Nitrate and phosphate removal by chitosan immobilized Scenedesmus

Synthesis and Design of a Synthetic-Living Material Composed of Chitosan, Calendula officinalis Hydroalcoholic Extract, and Yeast with Applications as a Biocatalyst

Design and development of materials that couple synthetic and living components allow taking advantage of the complexity of biological systems within a controlled environment. However, their design and fabrication represent a challenge for material scientists since it is necessary to synthesize synthetic materials with highly specialized biocompatible and physicochemical properties. The design of synthetic-living materials (vita materials) requires materials capable of hosting cell ingrowth and maintaining cell viability for extended periods. Vita materials offer various advantages, from simplifying product purification steps to controlling cell metabolic activity and improving the resistance of biological systems to external stress factors, translating into reducing bioprocess costs and diversifying their industrial applications. Here, chitosan sponges, functionalized with Calendula officinalis hydroalcoholic extract, were synthesized using the freeze-drying method; they showed small pore sizes (7.58 μm), high porosity (97.95%), high water absorption (1695%), and thermal stability, which allows the material to withstand sterilization conditions. The sponges allowed integration of 58.34% of viable Saccharomyces cerevisiae cells, and the cell viability was conserved 12 h post-process (57.14%) under storage conditions [refrigerating temperature (4 °C) and without a nutrient supply]. In addition, the synthesized vita materials conserved their biocatalytic activity after 7 days of the integration process, which was evaluated through glucose consumption and ethanol production. The results in this paper describe the synthesis of complex vita materials and demonstrate that biochemically modified chitosan sponges can be used as a platform material to host living and metabolically active yeast with diverse applications as biocatalysts.

Assessment of a novel microalgae-cork based technology for removing antibiotics, pesticides and nitrates from groundwater

Groundwater pollution has increased in recent years due to the intensification of agricultural and livestock activities. This results in a significant reduction in available freshwater resources. Here, we have studied the long term assessment of a green technology (1-4 L/day) based on a photobioreactor (PBR) containing immobilised microalgae-bacteria in polyurethane foam (PF) followed by a cork filter (CF) for removing nitrates, pesticides (atrazine and bromacil), and antibiotics (sulfamethoxazole and sulfacetamide) from groundwater. The prototype was moderately effective for removing nitrates (58%) at an HRT of 8 days, while its efficiency decreased at a HRT of 4 and 2 days (<20% removal). The combined use of PBR-CF enabled antibiotics and pesticides to be attenuated by up to 95% at an HRT of 8 days, but their attenuation decreased with shorter HRT, with pesticides being the compounds most affected (reducing from 97 to 98% at an HRT of 8 days to 23-45% at an HRT of 2 days). Pesticide transformation products were identified after the CF, supporting biodegradation as the main attenuation process. A gene-based metataxonomic assessment linked the attenuation of micropollutants to the presence of specific pesticide biodegradation species (e.g. genus Phenylobacterium, Sphingomonadaceae, and Caulobacteraceae). Therefore, the results highlighted the potential use of microalgae and cork to treat polluted groundwater.

Pharmaceuticals in the Aquatic Environment: A Review on Eco-Toxicology and the Remediation Potential of Algae

The pollution of the aquatic environment has become a worldwide problem. The widespread use of pesticides, heavy metals and pharmaceuticals through anthropogenic activities has increased the emission of such contaminants into wastewater. Pharmaceuticals constitute a significant class of aquatic contaminants and can seriously threaten the health of non-target organisms. No strict legal regulations on the consumption and release of pharmaceuticals into water bodies have been implemented on a global scale. Different conventional wastewater treatments are not well-designed to remove emerging contaminants from wastewater with high efficiency. Therefore, particular attention has been paid to the phycoremediation technique, which seems to be a promising choice as a low-cost and environment-friendly wastewater treatment. This technique uses macro- or micro-algae for the removal or biotransformation of pollutants and is constantly being developed to cope with the issue of wastewater contamination. The aims of this review are: (i) to examine the occurrence of pharmaceuticals in water, and their toxicity on non-target organisms and to describe the inefficient conventional wastewater treatments; (ii) present cost-efficient algal-based techniques of contamination removal; (iii) to characterize types of algae cultivation systems; and (iv) to describe the challenges and advantages of phycoremediation.

