Next-Generation Algae, Volume 1 E-Book
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- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Sprache: Englisch
NEXT-GENERATION ALGAE This book brings together experts in relevant fields to describe the successful application of algae and their derivatives in agriculture, improving agricultural sustainability, harvesting and processing, food security, fishery, aquafarming, agriculture pollution, and state-of-the-art developments of algae in commercial and agriculture utilization. This book provides up-to-date and cutting-edge information on the application of algae in producing sustainable solutions to various challenges that arise from an increase in agricultural production, as well as its utilization in the bioremediation of industrial wastewater. Moreover, the book provides detailed information about the recent advancements in smart microalgae wastewater treatment using Internet of Things (IoT) and edge computing applications. Other topics covered include the use of microalgae in various applications; the use of algae to remove arsenic; algae's role in plastic biodegradation, heavy metal bioremediation, and toxicity removal from industrial wastewater; the application of DNA transfer techniques in algae; the use of algae as food and in the production of food, ascorbic acid, health food, supplements, and food surrogates; relevant biostimulants and biofertilizers that could be derived from cyanobacterials and their role in sustainable agriculture; and algae's application in the effective production of biofuels and bioenergy. Audience This book is aimed at a diverse audience including professionals, scientists, environmentalists, industrialists, researchers, innovators, and policymakers who have an interest in bioremediation technologies for extremely polluted environments, especially in water, air, and soil.
