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Optimization of polyhydroxyalkanoates (PHA) synthesis with heat pretreated waste sludge
Qianru Liao1, Liang Guo2, Yihe Ran1
1College of Environmental Science and Engineering, Ocean University of China, Qingdao 266100, China.
Waste Management (New York, N.Y.)
|December 5, 2018
Summary
Waste sludge heat pretreated at 60°C efficiently produced polyhydroxyalkanoates (PHA), a bioplastic. This method offers a cost-effective way to synthesize PHA while reducing sludge disposal.
Area of Science:
- Biotechnology
- Environmental Engineering
- Polymer Science
Background:
- Polyhydroxyalkanoates (PHA) are biodegradable polyesters with diverse applications.
- Waste sludge disposal presents environmental and economic challenges.
- Utilizing waste sludge as a carbon source for PHA production can offer a sustainable solution.
Purpose of the Study:
- To investigate the feasibility of using heat-pretreated waste sludge as an external carbon source for PHA synthesis.
- To determine the optimal heat pretreatment temperature for maximizing PHA accumulation and production efficiency.
- To analyze the utilization of different organic components in sludge for PHA synthesis.
Main Methods:
- Waste sludge was pretreated at various temperatures (60°C, 80°C, 100°C, 120°C).
- Pretreated sludge was used as a carbon source for PHA synthesis by microorganisms.
- PHA accumulation, utilization efficiencies of chemical oxygen demand (COD), proteins, carbohydrates, and volatile fatty acids (VFAs), and kinetic parameters were analyzed.
- Three-dimensional fluorescence excitation-emission matrix (EEM) spectroscopy with fluorescence regional integration (FRI) was employed for further analysis.
Main Results:
- Maximal PHA accumulation of 24.1% of dry cell weight was achieved using sludge pretreated at 60°C.
- High utilization efficiencies for COD (74.3%), proteins (82.3%), and VFAs (81.4%) were observed with 60°C pretreated sludge.
- The highest PHA production rate (0.23 mg COD/mg X·h) and PHA conversion rate (0.46 mg COD/mg COD) were obtained with 60°C pretreated sludge.
Conclusions:
- Heat-pretreated waste sludge, particularly at 60°C, is a feasible and efficient external carbon source for PHA production.
- This approach simultaneously addresses PHA cost reduction and waste sludge disposal.
- Both VFAs and non-VFAs organic components in sludge can serve as carbon sources for PHA synthesis.
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