A Pilot Study of the Sludge Recycling Enhanced Coagulation–Ultrafiltration Process for Drinking Water: The Effects of Sludge Recycling Ratio and Coagulation Stirring Strategy
Abstract
:1. Introduction
- A high efficiency of adsorption, which allows for enhanced removal of dissolved organics.
- A high efficiency of coagulation enhancement; the high concentration of the sludge has a better sedimentation potential.
- The sludge provides suitable conditions for microorganism growth, which allows for the removal of biodegradable substances, and ammonia.
- The sludge recycling could decrease the coagulant dosage.
2. Methods and Materials
2.1. Raw Water Characteristics
2.2. Pilot Study Protocol
2.3. Analytical Methods
3. Results
3.1. Effects of the Sludge Recycling Ratio on the Coagulation Performance
3.2. Impact of Sludge Recycling Ratio on the UF Membrane Fouling
3.3. Impact of Coagulation Stirring Strategy on Sedimentation and UF Performance
3.4. Impact of the Coagulation Stirring Strategy on the Removal Efficiency
3.5. Optimization of Sludge Recycling Ratio and Coagulation Stirring Strategy
4. Conclusions
- (1)
- The sludge recycling at a ratio of 10% achieved the highest sedimentation efficiency and the best pollutant removal (ammonia and dissolved organics) in the sludge recycling enhanced coagulation–UF process. Moreover, membrane fouling was mitigated during this condition, which suggested that the sludge recycling contributed to energy saving.
- (2)
- Rapid mixing had the best performance in terms of enhancing the coagulation–UF process. A traditional coagulation stirring strategy should be modified when using the sludge recycling enhanced coagulation–UF process.
- (3)
- The DLVO theory is not appropriate during sludge recycling enhancement. The effect of overcoming the repulsion potential might not play a leading role, since the sludge particle size and solid content of mixed water were much higher than the raw water.
- (4)
- The adsorption of sludge could be a possible reason for pollutant removal by the sludge recycling enhanced coagulation–UF process.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Parameter | Unit | Value |
---|---|---|
Temperature | °C | 20–25 |
Turbidity | NTU | 8–15 |
DOC | mg·L−1 | 2.40–3.10 |
UV254 | cm−1 | 0.050–0.065 |
pH | / | 7.8–8.2 |
Algae | 104 Cell·mL−1 | 3.5–4.5 |
Bacteria | CFU·mL−1 | 20–50 |
No. | Coagulation Stirring Strategy |
---|---|
No. 1 | the raw water is rapidly mixed in the first stirring tank, and then flows into the sediment tank |
No. 2 | the raw water is stirred in the first and second stirring tank in series, and then flows into sediment tank |
No. 3 | the raw water is stirred in the first, second and third stirring tank in series, and then flows into sediment tank |
No. 4 | the raw water is stirred in the first, second, third and fourth stirring tank in series, and then flows into the sediment tank |
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Liu, B.; Qu, F.; Guo, S.; Yu, H.; Li, G.; Liang, H.; Van der Bruggen, B. A Pilot Study of the Sludge Recycling Enhanced Coagulation–Ultrafiltration Process for Drinking Water: The Effects of Sludge Recycling Ratio and Coagulation Stirring Strategy. Water 2017, 9, 183. https://doi.org/10.3390/w9030183
Liu B, Qu F, Guo S, Yu H, Li G, Liang H, Van der Bruggen B. A Pilot Study of the Sludge Recycling Enhanced Coagulation–Ultrafiltration Process for Drinking Water: The Effects of Sludge Recycling Ratio and Coagulation Stirring Strategy. Water. 2017; 9(3):183. https://doi.org/10.3390/w9030183
Chicago/Turabian StyleLiu, Bin, Fangshu Qu, Shaodong Guo, Huarong Yu, Guibai Li, Heng Liang, and Bart Van der Bruggen. 2017. "A Pilot Study of the Sludge Recycling Enhanced Coagulation–Ultrafiltration Process for Drinking Water: The Effects of Sludge Recycling Ratio and Coagulation Stirring Strategy" Water 9, no. 3: 183. https://doi.org/10.3390/w9030183
APA StyleLiu, B., Qu, F., Guo, S., Yu, H., Li, G., Liang, H., & Van der Bruggen, B. (2017). A Pilot Study of the Sludge Recycling Enhanced Coagulation–Ultrafiltration Process for Drinking Water: The Effects of Sludge Recycling Ratio and Coagulation Stirring Strategy. Water, 9(3), 183. https://doi.org/10.3390/w9030183