Search Results (26)

Transitioning from conventional wastewater treatment to circular wastewater management requires novel technologies that enable resource recovery, energy efficiency, and resilience under variable conditions. Within the NAMOR project, hybrid microalgae–bacteria Membrane PhotoBioReactors (MPBRs) are assessed as a sustainable solution for decentralized wastewater treatment and reuse. This study focuses on screening and optimizing mixed microalgae–bacterial consortia to treat municipal wastewater streams in the Mediterranean region, with an emphasis on achieving high nutrient removal, biomass productivity and robustness. A diverse set of strains will be evaluated under controlled temperature, light and nutrient regimes to enhance the symbiotic synergy between photosynthetic microalgae and heterotrophic bacteria, while minimizing aeration demand. Based on these results, a pilot demo in Lagadas, Greece, will integrate the optimized consortia into a moving-bed PBR equipped with polymeric carriers and membrane filtration for advanced effluent polishing, intended to produce reclaimed water for irrigation and biomass for valorisation into fertilizers or biogas. Full article

Microalgae dewatering is a major bottleneck for the industrial deployment of microalgal biorefineries due to its high energy and water requirements. This study investigates the optimization and modeling of an industrial-scale aerated submerged ultrafiltration (UF) system for microalgae pre-concentration under real operating conditions. A submerged hollow-fibre Koch LE8 UF module (348 m², 0.03 µm) was operated directly on Chlorella sp. cultures produced in an 800 m² outdoor photobioreactor. Filtration–backwash cycles were experimentally optimized, identifying an optimal sequence of 8.33 min filtration and 1 min backwash, enabling up to 80% net water removal per cycle while maintaining fouling largely reversible under the tested conditions. Long-term trials (6–7 h) achieved stable concentration factors of 3.6–4.3 with complete biomass retention and sustained permeate flux despite increasing solids concentration. Reuse of permeate for backwashing eliminated freshwater consumption without compromising membrane performance. A dynamic resistance-in-series (RIS) model, incorporating mass balances and an empirically derived concentration-polarisation resistance, accurately reproduced permeate flux and biomass concentration dynamics (R² > 0.83) using a single fitted parameter. The validated model was further applied as a digital twin to simulate operation up to the theoretical concentration factor of 10, quantifying the associated energy and water demands. The system exhibited a low estimated specific energy consumption of 1.25 kWh·kg⁻¹ biomass and a water demand of 0.30 m³·kg⁻¹, demonstrating that aerated submerged UF is a robust, scalable, and energy-efficient solution for industrial microalgae harvesting. Full article

The biological performance and carbon dioxide (CO₂) flux of the novel and emerging concept of a membrane carbonated microalgal biofilm photobioreactor (MC-MBPBR) for wastewater treatment were investigated using mathematical modelling in conjunction with the finite-difference method. A set of differential equations was established to model the performance of an MC-MBPBR. The impacts of CO₂ partial pressure, wastewater characteristics, and biofilm thickness on the concentration profiles and fluxes of CO₂ and nutrients (N and P) to the biofilm of the MC-MBPBR were systematically studied. The modelling results showed profound impacts of these parameters on process efficiency (CO₂ transfer and N and P removals) and the existence of an optimal biofilm thickness for maximum CO₂, N, and P fluxes into the biofilm. Penetration of CO₂ through the biofilm into the bulk water phase might occur under certain conditions. An increase in gaseous CO₂ and increased influent N and P concentrations led to higher CO₂, N, and P fluxes. The optimal biofilm thickness varied with the change in wastewater characteristics and gaseous CO₂ concentration. The modelling results were in relatively good agreement with experimental results from the literature. The proposed mathematical models can be used as a powerful tool to optimize the design and operation of the novel MC-MBPBR for wastewater treatment and microalgae cultivation. Full article

In accordance with growing environmental pressures and the demand for sustainable industrial practices, membrane technologies have emerged as key enablers for increasing efficiency, reducing emissions, and supporting circular processes across multiple sectors. This review focuses on the integration among microalgae-based systems, offering innovative and sustainable solutions for biomass production, carbon capture, and industrial wastewater treatment. In cultivation, membrane photobioreactors (MPBRs) have demonstrated biomass productivity up to nine times greater than that of conventional systems and significant reductions in water (above 75%) and energy (approximately 0.75 kWh/m³) footprints. For carbon capture, hollow fiber membranes and hybrid configurations increase CO₂ transfer rates by up to 300%, achieving utilization efficiencies above 85%. Coupling membrane systems with industrial effluents has enabled nutrient removal efficiencies of up to 97% for nitrogen and 93% for phosphorus, contributing to environmental remediation and resource recovery. This review also highlights recent innovations, such as self-forming dynamic membranes, magnetically induced vibration systems, antifouling surface modifications, and advanced control strategies that optimize process performance and energy use. These advancements position membrane-based microalgae systems as promising platforms for carbon-neutral biorefineries and sustainable industrial operations, particularly in the oil and gas, mining, and environmental technology sectors, which are aligned with global climate goals and the UN Sustainable Development Goals (SDGs). Full article

