Effect of CO₂ addition on biomass energy yield in wastewater treatment high rate algal mesocosms

详细信息    查看全文

• 作者：Abbas Mehrabadi^a ; ^{ameh820@aucklanduni.ac.nz} ; ^{mehrabadi_abbas@yahoo.com} ; Mohammed M. Farid^a ; ^{m.farid@auckland.ac.nz} ; Rupert Craggs^b ; ^{Rupert.Craggs@niwa.co.nz}
• 关键词：Wastewater treatment ; Microalgae ; High rate algal mesocosms ; CO2 addition ; Energy production ; Biofuel
• 刊名：Algal Research
• 出版年：2017
• 出版时间：March 2017
• 年：2017
• 卷：22
• 期：Complete
• 页码：93-103
• 全文大小：1839 K
• 卷排序：22

文摘

Carbon limitation in algal-based wastewater treatment ponds typically constrains microalgae growth and consequently biomass energy yield, particularly in summer. This study investigates the effect of CO2 addition on algal biomass energy yield in wastewater treatment high rate algal mesocosms (WWT HRAM). Two experiments (summer and winter) were conducted using 15 replicate HRAMs under outdoor conditions while the cultures were bubbled continuously with different air:CO2 mixtures including: air (control mesocosm), 0.5%, 2%, 5% and 10% CO2. The effects of CO2 addition were evaluated by determining the productivity, algal proportion, chemical composition, energy content, and settleability of the biomass. Under summer conditions there was a direct relationship between biomass productivity and CO2 concentration with the maximum productivity increase (50% higher than control) occurring in the 10% CO2-HRAMs. Under winter conditions there was no significant difference in biomass productivity between treatments. In both experiments, the biomass energy content varied slightly (19.3–22.8 kJ·g− 1) with %CO2 addition, with a slight trend of increasing at higher %CO2 level and where the biomass lipid content was higher. CO2 augmentation led to a change in the HRAM algal composition and consequently changed the biomass settleability. The total biomass energy yield and its gravity harvestable proportion (calculated by multiplying biomass concentration, energy content and harvest efficiency) were highest for the 5% CO2-HRAMs in summer and for the 0.5% CO2-HRAMs in winter. These results show that CO2 addition (indicated by maintaining a culture pH of 6–7 in summer and 7–8 in winter) not only improves biomass productivity and energy content but selects for easily harvestable colonial algal species which are less susceptible to zooplankton grazing.