Application Of Microalgae Research Articles

Phycoremediation of phenol-polluted petro-industrial effluents and its techno-economic values as a win-win process for a green environment, sustainable energy and bioproducts.

The discharge of the toxic phenol-polluted petro-industrial effluents (PPPIE) has severe environmental negative impacts, thus it is mandatory to be treated before its discharge. The objective of this review was to discuss the sustainable application of microalgae in phenols degradation, with a special emphasis on the enzymes involved in this bioprocess and the factors affecting the success of PPPIE phycoremediation. Moreover, it confers the microalgae bioenergetic strategies to degrade different forms of phenols in PPPIE. It also points out the advantages of the latest application of bacteria, fungi and microalgae as microbial consortia in phenols biodegradation. Briefly, phycoremediation of PPPIE consumes carbon dioxide emitted from petro-industries for; valorization of the polluted water to be reused and production of algal biomass which can act as a source of energy for such integrated bioprocess. Besides, the harvested algal biomass can feasibly produce; third-generation biofuels, biorefineries, bioplastics, fish and animal feed, food supplements, natural dyes, antioxidants and many other valuable products. Consequently, this review precisely confirms that the phycoremediation of PPPIE is a win-win process for a green environment and a sustainable future. Thus, to achieve the three pillars of sustainability; social, environmental and economic; it is recommendable to integrate PPPIE treatment with algal cultivation. This integrated process would overcome the problem of greenhouse gas emissions, global warming and climate change, solve the problem of water-scarce, and protect the environment from the harmful negative impacts of PPPIE.

Microalgae for Simultaneous Removal of Organic and Nitrogenous Compounds from Wastewater

The increasing population growth and rapid urbanization, particularly in the developing countries, have significantly contributed to the amount and the quality of domestic wastewater. Although in certain cities, centralized wastewater treatment facility is available, it mainly aims at removing organic substances as the system uses the conventional one. Even after the treatment, the effluent is still rich with nutrients pollutants, particularly nitrogenous compounds originated from bathrooms and kitchens. Consequently, excessive nitrogenous matter in the effluent will end up in the water bodies which can lead to eutrophication, stimulating algal bloom, changing the balance of organism and degrading the water quality. As the conventional wastewater treatment system is expensive to invest and operate, an alternative cheaper and reliable method for wastewater treatment should be available, meeting the need of the developing countries. In recent years many researches have shown that microalga have capability of simultaneously reducing organic and nitrogenous substances in the wastewater for further developed as sources for producing medicines, healthy foods, ingredients, chemicals, biofuels, electricity, animal feeds, and many more. In this paper, we will review and discuss the potential application of microalgae in wastewater treatment, with attention to simultaneously removal of organics and nitrogenous substances in wastewater.

Review on carbon dioxide fixation coupled with nutrients removal from wastewater by microalgae

The application of microalgae in carbon dioxide (CO2) fixation coupled with wastewater treatment has been regarded as a promising and cutting-edge technology in recent years, but it still faces some problems. The CO2 fixation capacity and nutrients removal capacity of microalgae should be considered simultaneously under various environmental conditions. Moreover, breeding microalgae using a photobioreactor is required and critical for CO2 fixation and wastewater treatment. In addition, the related influenced factors, mechanisms and kinetics of CO2 fixation and nutrients removal by microalgae remains complex and unclear. Thus, this work provides an updated review of the literature regarding the application of microalgae in the remediation of wastewaters from different sources coupled with CO2 fixation, discusses the main interactions between biological or environmental factors and how they can influence nutrient removal and CO2 fixation efficiencies, and further focuses on their mechanisms and kinetics. It is found that blue-green algae are most suitable to fix CO2 integrating treated wastewater, but more microalgal strains with excellent anti-fouling performance, tolerance to high concentrations of CO2 and NH3–N performance need to be screened. Additionally, wastewater and gas conditions during the cultivation process should be optimized in research and applications, and development of innovative photobioreactors with low cost is also required. Furthermore, modelling mainly focuses on estimating biomass yield, nutrient removal rates and CO2 fixation rates, while laboratory modelling results deviated from the natural modelling results. Finally, this paper also provides insight into what should be done in future work to support the development of CO2 fixation coupled with wastewater treatment by microalgae.

Anaerobic digestion and agronomic applications of microalgae for its sustainable valorization.

