Increased Methane Production by Microalgae Anaerobic Digestion with Ozone and High-pressure Pretreatment
Date Issued
2011
Date
2011
Author(s)
Yang, Ying-Chen
Abstract
In order to enhance the efficiency of anaerobic digestion, the effects of ozonation and high-pressure extraction were studied on microalgae. High-pressure extraction was performed with mildly elevated pressure in consecutive cycles of compression and decompression as pretreatment. Anaerobic digestion converts the organics present in microalgae into biogas, but the efficiency and the digestion rate are limited by the hydrolysis. Biodegradability of microalgae could be low depending on the nature of the cell wall, thus pretreatment was applied to rupture the cell wall in order to improve biodegradability efficiencies.
Chemical oxygen demand (COD) and matter solubilisation caused by pretreatments was focused on organic solids. In terms of ozone pretreatment, COD solubilisation was 19.63% and 52.16% on flesh water algae and sea water algae, respectively. No significant relationship between COD solubilisation and SCOD/TCOD was observed, however, it was found that SCOD increased with ozone feeding time and then decreased, while TCOD decreased with ozone feeding time.
In this study, anaerobic bacteria are unable to adapt the saline environment, and have low capability to deal with sea microalgae that has high saline contents. The experimental results showed that the methane production decreased when salt content is higher. However, if anaerobic digestion is used to treat the saline wastewater, the capability of anaerobic bacteria must be enhanced or remove the saline content.
In flesh water algae system, the final methane concentrations increased from 16.38 to 22.15% when adding 10.52 mg COD of algae; the final methane concentrations increased to 20.67% when adding 9.2 mg COD of algae with ozone pretreatment. The result suggested that ozone extraction did not have significant impact on methane production.
The final methane concentrations increased from 4.23 to 9.21% when the COD concentration of microalgae increased from 511 to 1262 mg/L. It could be concluded that inoculum/substrate ratio had a considerable effect on methane production.
Subjects
Anaerobic digestion
Microalgae
Ozonation
Pressure cycle
Methane
Type
thesis
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