Effects of the induction of anoxia in photobioreactor on effective cultivation of Scenedesmus acuminatus under mixotrophic cultivation mode

The purpose of this study was to investigate the optimum conditions of several factors (i.e. types and concentration of acetate, aeration rate, pH control) for maximizing the mixotrophic cultivation of Scenedesmus acuminatus using acetate as an organic carbon source. When acetate was used, dissolved oxygen (DO) was quickly consumed and resulted in an anoxic condition for 52 h. Then, DO increased quickly by photosynthetic reaction. Whenever we put acetate in a reactor after DO was recovered to higher than 7 mg/L, cells were quickly grown via cell respiration, which subsequently resulted in an anoxic condition. Compared to aeration, ammonium acetate, ammonium acetate with aeration tests, the highest maximum biomass productivity of 0.73 g/L/d was obtained for pH control test with ammonium acetate dosage. From this study, we found that DO was essential for the fast assimilation of acetate and depleted DO was quickly regenerated for pH control test. From this fact, we found that pH control test with ammonium acetate dosage was the best cultivation method for Scenedesmus acuminatus under mixotrophic condition. These findings could be a useful reference for maximizing the cultivation of S. acuminatus in industrial-scale applications.

Chitosan Silver and Gold Nanoparticle Formation Using Endophytic Fungi as Powerful Antimicrobial and Anti-Biofilm Potentialities

Nanotechnology is emerging as a new technology with encouraging innovations. Global antibiotic use has grown enormously, with antibiotic resistance increasing by about 80 percent. In view of this alarming situation, intensive research has been carried out into biogenic nanoparticles and their antibacterial, antifungal, and antitumor activities. Many methods are available to enhance stability and dispersion via peroration of conjugate with a polymer, such as chitosan, and other bioactive natural products. Two marine fungi were isolated and identified as Aspergillus sp. and Alternaria sp. via sequencing of the 16S rRNA gene. In this work, these strains were used to form the conjugation of biogenic silver nanoparticles (AgNPs) from Aspergillus sp. Silv2 extract and gold nanoparticles (AuNPs) from Alternaria sp. Gol2 extracts with chitosan to prepare chitosan–AgNPs and chitosan–AuNP conjugates. A variety of imaging and analytical methods, such as UV–vis, X-ray powder diffraction (XRD), FTIR spectroscopy, transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were utilized to characterize biogenic nanoparticles and conjugates. The biosynthesized Ag and Au nanoparticles along with the prepared conjugates were evaluated for their antimicrobial effects on Gram-negative and Gram-positive bacterial isolates, including Escherichia coli and Staphylococcus aureus. Both chitosan–AgNP and AuNP showed powerful antimicrobial activities compared to the control. On the other hand, chitosan–AgNP conjugation had better antibacterial ctivity than chitosan–AuNPs, which exhibited moderate activity against S. aureus and very low activity against E. coli. Furthermore, the antibiofilm potentials of the prepared conjugates were tested against four biofilm-forming bacteria, including P. aeruginosa, B. subtilis, E. coli, and S. aureus. The obtained results indicate that the chitosan–AgNP showed a promising anti-biofilm activities on all strains, especially S. aureus, while chitosan–AuNP conjugates showed moderate anti-biofilm against B. subtilis and weak activities against the other three strains. These results showed the superiority of chitosan–AgNP as a promising antibacterial as well as biofilm formation inhibitors.

An evaluation into the biosorption and biodegradation of azo dyes by indigenous siderophores-producing bacteria immobilized in chitosan