Microalgae are small, single-celled, or simple multicellular organisms that contain Chlorophyll a, allowing them to efficiently convert CO₂ and water into organic matter through photosynthesis. They are valuable in producing a range of products such as biofuels, food, pharmaceuticals, and cosmetics, making them economically and environmentally significant. Currently, CO₂ is delivered to microalgae cultivation systems mainly through aeration with CO₂-enriched gases. However, this method demonstrates limited CO₂ absorption efficiency (13–20%), which reduces carbon utilization effectiveness and significantly increases carbon-source expenditure. To overcome these challenges, innovative CO₂ supplementation technologies have been introduced, raising CO₂ utilization rates to over 50%, accelerating microalgae growth, and reducing cultivation costs. This review first categorizes CO₂ supplementation technologies used in photobioreactor systems, focusing on different mechanisms for enhancing CO₂ mass transfer. It then evaluates the effectiveness of these technologies and explores their potential for scaling up. Among these strategies, membrane-based CO₂ delivery systems and the incorporation of CO₂ absorption enhancers have shown the highest efficiency in boosting CO₂ mass transfer and microalgae productivity. Future efforts should focus on integrating these methods into large-scale photobioreactor systems to optimize cost-effective, sustainable production. Full article

The production of hydrogen via dark fermentation generates carbon dioxide, which needs to be separated and re-utilized to minimize the environmental impact. This research investigates the potential of utilizing algae for carbon dioxide sequestration in hydrogen production via dark fermentation. However, algae alone cannot fully use all the carbon dioxide produced, necessitating the implementation of a multistage separation process. This study proposes a purification approach that integrates membrane separation with a photobioreactor in a multistage design layout. Mathematical models were used to simulate the performance efficiency of multistage design layout using MATLAB 2015b (Version 9.3). A detailed parametric analysis and the key parameters influencing the separation efficiency were conducted for each stage. This study explores how reactor geometry, operational dynamics (such as gas transfer rates and light availability), and algae growth impact both CO₂ removal and hydrogen purity. An optimization strategy was used to obtain the set of optimal operating and design parameters. Our results have shown a significant improvement in hydrogen purity, increasing from 55% to 99% using this multistage separation process, while CO₂ removal efficiency rose from 35% to 85% over a week. This study highlights the potential of combining membrane technology with photobioreactors to enhance hydrogen purification, offering a more sustainable and efficient solution for hydrogen production. Full article

This study presents a theoretical and mathematical analysis and modelling of the emerging microalgal membrane photobioreactors (M-MPBRs) for wastewater treatment. A set of mathematical models was developed to predict the biological performances of M-MPBRs. The model takes into account the effects of hydraulic retention time (HRT), solid retention time (SRT), and the N/P ratio of influent on the biological performance of M-MPBRs, such as microalgal biomass production and nutrient (N and P) removals. The model was calibrated and validated using experimental data from the literature. This modelling study explained that prolonged SRT could promote biomass production and nutrient removal, while prolonging HRT exhibited a negative effect. Furthermore, biomass production could be improved by augmenting nutrient loading, and nutrient removal would be limited under insufficient conditions. The modelling results demonstrated that the best performance was achieved at HRT = 1 d and SRT = 40 d for typical municipal wastewater with an influent N concentration = 40 mg/L. The modelling results are in good agreement with the experimental results from the literature. The findings suggest that the proposed models can be used as a powerful mathematical tool to optimize these parameters to improve the removal of nutrients (N and P), as well as the productivity of biomass in M-MPBRs. This study provides new insights into the use of mathematical models for the optimal design and operation of the emerging M-MPBRs for sustainable wastewater treatment. Full article

With the increasing global concern regarding climate change and the need to reduce greenhouse gas emissions, carbon capture and utilization (CCU) technologies are seen as one of the primary steps toward large-scale decarbonization prospects. In this context, a thorough assessment of each CCU pathway is required from both the techno-economic and environmental perspectives. In this work, the potential of carbon biofixation through microalgae cultivation is evaluated through the preliminary technical design and calculation of plant economics in the case of the Turakurgan natural gas-fired combined cycle power plant located in the eastern part of Uzbekistan. The primary data used in this study are obtained from the open access project report of the targeted power station, along with recently published literature sources. According to the results, although the purchase and installation costs of photobioreactors require significant investments in the capital costs, the technology would still be cost competitive as long as there is a carbon tax imposition of around USD 50 per ton of CO₂ emissions. However, CO₂ biofixation can be relatively more suitable compared to benchmark absorption, particularly in low-CO₂-concentration conditions. Future research will involve a more comprehensive examination of CO₂-based microalgae cultivation and its comparison with chemical absorption and membrane-assisted separation techniques. Full article

