have variable concentration. Equalization tanks dampen peaks and protect the biology.
- High aeration capacity: Removing large amounts of COD requires proportionally large oxygen supply. Aeration is typically the largest CAPEX and OPEX item.
- Nutrient supplementation: Some industrial wastewaters lack nitrogen and phosphorus. Supplementation (urea + phosphoric acid) ensures optimal biofilm growth.
- Temperature management: Some high-COD streams are warm (food processing); heat may need to be managed or can be advantageous for kinetics.
Typical project parameters
High-COD MBBR project characteristics (indicative)
| Parameter | Typical Value | Unit | Notes |
|---|---|---|---|
| Influent COD | 2,000–20,000+ | mg/L | Depends on industry. |
| COD removal | 80–95+ | % | To sewer: 80–90 %; to discharge: 90–95+ %. |
| Stages | 2–3 | — | Roughing + intermediate + polishing. |
| Organic loading rate | 10–40 | g COD/m²·d | Roughing stage; lower for polishing. |
| Aeration demand | High | — | Proportional to COD removed. |
Frequently Asked Questions
Can MBBR alone treat COD above 10,000 mg/L?
Aerobic MBBR alone can treat up to about 10,000–15,000 mg/L COD in staged configurations. Above that, a combination of anaerobic pre-treatment (UASB, anaerobic MBBR) followed by aerobic MBBR polishing is often more economical because anaerobic treatment produces biogas energy and uses no aeration.
What industries produce the highest COD?
Dairy (up to 80,000 mg/L whey), starch production, sugar processing, rendering, and some chemical manufacturing. These often benefit from anaerobic pre-treatment before aerobic MBBR.
How does MBBR compare to activated sludge for high COD?
MBBR is more compact, more resilient to load variations and recovers faster from upsets. Activated sludge at high loading can suffer from poor settling (filamentous bulking), which is not an issue for MBBR. For very high COD, the technology choice often depends on the balance between aeration cost, footprint and operational simplicity.
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