The biodegradation and biosorption efficiency of an indigenous siderophores-producing bacterial community on azo dyes with immobilization in chitosan beads was evaluated in this study. 13 bacterial strains were isolated from textile wastewater streams. The bacterial strains were tested for the production of siderophores as well as their ability to decolorize toxic azo dyes in aqueous solution. Both qualitatively and quantitatively, all of the strains displayed high siderophores productivity. Furthermore, they displayed remarkable decolorization efficiency for azo dyes (Acid Black 1 and Reactive Black 5) in both free and immobilized form. The immobilization process was found not only to enhance the decolorization but also the degradation of azo dyes by the bacterial isolates. In a SEM micrograph, bacterial strains were immobilized, and the pores in chitosan bead to be trapped and adsorbed for dyes from synthetic wastewater. The extent of dye compounds degradation were examined using UV-visible and FTIR spectrophotometers on treated water samples and dye absorbed beads. After 72 h of incubation, the UV-visible analysis revealed that the bacterial community could significantly reduce both azo dyes in wastewater by 90% at 300 mgL^-1 dyes initial concentration. FTIR study confirmed the bonds of these dyes were broken to form less toxic chemicals via the bacterial community immobilized in chitosan beads. The immobilized bacterial community thus demonstrated effective approach of azo dye biosorption and biodegradation.

A Hybrid Biological-Adsorption Approach for the Treatment of Contaminated Groundwater Using Immobilized Nanoclay-Algae Mixtures

Mixing the Scenedesmus species with nanoclay and immobilizing in sodium alginate was evaluated as a sustainable treatment method for removing nitrate, atrazine, and metals from groundwater. Gel beads containing the hybrid mixture removed 100% of 10 mg/L N nitrate and 98% of 100 µg/L atrazine from synthetic groundwater in three days. The optimal amount of nanoclay was found to be 0.30 mg per bead. The experimental data fit well into a Freundlich adsorption isotherm and followed pseudo first-order kinetics. When tested in actual groundwater, 91% of nitrate and 100% of Cr, Se, and V were eliminated in three days without need for any nutrients or carbon source. Immobilizing algal beads embedded with nanoclay is a natural, low-cost alternative for groundwater treatment. The gel beads can be reused for at least two cycles without a compromise in performance. They are water-insoluble, easy to harvest, and offer high removal efficiency.

Integrating micro-algae into wastewater treatment: A review

Improving the ecological status of water sources is a growing focus for many developed and developing nations, in particular with reducing nitrogen and phosphorus in wastewater effluent. In recent years, mixotrophic micro-algae have received increased interest in implementing them as part of wastewater treatment. This is based on their ability to utilise organic and inorganic carbon, as well as inorganic nitrogen (N) and phosphorous (P) in wastewater for their growth, with the desired results of a reduction in the concentration of these substances in the water. The aim of this review is to provide a critical account of micro-algae as an important step in wastewater treatment for enhancing the reduction of N, P and the chemical oxygen demand (COD) in wastewater, whilst utilising a fraction of the energy demand of conventional biological treatment systems. Here, we begin with an overview of the various steps in the treatment process, followed by a review of the cellular and metabolic mechanisms that micro-algae use to reduce N, P and COD of wastewater with identification of when the process may potentially be most effective. We also describe the various abiotic and biotic factors influencing micro-algae wastewater treatment, together with a review of bioreactor configuration and design. Furthermore, a detailed overview is provided of the current state-of-the-art in the use of micro-algae in wastewater treatment.

Enhanced stability and nitrogen removal efficiency of Klebsiella sp. entrapped in chitosan beads applied in the domestic sewage system

Although numerous denitrifying bacteria have been isolated and characterized, their capacity is seriously compromised by traditional inoculant addition and environmental stress in open bioreactors for wastewater treatment. In this study, a biocompatible material, chitosan, was used as a carrier to immobilize a simultaneously heterotrophic nitrifying-aerobic denitrifying bacterium Klebsiella sp., KSND, for continuous nitrogen removal from domestic wastewater in an open purification tank. The results showed that immobilization had no significant effect on cell viability and was beneficial for the reproduction and adhesion of cells. The entrapped KSND exhibited a slightly higher nitrogen removal efficiency of 90.09% than that of free KSND (87.69%). Subsequently, repeated batch cultivation experiments and analysis of the effects of organic contaminants and metal ions were performed using artificial wastewater and domestic wastewater. The findings revealed that the immobilized KSND beads presented desirable biophysical properties with good mechanical stability, cell viability, and enrichment, remarkable stability in organic contaminants and metal ions, and high efficiency nitrogen removal capacity. In conclusion, the developed immobilized denitrifying bacteria system has great potential for continuous wastewater treatment in open bioreactors.