Microalgae are considered potential candidates in biorefinery processes, and due to their biochemical properties, they can be used in the production of biofuels such as biogas, as well as for bioremediation of liquid effluents. The objective of this review is to study the current status of microalgae anaerobic digestion and agricultural uses (as bio-stimulants and biofertilizers), starting from microalgae cultivation. Indeed, the efficiency of these processes necessarily depends on the evaluation of different biotic and abiotic factors that affect the growth of microalgae. However, the adaptation and the optimization of process parameters on a large scale is also limited by energy and economic constraints. Moreover, the integration of biogas production processes with microalgae cultivation allows a nutrients and CO2 virtuous loop, thus promoting the sustainability of the process. Finally, this paper provides a general overview of biogas and biofertilizers production combination, as well as the related challenges and recommended future research perspectives to complement the gap in the literature.

Cultivation and potential application of microalgae in treatment of Pesticide Manufacturing Effluent

Abstract Pesticides are used for improving productivity, quality, safety of crops. Large number of pesticides is manufactured, which contaminate environmental matrices due to spillage, disposal, etc of its effluent. Besides number of techniques and methods available for treatment of such type of wastes, each method has its own pros and cons considering its applicability, economy, efficiency, etc. This paper primarily focuses on cultivation of microalgae in natural sunlight and in lab with artificial light source, its potential application in treatment of effluent generated from pesticides manufacturing plant. Study reveals that by comparing different L/D ratios and time period; 16 h L/D ratio yielded maximum growth in 3 days of time period; this combination is chosen to determine and removal of parameters from wastewater. Results obtained showed COD removal of 49.09%; BOD removal of 55.56%; Phosphate removal of 96.06%; 32.47% Ammonia and sodium removal of 37.43% in natural sunlight. Similarly, it was observed that with artificial light source in lab, efficiencies improved and attained 87.42%, 84.44%, 99.97%, 80.99%, 48.38%, and 32.30% for COD, BOD, Phosphate, Ammonia, Sodium and Potassium respectively. It can be concluded that microalgae based treatment scheme can be prudent, friendly to environment and green in treatment of pesticide effluent.

Treatment of Wastewaters by Microalgae and the Potential Applications of the Produced Biomass—A Review

The treatment of different types of wastewater by physicochemical or biological (non-microalgal) methods could often be either inefficient or energy-intensive. Microalgae are ubiquitous microscopic organisms, which thrive in water bodies that contain the necessary nutrients. Wastewaters are typically contaminated with nitrogen, phosphorus, and other trace elements, which microalgae require for their cell growth. In addition, most of the microalgae are photosynthetic in nature, and these organisms do not require an organic source for their proliferation, although some strains could utilize organics both in the presence and absence of light. Therefore, microalgal bioremediation could be integrated with existing treatment methods or adopted as the single biological method for efficiently treating wastewater. This review paper summarized the mechanisms of pollutants removal by microalgae, microalgal bioremediation potential of different types of wastewaters, the potential application of wastewater-grown microalgal biomass, existing challenges, and the future direction of microalgal application in wastewater treatment.

Biotechnological Applications of Microalgal Oleaginous Compounds: Current Trends on Microalgal Bioprocessing of Products

The microalgal biotechnology industry is expanding rapidly and currently gaining attention due to multiple availabilities of high-value products such as pigments, carbohydrates, proteins, nutraceuticals, biopharmaceuticals, and unique oleaginous compounds fractionated by biomass biorefinery. Microalgae are efficient primary producers in the terrestrial and marine biotopes. They are major sources of global oxygen and are gaining topical prominence due to their concomitant role in the phycoremediation of wastewater effluents and biomass production. Despite their minuscule size, microalgae critically contribute to climate change mitigation through carbon fixation and play a major role in bioenergy applications. Furthermore, carotenoids and phycobiliproteins are the main accessory light-harvesting complexes in microalgae and cyanobacteria. The topical biomedical and pharmaceutical applications of microalgae include anticancer, antidiabetic, antiHIV, antimalarial, antimicrobial, inter alia. The endowment of unique indigenous microalgae and utilization of these biological resources must be harnessed by the biorefinery industry to exploit microalgal biomass opportunities. Therefore, this manuscript factually and critically explores the current status of the biorefinery approach, topical biomedical and pharmaceutical applications, biofuel applications, genetic manipulation of microalgae for enhancement of product yield, challenges and presents prospects, pros and cons, and outlook of the microalgal biotechnology industry.

