Algal Growth Rate Research Articles

Model development and process evaluation for algal growth and lipid production

Microalgae grabbed the attention worldwide because of their application in renewable energy with a number of environmental benefits such as carbon dioxide assimilation to produce biofuel. In this study, a kinetic model aiming to analyze algae growth and lipid production was developed. Biomass was divided into two parts, algae residual cell and lipid, to analyze their kinetics distinctively and to find out the inside process mechanism. The model was calibrated and validated with different experimental datasets, varying carbon sources, and phosphate concentrations. The capability of the model to predict the dynamics of algal culture over a broad range of growth conditions was investigated. The presence of acetate reduced the bicarbonate uptake for algal growth and growth on organic carbon was higher compared to that of carbon dioxide. The presence of ammonium showed a very strong inhibition effect on algae and lipid production rate but enhanced lipid content. Phosphate caused both limitation and inhibition effects on algae growth and lipid production rate. The maximum growth was found at 12 mg/L PO43- concentration and 3.10 mg/L NO3--N concentration. Lipid content was enhanced by limiting phosphate. Overall, the developed model allows optimizing of nutrient concentrations and operating conditions specifically to enhance lipid productivity.

Sensitivity analysis of a hydrodynamic and harmful algal model in a riverine system

Simulating algae blooms using a hydrodynamic-water quality model is challenging because it requires a thorough understanding of physical and biological processes and involves numerous parameters. This study conducted a sensitivity analysis of the EFDC+ hydrodynamic and water quality model for simulating cyanobacteria growth, an important Harmful Algal Bloom (HAB) species in the Ohio River, USA. The sensitivity analysis assessed 23 model input parameters, divided into nine functional groups according to their characteristics. This assessment analyzes the impact of changing these input parameters on four water quality model outputs including algae (i.e., cyanobacteria), dissolved oxygen, total nitrogen, and total phosphorus. Light extinction parameters, maximum algal growth rate, and algal base metabolism were identified as the most sensitive parameters for simulating algal growth. Solar radiation required for algal growth was moderately sensitive. Currently, there are only a few studies that simulate HAB dynamics in riverine systems. This study deepens our understanding of HAB development in rivers with lock and dam structures that create a series of pools along the river. Future work will involve focusing on the sensitive parameters in model calibration.

Realization of blue-red dual-emission via energy transfer in Na3KMg7(PO4)6: Eu2+, Mn2+ phosphor for plant growth application☆

A blue-red dual-emitting phosphor, Na3KMg7(PO4)6: Eu2+, Mn2+ was developed in this study. Eu2+ acts as a sensitizer ion in Na3KMg7(PO4)6: Mn2+, which significantly improves the undesirable luminous efficiency of Mn2+. The energy transfer between Eu2+ and Mn2+ significantly boosts both internal quantum efficiency (IQE) and external quantum efficiency (EQE) of the phosphor, achieving values of 72.5% and 42.6%, respectively. Additionally, the phosphor demonstrates exceptional thermal stability, at 150 °C, maintaining 71.49% of its initial emission intensity. The emission spectrum of the phosphor closely matches the chlorophyll’s absorption spectra, with similarities of 75.06% and 94.52%, respectively. This was further confirmed through a fabricated LED with a n-UV chip (395 nm). To further assess the potential for agritech applications, a light-conversion film incorporating the developed phosphor in PDMS glue was prepared. An outdoor cultivation trial with Chlorella showed that the algae's growth rate improves by 27.3% relative to a control group. These results reveal the significant potential of the Na3KMg7(PO4)6: Eu2+, Mn2+ phosphor for enhancing plant growth in practical applications.