Efficiency of pollutants removal in treated palm oil mill effluent (TPOME) using different concentrations of sodium alginate-immobilized Nannochloropsis sp. cells

Palm oil mill effluent (POME) has high chemical oxygen demand (COD), thus requires effective treatments to environmentally benign levels before discharge. In this study, immobilized microalgae cells are used for removing pollutants in treated palm oil mill effluent (TPOME). Different ratios of microalgae beads to TPOME concentration were examined at 1:2.5, 1:5, and 1:10. The biomass concentration and COD removal were measured through a standard method. The color of the cultivated microalgae beads changed from light green to darker green after the POME treatment for 9 days, hence demonstrating that microalgae cells were successfully grown inside the beads with pH up to 9.84. The immobilized cells cultivated in the POME at 1:10 achieved a higher biomass concentration of 1.268 g/L and a COD removal percentage of 72% than other treatment ratios. The increment of the ratio of microalgae cells beads to POME concentration did not cause any improvement in COD removal efficiency. This was due to the inhibitory effect of self-shading resulting in the slow growth rate of microalgae cells which responsible for low COD removal. Therefore, this system could be a viable technology for simultaneous biomass production and POME treatment. This will contribute to research efforts toward the development of new and improved technologies in treating POME.

Microalgae wastewater treatment: Biological and technological approaches

Current global environmental issues raise unavoidable challenges for our use of natural resources. Supplying the human population with clean water is becoming a global problem. Numerous organic and inorganic impurities in municipal, industrial, and agricultural waters, ranging from microplastics to high nutrient loads and heavy metals, endanger our nutrition and health. The development of efficient wastewater treatment technologies and circular economic approaches is thus becoming increasingly important. The biomass production of microalgae using industrial wastewater offers the possibility of recycling industrial residues to create new sources of raw materials for energy and material use. This review discusses algae-based wastewater treatment technologies with a special focus on industrial wastewater sources, the potential of non-conventional extremophilic (thermophilic, acidophilic, and psychrophilic) microalgae, and industrial algae-wastewater treatment concepts that have already been put into practice.

Denitrification performance and microbial diversity of immobilized bacterial consortium treating nitrate micro-polluted water

A heterotrophic denitrification process using bacterial consortium immobilized by polyurethane foams carriers to treat nitrate micro-polluted water was investigated. Nitrate reduction and nitrite accumulation were studied under several factors including initial COD/NO₃^--N concentration ratio, initial pH, initial NO₂^--N/NO₃^--N concentration ratio and inlet NO₃^--N concentration. Batch denitrification experiments showed that nitrate was completely removed at 5 h without nitrite accumulation under the optimum conditions of COD/NO₃^--N concentration ratio of 5.0-5.5 and initial pH of 7.2 ± 0.1. High initial NO₂^--N/NO₃^--N ratio enhanced denitrification rate mainly by accelerating nitrite reduction. Denitrification processes followed zero-order reaction kinetics at different initial NO₃^--N concentrations and obtained higher denitrification rate at higher inlet nitrate. High-throughput sequencing results showed that microbial community structure differed between the surface and interior space of polyurethane foams carriers while the dominant population in the inner zone of carriers was Pseudoxanthomonas.

Harvest of the Oleaginous Microalgae Scenedesmus obtusiusculus by Flocculation From Culture Based on Natural Water Sources

Harvest and dewatering poses a significant economical burden for industrial algae biomass production. To mitigate these effects, energy efficient techniques for these process steps have to be developed. Flocculation of the microalgae Scenedesmus obtusiusculus in salt based medium was induced by pH-shift and alternatively by addition of two biological flocculants, chitosan, and the commercial tannin CFL-PT. This is the first time that CFL-PT is used as an algae flocculant particularly focusing on harvesting of halophilic strains. The method was characterized and subsequently optimized. In comparison to biological flocculants, induction by pH shift is far cheaper, but due to buffering effects of the brackish cultivation medium infeasible amounts of base are required to raise the pH-value. tannin appears to be superior compared to chitosan not only in the absence of algae organic matter (AOM), but tannin-based harvest is also more robust regarding culture pH in presence of AOM. A higher flocculant-demand for modified tannin compared to chitosan is offset by the lower price. Given the employed strain and cultivation conditions, cultivation time had no pronounced effect on flocculation efficiencies (FE) while algae zeta-potential and bacterial communities also remained stable.

