No abstract

To achieve strong, successful and commercial aqua-biotechnological microalgae applications, screening, isolation, molecular identification, and physiological characterizations are needed. In the current study, a native cyanobacteria strain Arthrospira platensis NIOF17/003 was isolated from the surface water of El-Khadra Lake, a saline-alkaline lake located in Wadi El-Natrun, Egypt. The cyanobacterium was phylogenetically identified by 16S rRNA molecular marker and deposited in the GenBank database (accession number MW396472). The late exponential phase of A. platensis NIOF17/003 was reached at the 8th day of growth using Zarrouk medium, with a recorded dry weight (DW) of 0.845 g L−1. The isolated strain showed 52% of protein, 14% of carbohydrate, biomass productivity of 143.83 mg L−1 day−1, 8.5% of lipid, and lipid productivity of 14.37 mg L−1 day−1. In general, the values of cetane number, iodine value, cold filter plugging point (52.9, 85.5 g I2/100 g oil, and −2.2 °C, respectively) of the isolated fatty acid methyl esters are in accordance with those suggested by international standards. Besides, applying algal-free lipid (FL) as biodiesel byproduct in the production of rotifer (Brachionus plicatilis) revealed that a 0.6 g L−1 FL significantly increased the rotifer population females carrying eggs, confirming that FL can be used efficiently for B. plicatilis production. The current study concluded that the new isolate A. platensis NIOF17/003 is a promising strain for double sustainable use in biodiesel production and aquaculture feed.

In this study, a polymeric (acrylonitrile-co-styrene) P(AN-co-St) composite was impregnated with adsorbents, such as sulfonated and multiwall carbon nanotubes (MWCNTs), to increase the adsorptive characteristics of the nanocomposite upon the removal of methyl orange (MO) dye under different conditions. A novel nanocomposite copolymer mixture of P(AN-co-St) and SP(AN-co-St) was used. MWCNTs were prepared by a low-cost chemical vapor deposition (CVD) process. Variation in MO adsorption onto the three nanocomposites was examined in an aqueous solution via the batch technique with respect to contact time, initial MO concentration, adsorbent dosage, pH, and temperature. The surface of the nanocomposites was characterized by a scanning electron microscope (SEM), particle size distribution (PSD), Fourier transform infrared (FTIR), and Raman analysis. The experimental data showed that the efficiency of P(AN-co-St)/ MWCNT removal increased under the conditions of an acidic pH (3 and 5) with an agitation speed of 140 rpm, a sorbent weight of 0.01 g, and 20 mg of initial dye. The maximum sorption capacities were 121.95, 48.78, and 47.84 mg g−1 for the P(AN-co-St)/ MWCNTs, SP(AN-co-St), and P(AN-co-St) composites, respectively, as assessed by the Langmuir model. Additional isotherm models, such as the Freundlich, Temkin, and Halsey models, were used to examine the experimental data. A pseudo-second-order model was found to be more fitting for describing the sorption.

This study aims to produce green zinc oxide nanoparticles (ZnO-NPs) derived from red seaweed (Pterocladia Capillacea) and evaluate their potential to absorb Ismate violet 2R (IV2R) ions from an aqueous solution. UV-vis spectrophotometry, Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction (XRD), and a Brunauer–Emmett–Teller surface area analysis (BET) were used to analyze the structural, morphological, and optical features of the synthesized nanoparticles. The change in color of the chemical solution revealed the formation of zinc oxide nanoparticles. The FTIR examination confirmed the synthesis of both Zn and ZnO nanoparticle powder, with a BET surface area of 113.751 m2 g−1 and an average pore size of 2.527 nm for the synthesized adsorbent. Furthermore, the maximum removal effectiveness of IV2R was 99% when 0.08 g ZnO-NPs was applied at a pH of 6, a temperature of 55 °C, and a contact time of 120 min. The dye adsorption capacity of the ZnO-NPs was 72.24 mg g−1. The adsorption process was also controlled by the Freundlich adsorption model and pseudo-second-order reaction kinetics. The adsorption of IV2R ions onto the ZnO-NPs could be represented as a nonideal and reversible sorption process of a nonuniform surface, according to Freundlich adsorption isotherms. In addition, the constant values of the model parameters were determined using various nonlinear regression error functions. Moreover, thermodynamic parameters such as entropy change, enthalpy change, and free energy change were investigated; the adsorption process was spontaneous and endothermic. The high capacity of the ZnO-NPs synthesized by red seaweed promotes them as promising substances for applications in water treatment for the removal of IV2R dye from aqueous systems.

This study aims to investigate the abundance, community, and structure of phytoplankton, physicochemical parameters, and some eutrophication state indices, to estimate the water quality of eight selected beaches along the Alexandria Coast, in the southeast of the Mediterranean Sea. The samples were collected monthly from 2019 to 2020. Nutrient values ranged from 1.54 to 33.21 µM for nitrate, 0.01 to 1.98 µM for nitrite, 0.12 to 9.45 µM for ammonia, 0.01 to 1.54 µM for phosphate, and 0.67 to 29.53 µM for silicate. Phytoplankton biomass was characterized by chlorophyll-a concentration, which fluctuated between 0.12 and 12.31 µg L−1. The annual phytoplankton average was 63.85 ± 17.83 × 103 cells L−1. Phytoplankton was highly diversified (228 taxa), and the most diversified group was diatoms (136 taxa), followed by a remarkably low number of Dinophyta (36 taxa). Diatoms reached maximum abundance in December. Meanwhile, a dense bloom of microalga Chlorella marina occurred in June on some beaches. High temperature, high dissolved inorganic nitrogen, and less-saline waters have supported green algal proliferation. The Shannon–Wiener diversity index (H’) showed that there was a qualitative seasonal difference in the composition of the phytoplankton community. Waters of beaches 1–3 were classified as between clean and moderately polluted; and beaches 4–8 varied between moderately and heavily polluted. The study revealed that human activities might have triggered the algal bloom and may be responsible for alterations in the Alexandria coast ecosystem.