Rhodolith Beds Along the Southwest Atlantic Ocean: From Shallow to Mesophotic Habitats. Review of a Singular Ecosystem

ABSTRACTRhodolith beds are one of the major marine coastal ecosystems. Knowing the spatial distribution, environmental characteristics and composition is not only scientifically pertinent but also crucial to allow comparisons in case of changes due to local and global anthropogenic pressures. With slow algal growth rates, high associated diversity and potential importance as nursery grounds, rhodolith beds are present along the Brazilian coast of the Southwest Atlantic Ocean. This study provides an updated map of shallow and mesophotic rhodolith distribution after a systematic literature review. The prevailing oceanographic conditions along most parts of the Brazilian coast render the environment suitable for the developing rhodolith beds (a total of 68 taxa in this review), with 63 taxa along the East Brazilian Shelf, seven taxa for the North Brazilian Shelf and 10 taxa in the South Brazilian Shelf. According to composition, shallow and mesophotic communities were more similar in each large marine ecosystem than among them. In addition to gaps in terms of distribution, there are uncertainties about the taxonomic composition of the rhodoliths, associated fauna and flora and oceanographic and geological characteristics of the bottoms, which call attention to the importance of further studies, mainly in the mesophotic. This review provides a more precise distribution of these habitats along the Brazilian coast of the Southwest Atlantic Ocean. It contributes to a more detailed taxonomic composition of calcareous algae in an extremely relevant marine ecosystem, which is crucial for many species, including the endemic kelp, Laminaria abyssalis.

Microalgal production and nutrient recovery under mixotrophic mode using cheese whey permeate

Mixotrophic microalgal solutions are efficient nutrient recovery methods, with potential to prolong the cultivation seasons in temperate climates. To improve operation sustainability, the study used landfill leachate for nitrogen source and whey permeate for phosphorus and organic carbon. A non-axenic polyculture, dominated by green algae, was cultivated in mixotrophic mode on glucose or whey permeate compared to a photoautotrophic control in outdoor pilot-scaled raceway ponds during Nordic spring and autumn. The whey permeate treatment had the highest algal growth rate and productivity (0.48 d−1, 183.8 mg L−1 d−1), nutrient removal (total nitrogen: 21.71 mg L−1 d−1, total phosphorus: 3.05 mg L−1 d−1) and recovery rate (carbon: 85.19 mg L−1 d−1, nitrogen: 17.01 mg L−1 d−1, phosphorus: 2.58 mg L−1 d−1). When grown in whey permeate, algal cultures demonstrated consistent productivity and biochemical composition in high (spring) and low light conditions (autumn), suggesting the feasibility of year-round production in Nordic conditions.

Influence of growth medium on the species-specific interactions between algae and bacteria.

In this study, we investigated a species-specific algal-bacterial co-culture that has recently attracted worldwide scientific attention as a novel approach to enhancing algal growth rate. We report that the type of interaction between Chlorella vulgaris and bacteria of the genus Delftia is not solely determined by species specificity. Rather, it is a dynamic process of adaptation to the surrounding conditions, where one or the other microorganism dominates (temporally) depending on the growth conditions, in particular the medium. Under laboratory conditions, we found that Delftia sp. had a negative effect on C. vulgaris growth when co-cultured in a TAP medium. However, the co-culture of algae and bacteria under BG-11 and BG-11 + acetic acid resulted in an increase in algal concentration compared to algal cultures without bacteria under the same conditions. Additional chemical analysis revealed that the presence of different carbon (the main organic carbon source-acetic acid in TAP or BG-11 + acetic acid medium and inorganic carbon source-Na2CO3 in BG-11 or BG-11 + acetic acid medium) and nitrogen (NH4Cl in TAP medium and NaNO3 in BG-11 or BG-11 + acetic acid medium) species in the growth medium was one of the main factors driving the shift in interaction type.

Polyethylene terephthalate nanoparticles induce oxidative damage in Chlorella vulgaris