Potential of Zeolite and Algae in Biomass Immobilization

The interest in utilizing algae for wastewater treatment has been increased due to many advantages. Algae-wastewater treatment system offers a cost-efficient and environmentally friendly alternative to conventional treatment processes such as electrocoagulation and flocculation. In this biosystem, algae can assimilate nutrients in the wastewater for their growth and simultaneously capture the carbon dioxide from the atmosphere during photosynthesis resulting in a decrease in the greenhouse gaseousness. Furthermore, the algal biomass obtained from the treatment process could be further converted to produce high value-added products. However, the recovery of free suspended algae from the treated effluent is one of the most important challenges during the treatment process as the current methods such as centrifugation and filtration are faced with the high cost. Immobilization of algae is a suitable approach to overcome the harvesting issue. However, there are some drawbacks with the common immobilization carriers such as alginate and polyacrylamide related to low stability and toxicity, respectively. Hence, it is necessary to apply a new carrier without the mentioned problems. One of the carriers that can be a suitable candidate for the immobilization is zeolite. To date, various types of zeolite have been used for the immobilization of cells of bacteria and yeast. If there is any possibility to apply them for the immobilization of algae, it needs to be considered in further studies. This article reviews cell immobilization technique, biomass immobilization onto zeolites, and algal immobilization with their applications. Furthermore, the potential application of zeolite as an ideal carrier for algal immobilization has been discussed.

Fungal enzyme-mediated synthesis of chitosan nanoparticles and its biocompatibility, antioxidant and bactericidal properties

This paper reports the synthesis of chitosan nanoparticles (T-CSNPs) using the fungal enzyme of Trichoderma harzianum and its biocompatibility, antioxidant and bactericidal properties. The T-CSNPs synthesis was confirmed by absorbance at 280 nm using UV-Vis spectrophotometer. T-CSNPs were of spherical shape, as evident by field emission transmission electron microscopic (FETEM) analysis, and the average size of T-CSNPs was 90.8 nm, as calculated using particle size analyzer (PSA). The functional groups showed modifications of chitosan in T-CSNPs as evident by fourier-transform infrared spectroscopic (FTIR) analysis. T-CSNPs were found soluble at the wide range of pH, showing 100% solubility at pH 1-3 and 72% at pH 10. The T-CSNPs exhibited antioxidant property in a dose-dependent manner with pronounced activity at 100 mg·mL^-1. The T-CSNPs also showed bactericidal activity against Staphylococcus aureus and Salmonella enterica Typhimurium by causing detrimental effects on bacterial cells. The T-CSNPs (50 μg·mL^-1) did not display any cytotoxic effect on murine fibroblast NIH-3T3 cells, as evident by cell viability and acridine orange/ethidium bromide staining assays, which confirmed biocompatibility of the nanoparticles. This work suggested further investigations on the utilization of the mycosynthesized nanochitosan in biomedical applications.

Exploiting Microbial Polysaccharides for Biosorption of Trace Elements in Aqueous Environments-Scope for Expansion via Nanomaterial Intervention

With pollution sounding high alarms all around us, there is an immediate necessity for remediation. In most cases, the remediation measures require further remediation-the anti-pollutants themselves cause pollution. In this correspondence, the search deepens towards natural biogenic components that can be used for bioremediation. Polysaccharide and biosorption have been themes in discussion for quite some time, where a slow decline in the enthusiasm in this area has been observed. This review revisits the importance of using polysaccharide based materials for biosorption. The need for polysaccharide-based nanocomposites, which hold better promise for greater deliverables, is emphasized as a means of rejuvenating the future perspectives in this area of application.

