Exploring microalgae immobilization and advanced photo bioreactors for enhanced wastewater treatment efficiency

This study uses domestic sewage to dilute landfill leachate, conserve freshwater resources, and supplement phosphorus. The proportion of landfill leachate is increased, and the microalgae photosynthesis is coupled with the SBR system to process the diluted leachate. A bacterial and algal symbiotic photobioreactor (PBR) was constructed to improve the efficiency of sewage treatment by optimizing parameters (aeration rate, light) for investigating the synergy of microalgae and bacteria, and the effect of treating Landfill leachate. The long-term operational impact of the reactor under two different inoculation conditions was investigated: one group was inoculated only with activated sludge and controlled light to promote the spontaneous growth of microalgae (Rc), and the other group was inoculated with activated sludge and Chlorella (Rs). The highest pollutant removal efficiencies were observed in 4 : 1 (microalgae/sludge) cultures, with COD at 96.5%, NH4+-N at 97.4%, and PO43−-P at 92.3%. Synergistic growth of bacteria and microalgae was observed, with a total biomass concentration of 2.32 g L−1. Pollutant removal effect was best at an aeration rate of 0.6 L min−1, with removal efficiencies of 72.7% for COD, 78.3% for NH4+-N, and 62.5% for PO43−-P. A low-aeration method, mechanical aeration and microalgae photosynthesis cooperated to reduce operating costs. When light intensity was 108 µmol m−2 s−1, pollutant removal efficiencies of COD 82.6%, NH4+-N 84.9% and PO43−-P 75.9% were achieved. Treatment effect of the Rs system: average volume load of 36.22 mg per L per h COD, 8.53 mg per L per h NH4+-N, 0.44 mg per L per h PO43−-P. This provides new ideas for achieving high-efficiency, low-consumption green biological treatment of landfill leachate.

Long-term phycoremediation of hydroponic drainwater in a pilot-scale turbidostat.

This study examines the influence of photobioreactor (PBR) configuration on the cultivation performance of Chlorococcum sp. using aquaculture wastewater as the growth medium. Four systems were compared: horizontal without aeration (H-Plain), horizontal with aeration (H-Aerated), vertical with aeration (V-Aerated), and vertical with aeration and red LED illumination (V-LED). Over 14 days, the V-LED system achieved the highest biomass concentration (0.50 g L-1) and volumetric productivity (0.063 g L-1 day-1), accompanied by nitrate and phosphate removals of 94% and 55.6%, respectively. Statistical analysis (ANOVA, p < 0.05) confirmed significant differences among configurations, demonstrating that light quality and aeration act synergistically to enhance growth and nutrient assimilation. While aeration improved CO2 transfer and mixing, it was insufficient without adequate photon delivery. Conversely, red LED illumination mitigated photolimitation in vertical systems, promoting efficient photosynthesis and nutrient uptake. Energy assessment revealed that V-LED offered the highest productivity in expense of power input (1.08 kWh day-1). These findings highlight the critical role of integrated PBR design, emphasizing that optimal combinations of geometry, aeration, and spectral lighting as keys to achieving high biomass yields and efficient nutrient removal in sustainable microalgae-based wastewater treatment systems.

Abstract - This study evaluates the visual perception of traditional soil-based green facades compared to modern algae-integrated photobioreactor (PBR) systems within the context of urban Information Technology (IT) parks. While architectural discourse extensively covers the environmental performance of living systems, the aesthetic implications of biological decay remain under-researched. High-prestige corporate environments demand strict visual order, which traditional botanical systems often fail to maintain due to natural life cycles and climatic stress. This research employs a qualitative, secondary data-driven methodology, using a Grid-Based Observation technique to analyse two primary case studies: the Solaris building in Singapore (traditional facade) and the BIQ House in Hamburg (algae-integrated facade). The analysis compares these systems across five visual variables: texture, boundary, dilapidation, regulation, and transparency. The results show that traditional green walls carry high aesthetic risk because patchy biological death communicates institutional neglect. Conversely, algae systems utilize modular containment, allowing observers to perceive the biological material as a dynamic, high-tech building component. The study identifies two primary psychological mechanisms—the "Slime vs. Nature Trigger" and the "Modularity Trigger"—that determine public acceptance. The findings suggest that for corporate environments, modular algae systems offer a more reliable and professional visual identity than traditional soil-based systems. Keywords: Green Facades, Algae-Integrated Systems, Photobioreactors, Visual Perception, Corporate Architecture, Biophilic Design.

