Value-Added Products Derived from Waste Activated Sludge: A Biorefinery Perspective
Abstract
:1. Introduction
2. Amino Acids and Proteins
3. Short-Chain Fatty Acids
4. Enzymes
5. Bio-Pesticides
6. Bio-Plastics
7. Bio-Flocculants and Bio-Surfactants
8. Current Challenges
- (1)
- Biorefinery production of protein and enzymes are still considered to be higher cost routes compared with agro-industry residues and animal health in terms of pathogenic and metals toxicity, which has effectively stifled developments in this area [139].
- (2)
- Recovery of metabolic WAS products (e.g., bio-plastics, bio-pesticides, bio-flocculants and bio-surfactants) remains in its infancy and further optimisation of operational parameters and selection of non-toxic strains are needed to progress this research area.
- (3)
- Important factors such as optimum growth environment or wastewater matrix for harvesting WAS with the highest concentration of specific bio-products need to be further investigated and refined.
- (4)
- WAS bio-product production through biological processes such as fermentation, bioleaching or enzymatic extraction, while an evolving area of research, still requires further optimisation.
- (5)
- Anaerobic digestion as a potential option for enhancing the production of SCFAs and their extraction from WAS through fermentation in the presence of key chemical surfactants deserves further exploration.
- (6)
- Simple and efficient purification procedures for certain bio-products recovered from WAS (in line with the required purity for specific applications) need further development and would contribute to improving the overall economics of biorefinery approaches.
- (7)
- Scale of WAS-based biorefinery production is an important future challenge, since much of the research so far has been at laboratory scale. To scale up the biorefinery approach using WAS, further research must be carried out at larger scales (pilot- and ultimately full-scale) to optimize each biorefinery process. Only then can the full techno-economic performance of these processes be fully investigated and understood.
Acknowledgments
Author Contributions
Conflicts of Interest
References
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Amino Acid | WAS | Soybean Meal | White Fish Meal | FAO Ref. Protein | Wheat | Whole Egg |
---|---|---|---|---|---|---|
Alanine | 7.3 | - | - | - | - | - |
Glycine | 4.9 | - | - | - | - | - |
Valine | 4.1 | 5.2 | 4.7 | 4.2 | 4.4 | 7.3 |
Threonine | 4.2 | 4.4 | 3.8 | 2.8 | 2.9 | 5.1 |
Serine | 3.4 | - | - | - | - | - |
Leucine | 5.6 | 7.6 | 6.5 | 4.8 | 6.7 | 8.9 |
Isoleucine | 2.7 | 5.8 | 3.9 | 4.2 | 3.3 | 6.7 |
Proline | 3.1 | - | - | - | - | - |
Methionine | 1.45 | 1.3 | 2.9 | 2.2 | 1.5 | 3.2 |
Aspatic acid | 8.3 | - | - | - | - | - |
Phenylalanine | 3.1 | 5.3 | 3.5 | 2.8 | 4.5 | 5.8 |
Glutamic acid | 8.1 | - | - | - | - | - |
Lysine | 3.3 | 6.6 | 7.6 | 4.2 | 2.8 | 6.5 |
Tyrosine | 2.4 | 4.1 | 3 | 2.8 | - | - |
Arginine | 2.9 | 7.3 | 6.8 | - | - | - |
Histidine | 0.6 | 2.7 | 2 | - | - | - |
Cystine | 2.1 | 1.2 | 0.7 | 2 | 2.5 | 2.4 |
Tryptophan | 0.8 | 1.3 | 0.9 | 1.4 | 1.1 | 1.6 |
SCFAs Composition | Yield | Fermentation Conditions | Medium | References |
---|---|---|---|---|
Acetic, butyric, valeric and propionic acid | Max 520.1 mg/g VSS | 21 ± 1 °C, pH 8, 8 days | Wastewater sludge | [48] |
Acetic, butyric, valeric and propionic acid | Max 2599.1 mg/L | 21 ± 1 °C, pH 7.2, 6 days | Wastewater sludge | [37] |