Municipal wastewater treatment via co-immobilized microalgal-bacterial symbiosis: Microorganism growth and nutrients removal

A symbiotic microalgal-bacterial system may be an optional technology for wastewater treatment. In this study, co-immobilized of a bacterium isolated from a municipal wastewater treatment plant (Pseudomonas putida) and a microalgae Chlorella vulgaris was used in the study of cell growth and nutrient removal during wastewater treatment under batch and continuous culture conditions. Under batch culture conditions, co-immobilization treatment significantly increased the cell density of C. vulgaris and P. putida compared with other treatments. The co-immobilized treatment also showed higher removal of ammonium, phosphate and COD than any single treatment, indicating that the nutrient uptake capability of C. vulgaris and P. Putida was mutually enhanced mutually. When tested in continuous mode, the treatment with a hydraulic retention time of 24h at the organic load rate of 1159.2mgCODL^-1d^-1 was most appropriate for wastewater treatment.

Removal and Biodegradation of Nonylphenol by Four Freshwater Microalgae

The removal and biodegradation of nonylphenol (NP) by four freshwater microalgae, including three green algae (Scendesmus quadriauda, Chlorella vulgaris, and Ankistrodesmus acicularis) and one cyanobacterium (Chroococcus minutus) were studied in bacteria-free cultures exposed to different concentrations of NP for 5 days. All four algal species showed a rapid and high ability to remove NP (including bioaccumulation and biodegradation). Among these species, A. acicularis (Ankistrodesmus acicularis) had the highest NP removal rate (83.77%) at 120 h when exposed to different NP treatments (0.5–2.5 mg·L⁻¹), followed by C. vulgaris (Chlorella vulgaris) (80.80%), S. quadriauda (Scendesmus quadriauda) (70.96%) and C. minutus (Chroococcus minutus) (64.26%). C. vulgaris had the highest NP biodegradation percentage (68.80%) at 120 h, followed by A. acicularis (65.63%), S. quadriauda (63.10%); and C. minutus (34.91%). The extracellular NP contents were lower than the intracellular NP contents in all tested algae. The ratio of the extracellular NP content and the intracellular NP content ranged from 0.04 to 0.85. Therefore, the removal of NP from the medium was mainly due to the algal degradation. These results indicate that A. acicularis and C. vulgaris are more tolerant to NP and could be used for treatment of NP contaminated aqueous systems effectively by bioremoval and biodegradation.

Removal of endocrine disrupting compounds from wastewater by microalgae co-immobilized in alginate beads

Microalgae systems have been found to be efficient for removing microcontaminants from wastewater effluents, but the effectiveness of immobilized microalgae for removing endocrine disrupting compounds (EDCs) has not yet been addressed. This paper assesses the effect of free and immobilized microalgae on removal efficiency for 6 EDCs by mixing them in 2.5 L reactors with treated wastewater. The experimental design also included control reactors without microalgae. After 10 days of incubation, 64 and 89% of the NH₄-N and 90 and 96% of total phosphorous (TP) had been eliminated in the free microalgae and immobilized microalgae reactors, respectively, while the control reactors eliminated only 40% and 70% of the NH₄-N and TP, respectively. Both the free and immobilized microalgae reactors were able to remove up to 80% of most of the studied EDCs within 10 days of incubation. Free microalgae were found to increase the kinetic removal rate for bisphenol A, 17-α-ethinylestradiol, and 4-octylphenol (25%, 159%, and 41%, respectively). Immobilizing the microalgae in alginate beads additionally enhanced the kinetic removal rate for bisphenol AF, bisphenol F, and 2,4-dichlorophenol. This study shows that the use of co-immobilized microalgae-based wastewater treatment systems increases the removal efficiency for nutrients and some EDCs from wastewater effluents.

Marine polysaccharide-based nanomaterials as a novel source of nanobiotechnological applications

Research on marine polysaccharide-based nanomaterials is emerging in nanobiotechnological fields such as drug delivery, gene delivery, tissue engineering, cancer therapy, wound dressing, biosensors, and water treatment. Important properties of the marine polysaccharides include biocompatibility, biodegradability, nontoxicity, low cost, and abundance. Most of the marine polysaccharides are derived from natural sources such as fucoidan, alginates, carrageenan, agarose, porphyran, ulvan, mauran, chitin, chitosan, and chitooligosaccharide. Marine polysaccharides are very important biological macromolecules that widely exist in marine organisms. Marine polysaccharides exhibit a vast variety of structures and are still under-exploited and thus should be considered as a novel source of natural products for drug discovery. An enormous variety of polysaccharides can be extracted from marine organisms such as algae, crustaceans, and microorganisms. Marine polysaccharides have been shown to have a variety of biological and biomedical properties. Recently, research and development of marine polysaccharide-based nanomaterials have received considerable attention as one of the major resources for nanotechnological applications. This review highlights the recent research on marine polysaccharide-based nanomaterials for biotechnological and biomedical applications.

