Abstract
The effects of five different microalgae-fungi on nutrient removal and CO2 removal were investigated under three different CO2 contents (35%, 45% and 55%). The results showed that the highest nutrient and CO2 removal efficiency were found at 55% CO2 by cocultivation of different microalgae and fungi. The effect of different initial CO2 concentration on the removal of CO2 from microalgae was significant, and the order of CO2 removal efficiency was 55% (v/v) >45% (v/v) >35% (v/v). The best nutrient removal and biogas purification could be achieved by co-cultivation of C. vulgaris and G. lucidum with 55% initial CO2 content. The maximum mean COD, TN, TP and CO2 removal efficiency can reach 68.29%, 61.75%, 64.21% and 64.68%, respectively under this condition. All highest COD, TN, TP and CO2 removal efficiency were more than 85%. The analysis of energy consumption economic efficiency revealed that this strategy resulted in the highest economic efficiency. The results of this work can promote simultaneously biological purification of wastewater and biogas using microalgal-fungal symbiosis.
Highlights
Other components of the raw biogas from anaerobic digestion is typically composed of CH4 (40%–75%), H2S (0.005%–2%), and H2, O2, or N2 at trace levels[2,18] studied the biomass growth, nutrient removal, and biogas upgrading of green algae Chlorella sp. in a PBRb using LEDs and revealed that the removal efficiency (RE) of the main nutrients were affected by the CO2 concentration and microalgal species, and concluded that the successful mitigation of CO2 and production of renewable energy using microalgae require sorting of microalgae according to their growth rate, lipid content, and tolerance to high levels of CO2
This work focused on three objectives including: (1) appropriate selection of best fungal-microalgal interaction (i.e. P. geesteranus/C. vulgaris, G. lucidum/C. vulgaris, P. ostreatus/C. vulgaris, G. lucidum/S. obliquus and G. lucidum/S. capricornutum) for biogas slurry treatment with chemical oxygen demand (COD), nitrogen (N), phosphorus (P) and CO2 removal simultaneously. (2) the influence of three CO2 concentrations (35%, 45%, and 55%, v/v) in synthetic biogas on the nutrient removal from biogas slurry and CO2 removal from biogas were investigated. (3) the economic efficiency of biogas upgrading or biogas slurry nutrient removal was evaluated according to removal efficiency, electric power charge, illumination time and LED electrical power consumption
High CO2 concentration (55%, v/v) was chosen as the most effective treatment and G. lucidum/C. vulgaris strain can be ranked as the optimal fungal-microalgal mixture according to its high biomass production
Summary
In a PBRb (photobioreactor bag) using LEDs (light emitting diodes) and revealed that the removal efficiency (RE) of the main nutrients were affected by the CO2 concentration and microalgal species, and concluded that the successful mitigation of CO2 and production of renewable energy (bioethanol, biogas, biodiesel, and biohydrogen) using microalgae require sorting of microalgae according to their growth rate, lipid content, and tolerance to high levels of CO2. (3) the economic efficiency of biogas upgrading or biogas slurry nutrient removal was evaluated according to removal efficiency, electric power charge, illumination time and LED electrical power consumption These findings are essential for the effective design of crude biogas treatment systems, in order to address the demands of technology efficiency and environmental sustainability
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