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Veröffentlichungsjahr: 2023
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Table of Contents
Cover
Series Page
Title Page
Copyright Page
Preface
1 Smart Microalgae Wastewater Treatment: IoT and Edge Computing Applications with LCA and Technoeconomic Analysis
1.1 Introduction
1.2 Importance and Potential of Extremophilic Microalgae-Based Wastewater Treatment (WWT) Plant
1.3 Status of Microalgae-Based WWT Plants
1.4 IoT and Edge Computing-Based Monitoring and Modeling of Integrated Microalgae-Based WWT Plant
1.5 Techno-Economic Analysis of Integrated Microalgae-Based Wastewater Treatment (WWT) System
1.6 Brief Case Studies of Commercially Available Microalgae-Based Wastewater Treatment (WWT) Plants
1.7 Conclusion
References
2 The Use of Microalgae in Various Applications
2.1 Introduction
2.2 End Uses of Microalgae
2.3 Microalgal High-Value Compounds
2.4 Biomass
2.5 Potential Future Applications
2.6 Conclusion
References
3 Arsenic Bioremoval Using Algae: A Sustainable Process
3.2 Algae-Mediated Arsenic Removal
3.3 Conclusions and Future Perspectives
References
4 Plastics, Food and the Environment: Algal Intervention for Improvement and Minimization of Toxic Implications
4.1 Introduction
4.2 Constituents of Chemicals in Plastics and Waste Generation
4.3 Packaging of Food and Minimization Through Concept of ®
4.4 Current World Production Rate of Plastics
4.5 Toxic Implications of Microplastics from Food Packaging or Other Items
4.6 Conclusion
References
5 Role of Algae in Biodegradation of Plastics
5.1 Introduction
5.2 What are Microalgae?
5.3 Some Biodegradable Pollutants
5.4 Overview of Plastics
5.5 Bioremediation of Plastics
5.6 Microalgae’s Effect on Microplastics
5.7 Microplastics’ Effect on Microalgae
5.8 Techniques Used for Analysis of Plastic Biodegradation
5.9 Factors Influencing the Deterioration of Plastics Using Microorganisms
5.10 Future Prospects
5.11 Conclusion
References
6 Application of Algae and Bacteria in Aquaculture
6.1 Introduction
6.2 The Major Problem of Nitrite and Ammonia in Aquaculture
6.3 Techniques for Nitrite, Nitrate and Ammonia Removal
6.6 Conclusion
References
7 Heavy Metal Bioremediation and Toxicity Removal from Industrial Wastewater
7.1 Introduction
7.2 Environmental Heavy Metal Sources
7.3 Heavy Metal Sources of Water Treatment Plants
7.4 Heavy Metal Toxicity in Relation to Living Organisms
7.5 Remediation Technologies for Heavy Metal Decontamination
7.6 Biological Approach in the Remediation of Heavy Metals
7.7 Mechanism Involved in Biosorption
7.8 Alga-Mediated Mechanism
7.9 Application of Biosorption for Waste Treatment Technology
7.10 Microbial Heavy Metal Remediation Factors
7.11 Conclusion
7.12 Future Prospects
References
8 The Application of DNA Transfer Techniques That Have Been Used in Algae
8.1 Introduction
8.2 Conventional DNA Transfer Techniques in Algae
8.3 Novel Emerging DNA Transfer Techniques in Algae
8.4 Limitations to Genetic Transformation in Algae
8.5 Future Prospects of Algae Transformation
References
9 Algae Utilization as Food and in Food Production: Ascorbic Acid, Health Food, Food Supplement and Food Surrogate
9.1 Introduction
9.2 The Utilization of Algae
9.3 Pharmacological Potential of Algae in Foods
9.4 Future and Prospect of Edible Algae
9.5 Conclusion
References
10 Seasonal Variation of Phytoplanktonic Communities in Fishery Nurseries in the City of Inhumas (GO) and Its Surroundings
10.1 Introduction
10.2 Material and Methods
10.3 Results
10.4 Conclusion
References
11 Role of Genetical Conservation for the Production of Important Biological Molecules Derived from Beneficial Algae
11.1 Introduction
11.2 Application of Algae in Various Fuels
11.3 Algae and Their Pharmaceutical Application
11.4 Relevance of Some Algae Derivative Components as Well as Their Effects on Human Health
11.5 Genetic Resources and Algae
11.6 Conclusions
References
12 Relevance of Biostimulant Derived from Cyanobacteria and Its Role in Sustainable Agriculture
12.1 Introduction
12.2 Biostimulants Derived from Cyanobacteria for Boosting Agriculture
12.3 Modes of Action Involved in the Application Microorganism as Biostimulant
12.4 Conclusion and Future Recommendations
References
13 Biofertilizer Derived from Cyanobacterial: Recent Advances
13.1 Introduction
13.2 Biological Fertilizers
13.3 Biofuel Production Technology
13.4 Significant of Biofertilizers
13.5 Relevance of Cyanobacteria
13.6 Cyanobacteria as Biofertilizer
13.7 Conclusion
References
14 Relevance of Algae in the Agriculture, Food and Environment Sectors
14.1 Introduction
14.2 Fourth Generation Biofuel: Next Generation Algae
14.3 Next Generation Algae: Application in Agriculture
14.4 Next Generation Algae: Application in the Environment
14.5 Conclusion
References
15 Application of Biofuels for Bioenergy: Recent Advances
15.1 Introduction
15.2 General Overview
15.3 Algae Production and Cultivation
15.4 Algal Biofuels from Macroalgae
15.5 Algal Biofuels from Cyanobacteria and Microalgae
15.6 Types of Algal Biofuels
15.7 Biomass Supply
15.8 Organic Material-Based Energy: CO
2
Impartiality and Its Effects on Carbon Pools
15.9 Non-CO
2
GHG Emissions in Bioenergy Systems
15.10 Microalgae for Biodiesel Production
15.11 Futurity Progression in Bioenergy
15.12 Conclusion
References
Index
End User License Agreement
List of Tables
Chapter 1
Table 1.1 Microalgae-based WWT abiotic and biotic requirements, nutrients re...
Table 1.2 Microalgae growth systems –suspension and immobilization in PBRs....
Table 1.3 Performance evaluation of WWTPs.
Table 1.4 Some recent applications of machine learning (ML) approaches used ...
Table 1.5 Recent LCA studies associated with application of microalgae and W...
Chapter 3
Table 3.1 Removal of arsenic by algae.
Chapter 5
Table 5.1 Algae colonization on plastic surface.
Table 5.2 Analytical techniques for properties of polymers.
Chapter 7
Table 7.1 Heavy metals drinking water standards.
Table 7.2 Heavy metal toxicity to microorganisms.
Table 7.3 Common industrial units discharging toxic heavy metals [48].
Table 7.4 Algal species with biosorption capacity.
Table 7.5 Heavy metal-removing bacterial species.
Table 7.6 Use of fungal species and their capacity for biosorption.
Table 7.7 Factors affecting heavy metal bioremediation.
Chapter 8
Table 8.1 List of applications of genetic engineering in microalgae.
Chapter 10
Table 10.1 Taxonomic classification of the phytoplankton genera found in the...
Table 10.2 Occurrence of phytoplankton genera found in different Fish-Pays l...
