Part 1: Troubleshooting Biological Processes in Wastewater Treatment Systems** 🔧Troubleshooting biological processes in wastewater treatment ...
Published on by Hossein Ataei Far, Deputy Manager of the Research, Technology Development, and Industry Relations Center at NWWEC
Troubleshooting biological processes in wastewater treatment systems requires a systematic approach to identify and resolve issues that can affect treatment efficiency and effectiveness. Below is a guide to the key steps and common issues:
### **1. Identify Symptoms of Problems** 🔍
- **Increased Effluent BOD/COD** 📉
Symptoms: High biochemical oxygen demand (BOD) or chemical oxygen demand (COD) levels in treated effluent suggest the system is not effectively breaking down organic matter, possibly due to reduced microbial activity or inefficiencies in the treatment process.
Poor Settling Sludge** 🚱
Symptoms: Excessive sludge in the secondary clarifier or a high sludge volume index (SVI) may result in poor settling and elevated turbidity, leading to suboptimal effluent quality. Often caused by filamentous bacteria growth, this issue affects flocculation.
- **Foaming** 🧼
Symptoms: Persistent foam on the surface of aeration tanks or secondary clarifiers often indicates high surfactant levels or biological overgrowth, both of which contribute to excessive foam production.
Odors 👃
Symptoms: Unpleasant smells such as hydrogen sulfide or ammonia indicate anaerobic conditions or incomplete treatment, usually due to inadequate aeration or process failure.
### **2. Check Process Parameters** 📊
- **Temperature** 🌡️
Action: Ensure temperature is within the optimal range (typically 10-35°C) for microbial activity. Regularly monitor temperature readings and maintain the system within this ideal range to promote effective treatment.
- **pH** 🌡️
Action: Regularly monitor pH levels to ensure they stay between 6.5 and 8.5, which is the optimal range for most biological processes. Adjusting pH ensures microbial activity and process stability.
- **Dissolved Oxygen (DO)** 💧
Action: For aerobic processes, DO should be above 2 mg/L. Lower levels compromise microbial function. Adjust aeration rates or increase the return activated sludge (RAS) rate to maintain adequate DO levels.
Sludge Age (SRT)** ⏳
Action: Ensure the sludge age is within the recommended range for the specific process. Monitoring and adjusting sludge age ensures microbial balance, process stability, and treatment efficiency.
Hydraulic Retention Time (HRT)** 🕰️
Action: Verify that HRT meets design specifications. Ensuring proper contact time allows sufficient microbial breakdown of contaminants, optimizing treatment performance.
References 📚
[1] Metcalf & Eddy, Inc. (2020). Wastewater Engineering: Treatment and Resource Recovery.
[2] Tchobanoglous, G., et. al. (2023). Wastewater Engineering: Treatment and Reuse.
[3] Grady, C.P.L., et. al. (2022). Biological Wastewater Treatment.
[4] Seviour, T. & Nielsen, P.H. (2010). Microbial Ecology of Activated Sludge. IWA Publishing.
[5] Wanner, J. (1998). Microbial Ecology of Activated Sludge: Key Factors and Operational Aspects. IWA Publishing.