Could Plant-Based Flocculants Substitute the Conventional Synthetic Chemicals in the Sludge Dewatering Process?
Abstract
:1. Introduction
2. Sludge Properties and the Necessity for Dewatering
3. Chemical Flocculants for Improving Sludge Dewatering: Efficiency and Effects on the Environment and Human Health
4. Plant-Based Flocculants for Sludge Dewatering: Efficiency and Comparison with Chemical Flocculants
4.1. Moringa
4.2. Cactus and Aloe
4.3. Okra
5. Potential Dewatering Flocculants: Synthetic or Plant-Based Ones
6. Challenges and Future Prospects in the Application of Plant-Based Flocculants for Sludge Dewatering
7. Conclusions
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Conditioning Methods | Principle | Limitations |
---|---|---|
Biological methods | Lysis of EPS and microbial cells to release the bound water in the sludge through the addition of enzyme or microbial leachate [32]. |
|
Physical methods | Modification of the structural properties of the sludge to increase its filterability and settle ability via the addition of solid and porous material (skeleton builder) or through thermal treatment (freeze-thawing, thermal, and microwave treatment) [33]. |
|
Chemical methods | Modification of the physicochemical properties of the sludge via the addition of chemical reagents conducive to either solids degradation to ease bound water release as a result of pH alteration (alkali or acid treatment) or by the consolidation of solids to increase its permeability and promote solid/liquid separation (coagulation/flocculation) [34,35]. |
|
Raw Sludge | Chemical Flocculant | Dewatered Sludge Parameters | References | ||||
---|---|---|---|---|---|---|---|
SRF × 1012 (m/kg) | CST (s) | TTF (s) | DS (%) | MC (%) | |||
Anaerobically digested sludge SRF = 265 × 1012 m/kg CST = 283 s TTF = 600 s MC = 97.80% | Al2(SO4)3 Optimal dose = 300 mg/g | 51.94 | 57 | 140 | _ | 89 | [41] |
Fe2(SO4)3 Optimal dose = 300 mg/g | 43.99 | 51 | 137 | _ | 88 | ||
AlCl3 Optimal dose = 150 mg/g | 18.29 | 35 | 118 | _ | 87 | ||
FeCl3 Optimal dose = 150 mg/g | 13.25 | 32 | 129 | _ | 86 | ||
Biological sludge SRF = 11.30 × 1012 m/kg DS = 12% MC = 98.50% CST = 132 s | PACl Optimal dose = 10% | 3.90 | 55 | _ | 22.50 | 80.80 | [42] |
Sewage sludge SRF = 1.72 × 1012 m/kg | FeCl3 Optimal dose = 10% | 0.07 | _ | _ | _ | _ | [43] |
PACl Optimal dose = 10% | 0.50 | _ | _ | _ | _ | ||
Sewage sludge MC = 98% SRF = 2.19 × 1012 m/kg CST = 150 s | Cationic PAM Optimal dose = 2 g/kg | 1.07 | 9.77 | _ | _ | 74.70 | [46] |
Waste-activated sludge SRF = 14.20 × 1012 m/kg CST = 225 s | PAM Optimal dose = 3 mg/g | 0.40 | 19.70 | _ | _ | _ | [47] |
Raw Sludge. | Flocculant | Sludge Dewatering Performance | References |
---|---|---|---|
Sewage sludge SRF = 1.22 × 1016 m/kg | MO powder Optimal dose = 6 g/L | SRF = 3.43 × 1015 m/kg | [62] |
Waste-activated sludge SRF = 4.50 × 1012 m/kg | MO powder Optimal dose = 4 g/L | SRF = 2.50 × 1012 m/kg | [63] |
Sewage sludge SRF = 8.00 × 1010 m/kg CST = 6.8 s | MO powder Optimal dose = 2 g/L (for SRF) Optimal dose = 3 g/L (for CST) | SRF = 3.30 × 1010 m/kg CST = 5.60 s | [64] |
Chemical polymer (Zetag 7653) Optimal dose = 0.05 g/L | SRF = 3.30 × 1010 m/kg CST = 3.60 s | ||
Sewage sludge SRF = 4.45 × 1011 m/kg CST = 6.90 s | MO water extract Optimal dose = 4.69 g/L | SRF = 1.22 × 1011 m/kg CST = 4.50 s | [65] |