Acetic, butyric, valeric and propionic acid | Max 319.8 mg/g VSS | 15–55 °C, pH 10 ± 0.3, 48 days | Wastewater sludge | [49] |
Acetic, butyric, valeric and propionic acid | 450–790 mg/g VSS | 55 °C, pH 7, 1 rpm, 28 days | Wastewater and bagasse | [34] |
Acetic, butyric, valeric and propionic acid | Max 284 mg/g VSS | 35 ± 1 °C, pH 7, 200 rpm, 7 days | Wastewater sludge | [35] |
Acetic, butyric, valeric and propionic acid | 345.49–2708.02 mg/L | 21 ± 1 °C, pH 4–11, 80 rpm, 20 days | Wastewater sludge | [31] |
Acetic, butyric, valeric and propionic acid | Max 256.2 mg/g VSS | 20–22 °C, pH 4–11, 20 days | Wastewater sludge | [30] |
Acetic, butyric, valeric and propionic acid | Max 368.71 g/kg TS | 35 ± 1 °C, C/N ratio 26 to 7, 24 days | Wastewater sludge and perennial ryegrass | [50] |
Acetic, butyric, valeric and propionic acid | 704.9–1994.7 mg/L | 20 ± 2 °C, pH 7–10, 70 rpm, 15 days | Wastewater sludge | [33] |
Acetic, butyric, valeric and propionic acid | 18.1–539.4 mg/L | 21 ± 2°C, 2 days | Wastewater sludge and potato-processing wastewater | [51] |
Enzymes Type and Activities | Extraction Techniques and Conditions | Medium | References |
---|---|---|---|
Protease: max. ≈3 μmol min−1 g−1 VSS α-amylase: max. ≈20 μmol min−1 g−1 VSS α-glucosidase: max. >1 μmol min−1 g−1 VSS Alkaline phosphatase: max. ≈9 μmol min−1 g−1 VSS Acid phosphatase: max. ≈3 μmol min−1 g−1 VSS | Ultrasound 20–40 kHz, 2–20 min, 138–690 W/g VSS, pH 7 and EDTA 2% at 4 °C for 3 h | Wastewater sludge | [56] |
Protease: 1.06–28.2 μmol min-1 g-1 VSS α-amylase: 10.2–14.9 μmol min−1 g−1 VSS α-glucosidase: 188–319 μmol min−1 g−1 VSS | Ultrasound 40 kHz, 120 W, 2 min, 0–15 kW/L, pH 8 and 2% EDTA, 36.5% formaldehyde, CER 70 g/g VSS at 4 °C for 1 h | Wastewater sludge | [55] |
Protease: max. ≈37 μmol min−1 g−1 VSS α-amylase: max. ≈34 μmol min−1 g−1 VSS α-glucosidase: max. ≈3 μmol min−1 g-1 VSS Alkaline phosphatase: max. ≈16 μmol min−1 g−1 VSS Acid phosphatase: max. ≈16 μmol min−1 g−1 VSS | Ultrasound 20 kHz, 0–20 min, 0–15 kW/L, pH 7, 4 °C | Wastewater sludge | [32] |
Protease: max 52 units/g VSS Lipase: max 22.9 ± 0.8 units/g VSS | Ultrasound 24 kHz, 3.9 W/cm2, 20 min, 5 ± 1 °C, and Triton X100 0.1 to 2% (v/v) | Wastewater sludge | [58] |
Protease: max 57.4 units/g VSS Lipase: max 21.4 units/g VSS | Ultrasound 20–24 kHz, 3–8 W/cm2, 1–60 min, pH 7–8, 5 ± 1 °C, TX 100 0.1 to 10% (v/v), CER 0.24–0.8 g/mL | Wastewater sludge | [57] |
Protease: max. ≈4,000 units/g VSS Lipase: 108.4–335 units/g VSS | 1 h 900 rpm stirring followed by 30 min sonication (200 W + 15 kHz), pH 8, 0–2% Triton X-100 and EDTA, CER 60–70 g/g VSS | Wastewater sludge | [60] |
Protease: 3450 ± 124 units/g mixed liquor suspended solids (MLSS) Amylase: 111 ± 5 units/g MLSS Glucosidase: 59.5 ± 2.9 units/g MLSS Lipase: 8.8 ± 1.4 × 10−2 units/g MLSS Dehydrogenase: 36.6 ± 3.8 × 10−3 units/g MLSS | Agitation 200–4200 rpm, 4 °C, 1–10 min and ammonium sulphate | Wastewater and laboratory-cultivated sludge | [61] |
Type | Entomotoxicity | Fermentation Conditions | Medium | References |
---|---|---|---|---|
Bacillus thuringiensis | 9534–13,020 IU/μL | 30 °C, pH 6.9 ± 0.1, 400 rpm, inoculum concentration 2% (v/v) | Tryptic soy yeast broth and sludge | [70] |
Bacillus thuringiensis | 8300–10,813 IU/μL | 30 °C, pH 7.0 ± 0.1, 300 rpm, inoculum concentration 2% (v/v), C/N ratio 7.9–9.9, total solids up to 33 g/L | Tryptic soy yeast broth and sludge | [68] |
Bacillus thuringiensis | 8115–12,970 IU/μL | 31 °C, 250 rpm, inoculum concentration 1–5% (v/v), total solids 10–46 g/L | Tryptic soy yeast broth and sludge | [67] |
