Troubles in the Trenches: Spotting Symptoms of Biological Process Problems in Wastewater Treatment

Biological wastewater treatment systems thrive on microbial balance and environmental stability. But when something’s off, the signs often emerge before the data catches up. Recognizing these early symptoms can mean the difference between proactive intervention and a full-blown process upset.
Here are some key red flags to watch for:

🚱 1. Poor Settling and Bulking Sludge

• Symptoms: Cloudy supernatant, high SVIs, thick blanket formation in secondary clarifiers.
• Potential Causes: Overgrowth of filamentous bacteria (e.g., Microthrix parvicella), non-filamentous bulking, low DO, nutrient imbalance.
• Pro Tip: Microscopy can quickly differentiate bulking from pin floc issues—don't skip the slide.
  
  

💨 2. Foaming

• Symptoms: Thick, stable foam on aeration basins—especially white or brown foam.
• Likely Culprits: Nocardia, biosurfactant-producing organisms, FOG load shocks.
• When to Worry: Persistent foam despite operational tweaks may signal deeper organic loading problems or filamentous dominance.
  
  

🧪 3. Rising Effluent Ammonia or Nitrite

• Symptoms: Ammonia breakthrough, elevated nitrite, reduced nitrate.
• Mechanism: Inhibited nitrifiers due to toxins (e.g., phenols, heavy metals), low DO, or sudden temperature changes.
• Troubleshooting Tip: Check for industrial influent spikes or hidden toxicity in side streams.
  
  

🧼 4. Grease Balls, Scum, and Floating Solids

• Symptoms: Visible grease balls, floaters in clarifiers, or scum layers.
• Root Issues: Rapid increase in FOG or problems with pretreatment
• Operator Insight: Don’t just skim—trace these to upstream sources to prevent recurrence.
  
  

🔄 5. Loss of Biological Nutrient Removal (BNR) Performance

• Symptoms: Increased total nitrogen or phosphorus in effluent.
• Possible Failures: PAO washout, GAO takeover, incomplete denitrification.
• Checkpoint: Review carbon source availability and anaerobic/aerobic exposure times.
  
  

🔬 6. Filamentous vs Floc-forming Competition

• Symptoms: Weak floc structure, open and irregular flocs, poor settleability.
• Microscopic Signs: Dominance of filamentous organisms penetrating floc matrices.
• Management Strategies: Review F/M ratios, implement selector zone control, consider targeted biocides if needed.

Most biological symptoms stem from subtle shifts—temperature drops, carbon source changes, or microbial imbalances. That’s why routine microscopic checks and trend monitoring are non-negotiable. Early detection empowers operators to stay ahead of system upsets and keep biology thriving.

Want to explore how microbial community shifts play into these symptoms—or curious about using molecular tests for better biomass knowledge? Drop me a line!