Photobioreactor Technology Research Articles

Removal of chemicals from effluent using photobioreactor technology to improve environmental and health impacts

Abstract The treatment of industrial waste water using cyanobacteria in photobioreactor for the removal of sulphide, COD and phenol. The microorganisms were collected from the effluent treatment plant of a petroleum refinery and a biofilm was developed in nutrient medium. The reactor was fed with cyanobacteria. After biofilm formation and acclimatization, the same procedure was followed for 16 days in a rectangular tray type photo bioreactor for the treatment of industrial waste water. From continuous mode of operation, it was found that the phototrophic microorganisms can degrade the pollutants present in industrial waste water. The removal efficiency of hardness 75 %, sulphide 95.8 %, COD 98.7 %, phenol 99.9 % and nitrate 83.7 % was studied. The present works shows that it is feasible to use cyanobacteria in a photo bioreactor for the treatment of industrial waste water.

Eco-Friendly Innovation: Hydra-Enhanced Miniature Photobioreactor for Air Pollution Reduction

According to the WHO data in 2019, nearly all of the global population resides in areas that do not meet the WHO guidelines for air quality. This study is to address the issue of indoor air pollution through the use of Photobioreactor technology and Hydrilla Verticillata plants. The experimental findings demonstrate that the rate of photosynthesis and production of oxygen bubbles by the Hydrilla plants are significantly influenced by adequate light intensity and exposure to CO2. By employing this innovative Photobioreactor technology, it is anticipated that indoor air quality can be enhanced, thereby contributing to the resolution of air pollution problems. This research adopts a combination of descriptive and experimental methods, utilizing a prototype scale for conducting experiments. Secondary data, in the form of published scientific articles from both international and national journals, serve as the source of data. The collected data is then qualitatively analyzed through descriptive means. Based on the results of data analysis, it can be concluded that this research offers valuable insights into the use of Hydrilla plants in innovative technologies for the improvement of air quality and human health, particularly by implementing photosynthesis processes within Photobioreactor technology.

Systematic assessment of wastewater resource circularity and sustainable value creation

The circular use of wastewater has attracted significant attention in recent years. However, there is a lack of universal definitions and measurement tools that are required to achieve the circular economy's full potential. Therefore, a methodology was developed using three indicator typologies, namely resource flow, circular action, and sustainability indicators, to facilitate a robust and holistic circularity assessment. The method uses value propositions to integrate the assessment of intrinsic circularity performance with consequential circularity impacts, by quantifying sustainable value creation (using techniques such as life cycle assessment or cost-benefit analysis). Assessment method capabilities were exhibited by applying the defined steps to a wastewater treatment plant, comparing conventional and novel photobioreactor technologies. The resource flow indicator taxonomy results highlight improved outflow circularity, renewable energy usage, and economic efficiency of the novel system. Action indicators revealed that the photobioreactor technology was successful at achieving its defined circular goals. Lastly, sustainability indicators quantified a reduction of carbon footprint by two thirds and eutrophication by 41%, a M€ 0.5 per year increase of economic value, and that disability adjusted life year impacts are 58% lower. This supports that improving wastewater system circularity using photobioreactor technology results in environmental, economic, and social value for stakeholders.

Bidirectional diffusion of functional draw solutions in an osmotic photobioreactor coupling wastewater treatment and microalgal growth

The osmotic photobioreactor (OsPBR) technology has shown great potential by integrating forward osmosis with algal wastewater treatment. However, the reverse salt flux remains a key challenge. In order to reveal the diffusion behaviors and the transport mechanisms of reverse salt flux (RSF) in an OsPBR, the NH4HCO3 and (NH4)2HPO4 (DAP) were compared as draw solutions. The results showed that the biomass growth in OsPBR with NH4HCO3 as draw solution was higher than that of DAP initially, reached up to 0.78 g L−1. Although the reverse salt flux of NH4HCO3 was twice higher than that of DAP, the OsPBR using NH4HCO3 as draw solution exhibited better N & P removal rate than that of DAP, reached at 75% and 100%, respectively. A higher diffusion of cation to anion was further found for DAP as draw solution. This work showed the feasibility to use NH4HCO3 as draw solution in OsPBR, which allows the upgrade of microalgal osmotic photobioreactor technology not only in water treatment but also its carbon neutralization potential.