Inspired by the vast potential of microalgae in the bioeconomy and the numerous applications and benefits associated with their cultivation, a multitude of pilot- and industrial-scale microalgae production systems have been developed in recent years. Both open and closed cultivation systems have been successfully utilized, with closed photo-bioreactors (PBRs) emerging as the most versatile option for various applications and products, enabling the implementation of advanced optimization strategies. Therefore, this short review provides a comprehensive overview of the different PBR configurations and their recent applications, primarily in large-scale but also in pilot- and laboratory-scale microalgae cultivation. A detailed discussion of the advantages, limitations, specific applications and recent advancements of each type of PBR is presented to aid researchers, engineers and industry stakeholders in selecting the most suitable PBR design for their specific goals and constraints. Moreover, this review highlights the major challenges impeding the full commercialization of microalgal products and forecasts future trends in the microalgae-based industry. The diverse potential applications of microalgae in various sectors, including biofuels, nutraceuticals, pharmaceuticals, agriculture and environmental remediation, underscore the versatility and significance of the relevant cultivation technologies. By offering valuable insights into the future commercial scale and trends of microalgal biotechnology, this work sheds light on the challenges and opportunities facing this burgeoning industry. Full article

A cross-flow ultrafiltration harvesting system for a pre-concentrated microalgae culture was tested in an innovative anaerobic-based WRRF. The microalgae culture was cultivated in a membrane photobioreactor fed with effluent from an anaerobic membrane bioreactor treating sewage. These harvested microalgae biomasses were then anaerobically co-digested with primary and secondary sludge from the water line. Depending on the needs of this anaerobic co-digestion, the filtration harvesting process was evaluated intermittently over a period of 212 days for different operating conditions, mainly the total amount of microalgae biomass harvested and the desired final total solids concentration (up to 15.9 g·L⁻¹ with an average of 9.7 g·L⁻¹). Concentration ratios of 15–27 were obtained with average transmembrane fluxes ranging from 5 to 28 L·m⁻²·h⁻¹. Regarding membrane cleaning, both backflushing and chemical cleaning resulted in transmembrane flux recoveries that were, on average, 21% higher than those achieved with backflushing alone. The carbon footprint assessment shows promising results, as the GHG emissions associated with the cross-flow ultrafiltration harvesting process could be less than the emissions savings associated with the energy recovered from biogas production from the anaerobic valorisation of the harvested microalgae. Full article

This research lays a foundation for optimised membrane photobioreactor performance and introduces novel control parameters crucial for advancing microalgae cultivation techniques and promoting environmental sustainability. Particularly, this study presents an innovative solids retention time (SRT) controller designed for a pilot-scale membrane photobioreactor. Employing a fuzzy-logic knowledge-based approach, this controller uses the first derivative of pH data dynamics (pH′) as an input variable, directly correlated with nitrogen recovery rate and biomass productivity when normalised by average light irradiance (I2). Through a feedback mechanism, it regulates daily SRT variations, ensuring stable reactor operation, optimal volatile suspended solids concentration, efficient nitrogen removal, and enhanced biomass productivity. Normalised nitrogen recovery rate, considering solar light irradiance and volatile suspended solids concentration, increased by 51% compared to previous studies employing fixed SRT and hydraulic retention time (HRT). Combining this SRT controller with a previously studied HRT controller could potentially amplify biomass productivity efficiency. In addition, controlling or not controlling the HRT and SRT are assessed in terms of filtration performance and GHG emissions. Finally, a new dissolved-oxygen-based parameter shows promise for continuous microalgae culture control. Full article