Chapter 11
Table 11.1 Natural compounds available in algae and their relevance.
Table 11.2 Different species of algae and their various applications in the ...
Table 11.3 Some algae that play an important role against ultraviolet rays....
Table 11.4 Products derived from algae and their applications in the health ...
Table 11.5 Crop stimulatory effectiveness of algae.
Chapter 13
Table 13.1 Important microorganisms constituting biofertilizer and their app...
Chapter 15
Table 15.1 Techniques involved in algae production.
Table 15.2 Microalgae-based WWT abiotic and biotic requirements, nutrients r...
List of Illustrations
Chapter 1
Figure 1.1 Resource recovery from microalgae-based wastewater treatment syst...
Chapter 2
Figure 2.1 Biohydrogen production by microalgae.
Figure 2.2 Polyunsaturated fatty acids’ chemical structure.
Figure 2.3 Chemical structures of carotenoids.
Figure 2.4 Chemical structure of phycocyanin.
Figure 2.5 Chemical structure of clionasterol.
Chapter 3
Figure 3.1 Scanning electron micrographs (SEM) (1500×) and EDX of (a) native...
Figure 3.2 TEM images of EPS-C (a–c) and EPS-F (d–f) algal cells before and ...
Figure 3.3 SEM images of EPS-C (a–c) and EPS-F (d–f) algal cells before and ...
Figure 3.4 (a) Cell surface of control
Cladophora
sp. with no groves at 10 k...
Figure 3.5 Transmission electron micrographs of
S. quadricauda
cells after t...
Chapter 5
Figure 5.1 Algal colonization and biodegradation process.
Figure 5.2 (a) Effects of microalgae on microplastic particles; (b) Effects ...
Figure 5.3 Evaluation of degree of plastics deterioration.
Chapter 6
Figure 6.1 Outline of problem and remediation in aquaculture based on algae ...
Chapter 7
Figure 7.1 Mechanisms of biosorption.
Figure 7.2 Biosorption mechanisms based on metal removal site.
Figure 7.3 Mechanism of bacterial and algae heavy metal remediation.
Chapter 8
Figure 8.1 Graphical abstract representing the conventional and emerging DNA...
Chapter 10
Figure 10.1 Location of Inhumas/GO –Brazil.
Guide
Cover Page
Series Page
Title Page
Copyright Page
Preface
Table of Contents
Begin Reading
Index
Wiley End User License AgreemenT
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Scrivener Publishing100 Cummings Center, Suite 541JBeverly, MA 01915-6106
Publishers at ScrivenerMartin Scrivener ([email protected])Phillip Carmical ([email protected])
Next-Generation Algae
Volume I: Applications in Agriculture, Food and Environment
Edited by
Charles Oluwaseun AdetunjiJulius Kola OlokeNaveen DwivediSabeela Beevi UmmalymaShubha DwivediDaniel Ingo HefftandJuliana Bunmi Adetunji
This edition first published 2023 by John Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA and Scrivener Publishing LLC, 100 Cummings Center, Suite 541J, Beverly, MA 01915, USA© 2023 Scrivener Publishing LLCFor more information about Scrivener publications please visit www.scrivenerpublishing.com.
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Library of Congress Cataloging-in-Publication Data
ISBN 978-1-119-85727-3
Cover image: Pixabay.ComCover design by Russell Richardson
Preface
The global population is projected to reach 9 billion by the year 2050. It is imperative to begin preparing for the challenges that come with accommodating this rapidly growing population. One of the most significant challenges will be to ensure that we can provide adequate food and nutritious diets to this growing population, as well as a healthy environment. The orthodox agricultural practice has depended heavily on non-renewable inputs such as pesticides, fertilizers, herbicides, and insecticides. Due to the rapid pace of industrialization and the continuous growth of human population, we are witnessing an alarming increase in environmental pollution caused by various anthropogenic and industrial activities. This has resulted in extensive damage to our environment. The majority of these pollutants are derived from inappropriate utilization and discharge of industrial effluents, fertilizers, pesticides, smelting and mining of ores, as well as the release of automobile exhaust and effluent from storage batteries. Additionally, the release of metalloids, heavy metals, petrochemicals, and petroleum hydrocarbons also contribute significantly to the problem. However, their introduction has led to increased agricultural production and significant advancements for humankind, but the application of agro-chemicals has also resulted in numerous environmental and health hazards. Algae have been identified as a sustainable biotechnological resource that could help in resolving several of these problems.