A novel tubular photobioreactor immersed in open waters for passive temperature control and operated with the microalga Tetradesmus obliquus

Temperature control of outdoor photobioreactors is mandatory for stable microalgal growth rates. The large necessity of water and energy, however, imposes economic and ecologic drawbacks. A novel floating tubular photobioreactor, placed horizontally on a channel outdoors is presented in this study. It is equipped with a technology allowing variable immersion of the transparent parts into the water for passive temperature control. The photobioreactor was operated in three subsequent cycles with the microalga Tetradesmus obliquus . The horizontal immersion of 50 % of the photobioreactor tubes at high ambient temperatures up to 38.9 °C prevented the photobioreactor from temperature peaks above 33.5 °C without any energy input for cooling. While operating the photobioreactor without cooling through immersion the culture temperature exceeded the ambient temperature constantly during afternoon hours. The realised cultivations were stable and productivities from 161 mg L −1 day −1 to 230 mg L −1 day −1 were recorded. The harvested biomass contained up to 49.8 ± 0.8 % DW protein and 21.0 ± 2.0 % DW lipids with a high fraction of α -linolenic acid. • An immersible photobioreactor technology was designed and tested on open waters. • Immersion of photobioreactor into surface water shows significant tempering effect. • Stable cultivation of T. obliquus shows practicability of the photobioreactor. • Promising energy- and land-saving alternative for microalgae cultivation.

Membrane Photobioreactor Applied for Municipal Wastewater Treatment at a High Solids Retention Time: Effects of Microalgae Decay on Treatment Performance and Biomass Properties.

Membrane photobioreactor (MPBR) technology is a microalgae-based system that can simultaneously realize nutrient recovery and microalgae cultivation in a single step. Current research is mainly focused on the operation of MPBR at a medium SRT. The operation of MPBR at a high SRT is rarely reported in MPBR studies. Therefore, this study conducted a submerged MPBR to treat synthetic municipal wastewater at a long solids retention time of 50 d. It was found that serious microalgae decay occurred on day 23. A series of characterizations, including the biomass concentration, chlorophyll-a content, nutrients removal, and physical-chemical properties of the microalgae, were conducted to evaluate how microalgae decay affects the treatment performance and biomass properties. The results showed that the biomass concentration and chlorophyll-a/MLSS dropped rapidly from 3.48 to 1.94 g/L and 34.56 to 10.71 mg/g, respectively, after the occurrence of decay. The effluent quality significantly deteriorated, corresponding to the total effluent nitrogen and total phosphorus concentration sharply rising and exceeding that of the feed. In addition, the particle became larger, the content of the extracellular polymeric substances (EPSs) decreased, and the soluble microbial products (SMPs) increased instantaneously. However, the filtration resistance had no significant increase because of the comprehensive interactions of the floc size, EPSs, and SMPs. The above results suggest that the MPBR system cannot maintain long-term operation under a high SRT for municipal wastewater treatment. In addition, the biological treatment performance of the MPBR deteriorated while the antifouling performance of the microalgae flocs improved after the occurrence of decay. The occurrence of microalgae decay was attributed to the double stresses from the light shading and intraspecific competition under high biomass concentration. Therefore, to avoid microalgae decay, periodic biomass removal is required to control the environmental stress within the tolerance range of the microalgae. Further studies are required to explore the underlying mechanism of the occurrence of decay.

Characterisation of a simple ‘hanging bag’ photobioreactor for low‐cost cultivation of microalgae