Polyethylene Terephthalate (PET) is a type of plastic largely used for packing food and beverages. Unfortunately, it includes a major portion of the plastic distributed through aquatic systems wherever systematic collection and recycling are lacking. Although PET is known to be non-toxic, it is not obvious whether the nanoparticles (NPs) formed due to their degradation have any direct/indirect effect on aquatic organisms. In order to study the effects on aquatic environment, fresh water algae Chlorella vulgaris was subjected to incremental concentrations of the NPs. We observed a concentration and duration of exposure dependent decrease in algal growth rate along with reduced total chlorophyll content. Scanning electron microscopy revealed deformities in cell shape and the uptake of Propidium Iodide suggested membrane damage in response to NP exposure. Intracellular Reactive Oxygen Species level was also found significantly higher, evidenced by Dichlorodihydrofluorescein diacetate staining. Activity of antioxidant enzymes Superoxide dismutase (SOD), Peroxidase (POD) and Catalase (CAT) were significantly higher in the NP exposed groups suggesting the cellular response to regain homeostasis. Further, expression levels of the genes psaB, psbC, and rbcL associated with photosynthesis increased above two fold with respect to the control inferring the possibility of damage to photosynthesis and the initial molecular responses to circumvent the situation. In short, our studies provide evidence for oxidative stress mediated cellular damages in Chlorella vulgaris exposed to NPs of PET.

Optimizing biofuel production from algae using four-element framework: Insights for maximum economic returns

This paper introduces a Four Element Strategy (FES) focused on concentration of CO2 gas (Cc,g), energy input to the process, concentration of nutrients, and the type of algal strain to maximize biofuel production (BYP) from algae strains and evaluate associated economic benefits. Two algal strains encompassing slain algae Nannochloropsis sp. (Ns), and freshwater strain Chlorella vulgaris (Cv) were used in the current study. Response Surface Methodology (RSM) and Box Behnkin Design (BBD) are integrated with a biokinetic model to explore the relationships among growth parameters in the ranges; Cc,g ∼ 0.03–20 %), Nitrogen (N) to phosphorus (P) ratio (RN/P)∼1–11, and light intensity (LI)∼ 100–400 µE m⁻² s⁻¹ with corresponding CO2 bio-fixation rate (RCO2, g L⁻¹ d⁻¹), biomass accumulation (X, g L⁻¹), and algal growth rate (µ, d⁻¹). Optimization results indicate that the most productive conditions involve LI in the range of 100–270 µE m⁻² s⁻¹, Cc,g between 0.03 % and 15 %, and RN/P of 3.5–11, achieving maximum RCO2, X, and µ at 1 g L⁻¹ d⁻¹, 6 g L⁻¹, and 1.6 d⁻¹, respectively. Further optimization using the desirability function supports achieving RCO2 of 1.2 g L⁻¹ d⁻¹, X of 1.8 g L⁻¹, and µ of 1.7 d⁻¹, with RN/P, Cc,g, and LI at 11, 4.5 %, and 200 µE m⁻² s⁻¹, respectively. Notably, Ns demonstrated higher nutrient uptake rates and BYP compared to Cv, with total production costs of $0.629/L and respective required cost coverages of $0.138 and $0.375 for Ns and Cv. This study offers a comprehensive guideline for large-scale microalgae cultivation technology (MCT) processes, providing insights into optimizing conditions for biofuel production while considering economic viability.

Unlocking the potential of Spirulina microalgae: Cultivating in wastewater treatment for sustainable biofuel production

Municipal wastewater, known for its high nitrogen and phosphorus levels, disrupts natural biogeochemical cycles. However, these nutrients are vital for cultivating green algae, which show potential as a sustainable energy source. In this study, Spirulina microalgae biomass was cultivated from diluted municipal wastewater and converted into biofuel to assess its compatibility with conventional diesel applications. Algae growth rate, nutrient removal from wastewater, and proximate and ultimate analyses of the biomass were conducted. Elemental, functional group, and chemical analyses of the biodiesel were also performed using an elemental analyzer, Fourier-transform infrared (FTIR) spectroscopy, and Gas Chromatography-Mass Spectrometry (GC-MS), respectively. Results showed effective removal of calcium, magnesium, potassium, and nitrogen nutrients by 44.7%, 71.7%, 50%, and 55.6%, respectively, through algae cultivation. Proximate and ultimate analyses confirmed the biomass's energy content and efficiency for energy production. Elemental analysis of biodiesel revealed significant contributions of carbon, hydrogen, and oxygen, while FTIR and GC-MS analyses identified carbon-based components and methyl esters as major constituents, respectively. Physicochemical properties of algae biodiesel met ASTM D6751 limits. This comprehensive assessment suggests that Spirulina algae from wastewater treatment holds promise as a viable energy source for diesel applications.