Hints at the Applicability of Microalgae and Cyanobacteria for the Biodegradation of Plastics

Massive plastic accumulation has been taking place across diverse landscapes since the 1950s, when large-scale plastic production started. Nowadays, societies struggle with continuously increasing concerns about the subsequent pollution and environmental stresses that have accompanied this plastic revolution. Degradation of used plastics is highly time-consuming and causes volumetric aggregation, mainly due to their high strength and bulky structure. The size of these agglomerations in marine and freshwater basins increases daily. Exposure to weather conditions and environmental microflora (e.g., bacteria and microalgae) can slowly corrode the plastic structure. As has been well documented in recent years, plastic fragments are widespread in marine basins and partially in main global rivers. These are potential sources of negative effects on global food chains. Cyanobacteria (e.g., Synechocystis sp. PCC 6803, and Synechococcus elongatus PCC 7942), which are photosynthetic microorganisms and were previously identified as blue-green algae, are currently under close attention for their abilities to capture solar energy and the greenhouse gas carbon dioxide for the production of high-value products. In the last few decades, these microorganisms have been exploited for different purposes (e.g., biofuels, antioxidants, fertilizers, and ‘superfood’ production). Microalgae (e.g., Chlamydomonas reinhardtii, and Phaeodactylum tricornutum) are also suitable for environmental and biotechnological applications based on the exploitation of solar light. Can photosynthetic bacteria and unicellular eukaryotic algae play a role for further scientific research in the bioremediation of plastics of different sizes present in water surfaces? In recent years, several studies have been targeting the utilization of microorganisms for plastic bioremediation. Among the different phyla, the employment of wild-type or engineered cyanobacteria may represent an interesting, environmentally friendly, and sustainable option.

Pyridoxal kinase PdxY mediated carbon dioxide assimilation to enhance the biomass in Chlamydomonas reinhardtii CC-400

Microalga served as the promising bioresources due to the high efficiency of carbon dioxide conversion. However, the application of microalga is still restricted by low biomass, easier contamination, and high cost of production. To overcome the challenge, engineered Chlamydomonas reinhardtii CC-400 with pyridoxal kinase gene (pdxY) has demonstrated in this study. The results indicated CC-400 with pdxY reached enhanced algal biomass in three different systems, including flask, Two-layer Photo-Reactor (TPR) and airlift Photo-Bioreactor (PBR). The genetic strain PY9 cultured with 1% CO2 in the PBR showed a significant enhancement of biomass up to 1.442 g/L, a 2-times of that of the wild type. We also found the transcriptional levels of carbonic anhydrase (CA) dropped down in PY9 while higher levels of RuBisCo and pdxY occurred, thus the carbon dioxide assimilation under mixotrophic culture dramatically increased. We proofed that pdxY successfully mediated carbon dioxide utilization in CC-400.

Single-step dynamic dewatering of microalgae from dilute suspensions using flocculant assisted filtration

BackgroundDewatering constitutes a major challenge to the production of microalgae, accounting for 20–30% of the product cost. This presents a setback for the applicability of microalgae in the development of several sustainable products. This study presents an investigation into the dynamic dewatering of microalgae in a combined flocculation-filtration process. The effect of process conditions on the performance of 12 flocculants and their mixtures was assessed.ResultsThe mechanism of flocculation via the electrostatic path was dominated by charge neutralization and subsequently followed bridging in a ‘sweep flocculation’ process. Cationic polyacrylamide (CPAM) based flocculants recorded the highest biomass retention with PAM1 and PAM2 attaining 99 and 98% retention with flocculant dosages of 10 and 15 mg/L respectively. Polyvinylamine (PVAM) was also found to improve system stability across the pH range 4–10. Alum was observed to be only effective in charge neutralization, bringing the system close to its isoelectric point (IEP). Chemometric analysis using the multi-criteria decision methods, PROMETHEE and GAIA, was applied to provide a sequential performance ranking based on the net outranking flow (ф) from 207 observations. A graphical exploration of the flocculant performance pattern, grouping the observations into clusters in relation to the decision axis (pi), which indicated the weighted resultant of most favorable performance for all criteria was explored.ConclusionCPAM based flocculants and their mixtures demonstrated superior performance due to their viscoelastic behaviour under turbulence. The use of PVAM or alum in mixtures with CPAM reduced the required doses of both flocculants, which will provide beneficial financial impact for largescale microalgae dewatering in a flocculant assisted dynamic filtration process. Chemometric analysis based on the physico-chemical properties of the system provides a time saving assessment of performance across several criteria. The study findings provide an important foundation for flocculant assisted dynamic filtration processes.

