Part 3: 🌊 Troubleshooting High Sludge Blanket in Secondary ClarifierA. High Secondary Clarifier Sludge Blanket1. Diagnostic Tools and Calcula...

Published on by

Part 3: 🌊 Troubleshooting High Sludge Blanket in Secondary Clarifier

A. High Secondary Clarifier Sludge Blanket

1. Diagnostic Tools and Calculations 🔍
Accurate diagnosis of the sludge blanket issue is critical for effective treatment. Use the following tools and calculations:
Settleometer Test: Measure sludge settleability, tracking its settling velocity and compacting capability.
Microscopic Examination of MLSS: Identify the health of microbial communities and assess the presence of undesirable filaments.
Sludge Volume Index (SVI) and Sludge Density Index (SDI): Calculate and interpret these indices to pinpoint compaction problems or assess biomass stability.
SVI: High values often suggest filamentous bulking.
SDI: Indicates the density and compactness of the biomass.
References: 1, 3

2. High SVI, Low SDI
a. Filamentous Bulking 🦠
Filamentous bulking is often a result of excessive filamentous bacteria that hinder sludge settling. Mitigation measures include:
Causes and Corrective Actions: Low Dissolved Oxygen (DO): Ensure aeration tanks maintain 2–3 mg/L of DO.
Organic Loading Rate Imbalances: Monitor F/M (food-to-microorganism) ratios to prevent underloading or overloading.
Nutrient Deficiency: Optimize the Carbon:Nitrogen: Phosphorus (C: N:P) ratio, typically 100:5:1.
Septic Conditions: Reduce sulfide production from anaerobic conditions upstream by aerating influent or adjusting flow rates.
Specific Filamentous Bacteria: Microthrix parvicella: Tends to thrive under low DO and high FOG (fats, oils, and grease) conditions; apply selective chemical treatments or increase wasting to control growth.

Hydrogen Peroxide or Chlorination: Apply selectively for short-term control while addressing root causes.
References: 2, 3, 4

3. Normal SVI, SDI
If indices appear normal, other factors may contribute to sludge blanket elevation:
a. Excessive Biomass 🌱
High biomass concentrations can overwhelm clarifiers. Actions include:
Recalculate CRT (Critical Retention Time) and Wasting Rate: Optimize to reduce sludge buildup.
Enhance Sludge Handling: Check for poor compaction in sludge storage or improper thickening.
Check for Solids Carryover: Prevent WAS (Waste Activated Sludge) bypass from primary clarifiers.
References: 1, 3

b. Inadequate Return Sludge Rate (RAS) 💧
Insufficient RAS rates can cause sludge blankets to rise. Recommendations:
Control and Adjust RAS Pumps: Calibrate pump speeds to balance sludge removal.
Mechanical Maintenance: Ensure pumps and valves are operational and free of debris.

References 📚
[1] State of Michigan Department of Environmental Quality - Activated Sludge Process Control.
[2] AquaFix, Microthrix Bulking in Summer.
[3] Jenkins, Richard D., Manual on Activated Sludge Bulking and Foaming Problems.
[4] WEF (Water Environment Federation), Filamentous Bacteria in Activated Sludge.

You can see this picture on the Lil' Critters in the Sludge website: https://lnkd.in/dtAQBeNB

Media