Combined effect of light and glyphosate herbicide on growth rate of marine diatom algae.

The effect of glyphosate herbicide at concentrations of 25, 100, 150 and 200 μg.L-1 on growth characteristics of diatoms C. caspia and T. weissflogii under accumulative growth conditions was investigated. Increasing herbicide concentration in the medium resulted in growth suppression of both species and decreased the final abundance of the cultures in the stationary growth phase. The calculated concentrations of herbicide EC10 and EC50 (10 and 90 μg.L-1 for C. caspia and 7 and 25 μg·L-1 for T. weissflogii, respectively) led to a 10 and 50% reduction in the abundance of the studied cultures relative to the control, are ecologically significant and correspond to the values recorded in aquatic areas. The combined effect of light (in the range of 20-250 µE.m-2.s-1) and glyphosate (calculated concentrations of EC10 and EC50) on the growth characteristics of microalgae was evaluated. An increase in algal sensitivity to light was observed with glyphosate exposure. In both species, the increase in the concentration of glyphosate in the medium led to a decrease in the initial angle of slope of the light curve of growth under conditions of light limitation, a reduction in the value of light saturation of growth, narrowing of the boundaries of the light optimum and an increase in the degree of light inhibition. It is shown that the effect of the combined action of light and glyphosate exceeds the sum of the effects of each factor. This fact should be taken into account in ecotoxicological monitoring when assessing the risks of glyphosate ingress into aquatic ecosystems. An increase in glyphosate concentration in water during periods with high values of solar insolation is potentially dangerous due to a decrease in the photosynthetic activity of algae and a reduction in diatom algae abundance.

Seasonal effects and trophic pressure shape the responses of species interactions in a tropical seagrass meadow to marine heatwaves

Species interactions are influenced by changes to the environment, such as seasonal variations in temperature, and human‐driven warming including marine heatwaves (MHWs). Alteration of species interactions, particularly those involving foundation species, can shape ecosystem structure, stability and dynamics. Marine habitats, notably seagrass meadows, are threatened by human‐driven environmental changes including MHWs which have the potential to alter trophic interactions through effects on various community members including seagrasses, epiphytic algae, and epiphytic algae grazers. Here we examined the effects of a simulated marine heatwave (control versus + 4°C) in different seasons and grazer occurrence on seagrass traits, epiphytic algae growth, grazer biomass and grazing rate. We found the season in which the MHW occurred affected the seagrass response and grazer influence. In winter, the MHW had positive effects on seagrass growth and nitrogen content and caused significant decreases in epiphytic algae growth. However, in summer, grazer presence increased seagrass growth and biomass, but growth was reduced by the interaction with the MHW. The season in which the MHW occurred affected the magnitude of change in leaf tissue isotopic values and C:N ratio, with greater changes occurring in summer. Epiphytic algal growth was markedly reduced by the interaction between all three factors, leading to the near lack of epiphyte growth in summer with grazers present under the MHW. Summer was also associated with a greater increase in snail biomass (most notably under MHW conditions), and increased snail grazing rate. From these results, we show that winter MHWs can drive increased growth of seagrasses but minimal impacts on grazers, while in summer increased grazer activity can interact with elevated temperatures from a MHW to increase their algal consumption. By examining responses across multiple trophic levels and distinct seasons, we achieve a more representative and realistic depiction of human‐induced environmental impacts on ecosystems.