Performance evaluation of bubble column photobioreactor along with CFD simulations for microalgal cultivation using human urine

Optimization of microalgae cultivation to reduce the associated costs is one of the major objectives in a biorefinery model. The present study optimized the microalgal cultivation using 4.5–8.5 % v/v of DHU (diluted human urine) as a cost-effective resource, in a bubble column photobioreactor (BCPBR) under real-time conditions. Media with 5.5 % DHU and 4% CO2 showed maximal biomass productivity of 0.14 g L−1 day−1 with a final concentration of 1.06 g L−1. Phosphate and ammonium removal of 90.70 % and 84.10 % respectively was achieved. The biofixation of CO2 obtained for 6 days, during the cultivation in 5.5 % DHU, by supplying 4% of CO2 enriched air was 0.29 g L-1 d-1. Computational fluid dynamics (CFD) simulations were used to study the effects of velocity magnitude, shear stress, turbulent kinetic energy, and irradiance on the microalgal growth inside the BCPBR. The developed kinetic model predicted the biomass concentration and phosphate removal up to 98 % and 82 % accuracy respectively. Such studies would aid in comprehending the large scale commercial cultivation and thereby facilitate the application of microalgae in the future.

Potential of an Automated- and Image-Based Cell Counter to Accelerate Microalgal Research and Applications

Efforts to achieve Sustainable Development Goals (SDGs) have resulted in enhancement of the position of microalgae in feedstocks for food, feed, healthcare, and biofuels. However, stabile microalgal biorefineries require a sustainable and reliable management system of microalgae, which are sensitive to environmental changes. To expand microalgal applicability, assessment and maintenance of microalgal quality are crucial. Compared with conventional methods, including hemocytometry and turbidity, an automated- and image-based cell counter contributes to the establishment of routine management of microalgae with reduced work burden. This review presents the principle of an automated cell counter and highlights the functional capacities of the device for microalgal management. The method utilizing fluorescence function to evaluate the chlorophyll integrity of microalgae may lay the groundwork for making a large variety of microalgal biorefineries, creating an important step toward achieving SDGs.

Application of photosynthetic microalgae in the direct desalination pretreatment of seawater

AbstractThe abilities of three species of freshwater microalgae to grow in, and desalinate untreated and undiluted seawater were investigated. The salinities of the seawater were reduced from 37.5g/L to 26.25 ± 1.33, 27.19 ± 1.33 and 30.0 ± 0.00 g/L by Desmodesmus subspicatus LC172266, Desmodesmus armatus LC172263 and Dictyosphaerium spp. LC172264 on the fourth, eighth and tenth week of the experiment, respectively, while the control had no change in the salinity. D. subspicatus cell concentration initially dropped from 1.25 × 106 cells/ml to 9.68 × 105 cells/ml and then gradually increased to 4.86 × 107 cells/ml by the tenth week. With D. armatus and Dictyosphaerium spp., the cell concentrations increased steadily from 1.25 × 106 cells/ml to 4.97 × 108 cells/ml and 3.25 × 108 cells/ml, respectively. There were increases in the pH during desalination by the three species. This demonstrates the halotolerant potentials of these species and their abilities to reduce the salinity of seawater.

Cyanobacteria and Microalgae as Sources of Functional Foods to Improve Human General and Oral Health.

In the scenario of promising sources of functional foods and preventive drugs, microalgae and cyanobacteria are attracting global attention. In this review, the current and future role of microalgae as natural sources of functional foods for human health and, in particular, for oral health has been reported and discussed in order to provide an overview on the state of art on microalgal effects on human oral health. It is well known that due to their richness in high-valuable products, microalgae offer good anti-inflammatory, antioxidant, antitumoral, anti-glycemic, cholesterol-lowering, and antimicrobial activity. Moreover, the findings of the present research show that microalgae could also have a significant impact on oral health: several studies agree on the potential application of microalgae for oral cancer prevention as well as for the treatment of chronic periodontitis and different oral diseases with microbial origin. Thus, beneficial effects of microalgae could be implemented in different medical fields. Microalgae and cyanobacteria could represent a potential natural alternative to antibiotic, antiviral, or antimycotic therapies, as well as a good supplement for the prevention and co-adjuvant treatment of different oral diseases. Nevertheless, more studies are required to identify strains of interest, increase overall functioning, and make safe, effective products available for the whole population.