Microalgae Production and Utilization as an Alternative Protein Source in Poultry Nutrition: A Comprehensive Review

Sphagnum founder material used for the restoration of rewetted bogs and installation of Sphagnum paludiculture areas can be provided by submerged cultivation in photobioreactors (PBRs). This study represents the first investigation of the photoautotrophic cultivation of Sphagnum palustre L. in different PBRs at laboratory scale. One commercially available reactor - a 60 L flat-panel bioreactor - along with three self-developed PBRs - a 3 L wave-bag bioreactor, a 10 L bottle bioreactor and a 50 L tank bioreactor - were used. Using an inorganic Sphagnum medium , artificial light, and CO 2 enriched air, the moss morphology, biomass productivity, specific power input and specific light availability were determined. The results suggest that the wave-bag bioreactor is not suitable for Sphagnum cultivation, while for the bubble columns, a minimum superficial gas velocity u g and specific power input ( P G /V L ), as well as specific light intensity ( I spec ), are decisive process parameters. Submerse, photoautotrophic production of Sphagnum palustre L. in a bubble column PBR is highly feasible (0.14 ± 0.03 g L −1 d −1 ), and this reactor type shows potential for Sphagnum founder material production for peatland rewetting due to its simplicity and low pneumatic power input (9.9 W m −3 ). Investigation on growth of peat moss Sphagnum palustre L. in different photobioreactors • Four photobioreactors for the production of Sphagnum palustre • 0.14 ± 0.03 g L −1 d −1 dry biomass productivity under photo-autotrophic condition • Power input, gas transfer, light availability and photoconversion efficiency data • Comparison of Sphagnum palustre morphologies from different photobioreactors

ABSTRACT Photosynthetic bacteria (PSB) present a sustainable approach for wastewater treatment by converting organic pollutants into valuable biomass using solar energy. However, conventional photobioreactor (PBR) fail to optimize PSB’s photoheterotrophic metabolism under natural illumination. This study bridges critical gaps by systematically evaluating four pilot-scale PBRs (raceway pond, cylindrical, flat-panel, tubular) for PSB-driven sugar wastewater treatment to optimize reactor geometry, light provision, and resource recovery. Results showed that tubular PBRs performed best in biomass yield and daily productivity at batch mode. In outdoor pilot semi-batch operation, the tubular PBR group showed the highest biomass production (3488.4 mg/L) and COD removal (99.0%). The highest carbon recovery ratio (31.5-51.2%) was also obtained in the tubular PBR group, surpassing flat-panel and cylindrical designs by 12.6-118.6%. These findings highlight the potential of tubular PBRs for scalable, light-driven wastewater treatment and establish design principles to balance organic load, light penetration, and metabolic efficiency under natural conditions. This study lays the foundation for the application of photosynthetic bacteria in industrial-scale wastewater resource recovery and holds great significance for advancing sustainable biotechnology.

Chlorella, a genus of green algae, exhibits rapid growth and high lipid accumulation as self-defense against adverse conditions. This study aimed to identify optimal conditions for the growth and lipid accumulation of Chlorella sorokiniana in a two-stage process for biofuel production. In the first stage, C. sorokiniana grew best in BG-11 medium with 3 g L−1 NaNO3 and 10 g L−1 glucose, achieving highest dry cell weight (DCW) of 2.87 ± 0.35 g L−1 and lipid content of 23.25 ± 0.15 % DCW after 4 d of cultivation. The second stage cultivation reached a C. sorokiniana biomass concentration of 2.18 ± 0.08 g L−1 and lipid content of 40.78 ± 0.61 % DCW with the addition of 30 g L−1 NaCl, 6 g L−1 NaHCO3 and a light intensity of 150 µmol m−2 s−1 after 2 d cultivation in 1 L Erlenmeyer flasks. C. sorokiniana cultured in 20 L, 50 L, and 300 L closed photobioreactors (PBRs) achieved DCW ranging from 1.35 ± 0.06 to 1.94 ± 0.04 g L−1 and lipid contents from 33.21 ± 0.67 % to 38.48 ± 0.76 % DCW, respectively, after 4 d in the first and 2 d in the second stage under optimal conditions of cultivation. Fatty acids profile, including C16:0, C18:2, and C18:3, indicated high-quality biodiesel, meeting 4-5 out of 5 parameters according to US and European standards. Therefore, C. sorokiniana is a potential feedstock for biodiesel.