AbstractBACKGROUNDMicroalgae are a diverse group of photosynthetic microorganisms of significant interest to the biotechnology industry, either as a sustainable source of natural compounds, or as light‐driven cell factories to produce recombinant metabolites and proteins. Their ability to utilise light, CO2, and basic nutrients leads to a simple and low‐cost phototrophic cultivation process. This is particularly relevant to low‐ and middle‐income countries, all of which require a cultivation system that is cheap, technically simple to operate, readily scalable, and can meet basic Good Manufacturing Practice requirements. A disposable ‘hanging bag’‐type photobioreactor operated as a bubble column fits these criteria.RESULTSIn this study, the characterisation and design modifications to improve the performance of a 15 L hanging bag is reported. The bubble behaviour using different sparger designs was investigated together with gas hold‐up, mixing time, and mass transfer coefficient of CO2. A gas flow rate of 5 L min−1 using a new sparger design and a modified height‐to‐diameter ratio of the bag led to a two‐fold improvement in algal biomass productivity when culturing the green microalga Chlorella sorokiniana. The cultivation of a luciferase‐expressing Chlamydomonas reinhardtii strain in the modified hanging bag also demonstrated an 11% increase in luciferase content.CONCLUSIONThis is the first attempt to characterise this simple hanging bag system that brings the industry‐favoured single‐use bag concept into the research field of photobioreactor technology. The hanging bag with modified sparger and dimensions improves microalgal biomass productivity and demonstrates the potential of simple and low‐cost systems for microalgal cultivation. © 2021 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Green technologies for air pollution treatment by microalgae in tubular photobioreactor

Air pollution in general and motorcycle exhaust, in particular, is a big problem attracting a lot of attention from people and researchers worldwide because of the significant impacts it has on humans and the environment. The issue of air pollution is growing, and the impact is more evident than ever. Carbon dioxide represents a series of problems that we face daily but have not yet been effectively solved. Currently, microalgae are known to photosynthesize and use free CO2, bicarbonate ions as a source of nutrients to grow. Microalgae are developed under appropriate environmental conditions, which will bring admirable CO2 treatment efficiency and obtain biomass for other applications. The study approach was an inexpensive and natural air purification solution by microalgae, which is designed as a tubular photobioreactor. The study was conducted by evaluating the ability of Chlorella Vulgaris to grow and absorb CO2 emissions in the newly established system with exhaust gas supplied from a mini motorcycle engine. The results showed that microalgae grew stably in the tubular photobioreactor system with a biomass concentration of 6×106 cells/ml after 42 days of the experiment. Simultaneously with the stable growth of microalgae, the CO2 emission concentration was reduced with 26.59% absorption efficiency after 11 days of the experiment. Finally, establishing the tubular photobioreactor technology system has yielded impressive initial results in cultivating stable growing microalgae combined with CO2 emission treatment.

Removal of Nitrate from Water Using TiO2/ PVDF Membrane Photobioreactor

Removing low-concentration nitrate from water is desirable because it may cause eutrophication when discharged, but it is challenging using current technologies. Membrane photobioreactor (MPBR) technology (which is the combination of membrane and microalgae cultivation) emerges as a suitable option to efficiently reduce the nutrient load from wastewater. This study developed a high-efficiency microalgal-bacterial Membrane PhotoBioReactor (MPBR) to biologically remove nitrate from water. In order to obtain low-fouling membranes, TiO2 nanoparticles were entrapped in PVDF membranes prepared by the phase inversion method. Successful fabrication of composite membranes (PVDF/TNT) was confirmed by using XRD, FTIR, DSC, TGA, SEM, and AFM. Membrane properties were studied using contact angle, tensile strength, pure water flux, Bovine Serum Albumin (BSA) rejection, antifouling properties, and porosity. Compared with the pristine PVDF films, the hydrophilicity, permeability, and antifouling performance of the proposed membrane were improved. A laboratory-scale MBR equipped with a synthesized membrane was used to evaluate the performance of mixotrophic denitrification under different Carbon Nitrogen (C/N) ratios, Hydraulic Retention Times (HRT), Nitrate loading, and Influent alkalinity. Methanol was supplied as a carbon source. Almost complete denitrification was achieved when the bioreactor was fed with 75 mg/L NO3−–N, 150 mg/L methanol at 4 h HRT without external alkalinity supplementation. The results as a whole indicated that the MPBR can be applied effectively to the removal of nitrate from real wastewater.

