Optimization of cultivation conditions for combined nutrient removal and CO₂fixation in a batch photobioreactor

Abstract

BACKGROUND: The application of Chlorella vulgaris for simultaneous CO 2 biofixation and nutrient removal has been optimised using response surface methodology (RSM) based on Box Behnken design (BBD). Experimental conditions employed comprised CO 2 concentrations (C c,g ) of 0.03-22% CO 2 , irradiation intensities (I) of 100-400 E, temperatures of 20-30 ∘ C and nutrient concentrations of 0-56 and 0-19 mg L −1 nitrogen and phosphorus, respectively, the response parameters being specific growth rate , CO 2 uptake rate R c and %nutrient removal. RESULTS: Over 10 days the biomass concentration reached almost 3 g L −1 for C c,g of 5% CO 2 , with corresponding values of 0.74 g L −1 day −1 and 1.17 day −1 for R c and , respectively, and 100% nutrient (N and P) removals. At 22% CO 2 the R c and decreased by around an order of magnitude, and nutrient removal also decreased to 79% and 50% for N and P, respectively. CONCLUSION: Optimum values 5% CO 2 , 100 E and 22 ∘ C were identified for C c,g , I and T, respectively, with and R c reaching 1.53 day −1 and 1 g L −1 day −1 , respectively, along with associated nutrient removal of 100%. Regression analysis indicated a good fit between experimental and model data.

Enhancement of CO2 biofixation and lipid production by Chlorella vulgaris using coloured polypropylene film

“…Recorded growth rates were higher than those of Kim et al [14], who reported X and C d values of 0.78 g L -1 and 17.5× 10 6 cells mL -1 respectively using LED lighting providing a wavelength band of 400-460 nm and an I of 100 µE m -2 s -1 . A 78% reduction in incident I to approximately 55 µE m -2 s -1 was recorded for CT B , decreasing the level of photosynthesis active radiation (PAR) and thus photosynthesis activity accordingly [24]. At lower I up to 80% of the theoretical maximum photosynthesis efficiency (PE) can be achieved [4][5][6][7], although a reduced I value results in a proportionally lower biomass production.…”

“…CT w provided a light wavelength range of 750-350 nm, with a peak of 413 nm, and reduced the control I (U) of 250 µE m -2 s -1 by about 50%. Non-photochemical quenching (NPQ) is known to arise if the rate of photo-inhibition exceeds the rate of repair, resulting in a large proportion of the captured light being dissipated at high I [24]. The lower X and µ values obtained for U suggest that growth is reduced at longer random wavelengths [10].…”

Impact of CO2 concentration and ambient conditions on microalgal growth and nutrient removal from wastewater by a photobioreactor

“…Light intensities providing a reasonable specific growth rate (μ) and biomass productivity (P bio ) reported for Chlorella vulgaris (C.V), the most commonly studied strain, varied widely at 40-1240 μE.m −2 .s −1 (Abou -Shanab et al, 2013;Abreu et al, 2012;AlMomani and Örmeci, 2016;Lam and Lee, 2013;Li et al, 2003;Marbelia et al, 2014;Ruiz-Martinez et al, 2012;Znad et al, 2018a). According to the C.V literature at an optimum light intensity of 100 μE.m -2 .s -1 and 5% C c,g , the associated maximum μ, and P bio values are around 1.17 d -1 and 0.74 g.L -1 .d -1 respectively at a temperature of 24°C for a batch cultivation process (Abreu et al, 2012;Al Ketife et al, 2017;Li et al, 2013). This compares to a reasonable growth rate at a narrower range of 68-400 μE.m −2 .s −1 for SP.PL (Ho et al, 2018;Kumari et al, 2014;Liu et al, 2018;Singh et al, 2016;Xue et al, 2011;Yuan et al, 2011;Zhou et al, 2017b).…”

“…There has been increasing focus on the use of microalgal culture technology (MCT) for both bio-fixation of CO 2 from flue gases (Adamczyk et al, 2016;Al Ketife et al, 2017;Almomani et al, 2017;Razzak et al, 2013;Toledo-Cervantes et al, 2018;Zhou et al, 2017a;Zhou et al, 2017b) and removal of nutrients from wastewater (AlMomani and Örmeci, 2016;Arbib et al, 2017;Gao et al, 2018;Sutherland et al, 2014;Sutherland et al, 2015;Zhou et al, 2017a;Znad et al, 2018a), with the technical and cost implications of the combined process also recently considered (Judd et al, 2017;Kasprzyk and Gajewska, 2019). The use of biology for carbon capture and direct generation of useful products, predominantly biofuel (Bai and Acharya, 2017;de Godos et al, 2014;Fernández et al, 2012;Kassim and Meng, 2017;Singh et al, 2016;Zhang et al, 2011), obviates the energy-intensive solvent regeneration step of the conventional absorption process for carbon capture (Hammond and Spargo, 2014;Wang et al, 2017;Wilberforce et al, 2019).…”

“…However, the economic viability of the process is highly sensitive to the rate of CO 2 fixation, in CO 2 mass per day captured per unit of volume of biomass, and the corresponding algal growth rate. Published works on the use of MTC have thus far predominantly been at the bench scale, for short time and using artificial light during cultivation periods (Abou-Shanab et al, 2013;Abreu et al, 2012;Al Ketife et al, 2017;AlMomani and Örmeci, 2016;Marbelia et al, 2014;Znad et al, 2018a). Published works that deal with algae growth under natural solar irradiation are limited and in most cases deal with carbon capture (Lam and Lee, 2014;Li et al, 2013) or nutrient removals (Sutherland et al, 2014;Zhimiao et al, 2016) individually, the latter mainly relating to biofuel production (Do et al, 2018).…”