The phycosphere and its role in algal biofuel production

Oleaginous microalgae have become a focus for large-scale biofuel production due to their ability to accumulate large quantities of lipids. However, production is currently limited by cost and predation. At present, algal biofuel cultivation is optimized through starvation, supplementing media with nutrients, or genetic engineering; these methods can often be costly with little to no increase in lipid production or the culture’s defense. Investigating the phycosphere of algal-bacterial interactions may overcome these current barriers to large-scale production. The phycosphere of algal-bacterial interactions have formed over millions of years through mutualistic and symbiotic relationships and can provide a more direct source of nutrients compared to adding the nutrients in bulk. The most promising of these interactions include the production of phytohormones and quorum signaling compounds that alter the behaviors of the consortia. Phytohormones can improve algal growth rates, lipid production, and stress resistance. Quorum signaling could create consortia capable of warding off invaders—such as rotifers—while self-regulating and altering behavior based on population density. Mechanisms within the algal phycosphere present many opportunities for the development of novel engineering strategies to further improve algal lipid production and operational costs. This review outlines previous preliminary phycosphere research as well as posing possible opportunities to be pursued in future biofuel production.

Co-cultured of red hybrid tilapia and Gracilaria changii (Gracilariaceae: Rhodophyta): Effects on water quality, growth performance and algal density

ABSTRACT We evaluated the potential for co-cultured of red hybrid tilapia with Gracilaria changii in two different densities in zero water exchange conditions. Five treatments were performed, consisting of three monoculture systems as controls: algae at two different densities (M1 and M2 with 1 g L−1 density and 3 g L−1 density, respectively) and fish without algae (Mfish). For comparison purposes, the other two treatments were co-cultured fish with algae at densities of 1 g L−1 (P1) and 3 g L−1 (P2). The effects of different culture systems and densities on the water quality, growth performance, nutrient content and C/N ratio of the algae were determined. During the experimental period, the dissolved oxygen (DO) and pH values in the algal tanks (monoculture and co-culture) were significantly higher than those in the Mfish tank. The ammonia and nitrate concentrations in P1 and P2 were significantly lower compared to initial measurements. The water parameters indicated that the algae improved the water quality of the culture system. Compared to the fish monoculture (Mfish), the fish grew better with algae (P1 and P2) maybe due to the more favourable water conditions in the tanks. On day 20, the algae growth rates in the co-culture tanks (P1 and P2) were significantly higher than those in the monoculture tanks. Additionally, P1 and P2 improved the nutrient composition and C/N ratio of the algae. This study found that although the co-culture system resulted in better water quality and nutrient content in the alga, the algal density had no significant effect on fish or algal growth.

Impacts of Differentially Shaped Silver Nanoparticles with Increasingly Complex Hydrophobic Thiol Surface Coatings in Small-Scale Laboratory Microcosms.

We investigated the impacts of spherical and triangular-plate-shaped lipid-coated silver nanoparticles (AgNPs) designed to prevent surface oxidation and silver ion (Ag+) dissolution in a small-scale microcosm to examine the role of shape and surface functionalization on biological interactions. Exposures were conducted in microcosms consisting of algae, bacteria, crustaceans, and fish embryos. Each microcosm was exposed to one of five surface chemistries within each shape profile (at 0, 0.1, or 0.5 mg Ag/L) to investigate the role of shape and surface composition on organismal uptake and toxicity. The hybrid lipid-coated AgNPs did not result in any significant release of Ag+ and had the most significant toxicity to D. magna, the most sensitive species, although the bacterial population growth rate was reduced in all exposures. Despite AgNPs resulting in increasing algal growth over the experiment, we found no correlation between algal growth and the survival of D. magna, suggesting that the impacts of the AgNPs on bacterial survival influenced algal growth rates. No significant impacts on zebrafish embryos were noted in any exposure. Our results demonstrate that the size, shape, and surface chemistry of AgNPs can be engineered to achieve specific goals while mitigating nanoparticle risks.

Mathematical Model of Closed Microecosystem “Algae – Heterotrophic Bacteria”