This book provides up-to-date and cutting-edge information on the application of algae in producing sustainable solutions to various challenges that arise from an increase in agricultural production, as well as its utilization in bioremediation of industrial wastewater. Moreover, this book provides detailed information about the recent advancements in smart microalgae wastewater treatment using Internet of Things (IoT) and edge computing applications. Other topics covered include the use of microalgae in various applications (with past, present and future projections); the use of algae to remove arsenic; algae’s role in plastic biodegradation, heavy metal bioremediation, and toxicity removal from industrial wastewater; the application of DNA transfer techniques in algae; the use of algae as food and in the production of food, ascorbic acid, health food, supplements, and food surrogates; relevant biostimulants and biofertilizers that could be derived from cyanobacterials and their role in sustainable agriculture; and algae’s application in the effective production of biofuels and bioenergy.
This book is aimed at a diverse audience, including global leaders, industrialists, individuals in the food industry, agriculturists, the fishery sector, animal husbandry practitioners, investors, innovators, farmers, policy makers, extension workers, educators, researchers, and those in other interdisciplinary fields of science. It also serves as an educational resource manual and project guide for undergraduate and postgraduate students, as well as for educational institutions that seek to carry out research in the field of algae. Additionally, this book unites experts in relevant fields to describe the successful application of algae and its derivatives for bioremediation of extremely polluted environments, especially in water, air and soil. This book is highly recommended to a diverse community of professionals, scientists, environmentalists, industrialists, researchers, students in higher education, innovators, and policy makers who have an interest in bioremediation technologies and sustainable development.
I want to express my deepest appreciation to all the contributors who have dedicated their time and efforts to make this book a success. Furthermore, I want thank my coeditors for their effort and dedication during this project. Moreover, I wish to gratefully acknowledge the suggestions, help, and support of Martin Scrivener and others from Scrivener Publishing.
Charles Oluwaseun Adetunji
(Ph.D, AAS affiliate MNYA; MBSN; MNSM, MNBGN)
Dean Faculty of Science, Edo State University, Uzairue, Nigeria March 2023
1Smart Microalgae Wastewater Treatment: IoT and Edge Computing Applications with LCA and Technoeconomic Analysis
Mohd. Zafar1*, Avnish Pareek1, Taqi Ahmed Khan1, Ramkumar Lakshminarayanan2 and Naveen Dwivedi3
1 Department of Applied Biotechnology, College of Applied Sciences & Pharmacy, University of Technology and Applied Sciences - Sur, Sultanate of Oman
2 Department of Information Technology, College of Computing & Information Sciences, University of Technology and Applied Sciences - Sur, Sultanate of Oman
3 Department of Biotechnology, S. D. College of Engineering and Technology, Muzaffarnagar, India
Abstract
The application of microalgae in applied biotechnological studies for different bio-materials, such as biodiesel, bioethanol, and other high-value bioproducts, has been gaining attention in recent years. Large-scale integrated microalgae-wastewater treatment facilities have emerged as a promising technology. Technoeconomic and life cycle analyses of integrated algae technology in municipal wastewater treatment plants (WWTPs) can reveal its potential as a viable market technology. Thus, integrated microalgae WWTPs is seen as a promising field and is getting attention from the scientific community due to its multifold benefits in terms of nitrogen and phosphorous removal with reduction of organic load, accumulation of heavy metals, and simultaneous production of value-added biomaterials.
This chapter was designed to provide concise details on recent advancements in biological and technological approaches, LCA studies, and IoT and edge computing-based modeling and monitoring of integrated microalgae WWTPs with a technoeconomic feasibility analysis for its assessment as a promising market technology. It is noteworthy that stakeholders have an interest in integrated microalgae WWTPs, but are looking for a standardized process, including design, data availability, and management aspects, along with a legislative framework that makes it simple to implement.