Development of microalgal industries in the past 60 years due to biotechnological research in China: a review

Microalgae are unicellular photosynthetic microorganisms. About 1500 years ago, at the Jin Dynasty, the Chinese consumed microalgae as food and tried its use as traditional medicines. During the “three-year period of famine” from 1959 to 1962, the central Chinese government encouraged scientists to conduct research on the cultivation of Chlorella as a food substitute, thus initiating the early developmental stage of microalgal biotechnology. A newer biotechnological innovation was conceived in the 1980s, when the national strategy which states that “ Spirulina should be taken as a protein supplement by the Chinese” was instituted. Since then several key biotechnological innovations have been developed over the past 60 years, which are related to the breeding of microalgal species, raceway pond and tubular photobioreactor technology and “from 0–1” originality of microalgal cultivation modes. In China, a series of breakthroughs as regards the biomass scaling-up of Spirulina , Chlorella , Haematococcus pluvialis , and Euglena gracilis have been achieved; this has therefore made China the largest producer of microalgal biomass globally. The core missions of the research and development of microalgal biotechnology in China are to reduce production cost, and develop new bio-economy modes for both precise application and environmental governance through microalgal biomass usage.

Transparent polyvinyl-alcohol cryogel as immobilisation matrix for continuous biohydrogen production by phototrophic bacteria

BackgroundPhototrophic purple non-sulfur bacteria (PNSB) have gained attention for their ability to produce a valuable clean energy source in the form biohydrogen via photofermentation of a wide variety of organic wastes. For maturation of these phototrophic bioprocesses towards commercial feasibility, development of suitable immobilisation materials is required to allow continuous production from a stable pool of catalytic biomass in which energy is not diverted towards biomass accumulation, and optimal hydrogen production rates are realised. Here, the application of transparent polyvinyl-alcohol (PVA) cryogel beads to immobilisation of Rhodopseudomonas palustris for long-term hydrogen production is described. PVA cryogel properties are characterised and demonstrated to be well suited to the purpose of continuous photofermentation. Finally, analysis of the long-term biocompatibility of the material is illustrated.ResultsThe addition of glycerol co-solvent induces favourable light transmission properties in normally opaque PVA cryogels, especially well-suited to the near-infrared light requirements of PNSB. Material characterisation showed high mechanical resilience, low resistance to diffusion of substrates and high biocompatibility of the material and immobilisation process. The glycerol co-solvent in transparent cryogels offered additional benefit by reinforcing physical interactions to the extent that only a single freeze–thaw cycle was required to form durable cryogels, extending utility beyond only phototrophic bioprocesses. In contrast, conventional PVA cryogels require multiple cycles which compromise viability of entrapped organisms. Hydrogen production studies of immobilised Rhodopseudomonas palustris in batch photobioreactors showed higher specific hydrogen production rates which continued longer than planktonic cultures. Continuous cultivation yielded hydrogen production for at least 67 days from immobilised bacteria, demonstrating the suitability of PVA cryogel immobilisation for long-term phototrophic bioprocesses. Imaged organisms immobilised in cryogels showed a monolithic structure to PVA cryogels, and demonstrated a living, stable, photofermentative population after long-term immobilisation.ConclusionTransparent PVA cryogels offer ideal properties as an immobilisation matrix for phototrophic bacteria and present a low-cost photobioreactor technology for the further advancement of biohydrogen from waste as a sustainable energy source, as well as development of alternative photo-bioprocesses exploiting the unique capabilities of purple non-sulfur bacteria.

Timing is everything: Diel metabolic and physiological changes in the diatom Cyclotella cryptica grown in simulated outdoor conditions

Microalgal cultures grown on a light-dark cycle experience diel patterns in metabolic and physiological processes, including cell cycle synchronization, but the implications for productivity in terms of biomass and commercially-appealing molecules are not commonly appreciated. Despite a long history of diel response studies, only recently have photobioreactor technology advances enabled the use of sinusoidal light and temperature to more accurately mimic outdoor conditions. The present study investigates cell cycle progression and dynamic changes on a 24-hour scale in triacylglycerol (TAG), photosynthetic pigments, and optical density at 750 nm (OD750) as a proxy for biomass in the production candidate diatom Cyclotella cryptica grown using a sinusoidal light and temperature regime. Cell division synchronized to occur predominantly in the middle of the light period while OD750 started to increase several hours earlier, as the cells prepared to divide. TAG levels increased during the day and decreased at night, with a mid-day dip corresponding to the time when lipid needs for cell division-associated membrane biosynthesis would be high. Photosynthetic pigment dynamics data was overlaid with cell cycle progression, indicating that while some photosynthetic pigments respond primarily to light, others are influenced by the cell cycle. Additionally, the results indicate that in a synchronized culture, potential product yields change substantially throughout the day. This may inform harvest timing to significantly increase yield.