Microalgae photobioreactors (PBRs) are promising building-integrated biotechnologies for carbon capture and biomass production; however, their high energy requirements for artificial lighting remain a significant energy barrier in cold climates. This study developed an integrated spectral–optical energy modeling framework to evaluate two PBR deployment strategies in State College, PA: rooftop daylight-exposed integration and basement installation with solar-assisted lighting. Results show that fiber-optic daylighting can supply a substantial fraction of photosynthetically useful light without introducing additional internal heat loads, while photovoltaics sized at approximately 0.40–0.55 kWDC per reactor can offset the annual PBR lighting energy use when sufficient roof area is available. Whole-building energy simulations further reveal that rooftop PBR integration reduces total annual space energy consumption by ~21% relative to basement placement due to lower artificial lighting and cooling loads. When combined, PV and fiber systems can fully meet basement PBR lighting demand, whereas rooftop configurations may rely more on grid electricity. Economically, fiber-optic daylighting achieves comparable lighting offsets at roughly half the annualized cost of PV-based systems, subject to surface-area and routing constraints. Overall, solar-assisted lighting strategies markedly improve the operational sustainability of building-integrated PBRs in cold climates, with fiber-optic daylighting offering substantial spectral and thermal advantages, subject to surface-area availability and routing-related design constraints.

In tropical countries like Indonesia, architectural design faces the pressing challenge of mitigating excessive heat, humidity, and solar exposure, yet many buildings continue to adopt imported, non-contextual design models. This study explores the implementation and transitional trajectory of a novel microalgae-based photobioreactor (PBR) window façade—an innovation that integrates biological systems into building envelopes for thermal shading, light modulation, and ecological performance. Using the Multi-Level Perspective (MLP) framework, this research examines the interplay between niche experimentation, regime-level constraints, and landscape drivers shaping the adoption of green building technologies in Indonesia. The PBR façade, developed through a university–industry collaboration and installed in Semarang, demonstrates how architectural innovation can evolve through iterative learning, cross-sector collaboration, and real-environment testing. However, its broader uptake is constrained by entrenched design norms, lack of regulatory standards, and limited institutional mechanisms for certification. Landscape pressures such as ESG imperatives and climate adaptation goals offer promising opportunities, but systemic change requires alignment across policy, professional practice, and cultural narratives. The study contributes a process-oriented roadmap for embedding biologically integrated façades into the sustainability transition of tropical urban architecture.

The increasing demand for environmentally friendly and sustainable energy sources worldwide has placed microalgae at the center of biotechnological research. Compared to traditional methods for producing biomass, algal photobioreactors (PBRs) have emerged as promising technologies for efficiently cultivating cyanobacteria and microalgae. This review thoroughly explores the biology, classification, design, technological advancements, and diverse applications of photobioreactors, highlighting their important role in addressing current industrial and environmental challenges. Starting with the biological foundation, the study outlines the key metabolic features of microalgae that make them ideal for industrial use. These features include their ability to accumulate lipids, their high photosynthetic efficiency, and their specific nutritional needs. The paper then analyzes the structural designs, working principles, advantages, and limitations of PBRs, categorizing them into open, closed, and hybrid systems. Algal productivity is significantly influenced by operational factors such as light intensity, carbon dioxide supply, mixing, temperature control, and contamination management, all of which are carefully optimized. The review also examines recent technological innovations, such as the use of smart materials, IoT- based automation, AI-driven monitoring, 3D printing, and biofilm growth techniques, which can enhance the performance and scalability of PBRs. It covers a wide range of applications, including the production of biofuels like biodiesel, bioethanol, and biogas, the treatment of wastewater, carbon capture, and the creation of valuable bioproducts such as pigments, antioxidants, and biofertilizers. The environmental advantages, such as reduced greenhouse gas emissions, minimal land use, and the ability to remove pollutants, are highlighted. Additionally, an economic comparison is made between PBR technologies and conventional methods in terms of cost-effectiveness, scalability, and market potential. While the benefits of PBRs are clear, the study also notes challenges that hinder their widespread commercial use, including high initial costs, complex operations, and regulatory constraints. The review recommends further research into biorefinery models, genetic engineering, and integration with renewable energy systems to fully unlock the potential of algal PBRs. Finally, the study calls for interdisciplinary collaboration, supportive legislation, and financial backing to accelerate the transition to a circular, bio-based economy driven by innovations in algal technology.

