COD vs BOD in Wastewater: Definitions, Differences & Treatment Solutions

What are COD and BOD?

COD (Chemical Oxygen Demand)
COD measures the total oxygen required to chemically oxidize organic and inorganic contaminants in water.

• Key Value: Rapid pollution assessment (results in 2-4 hours).

• Testing Scope: All chemically oxidizable organics + some inorganics.

BOD (Biochemical Oxygen Demand)
BOD indicates the oxygen consumed by microorganisms to biologically degrade organic matter over 5 days at 20°C.

• Key Value: Evaluates biodegradability of wastewater (requires 5-day incubation).

• Testing Scope: Only biodegradable organics.

COD vs BOD: Critical Differences

Compliance Standards:

• Municipal WWTPs: BOD₅ ≤30mg/L (EPA 40 CFR Part 133)

• Food Industry: COD ≤500mg/L (EU Directive 2020/741)

Effective COD/BOD Reduction Technologies

1. Biological Treatment (BOD/COD ≥0.3)

• MBBR + Disc Diffuser Systems:
  Juntai’s Mbbr Carriers increase biofilm surface area by 30x vs. activated sludge. Combined with fine bubble disc diffusers (O₂ transfer efficiency ≥30%), achieve >80% BOD removal.
  Case Study: Dairy plant reduced COD from 1200mg/L to 150mg/L.

2. Chemical Oxidation (COD/BOD >3)

• Recommended Agents: Fenton’s reagent, ozone catalysis.

• Post-Treatment: Tube Settlers achieve >90% SS removal.

3. Physicochemical Hybrid Process

• Workflow: Screening → Equalization → Coagulation → Juntai Tube Settler → Discharge.

• Advantage: Handles COD fluctuations in textile/electroplating wastewater.

Juntai Equipment Solutions

✅ MBBR Biofilm Carriers

• Surface Area: ≥800m²/m³

• Material: Impact-resistant HDPE, lifespan >15 years.

• Performance: 3-5x biomass increase, 40% higher BOD removal.

✅ Fine Bubble Disc Diffusers

• O₂ Transfer Efficiency: 8-12% (5m water depth).

• Membrane Material: Acid-resistant EPDM, 3-year warranty.

• Energy Savings: 25-35% less power than conventional aerators.

✅ Tube Settler Clarifiers

• Surface Load: 15-20m³/m²·day.

• Client Case: Malaysian paper mill achieved 65% COD reduction.

FAQ

Q: Should I test COD or BOD?
A: Use COD for rapid industrial screening; test both for municipal/food wastewater.

Q: High COD but normal BOD?
A: Indicates non-biodegradable pollutants (e.g., microplastics). Add advanced oxidation.

Q: How to cut testing costs?
A: Rent Juntai’s online COD analyzers – 70% cheaper than lab tests.

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