Integrating algaculture into small wastewater treatment plants: process flow options and life cycle impacts

Algaculture has the potential to be a sustainable option for nutrient removal at wastewater treatment plants. The purpose of this study was to compare the environmental impacts of three likely algaculture integration strategies to a conventional nutrient removal strategy. Process modeling was used to determine life cycle inventory data and a comparative life cycle assessment was used to determine environmental impacts. Treatment scenarios included a base case treatment plant without nutrient removal, a plant with conventional nutrient removal, and three other cases with algal unit processes placed at the head of the plant, in a side stream, and at the end of the plant, respectively. Impact categories included eutrophication, global warming, ecotoxicity, and primary energy demand. Integrating algaculture prior to activated sludge proved to be most beneficial of the scenarios considered for all impact categories; however, this scenario would also require primary sedimentation and impacts of that unit process should be considered for implementation of such a system.

Green synthesis of Fe nanoparticles using eucalyptus leaf extracts for treatment of eutrophic wastewater

Iron nanoparticles were firstly synthesized through a one-step room-temperature biosynthetic route using eucalyptus leaf extracts (EL-Fe NPs). Scanning electron microscopy (SEM) and X-ray energy-dispersive spectrometer (EDS) confirmed the successful synthesis of the spheroidal iron nanoparticles. Furthermore, X-ray diffraction (XRD) and Fourier Transform Infrared spectrometer (FTIR) indicated that some polyphenols are bound to the surfaces of EL-Fe NPs as a capping/stabilizing agent. Reactivity of EL-Fe NPs was evaluated for the treatment of swine wastewater and results indicated that 71.7% of total N and 84.5% of COD were removed, respectively. This demonstrated the tremendous potential of EL-Fe NPs for in situ remediation of eutrophic wastewater.

Wastewater treatment to enhance the economic viability of microalgae culture

Microalgae culture is still not economically viable and it presents some negative environmental impacts, concerning water, nutrient and energy requirements. In this context, this study aims to review the recent advances on microalgal cultures in wastewaters to enhance their economic viability. We focused on three different culture concepts: (1) suspended cell systems, (2) cell immobilization, and (3) microalgae consortia. Cultures with suspended cells are the most studied. The nutrient removal efficiencies are usually high for wastewaters of different sources. However, biomass harvesting is difficult and a costly process due to the small cell size and lower culture density. On the other hand, the cell immobilization systems showed to be the solution for this problem, having as main limitation the nutrient diffusion from bulk to cells, which results in a reduced nutrient removal efficiency. The consortium between microalgae and bacteria enhances the growth of both microorganisms. This culture concept showed to be a promising technology to improve wastewater treatment, regarding not only nutrient removal but also biomass harvesting by bioflocculation. The aggregation mechanism must be studied in depth to find the process parameters that would lead to an effective and cheap harvesting process.

Chitosan-based nanomaterials: a state-of-the-art review

This manuscript briefly reviews the extensive research as well as new developments on chitosan based nanomaterials for various applications. Chitosan is a biocompatible and biodegradable polymer having immense structural possibilities for chemical and mechanical modification to generate novel properties and functions in different fields especially in the biomedical field. Over the last era, research in functional biomaterials such as chitosan has led to the development of new drug delivery system and superior regenerative medicine, currently one of the most quickly growing fields in the area of health science. Chitosan is known as a biomaterial due to its biocompatibility, biodegradability, and non-toxic properties. These properties clearly point out that chitosan has greater potential for future development in different fields of science namely drug delivery, gene delivery, cell imaging, sensors and also in the treatment as well as diagnosis of some diseases like cancer. Chitosan based nanomaterials have superior physical and chemical properties such as high surface area, porosity, tensile strength, conductivity, photo-luminescent as well as increased mechanical properties as comparison to pure chitosan. This review highlights the recent research on different aspect of chitosan based nanomaterials, including their preparation and application.

