## **Part 5: Troubleshooting Biological Processes in Wastewater Treatment Systems** 🔧### **Microorganisms in Activated Sludge** 🔬Biologica...
Published on by Hossein Ataei Far, Deputy Manager of the Research, Technology Development, and Industry Relations Center at NWWEC
### **Microorganisms in Activated Sludge** 🔬
Biological processes in wastewater treatment rely heavily on the balance and health of microorganisms in the activated sludge system. Effective monitoring and control of these organisms ensure optimal system performance.
#### **Key Microorganism Groups**
1. **Bacteria**:
- **Role**: Primary agents for breaking down organic nutrients and converting pollutants into more stable forms.
- **Best Practices**: Maintain a steady supply of dissolved oxygen (DO), appropriate sludge age, and balanced nutrient levels to promote bacterial growth.
2. **Protozoa**:
- **Role**: Enhance effluent clarity by consuming dispersed bacteria and suspended particles.
- **Types**:
- **Amoebae**: Thrive during startup phases or under low nutrient conditions. Minimal impact on overall performance.
- **Flagellates**: Feed on dissolved organic matter; their dominance may signal low organic load.
- **Ciliates**: Crucial for water clarification. Types include:
- **Crawling ciliates**: Predominate in well-functioning systems.
- **Stalked ciliates**: appear toward the process end, signifying maturation.
3. **Metazoa**:
- **Role**: System health indicators, though less influential on organic material removal.
- **Types**:
- **Rotifers**: sensitive to toxins, providing early warnings of system stress.
- **Nematodes**: Consume bacteria and protozoa, maintaining ecosystem balance.
- **Tardigrades**: Their presence highlights resilience under extreme conditions.
4. **Filamentous Bacteria:
- **Role**: Cause sludge settling issues and foam formation when overgrown.
- **Control Measures**: Adjust operating conditions such as pH, DO, nutrient ratios, and sludge age to prevent their dominance.
5. **Algae and Fungi:
- **Role**: Typically benign, though they may indicate pH imbalances or aging sludge.
#### **Operational Tips for Microorganism Management**
- **Aeration Control**: Ensure adequate oxygen supply (DO > 2 mg/L) to support aerobic microorganisms.
- **pH Monitoring**: Maintain pH levels between 6.5 and 8.5 to optimize microbial activity.
- **Sludge Age**: Monitor and adjust sludge age to balance microorganism populations and prevent the overgrowth of undesirable species.
- **Nutrient Balance**: Provide sufficient nitrogen and phosphorus to avoid nutrient limitation.
References
[1] Tchobanoglous, G., et. al. (2023).
[2] Metcalf & Eddy, Inc. (2020).
[3] Grady, C.P.L., et. al. (2022). Biological Wastewater Treatment. CRC Press.
[4] "Control of Activated Sludge, Including Troubleshooting" (https://lnkd.in/dcEjHtvT).
[5] Water Environment Federation (WEF) (2021). Manual of Practice No. 11: Operation of Municipal Wastewater Treatment Plants.
[6] EPA. Wastewater Technology Fact Sheets.
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