RETRACTED: Effects of nutrient ratios and carbon dioxide bio-sequestration on biomass growth of Chlorella sp. in bubble column photobioreactor

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editors-in-Chief. The article is a duplicate of a paper that has already been published in [Bioresource Technology, volume 208 (2016) 1 - 6. https://doi.org/10.1016/j.biortech.2016.02.043]. Redundant publications overweigh the relative importance of published findings and distort the academic record of the authors. One of the conditions of submission of a paper for publication is therefore that authors declare explicitly that the paper has not been previously published and is not under consideration for publication elsewhere. As such this article represents a misuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.

Assessment of membrane photobioreactor (MPBR) performance parameters and operating conditions

Membrane photobioreactor (MPBR) technology is an emerging algae-based wastewater treatment system. Given the limitations due to the general use of conventional analytical approaches in previous research, this study aims to provide a more comprehensive assessment of MPBR performance through advanced characterisation techniques. New performance parameters are also proposed, encompassing five important aspects of MPBR system efficiency (i.e. biomass concentration, composition, production, nutrient uptake and harvesting potential). Under initial standard operating conditions, performance parameters, such as cell count/MLSS ratio, cell viability, proportion of bacteria and biomass yield coefficient, were found to offer new insights into the operation of MPBR. These parameters were then used, for the first time, to systematically investigate MPBRs operated under different hydraulic retention times (HRTs) and solids retention times (SRTs). Applying shorter HRT and SRT was observed to increase cell viability and productivity (up to 0.25 × 107 cells/mL·d), as anticipated due to the higher nutrient loading. It was noted that the faster growing algal cells featured lower requirement for nutrients. On the other hand, extending HRT and SRT resulted in a more heterogeneous culture (lower cell count/MLSS ratio and higher proportion of bacteria), achieving a higher degree of autoflocculation and greater NO3-N and PO4-P removals of up to 79% and 78% respectively. The results demonstrate the trade-off between applying different HRTs and SRTs and the importance of fully characterising system performance to critically assess the advantages and limitations of chosen operating conditions.

Managing anaerobic digestate from food waste in the urban environment: Evaluating the feasibility from an interdisciplinary perspective

Abstract Anaerobic digestion of food waste within urban areas can generate decentralised renewable energy and support community enterprise activities, thereby contributing to closing the waste-energy-food loop. However, widespread uptake of small-scale, urban anaerobic digestion networks is limited by economic costs and the safe disposal of surplus digestate. This paper uses an interdisciplinary approach to assess the feasibility of anaerobic digestate management through the installation of hydroponics or algae cultivation systems, based on a case study of a micro anaerobic digestion system in London, England. Results show that installing a dewatering sifter together with a hydroponics system is a technically and economically feasible option for digestate enhancement in the urban environment. Its installation is, however, not currently justified for the system under consideration due to cost, regulatory, spatial, and contextual constraints identified using actor-network analysis. Nevertheless, if regulatory and wider contextual issues are accommodated, and more than 30 L of digestate are produced daily, a dewatering and vertical hydroponic system could result in a profit of approximately £100,000 over 10 years. While the microalgal system was also able to upgrade digestate, at present productivity is too low and the capital cost of photobioreactor technology is prohibitively expensive. This underlines the need for technical improvements and low-cost enhancement options to achieve justifiable paybacks until regulatory reforms and the wider economic situation are more favourable to anaerobic digestion treatment within cities.