This work shows the potential of a new way of co-treatment of domestic wastewater (DWW) and a liquid stream coming from the thermal hydrolysis of the organic fraction of municipal solid waste (OFMSW) mediated by a mixed culture of purple phototrophic bacteria (PPB) capable of assimilating carbon and nutrients from the medium. The biological system is an open single-step process operated under microaerophilic conditions at an oxidative reduction potential (ORP) < 0 mV with a photoperiod of 12/24 h and fed during the light stage only so the results can be extrapolated to outdoor open pond operations by monitoring the ORP. The effluent mostly complies with the discharge values of the Spanish legislation in COD and p-values (<125 mg/L; <2 mg/L), respectively, and punctually on values in N (<15 mg/L). Applying an HRT of 3 d and a ratio of 100:7 (COD:N), the presence of PPB in the mixed culture surpassed 50% of 16S rRNA gene copies, removing 78% of COD, 53% of N, and 66% of P. Furthermore, by increasing the HRT to 5 d, removal efficiencies of 83% of COD, 65% of N, and 91% of P were achieved. In addition, the reactors were further operated in a membrane bioreactor, thus separating the HRT from the SRT to increase the specific loading rate. Very satisfactory removal efficiencies were achieved by applying an HRT and SRT of 2.3 and 3 d, respectively: 84% of COD, 49% of N, and 93% of P despite the low presence of PPB due to more oxidative conditions, which step-by-step re-colonized the mixed culture until reaching >20% of 16S rRNA gene copies after 49 d of operation. These results open the door to scaling up the process in open photobioreactors capable of treating urban wastewater and municipal solid waste in a single stage and under microaerophilic conditions by controlling the ORP of the system. Full article

This work presents recent developments of algal bioreactors used for CO₂ removal and the factors affecting the reactor performance. The main focus of the study is on light intensity and photoperiods. The role of algae in CO₂ removal, types of algal species used in bioreactors and conventional types of bioreactors including tubular bioreactor, vertical airlift reactor, bubble column reactor, flat panel or plate reactor, stirred tank reactor and specific type bioreactors such as hollow fibre membrane and disk photobioreactors etc. are discussed in details with respect to utilization of light. The effects of light intensity, light incident, photoinhibition, light provision arrangements and photoperiod on the performance of algal bioreactors for CO₂ removal are also discussed. Efficient operation of algal photobioreactors cannot be achieved without the improvement in the utilization of incident light intensity and photoperiods. The readers may find this article has a much broader significance as algae is not only limited to removal or sequestration of CO₂ but also it is used in a number of commercial applications including in energy (biofuel), nutritional and food sectors. Full article

Polyphenols and their intermediate metabolites are natural compounds that are spread worldwide. Polyphenols are antioxidant agents beneficial for human health, but exposure to some of these compounds can be harmful to humans and the environment. A number of industries produce and discharge polyphenols in water effluents. These emissions pose serious environmental issues, causing the pollution of surface or groundwater (which are used to provide drinking water) or harming wildlife in the receiving ecosystems. The treatment of high-polyphenol-content waters is mandatory for many industries. Nowadays, biotechnological approaches are gaining relevance for their low footprint, high efficiency, low cost, and versatility in pollutant removal. Biotreatments exploit the diversity of microbial metabolisms in relation to the different characteristics of the polluted water, modifying the design and the operational conditions of the technologies. Microbial metabolic features have been used for full or partial polyphenol degradation since several decades ago. Nowadays, the comprehensive use of biotreatments combined with physical-chemical treatments has enhanced the removal rates to provide safe and high-quality effluents. In this review, the evolution of the biotechnological processes for treating high-polyphenol-content water is described. A particular emphasis is given to providing a general concept, indicating which bioprocess might be adopted considering the water composition and the economic/environmental requirements. The use of effective technologies for environmental phenol removal could help in reducing/avoiding the detrimental effects of these chemicals. In addition, some of them could be employed for the recovery of beneficial ones. Full article

The treatment of nutrients and organic contaminants in wastewater using microalgae has drawn significant interest thanks to its advantages of environmental friendliness, low cost, CO₂ emission reduction, and recycling of valuable biomass. Among other algae species, Chlorella sp. showed good vitality, simplicity in cultivation, and high nutrient accumulation in harsh conditions of wastewater. In this study, Chlorella vulgaris was inoculated in a membrane photobioreactor (MPBR) with piggery digestate to investigate the C. vulgaris growth rate and the removal efficiency of nutrients and chemical oxygen demand (COD). The results indicated that the cultivation of C. vulgaris in an MPBR system exhibited continuous and simultaneous removal of NH₄⁺, PO₄³⁻, and COD from two-fold diluted piggery wastewater. Both the algae growth rate and nutrient removal depended on the liquid hydraulic retention time in the MPBR. The highest removal efficiency of NH₄⁺ (74.55%), PO₄³⁻ (70.20%), and COD (65.85%) was obtained in the longest HRT of 5 days with the highest microalgae biomass concentration of around 1.1 g/L. The algae washout phenomenon was negligible in the continuous cultivation in the MPBR system. Compared to the cultivation in batch mode, the MPBR could achieve a similar algae growth rate and treatment efficiency with a much shorter hydraulic retention time. Full article