The diatom &lt;i&gt;Phaeodactylum tricornutum&lt;/i&gt; is known for its rapid growth and high fucoxanthin content (1–3% of dry weight), a photosynthetic pigment with considerable pharmaceutical and nutraceutical potential. Despite these advantages, the commercial biotechnological applications of this organism have not yet been realized, primarily due to challenges in scaling up photobioreactor (PBR) systems, as well as issues with the organism’s robustness and production processes. In this study, we present a multifaceted approach to enhance fucoxanthin productivity by combining innovations in PBR design, strain improvement, and LED light recipes. Systematic evaluation of &lt;i&gt;P. tricornutum&lt;/i&gt; in 700 mL column PBRs identified optimal light conditions (e.g., 660 nm red light at 50 μmol photons m&lt;sup&gt;–2 &lt;/sup&gt; s&lt;sup&gt;−1&lt;/sup&gt; with optimized light regimes), which were subsequently scaled up to novel 200 L and 10,000 L PBRs. Meanwhile, atmospheric and room temperature plasma mutagenesis, coupled with an adaptive evolution screening technique, generated superior mutant consortia exhibiting enhanced phenotypic characteristics, including higher fucoxanthin yield and long-term stability of cultivation. Comparative cultivation experiments in the 10,000 L PBR demonstrated the superiority of the mutant consortia, yielding 0.59 g L&lt;sup&gt;–1&lt;/sup&gt; biomass (an 18% increase) and 7.29 mg L&lt;sup&gt;–1&lt;/sup&gt; fucoxanthin (a 32.79% increase) compared to the wild type strain. Productivity was significantly improved, with biomass and fucoxanthin production rates reaching 0.12 g L&lt;sup&gt;–1&lt;/sup&gt; d&lt;sup&gt;–1&lt;/sup&gt; (a 33.33% increase) and 1.47 mg L&lt;sup&gt;–1&lt;/sup&gt; d&lt;sup&gt;–1&lt;/sup&gt; (a 54.74% increase) in the 10,000 L PBR, respectively. This work provides an optimized light recipe, superior mutant consortia, and scalable PBR design, effectively bridging laboratory-scale research with industrial application potential.

Microalgae have been characterized as an effective raw material for obtaining bioproducts from a biorefinery approach. However, production costs limit the large-scale production of microalgae, which makes these processes uncompetitive in the market. Therefore, in the present work, different agricultural fertilizers were evaluated as low-cost culture media for microalgae growth and the use of the biomass for biocrude production. The tests were carried out in three phases: phase I, Laboratory scale 1 L Erlenmeyer (Boeco, Hamburg, Germany) and phase II–III Pilot scale with cylindrical photobioreactors (PBRs) (Atb services S.A.S, Medellin, Colombia) with a capacity of 20 L. In phase I, four commercial fertilizers Crecilizer® (C), Florilizer® (F) (Fertilizer, Bogota, Colombia), AcuaLeaf Macros® (Ma), and AcuaLeaf Micros® (Mi) (Deacua, Medellin, Colombia) were tested separately and in combination (C + Ma, F + M, and Ma + Mi). The most effective treatments (C and F) in phase I were chosen for scale-up during phase II. In phase III, the concentration of the best treatment from phase II was increased. The biomass obtained from the best phase III treatment showed a cultivation medium cost 50% lower than the biomass obtained using Bold’s Basal Medium (BBM). Following each treatment, the harvested biomass was processed via hydrothermal liquefaction (HTL) to yield biocrude. The reduction in culture medium cost contributed to an estimated 40% decrease in the relative biocrude yield cost.