Effect of the Foliar Application of Microalgae Hydrolysate (Arthrospira platensis) and Silicon on the Growth of Pelargonium hortorum L.H. Bailey under Salinity Conditions

Plant growth is limited by salinity stress. There are few strategies for alleviating it although Arthrospira platensis and silicon can stimulate plants to grow under stress conditions. The aim of this work was to study the effects of both a single and a joint application of Arthrospira platensis and silicon on the growth of Pelargonium hortorum L.H. Bailey under salt stress conditions. Plants were exposed to 2.0, 3.0, and 3.5 dS m−1 EC (electrical conductivity), with and without the application of microalgae and silicon. At the end of the trial, the biometric parameters and the plant analysis were determined. The microalgae hydrolysate concentration was 5 g L−1 and the silicon concentration was 150 mg L−1. Foliar spraying was applied weekly. Pelargonium can be grown in moderately saline irrigation water (3.0 dS m−1). This bedding plant mitigates salt stress by avoiding the uptake of Cl− ions and by tolerating a high Na+ concentration in the tissue. The joint foliar application of Arthrospira microalgae and silicon stimulates root, shoot, leaf, and flower formation in the Pelargonium hortorum L.H. Bailey crop under salinity conditions (3.5 dS m−1).

Application of micro algae in poultry nutrition; a review

In this review, we unveil the the use of microalgae as a feed ingredient in poultry nutrition. Microalgae are small-sized algae, unicellular, photosynthetic aquatic plants which have been studied as a natural marine resource for a number of economically applications, including animal feed. They are introduced to poultry diets mainly as a rich source of n-3 long chain polyunsaturated fatty acids, including docohexaenoic and eicosapentaenoic acid, but they can also serve as a protein, microelement, vitamin and antioxidants source, as well as a pigmentation agent for skin and egg yolks. The majority of experiments have shown that microalgae, mainly Spirulina and Chlorella sourced as a defatted biomass from biofuel production, can be successfully used as a feed ingredient in poultry nutrition. They can have beneficial effects on meat and egg quality, through an increased concentration of n-3 polyunsaturated fatty acids and carotenoids, and in regards to performance indices and immune function. Positive results were obtained when fresh microalgae biomass was used to replace antibiotic growth promoters in poultry diets. Because of their chemical composition, microalgae can be efficiently used in poultry nutrition to enhance the pigmentation and nutritional value of meat and eggs, as well as partial replacement of conventional dietary protein sources.

Removal of atrazine in catalytic degradation solutions by microalgae Chlorella sp. and evaluation of toxicity of degradation products via algal growth and photosynthetic activity

Degradation solutions containing atrazine need to be further purified before they are discharged into the aquatic environment. With the objectives of evaluating removal capacity of the microalga Chlorella sp. toward atrazine in degradation solutions and toxicity of the degradation products, we investigated the removal efficiency (RE) and bioaccumulation of atrazine in the microalgae after an 8 d exposure to diluted degraded solutions containing 40 μg/L and 80 μg/L of atrazine as well as degradation products in the present study. Moreover, pure atrazine solutions with similar concentrations were simultaneously inoculated with the microalgae in order to distinguish the influence of the products. The photocatalytic degradation results showed that 31.4% of atrazine was degraded after 60 min, and three degradation products, desisopropyl-atrazine (DIA), desethyl-atrazine (DEA), and desethyl-desisopropyl-atrazine (DEIA) were detected. After an 8-d exposure, 83.0% and 64.3% of atrazine were removed from the degraded solutions containing 40 μg/L and 80 μg/L of atrazine, respectively. In comparison with the control, i.e., pure atrazine solution with equal concentration, Chlorella sp. in the degraded atrazine solution showed lower RE and growth rate. The photosynthetic parameters, especially performance index (PIABS), clearly displayed the differences between treatments. The values of PIABS of Chlorella sp. cultured in degradation atrazine for 8 days were significantly lower (P < 0.01) than that in the corresponding pure atrazine, suggesting potential inhibitory effect of degradation products on the microalgae. Atrazine and the degradation products inhibited algal photosynthesis via depressed light absorption and electron transport, and reduced utilization of light energy via energy dissipation. Our results demonstrated that microalgae Chlorella sp. had an encouraging atrazine removal potential and the degradation products of atrazine may inhibit algal growth and removal capability. This study may be useful for the application of microalgae in herbicide wastewater treatment and understanding algal removal of atrazine in natural aquatic environment.