Model of closed microecosystem “algae - heterotrophic bacteria” is proposed in this paper. Mathematical model is the Cauchy problem for system of nonlinear ordinary differential equations. To develop the model the Liebig’s law of the minimum is consistently used for both specific rate of biomass growth and specific death rate of algae and bacteria cells. To describe the specific rate of substrate utilization by algae and bacteria the Andrew’s model (substrate inhibition) is used. It is assumed that specific death rate of algae and bacteria cells increases with decreasing substrate concentration. It is also assumed that carbon and nitrogen are main biogenic elements, and in the system they are in the form of mineral substrate (CO2, NO2, NO3, NH4) and biological substrate (proteins, lipids and carbohydrates). Mathematical model describing time variations in concentration of elements of microecosystem is formulated under the following assumptions: 1) stoichiometric coefficients of algae and bacteria cells are constant in the development of microecosystem; 2) utilization of carbon and nitrogen by algae and bacteria occurs independently; 3) oxygen produced by algae cells during photosynthesis completely covers the demand for oxygen for algae and bacteria cells. To verify the proposed model experimental data for microecosystems «Clorella vulgaris – Pseudomonas sp.» и «Scenedesmus obliquus – Pseudomonas sp.» are used. These systems were studied in laboratory conditions, and concentrations of elements of microecosystems in stationary state were obtained. Parameters of functions describing specific rate of utilization of biogenic elements were derived from experimental data for growth kinetics of algae and bacteria. Concentration of the biomass in stationary state obtained with the use of the proposed model is in reasonable agreement with experimental data.

Screening of efficient microalgae strains isolated from Tunisian ecosystems: Assessment of algal growth rate and added-value bioproducts for biorefinery applications

Microalgae are highly diverse organisms with significant applications in the production of high-value molecules and biodiesel from microalgae rich in oils. In this study, our main objectives were to evaluate the potential applications of four isolated microalgae strains, namely Scenedesmus sp., Nannochloris sp., Oscillatoria sp., and Amphora sp., which were selected from the natural environment. These strains were batch cultured, and their growth was monitored. We determined the content of chlorophyll a, carotenoids, and lipids, and analyzed the fatty acid profile of each cultivated strain to assess their lipid potential for biodiesel production. Our findings revealed that these strains exhibited high biomass production, ranging from 3000 mg. L−1 for Amphora sp. to 3800 mg. L−1 for Oscillatoria sp. Notably, Oscillatoria sp. and Scenedesmus sp. were found to be the richest in saturated fatty acids, with 10.68% and 9.36% of dry cell weight, respectively, suggesting their potential use in the production of biodiesel from microalgal oils with possibility of blending with other oils feedstock to improve biodiesel final quality. Furthermore, our results showed that the Nannochloris sp. strain could be cultivated to extract pigments for various applications, as it exhibited high levels of chlorophyll a (38.43 mg. L−1) and carotenoids (4.153 μg. mL−1).

The role of zooplankton in the growth of algal bloom: a mathematical study

Here a nonlinear mathematical model for an aquatic ecosystem containing both non-toxic and toxin-producing algal blooms is formulated and analyzed. The presence of harmful algae impacts the aquatic population, subsequently affecting the human population that relies on zooplankton (fish, crabs, etc.). It also deteriorates the water quality, and it is advisable not to use water from lakes containing harmful algae. Here, our focus is to understand the dynamics of aquatic ecosystems when we have both types of algae, one that is non-toxic and acts as food to zooplankton, and another that is toxin-producing algae that causes death to zooplankton. The predation of zooplankton on algae influences the growth of the algae population. First, we consider a deterministic model, and later, this model is extended to stochastic model to check whether it has any impact on the dynamics of the populations under consideration. Various equilibria of the proposed model are derived, and the local stability of these equilibria is thoroughly examined. The existence of Hopf-bifurcation is also demonstrated for a suitable set of parameters. The results of deterministic and stochastic models are compared using numerical simulation. Upon examining our results and simulation data, it is evident that modifying specific key parameters, such as the growth rate of non-toxic algae due to nutrient intake and the parameter associated with the predation of non-toxic algae by zooplankton, has a substantial impact on algal bloom dynamics. Minor adjustments to these parameters can result in an augmented presence of non-toxic algae and a simultaneous decrease in toxin-producing algae, aligning with the primary objectives set by policymakers.

