What High BOD Usually Means
High BOD means:
👉 too much organic material entering or remaining in the system.
That usually signals:
- overload
- poor treatment
- industrial discharge
- biological instability
Cause 1: High Organic Loading
Large increases in:
- food waste
- industrial waste
- septage
- storm events
Can spike BOD quickly.
Cause 2: Poor Aeration
If biology lacks oxygen:
- treatment efficiency drops
- organics remain untreated
I always check DO first.
Cause 3: Sludge Age Problems
Young sludge or washed-out biology can reduce BOD removal efficiency.
I review:
- wasting rates
- MLSS
- sludge age
Cause 4: Toxic Loads
Industrial chemicals or toxic discharges can damage microorganisms.
Signs:
- sudden performance drops
- ammonia spikes
- poor settling
Final Thought
High BOD is usually a symptom of process instability—not just a random lab number.