Immobilization of nitrite oxidizing bacteria using biopolymeric chitosan media

The effects of chitosan characteristics including the degree of deacetylation, molecular weight, particle size, pH pretreatment and immobilization time on the immobilization of nitrite-oxidizing bacteria (NOB) on biopolymeric chitosan were investigated. Nitrite removal efficiency of immobilized NOB depended on the degree of deacetylation, particle size, pH pretreatment on the surface of chitosan and immobilization time. Scanning electron microscope characterization illustrated that the number of NOB cells attached to the surface of chitosan increased with an increment of immobilization time. The optimal condition for NOB immobilization on chitosan was achieved during a 24-hr immobilization period using chitosan with the degree of deacetylation larger than 80% and various particle size ranges between 1-5 mm at pH 6.5. In general, the NOB immobilized on chitosan flakes has a high potential to remove excess nitrite from wastewater and aquaculture systems.

Plant based phosphorus recovery from wastewater via algae and macrophytes

At present, resource recovery by irrigation of wastewater to plants is usually driven by the value of the water resource rather than phosphorus recovery. Expanded irrigation for increased phosphorus recovery may be expected as the scarcity and price of phosphorus increases, but providing the necessary treatment, storage and conveyance comes at significant expense. An alternative to taking the wastewater to the plants is instead to take the plants to the wastewater. Algal ponds and macrophyte wetlands are already in widespread use for wastewater treatment and if harvested, would require less than one-tenth of the area to recover phosphorus compared to terrestrial crops/pastures. This area could be further decreased if the phosphorus content of the macrophytes and algae biomass was tripled from 1% to 3% via luxury uptake. While this and many other opportunities for plant based recovery of phosphorus exist, e.g. offshore cultivation, much of this technology development is still in its infancy. Research that enhances our understanding of how to maximise phosphorus uptake and harvest yields; and further add value to the biomass for reuse would see the recovery of phosphorus via plants become an important solution in the future.

Removal and biodegradation of nonylphenol by immobilized Chlorella vulgaris

The removal and biodegradation of nonylphenol (NP) by alginate-immobilized cells of Chlorella vulgaris were compared with their respective free cultures. The effects of four cell densities of 10(4) per algal bead were investigated, as were the four algal bead concentrations, with regard to the removal and biodegradation of NP. Although immobilization significantly decreased the growth rate and NP's biodegradation efficiency of C. vulgaris, NP removal over a short period was enhanced. The NP removal mechanism by immobilized cells was similar to that by free cells, including adsorption onto alginate matrix and algal cells, absorption within cells and cellular biodegradation. The optimal cell density and bead concentration for the removal and biodegradation of NP was 50-100×10(4) cells algal bead(-1) and 2-4 beads ml(-1) of wastewater, respectively. These results demonstrated that immobilized C. vulgaris cells under optimal biomass and photoautotrophic conditions are effective in removing NP from contaminated water.

Biofuels from algae: challenges and potential

Algae biofuels may provide a viable alternative to fossil fuels; however, this technology must overcome a number of hurdles before it can compete in the fuel market and be broadly deployed. These challenges include strain identification and improvement, both in terms of oil productivity and crop protection, nutrient and resource allocation and use, and the production of co-products to improve the economics of the entire system. Although there is much excitement about the potential of algae biofuels, much work is still required in the field. In this article, we attempt to elucidate the major challenges to economic algal biofuels at scale, and improve the focus of the scientific community to address these challenges and move algal biofuels from promise to reality.

Immobilized microalgae for removing pollutants: review of practical aspects

This review analyzes the state-of-the-art of a specific niche in biological wastewater treatment that uses immobilized eukaryotic microalgae (and several prokaryotic photosynthetic cyanobacteria), with emphasis on removing nutrients with the support of microalgae growth-promoting bacteria. Removal of other pollutants by this technology, such as heavy metals and industrial pollutants, and technical aspects related to this specific subfield of wastewater treatment are also presented. We present a general perspective of the field with most known examples from common literature, emphasizing a practical point of view in this technologically oriented topic. The potential venues of future research in this field are outlined and a critical assessment of the failures, limitations, and future of immobilized microalgae for removal of pollutants is presented.