PHYSICO-CHEMICAL PARAMETERS AND CLIMATE CHANGE IMPACT ON ALGAL GROWTH

Identifying the biological processes that influence algal growth is essential for ecosystem management. Algae are little aquatic plants that exist either as solitary cells or in regions of diverse dimensions. Zooplankton rely on them as a crucial component of the aquatic food chain, since they provide as their primary source of nutrition. Algae, via the process of photosynthesis, produce oxygen that is subsequently released into the water, serving as a vital resource for fish and other aquatic organisms. This work presents a methodology for estimating the biological characteristics of algae, which play a crucial role in the regulation of eutrophication, via the use of modelling and exploration methodologies. The estimation of algae growth and respiration rates was conducted by using a one-dimensional water quality model and two-dimensional regionally distributed water quality data taken from Lower Manair Dam of Karimnagar District, Telangana. A total of 24 algae were detected in the sample. The most abundant types of algae include Green algae, Flagellate algae, Cyanobacteria, and Diatoms. In the summer season, 17 types of algae were found, while in the spring season, 20 types were detected. The estimation of biological characteristics of algae in natural freshwater environments may be achieved by a physico-chemical technique, which offers an alternate option to sampling and in situ testing. KEYWORDS: Algal growth, biological parameters, Lower Manair Dam, eutrophication, in situ testing

Boosting wastewater treatment and CO2 bioremediation with Nile River microalgae: Resilience to simulated smoke and enhanced biomass production

This study investigated the potential of Nile River microalgae for treating wastewater under simulated air pollution conditions. We evaluated microalgal growth and nutrient removal efficiency in wastewater with and without microalgal inoculation. Results demonstrated enhanced algal growth rates in all wastewater samples, with maximum chlorophyll (a) concentrations reaching 3093.2 μg/L and 4157.4 μg/L, respectively. This suggests efficient utilization of organic pollutants, with nutrient removal exceeding 90 % efficiency. Notably, Scenedesmus sp. emerged as the most resilient species, achieving the highest biomass production (735.5 mg/L) at a moderate CO2 concentration (16.6 mg/L). Interestingly, optimal CO2 concentrations enhanced the highest growth rate by 0.84 day−1, demonstrating the potential for simultaneous wastewater treatment and CO2 bioremediation. These findings highlight the promise of Nile River microalgae, particularly Scenedesmus sp., for sustainable wastewater treatment even in polluted environments, offering a dual benefit of environmental remediation and bioresource production.

Defect evolution on the activity of samarium doped Na2TinO2n+1 with different sodium/titanium ratio for photocatalytic degradation of fluoroquinolones drugs, toxicity assessments and eco-toxicity prediction

In this study, samarium (Sm) doped sodium titanate (Na2TinO2n+1) with different Na/Ti molar ratios {n: 3, 6, and 9} were synthesized by using sol-gel method. The prepared nanostructures were characterized by XRD, SEM, EDS, BET, UV–vis, EIS and photoluminescence analysis. XRD analysis depicts the Na2Ti6O13 was the main substance, while Sm–Na2Ti9O19 contained a minor proportion of Na2Ti6O13, and rutile phase TiO2. The pore size distribution for all samples is between 2 nm and 20 nm, indicating that most of the pores are in the range of meso porosity. The adsorption-desorption isotherms shows the mesoporous properties of the prepared samples. The band gap energies for samarium doped sodium titanate were lower than the sodium titanate nanostructures. The productivity of hydroxyl radicals on the samarium doped sodium titanates was in the sequence Sm–Na2Ti9O19 > Sm–Na2Ti6O13 > Sm–Na2Ti3O7. The different samarium doped sodium titanates samples were utilized for degradation ofloxacin and ciprofloxacin under UV light irradiation. The results showed that the complete degradation ofloxacin (94.2 %) and ciprofloxacin (99.7 %) were obtained by using Sm–Na2Ti9O19 within 70 min, while the degradation efficiency of Sm–Na2Ti6O13 and Sm–Na2Ti3O7 were lower than Sm–Na2Ti9O19 nanostructures. Also, the marine microalgaes growth rate and biotoxicity of the Sm-doped sodium titanates were investigated on Chaetoceros calcitrans, and Nannochloropsis oculata. The results showed that high concentration of the samarium doped sodium titanates were inhibited the algae growth rate.