Aspects of carbon dioxide mitigation in a closed microalgae photo-bioreactor supplied with flue gas

The aim of the present study is to investigate the potential of flue gases to be efficiently and economically applied in production of algal biomass in a photobioreactor (PBR). Various microalgae strains (Chlorella sorokiniana 211-234, Bracteacoccus minor 61.80, Radiosphaera negevensis 87.80, Chlorosarcinopsis negevensis 67.80 and Chlorococcum novae-angliae 5.85) had been tested for CO2 mitigation, growth and tolerance to high CO2 levels. The flue gas and CO2 bubbling induced a significant algal mass growth compared to control (ambient air). Removal of CO2 and NO by the studied microalgae strains was found to be 44% and 33% along daily intervals, respectively. A growth rate of ~0.4g L−1 d−1 was obtained for all algal species tested. Growth conditions for tested algae can be optimised through PBR technology in order to obtain highest biomass yield for production of valuable biochemicals (i.e., low-cost biofuel).

Aspects of carbon dioxide mitigation in a closed microalgae photo-bioreactor supplied with flue gas

The aim of the present study is to investigate the potential of flue gases to be efficiently and economically applied in production of algal biomass in a photobioreactor (PBR). Various microalgae strains (Chlorella sorokiniana 211-234, Bracteacoccus minor 61.80, Radiosphaera negevensis 87.80, Chlorosarcinopsis negevensis 67.80 and Chlorococcum novae-angliae 5.85) had been tested for CO2 mitigation, growth and tolerance to high CO2 levels. The flue gas and CO2 bubbling induced a significant algal mass growth compared to control (ambient air). Removal of CO2 and NO by the studied microalgae strains was found to be 44% and 33% along daily intervals, respectively. A growth rate of ~0.4g L−1 d−1 was obtained for all algal species tested. Growth conditions for tested algae can be optimised through PBR technology in order to obtain highest biomass yield for production of valuable biochemicals (i.e., low-cost biofuel).

Review of Microfluidic Photobioreactor Technology for Metabolic Engineering and Synthetic Biology of Cyanobacteria and Microalgae.

One goal of metabolic engineering and synthetic biology for cyanobacteria and microalgae is to engineer strains that can optimally produce biofuels and commodity chemicals. However, the current workflow is slow and labor intensive with respect to assembly of genetic parts and characterization of production yields because of the slow growth rates of these organisms. Here, we review recent progress in the microfluidic photobioreactors and identify opportunities and unmet needs in metabolic engineering and synthetic biology. Because of the unprecedented experimental resolution down to the single cell level, long-term real-time monitoring capability, and high throughput with low cost, microfluidic photobioreactor technology will be an indispensible tool to speed up the development process, advance fundamental knowledge, and realize the full potential of metabolic engineering and synthetic biology for cyanobacteria and microalgae.

Current Status, Future Developments and Recent Patents on Photobioreactor Technology

Current Status, Future Developments and Recent Patents on Photobioreactor Technology

Reduction of oxygen inhibition effect for microalgal growth using fluoroalkylated methoxy polyethylene glycol-stabilized perfluorocarbon nano-oxygen carriers

Oxygen accumulation in the medium has long been considered as one of the major limitations for closed and mass cultivation of microalgae. Although the dissolved oxygen may be removed via air sparging-based photobioreactor technology, disadvantages such as high cost, increased contamination, and severe cell damage caused by hydrodynamic stress remain obstacles for microalgal culture. To overcome the effect of oxygen inhibition on microalgal growth, a strategy of using perfluorocarbon nanoemulsions (PNEs) as oxygen scavengers was explored. Our results showed that the PNEs prepared by fluoroalkylated methoxy polyethylene glycol (MPEG; MW=2000) and perfluorooctyl bromide (PFOB) with a volume ratio of 9:1 (PNEs-2000/PFOB (9:1)) exhibited the highest stability and capacity of deoxygenation under the photobioreactor operation. With the aid of 1% (v/v) PNEs-2000/PFOB (9:1), the Nannochloropsis oculata successfully multiplied in the hyperoxygenated environment where the growth rate of 0.467day−1 was comparable to the normal breeding with neither PNEs nor oxygen injection (0.498day−1), and the biomass production was five-fold higher than the O2-treated group without PNEs after seven-days cultivation. In summary, the developed PNEs-2000/PFOB (9:1) enabled to efficiently remove the dissolved oxygen in the photobioreactor that provided a feasible means for mass culture of microalgae in closed setting.