This article presents the creation of an eco-art installation that integrates microalgae cultivation through a photobioreactor (PBR) system. Motivated by ecological empowerment and clean air preservation, the work combines artistic research with technological innovation. Inspired by Tatlin’s work and a previous eco-art project, the piece titled “Repeating Pillar Structure” uses transparent acrylic pipes to circulate microalgae for CO2 absorption and O2 production. The installation serves a functional environmental purpose and offers contemporary aesthetic value suitable for public spaces. This project demonstrates how art can engage ecological issues by blending scientific methods and creative practice to foster environmental awareness.

This study evaluated the performance of a single-stage photobioreactor (PBR), under varying hydraulic retention times (HRT) (4, 3 and 2 days), biomass concentrations (2.7 and 1.6 g TSS L −1 ) and illuminated surface/volume ratios (17.8 and 26.7 m 2 m −3 ) in a continuous system operated for 192 days. The system achieved removal efficiencies of Total Organic Carbon of 94–96 %, Total Nitrogen of 92–97 % and phosphate of 91–100 % regardless of the operational conditions. N-NH 4 + removal was primarily driven by assimilation into algal-bacterial biomass. Nitrate and nitrite accumulation in the cultivation broth was not observed and N 2 O generation was negligible. Increased light availability boosted biomass productivity up to 335.7 ± 77.8 g m −3 d −1 . The reduction in biomass concentrations from 2.7 to 1.6 gTSS L −1 decreased microalgal concentration and diversity, particularly affecting filamentous bacteria. These results demonstrate that a single-stage PBR can achieve performance comparable to conventional two stages anoxic-aerobic photobioreactors, while being more cost-effective and sustainable, highlighting its potential for advanced wastewater treatment and resource recovery. • Reducing hydraulic retention time boosted carbon and nitrogen removal over 130 %. • Short solid retention time prevented nitrite accumulation, favoring nitrogen uptake. • N 2 O emissions were undetectable below 2 gTSS L −1 of biomass concentration. • Higher light intensity maximized inorganic carbon removal (38.9 mg L −1 d −1 ) • Scenedesmus outcompeted Pseudanabaena under high surface-to-volume ratio.

Monte-Carlo ray tracing simulation of view factors for diffuse solar radiation determination in cylindrical photobioreactor arrays for microalgae cultivation.

Developing kinetic models is crucial for understanding and optimizing purple phototrophic bacteria (PPB) growth in photobioreactors (PBR). Given the significant role of radiation transfer, integrating light into PPB kinetic models is fundamental for enhancing PBR design and operation. In this study, batch experiments were conducted under monochromatic light intensity conditions ranging from 10 to 60W·m-2 to assess the influence of this parameter on a mixed PPB culture. An existing biokinetic model was adapted to incorporate the light dependence of PPB growth using a Monod-type light function, which included light attenuation based on experimentally measured mass extinction coefficients. Microbiological characterizations evidenced the selective pressure of light on the PPB mixed culture, and the developed model could effectively describe the population behavior. Estimated parameters were validated in a continuous PBR operated at 40W·m-2, demonstrating the model ability to predict biomass growth and substrate consumption, and to support technological upscaling.

Evaluating microalgal-induced carbonate precipitation for marine carbon sequestration using Chlorella species.

Marine diatoms are prolific producers of bioactive metabolites, but Arctic species remain underexplored as sources of antibacterial and antibiofilm agents. Here, seven species were grown in photobioreactors (PBRs) and systematically screened for antibacterial, antibiofilm, and cytotoxic activities. All strains inhibited Gram-positive bacteria, and four reduced Staphylococcus epidermidis biofilm formation. Porosira glacialis emerged as a lead species, combining potent antibiofilm activity with favourable traits for large-scale cultivation, and no detectable cytotoxicity. Bioactivity-guided fractionation of P. glacialis yielded two antibiofilm compounds: methyl 3-hydroxyoctadecanoate, the first time reported in diatoms and newly associated with antibiofilm bioactivity, and pheophorbide a, a chlorophyll degradation product. Both inhibited S. epidermidis biofilm formation without any observed cytotoxicity. Notably, Cylindrotheca closterium exhibited cultivation-dependent antibiofilm activity, underscoring the importance of growth conditions for metabolite production. These findings highlight the potential of Arctic diatoms as a sustainable source of antibiofilm agents and support further exploration of their metabolites for antimicrobial and industrial applications.