Bacillus thuringiensis | 900–4100 IU/μL | 30 °C, pH 7.0, 250 rpm | Wastewater sludge | [72] |
Bacillus thuringiensis | 3400–10,000 IU/μL | 30–36 °C, pH 7.0, 50–350 rpm, inoculum concentration 5% (v/v), total solids up to 13 g/L | Wastewater sludge | [69] |
Bacillus thuringiensis | 4500–10,840 IU/μL | 31 °C, pH 7.0, 250 rpm, inoculum concentration 1% and 5% (v/v) | Wastewater sludge | [66] |
Trichoderma sp. | 6278–15,036 SBU/μL | 28 ± 1 °C, pH 6.0 ± 0.01, 250 ± 5 rpm, total solids 10–50 g/L | Wastewater sludge | [73] |
Organism | PHA Yield (mg/g Biomass) | Fermentation Conditions | Medium | Additional Carbon Source | References |
---|---|---|---|---|---|
Unspecified | - | pH 7, 25 °C, solids concentration 15 g/L, 0.3–0.5 vvm aeration, 60 h SRT | Paper and pulp wastewater | Acetate | [91] |
Unspecified | 111 | pH 7, 30 °C, C/N ratio 20–140, 300 rpm shaking, 48 h SRT | Domestic WAS | Valeric acid | [78,86] |
Bacillus | - | 37 °C, 250 rpm shaking, 18 h SRT | Beer brewery WAS | None | [80] |
Unspecified | 792 | Solids concentration 3 g/L, C/N ratio 144, 30 °C, 150 rpm shaking, 48 and 96 h SRT | Dairy and food processing WAS | Acetic acids | [87,92] |
Alcaligenes eutrophus | - | pH 7, 30 °C, 50 rpm shaking, 0.15 vvm aeration | Domestic WAS | None | [93] |
Unspecified | - | pH 7.5, 15–35 °C, 450 rpm shaking, 0.29 vvm aeration, 60 h SRT | Domestic WAS | Acetate | [85] |
Halomonas boliviensis | - | pH 7.5, inoculum size 2%, 35 °C, 850–1300 rpm stirring | Bakery WAS and seawater | None | [94] |
Bio-Flocculants Composition and Yield | Organisms | Medium | Fermentation Conditions | Reference |
---|---|---|---|---|
Polysaccharide, 2.58 g/L | Klebsiella mobilis | Dairy wastewater | Inoculum size 5% (v/v), pH 6.0, 30 °C | [115] |
Polysaccharide and protein, 15 g/L | Staphylococcus sp. and Pseudomonas sp. | Brewery wastewater | Inoculum size 2% (v/v), pH 6.0, 30 °C and shaking speed 160 rpm | [116] |
91.2% polysaccharide, 7.6% protein and 1.2% DNA, 1.6 g/L | Rhodococcus erythropolis | Livestock wastewater | Inoculum size 2% (v/v), pH 7, Na2HPO4 0.5 g/L | [117] |
Unspecified, 1.5–3.4 g/L | Serratia sp. | Pretreated WAS | Inoculum size 3% (v/v), 25 °C, shaking speeding 250 rpm, 72 h | [104] |
Carbohydrates (91% w/w), 2.1 g/L | Bacillus subtilis, Bacillus fusiformis, Bacillus flexus | WAS digestion liquor | Inoculum size 10% (v/v), pH 4–5, 24 h | [118] |
Chitosan-like polymer, 4.6 g/L | Citrobacter sp. | WAS digestion liquor | pH 8.5, 30 °C, shaking speed 120 rpm | [112] |
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Zhang, W.; Alvarez-Gaitan, J.P.; Dastyar, W.; Saint, C.P.; Zhao, M.; Short, M.D. Value-Added Products Derived from Waste Activated Sludge: A Biorefinery Perspective. Water 2018, 10, 545. https://doi.org/10.3390/w10050545
Zhang W, Alvarez-Gaitan JP, Dastyar W, Saint CP, Zhao M, Short MD. Value-Added Products Derived from Waste Activated Sludge: A Biorefinery Perspective. Water. 2018; 10(5):545. https://doi.org/10.3390/w10050545
Chicago/Turabian StyleZhang, Wei, Juan Pablo Alvarez-Gaitan, Wafa Dastyar, Christopher P. Saint, Ming Zhao, and Michael D. Short. 2018. "Value-Added Products Derived from Waste Activated Sludge: A Biorefinery Perspective" Water 10, no. 5: 545. https://doi.org/10.3390/w10050545
APA StyleZhang, W., Alvarez-Gaitan, J. P., Dastyar, W., Saint, C. P., Zhao, M., & Short, M. D. (2018). Value-Added Products Derived from Waste Activated Sludge: A Biorefinery Perspective. Water, 10(5), 545. https://doi.org/10.3390/w10050545