An environmental imperative in the development of the national economy: increasing the potential of microalgae

Aim. To study the methodological basis for increasing the potential of applications of microalgae in the national economy, as one of the environmental imperatives in the development of new natural resources for future generations.Materials and Methods. The research was conducted on the basis of content analysis of Russian and foreign scientific publications and materials obtained in the course of expeditions and experimental and sociological research. The clustercognitive approach and economic-mathematical modeling were used for a more complete exposition of the topic.Discussion. According to imperatives of the green economy, environmental technologies will become leading factors in the development of the world economy. The most important incentive for entrepreneurs in the environmental market will be growing the demand of consumers and of governments. Promising areas include the use of microalgae in the production of foods beneficial to human health, feed additives in animal husbandry, poultry farming and fish farming, substances for improving water quality in reservoirs and the clean-up of oil spills. The issue of increasing the potential of microalgae at the regional level on the basis of a cognitive cluster approach is most relevant. The procurement of live microalgae biomass in amounts necessary to thoroughly supply world and national markets remains challenging in both technological and technical terms. Economic and mathematical models and sociological research, as well as the opinions of experts, allow us to justify business decisions in opening microalgae production facilities. Microalgae Chlorella vulgaris and Spirulina platensis present promising prospects for entrepreneurial investment due to the high value of their metabolites.Conclusion. The increase in production and applications of microalgae is of major strategic potential in the development of the national economy, as the manufacture of bio-products and immune-stimulating drugs increases every year in response to climate change, pandemics, environmental pollution, food shortages and difficulties in accessing clean water. It is necessary to adopt legislative and regulatory instruments and organizational measures aimed at stimulating the investment of funding entities and entrepreneurs in the production of microalgae products in various sectors of the economy. International collaborations, industrial enterprises and space agencies (e.g. Roscosmos and NASA) are actively conducting research into the use of microalgae for the processing of organic waste in human living facilities in space as a source of both oxygen and food. The issue of creating clusters and applying mechanisms of public-private partnership aimed at increasing the profitability of bio-product manufacture from microalgae in various industries and sectors of the economy at the macro-and meso-level remains relevant.

Biology and biotechnological applications of microalgae and photosynthetic prokaryotes: part 2

This issue of the New Zealand Journal of Botany is the second of a two-part Special Issue arising from the 3rd New Zealand Symposium on the Biology and Biotechnological Applications of Microalgae a...

Microalgal potential for nutrient-energy-wastewater nexus: Innovations, current trends and future directions

Agricultural, domestic and industrial activities contribute in releasing several organic and inorganic substances into the water streams that result in environmental pollution. Biological treatment of industrial and domestic wastewater using Activated Sludge Nutrient Removal (ASNR), the conventional process, is well known; however, it is relatively expensive due to the requirement for high energy inputs. Microalgal applications have been gaining interest as they offer potential cost-effective measures for the treatment of wastewater in the peri-urban and rural areas. Such systems provide an interesting tertiary biological treatment method where valuable biomass is produced with simultaneous uptake of nutrients such as nitrogen and phosphorous with reduction in coliform bacteria, heavy metals, chemical and biochemical oxygen demand (COD &amp; BOD) and the removal/degradation of xenobiotic compounds etc. This paper provides a systematic review on the current microalgal applications (phycoremediation) for wastewater treatment with advanced information on their role towards nutrient recovery and energy (biogas) production under the third generation biorefinery concept. The use of advanced algal pond systems for wastewater treatment including pollutant degradation, microalgal cultivation and employing such facilities for biogas production in view of technology applications is emphasized. This inter-linked network indicating microalgal role into the Nutrient-Energy-Wastewater nexus with future directions and concluding remarks are discussed.