Sewage sludge SRF = 0.90 × 1012 m/kg CST = 9 s | MO water extract Optimal dose = 3 g/L (for SRF) Optimal dose = 5 g/L (for CST) | SRF = 3.64 × 1011 m/kg CST = 7.10 s | [66] |
Chemical polymer (Zetag 8140) Optimal dose = 13 mg/L | SRF = 1.48 × 1011 m/kg CST = 5.50 s | ||
Synthetic Kaolin sludge SRF = 3.90 × 1011 m/kg | MO salt extract Optimal dose = 235.58 mg/L | SRF = 1.10 × 1011 m/kg | [67] |
Alum Optimal dose = 212.02 mg/L | SRF = 0.80 × 1011 m/kg | ||
Water treatment sludge SRF = 35.10 × 1012 m/kg CST = 175.4 s | MO salt extract Optimal dose = 40 mL/L | SRF = 12.10 × 1012 m/kg CST = 59.70 s | [68] |
Alum Optimal dose = 40 mL/L | SRF = 6.64 × 1012 m/kg CST = 42.20 s | ||
Water treatment sludge SRF = 1.61 × 1013 m/kg CST = 44 s | Moringa Pergerina Optimal dose = 100 mL/L | SRF = 1.21 × 1013 m/kg CST = 19 s | [69] |
Ferric chloride Optimal dose = 100 mL/L | SRF = 0.97 × 1013 m/kg CST = 9 s |
Raw Sludge | Flocculant | Sludge Dewatering Performance | References |
---|---|---|---|
Sewage sludge SRF = 1.03 × 1013 m/kg | Cactus juice Optimal dose = 0.4 g/kg | SFR = 0.17 × 1012 m/kg | [11] |
Cationic polyacrylamide (Chimfloc C4346) Optimal dose = 6 g/kg | SFR = 0.3 × 1012 m/kg | ||
Non-ionic polyacrylamide (Sedipur NF 102) Optimal dose = 6 g/kg | SFR = 4 × 1012 m/kg | ||
Alum Optimal dose = 40 g/kg | SFR = 1.3 × 1012 m/kg | ||
FeCl3 Optimal dose = 80 g/kg | SFR = 1.3 × 1012 m/kg | ||
Municipal wastewater sludge Settling rate = 55% | Aloe vera gel Optimal dose = 3 mL/L | Settling rate = 67.50% | [59] |
Raw Sludge | Flocculant | Sludge Dewatering Performance | References |
---|---|---|---|
Synthetic Kaolin sludge | Okra water extract Optimal dose = 175 mg/L | SS removal ≥ 98% Water recovery ≥ 68% | [12,71,72] |
Okra oven-dried powder Optimal dose = 150 mg/L | SS removal ≥ 98% Water recovery ≥ 68% | ||
Okra microwave-extracted powder Optimal dose = 30 mg/L | SS removal ≥ 99% Water recovery ≥ 75% | ||
Cationic polyacrylamide (FO 4400 SH) Optimal dose = 70 mg/L | SS removal ≥ 98% Water recovery ≥ 65% | ||
Anionic polyacrylamide (AN 934 SH) Optimal dose = 50 mg/L | SS removal ≥ 95% Water recovery ≥ 60% |
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Hadj Mansour, Y.; Othmani, B.; Ben Rebah, F.; Mnif, W.; Saoudi, M.; Khadhraoui, M. Could Plant-Based Flocculants Substitute the Conventional Synthetic Chemicals in the Sludge Dewatering Process? Water 2023, 15, 2602. https://doi.org/10.3390/w15142602
Hadj Mansour Y, Othmani B, Ben Rebah F, Mnif W, Saoudi M, Khadhraoui M. Could Plant-Based Flocculants Substitute the Conventional Synthetic Chemicals in the Sludge Dewatering Process? Water. 2023; 15(14):2602. https://doi.org/10.3390/w15142602
Chicago/Turabian StyleHadj Mansour, Yosra, Bouthaina Othmani, Faouzi Ben Rebah, Wissem Mnif, Mongi Saoudi, and Moncef Khadhraoui. 2023. "Could Plant-Based Flocculants Substitute the Conventional Synthetic Chemicals in the Sludge Dewatering Process?" Water 15, no. 14: 2602. https://doi.org/10.3390/w15142602
APA StyleHadj Mansour, Y., Othmani, B., Ben Rebah, F., Mnif, W., Saoudi, M., & Khadhraoui, M. (2023). Could Plant-Based Flocculants Substitute the Conventional Synthetic Chemicals in the Sludge Dewatering Process? Water, 15(14), 2602. https://doi.org/10.3390/w15142602