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New approaches to minimize excess sludge in activated sludge systems
1Department of Civil Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon.
Summary
Three novel methods were tested to reduce excess sludge in activated sludge systems. One method, the OSA process, effectively reduced sludge by over 50% while maintaining effluent quality.
Area of Science:
- Environmental Engineering
- Microbiology
- Wastewater Treatment
Background:
- Activated sludge systems generate significant excess sludge, posing operational and disposal challenges.
- Reducing excess sludge production is crucial for sustainable and cost-effective wastewater treatment.
Purpose of the Study:
- To investigate three innovative approaches for minimizing excess sludge production in activated sludge wastewater treatment.
- To evaluate the efficacy and feasibility of each method in reducing sludge yield and maintaining treatment performance.
Main Methods:
- Modification of activated sludge process (OSA) with a sludge holding tank.
- Chlorination of excess sludge to inhibit microbial growth.
- Utilization of a metabolic uncoupler, 3,3',4',5-Tetrachlorosalicylanilide (TCS), to increase microbial futile activity.
Main Results:
- The OSA process reduced excess sludge by over 50% at an ORP of -250 mV, improving sludge settleability.
- Chlorination reduced sludge by 60% but negatively impacted sludge settleability, rendering it unsuitable for conventional systems.
- TCS addition at 0.8 ppm reduced excess sludge by 45% and increased the proportion of active sludge microorganisms.
Conclusions:
- The OSA process offers an effective solution for excess sludge reduction with improved effluent quality and sludge settleability.
- Sludge chlorination is not a viable option for conventional systems due to detrimental effects on sludge settleability.
- Metabolic uncouplers like TCS show promise for reducing sludge growth by enhancing microbial futile activity.