Pilot-scale crossflow ultrafiltration of four different cell-sized marine microalgae to assess the ultrafiltration performance and energy requirements

Four marine microalgae (e.g., Tetraselmis, Picochlorum, Dunaliella, and Synechococcus) with different cell sizes were harvested using pilot-scale ultrafiltration. Average permeate fluxes were 16.75, 19, 25.35, and 33.75 L/m2h at 60 min for Synechococcus, Dunaliella, Picochlorum, and Tetraselmis, respectively. The concentrating factors for Synechococcus, Picochlorum, Dunaliella, and Tetraselmis were 46.6, 42, 39.2, and 39.5, respectively. The highest and lowest microalgal biomass retention was 47.1 and 41.7% for Tetraselmis and Synechococcus, respectively. Due to higher microalgal biomass retention, initial crossflow velocities of 0.16 to 0.18 m/s were reduced to 0.02 to 0.05 m/s for Tetraselmis and Dunaliella sp. The total harvesting energy requirement by membrane and centrifuge was 16.44 - 28.48 GJ/tonne biomass; the smaller the cell size, the lower the energy requirement. The optimum biomass concentrating factor by the membrane filtration process also depended on size; for optimum total energy requirement, tangential flow filtration (TFF) could concentrate a smaller strain more than a larger strain.The authors would like to acknowledge the support of the Qatar National Research Fund (QNRF, a member of Qatar Foundation) for providing funding under grant MME01-0910-190028 for this study. Further, the authors also acknowledge the support of Qatar Fertilizer Company (QAFCO) for providing waste urea fertilizers.Scopu

Aquaculture from inland fish cultivation to wastewater treatment: a review

The aquaculture industry is rapidly developing, generating a high amount of wastewater. Inland aquaculture effluents contain nutrients and other substances that can cause eutrophication and the emergence of resistive organisms if released into the environment. Hence, aquaculture wastewater should be treated appropriately for reuse in different applications or safely released into the environment, promoting a sustainable industry and a circular economy. The current review provides insight into aquaculture wastewater generation, constituents, and treatment through various technologies. This study’s treatment technologies could be classified as physical, chemical, and biological. SWOT analysis was conducted on each technology to provide an in-depth understanding of the advantages and drawbacks. Suggestions were also stated to shed light on the importance of a sustainable aquaculture industry and the means to transition toward a circular economy. Graphical abstract: [Figure not available: see fulltext.].This work was funded by Qatar National Research Fund (QNRF) - grant no. (GSRA8-L-2-0509-21037)

Microalgal bioremediation of brackish aquaculture wastewater

Rapid aquaculture industry development contributed to a major increase in aquaculture wastewater generation. In the context of a circular economy, aquaculture wastewater treatment should simultaneously recover nutrients from the wastewater. Among many treatment methods, bioremediation using microalgae could be a cost-effective and environmentally friendly system that can be applied to treat aquaculture wastewater and simultaneously produce high-value microalgal biomass. This study explored the feasibility of treating brackish wastewater (0.8 % NaCl) generated from a Qatari commercial tilapia farm by microalgae. At first, 10 strains were grown using wastewater from the local farm in an indoor experiment. Based on nitrogen assimilation, biomass yield, biomass quality, and ease of harvesting, 4 candidate strains (Haematococcus sp., Neochloris sp., Monoraphidium sp., and Nostoc sp.) were shortlisted for outdoor growth experiments. Although Nostoc sp. could not grow outdoor in the wastewater, the other three strains were able to assimilate at least 70.5 % of the total nitrogen in the wastewater. Haematococcus sp. and Neochloris sp. could be harvested using self-settling, whereas Monoraphidium required an energy-intensive tangential flow filtration membrane process. Hence, the overall energy requirement for bioremediation, including biomass dewatering, for Haematococcus sp., Neochloris sp., and Monoraphidium sp. were determined as 0.64, 0.78, and 5.68 MJ/m3, respectively. Neochloris sp. had almost twice the biomass yield compared to Haematococcus sp. - suggesting that Neochloris sp. could be a potential candidate for aquaculture wastewater treatment. 2023 Elsevier B.V.The authors would like to acknowledge the support of the Qatar National Research Fund (QNRF, a member of Qatar Foundation) for providing the funding (under grant GSRA8-L-2-0509-21037 ) for this study.Scopu