High-Density Microalgae Cultivation in Open Thin-Layer Cascade Photobioreactors with Water Recycling

Abstract

(1) Background: Recycling of water and non-converted nutrients is considered to be a necessity for an economically viable production of microalgal biomass as a renewable feedstock. However, medium recycling might also have a negative impact on algal growth and productivity due to the accumulation of growth-inhibiting substances. (2) Methods: Consecutive batch processes with repeated water recycling after harvesting of algal biomass were performed with the saline microalga Microchloropsis salina in open thin-layer cascade photobioreactors operated at a physically simulated Mediterranean summer climate. The impact of water recycling on culture performance was studied and the composition of the recycled water was analyzed. (3) Results: Water recycling had no adverse effect on microalgal growth and biomass productivity (14.9−21.3 g m−2 d−1) if all necessary nutrients were regularly replenished and KNO3 was replaced by urea as the nitrogen source to prevent the accumulation of K+ ions. Dissolved organic carbon accumulated in recycled water, probably promoting mixotrophic growth. (4) Conclusion: This study shows that repeated recycling of water is feasible even in high-density cultivation processes with M. salina of more than 30 g L−1 cell dry weight, increasing culture performance while reducing nutrient consumption and circumventing wastewater production.

Developing food waste biorefinery: using optimized inclined thin layer pond to overcome constraints of microalgal biomass production on food waste digestate

“…However, productivities obtained for the ORWP in this study are significantly higher than reported for anaerobic digestate of piggery waste effluent of similar turbidity with productivities of 6.2 g m −2 day −1 and 0.024 g L −1 day −1 (Nwoba et al 2016; Raeisossadati et al 2019) and similar to that reported by Serejo et al (2015) at 11.8 g m −2 day −1 using diluted vinasse digestate of lower turbidity. The productivities reported for the ITLP in this study are significantly higher than reported for a lot of the works done on ITLPs in clear synthetic media ranging from 9 -23 g m −2 day −1 (Doucha et al 2005;Silva Benavides et al 2017;Grivalský et al 2019;Schadler et al 2020). Also, productivities of the ITLP here are significantly higher than we reported in our first trial of this system on high turbidity anaerobic digestate of piggery effluent, and our depth optimization work using ADF ranging from 2 -21 g m −2 day −1 (Raeisossadati et al 2019;Chuka-ogwude et al 2021).…”

Overview and Challenges of Large-Scale Cultivation of Photosynthetic Microalgae and Cyanobacteria

“…Moreover, biomass harvesting and concentration are extremely costly due to these low algal cell densities [ 38 ]. There are systems, such as thin-layer cascade photobioreactors, that can reach a biomass density of more than 30 g/L [ 39 ]. However, these high-density systems face other challenges, such as light limitations.…”

Sustainable production of microalgae biomass for biofuel and chemicals through recycling of water and nutrient within the biorefinery context: A review

“…Yellow and yellow‐orange color of growth media during water recycling reduce the light penetration in microalgae culture in recycled water (Das, Thaher, et al, 2019; Rodolfi et al, 2003). Xanthophyll accumulation is believed to be responsible for this change in color (Schädler et al, 2020).…”

“…Water was successfully recycled for eight batches when KNO 3 was replaced with urea and sulfate was supplied. Higher DOC (0.28-1.94 mg/L) with subsequent number of recycle was believed to promote the mixotrophic growth (Schädler et al, 2020). Scenedesmus almeriensis growth was inhibited in recycled water at low CO 2 supply and limited availability of nutrients (Molino et al, 2020).…”