Arthrospira platensis is one of the most important cultured microalgal species in the world. Arthrospira complete dry biomass (ACDB) has been reported as an interesting feedstock for many industries, including biodiesel production. The A. platensis by-product of biodiesel production (lipid-free biomass; LFB) is a source of proteins, functional molecules, and carbohydrates, and can also be reused in several applications. The current study investigated the efficiency of ACDB and LFB in bioremediation of dye (Ismate violet 2R, IV2R) from textile effluents. In addition, the potential of ACDB and LFB loaded by IV2R as a feed for Rotifer, Brachionus plicatilis, was examined. The surface of the adsorbents was characterized by SEM, FTIR, and Raman analysis to understand the adsorption mechanism. The batch sorption method was examined as a function of adsorbent dose (0.02–0.01 g L−1), solution initial concentration (10–100 mg L−1), pH (2–10), and contact time (15–180 min). The kinetic studies and adsorption isotherm models (Freundlich, Langmuir, Tempkin, and Halsey) were used to describe the interaction between dye and adsorbents. The results concluded that the adsorption process increased with increasing ACDB and LFB dose, contact time (120 min), initial IV2R concentration (10 mg L−1), and acidity pH (2 and 6, respectively). For the elimination of industrial textile wastewater, the ACDB and LFB sorbents have good elimination ability of a dye solution by 75.7% and 61.11%, respectively. The kinetic interaction between dye and adsorbents fitted well to Langmuir, Freundlish, and Halsey models for LFB, and Langmuir for ACDB at optimum conditions with R2 > 0.9. In addition, based on the bioassay study, the ACDB and LFB loaded by IV2R up to 0.02 g L−1 may be used as feed for the marine Rotifer B. plicatilis.

Burullus Lake is Egypt’s second most important coastal lagoon. The present study aimed to shed light on the different types of polluted waters entering the lake from various drains, as well as to evaluate the zooplankton community, determine the physical and chemical characteristics of the waters, and study the eutrophication state based on three years of seasonal monitoring from 2017 to 2019 at 12 stations. The results revealed that Rotifera, Copepoda, Protozoa, and Cladocera dominated the zooplankton population across the three-year study period, with a total of 98 taxa from 59 genera and 10 groups detected in the whole-body lake in 2018 and 2019, compared to 93 species from 52 genera in 2017. Twelve representative surface water samples were collected from the lake to determine physicochemical parameters, i.e., temperature, pH, salinity, dissolved oxygen, biological oxygen demand, chemical oxygen demand, ammonia-N, nitrate–N, nitrate-N, total nitrogen, total phosphorus, dissolved reactive phosphorus, and chlorophyll-a, as well as Fe, Cu, Zn, Cr, Ni, Cd, and Pb ions. Based on the calculations of the water quality index (WQI), the lake was classified as having good water quality. However, the trophic state is ranked as hyper-eutrophic and high trophic conditions.

The present work evaluated the capability of Arthrospira platensis complete biomass (ACDW) and the lipid-free biomass (LFB) to remove ammonium ions (NH4+) from aquaculture wastewater discharge. Under controlled conditions in flasks filled with 100 mL of distilled water (synthetic aqueous solution), a batch process ion-exchange was conducted by changing the main parameters including contact times (15, 30, 45, 60, 120, and 180 min), initial ammonium ion concentrations (10, 20, 30, 40, 50, and 100 mg·L−1), and initial pH levels (2, 4, 6, 8, and 10) at various dosages of ACDW and LFB as adsorbents (0.02, 0.04, 0.06, 0.08, and 0.1 g). After lab optimization, ammonia removal from real aquaculture wastewater was also examined. The removal of ammonium using ACDW and LFB in the synthetic aqueous solution (64.24% and 89.68%, respectively) was higher than that of the real aquaculture effluents (25.70% and 37.80%, respectively). The data of IR and Raman spectroscopy confirmed the existence of various functional groups in the biomass of ACDW and LFB. The adsorption equilibrium isotherms were estimated using Freundlich, Langmuir, and Halsey models, providing an initial description of the ammonia elimination capacity of A. platensis. The experimental kinetic study was suitably fit by a pseudo-second-order equation. On the other hand, as a result of the treatment of real aquaculture wastewater (RAW) using LFB and ACDW, the bacterial counts of the LFB, ACDW, ACDW-RAW, and RAW groups were high (higher than 300 CFU), while the LFB-RAW group showed lower than 100 CFU. The current study is the first work reporting the potential of ammonia-loaded microalgae biomass as a feed source for the rotifer (Brachionus plicatilis). In general, our findings concluded that B. plicatilis was sensitive to A. platensis biomass loaded with ammonia concentrations. Overall, the results in this work showed that the biomass of A. platensis is a promising candidate for removing ammonia from aquaculture wastewater.