Keywords: Microalgae biorefinery, wastewater treatment, life cycle assessment, emergy analysis, IoT and edge computing
1.1 Introduction
It is noteworthy that global warming is considered a major issue for many countries around the world. Due to the recent pace of industrialization and urbanization, the emission of different greenhouse gases (GHGs), such as carbon dioxide (CO2), has led to climate change. Thus, the agreement between world nations known as the Kyoto Protocol was enforced in 1997 to ensure the specific reduction of GHGs by countries. Among the different GHGs, CO2 is considered to be the largest contributor to the greenhouse effect, and CO2 mitigation strategies will directly affect the total GHGs emissions. In order to remove the excess atmospheric CO2 emission, the following methods have been adopted worldwide: (i) Physicochemical processes, including solvent scrubbing, adsorption, absorption, cryogenics and membranes, (ii) Ocean storage of CO2 and (iii) Biological transformation and mitigation of CO2 to organic matter using a biological system [1].
Globally, about a 40% water deficit is predicted by 2030, along with several unavoidable challenges associated with societal and economic development in view of current perspectives on the increasing demand for water and lack of water reclamation technology [2]. The conventional wastewater treatment processes, viz. aerobic activated sludge-based process, nitrification-denitrification, and phosphorous removal, are facing challenges to meet the stringent nutrients discharge standards and a large amount of wastewater effluent is still being discharged with nutrients contents, resulting in eutrophication in the aquatic environment [2]. In addition, there are several other disadvantages, such as the high energy consumption, carbon emission, additional sludge discharge, and instability associated with these conventional processes, which can hinder the sus-tainability-based low carbon, low energy consumption, and resource recycling associated wastewater treatment [1].
Thus, the microalgae-related wastewater treatment (MBWT) process has been gaining attention in recent years and is considered as one of the most promising advanced technologies for sustainable wastewater treatment and efficient nutrient recovery from wastewater. The feasibility of microalgae-related treatment of wastewater generated from different sources, such as municipal, agricultural, and industrial, is being exploited as a tertiary wastewater treatment bymany researchers because of its advantages as a highly efficient process for nutrient removal [3–7]. A symbiotic relationship between microalgae and the bacterial population of wastewater was reported by Oswald et al., who observed the efficiency of microalgae in the enhancement of hazardous compounds removal with protection of the bacterial population [8]. Under symbiotic relationship, microalgae utilize CO2 (produced through aerobic metabolism of bacteria) through the process of photosynthesis and generated O2 could be utilized by the heterotrophic bacterial population for the assimilation of waste organic compounds. This created the idea of utilizing microalgae for wastewater treatment for the removal of excess nutrients of wastewater effluent and to reduce the risk of the eutrophication threat to natural water bodies. Furthermore, the microalgal biomass produced in wastewater treatment could be considered for “value-added product from waste” as a feedstock in further biorefinery processes [9–11] (Figure 1.1).
In this chapter, recent advancements with respect to diversity of microalgae, process system, internet of things (IoT) and edge computing-based process monitoring and control, and life cycle assessment (LCA)-based techno-economic feasibility analysis of microalgae-based wastewater treatment process are discussed. The details of psychrophilic, thermophilic and acidophilic microalgae and their roles in high-tech, low-cost, and environmentally friendly wastewater treatment process are discussed. Also, the different process systems associated with CO2 bio-fixation with simultaneous wastewater treatment are discussed. In addition, the application of emerging technologies, such as IoT automation, to microalgae-related technologies and machine learning approaches for data acquisition, monitoring and analysis of microalgae-based wastewater treatment system is discussed in view of the establishment of an integrated microalgae-wastewater treatment-based biorefinery and bioeconomy. Finally, the evaluation of microalgae-based carbon capture technology associated with wastewater is provided in terms of life cycle assessment, emergy analysis, and material flow analysis.
Figure 1.1 Resource recovery from microalgae-based wastewater treatment system for circular bioeconomy.
1.2 Importance and Potential of Extremophilic Microalgae-Based Wastewater Treatment (WWT) Plant
The essential importance of water to life on Earth is threatened by water pollution, which is a significant environmental concern [12]. Water contamination may be caused by anthropogenic or natural activity. The most important causes of human-made water pollution are harmful products from manufacturing processing and effluent making from businesses such as petrochemical plants and pulp and paper mills [13]. The hazardous and carcinogenic organic pollution emitted by crude oil, pharma, petrochemical and coal industries is recognized as being phenol and phenol compounds [14, 15]. Several research studies have examined the biological removal by microalgae of carbonate, nitrogen, and phosphorus through wastewater fluids. Different microalgal species are used in diverse types of wastewaters, including municipal, farming, brewery, refineries and industrial effluents with different efficiencies of treatment and microalgal growth [16–18].
There are numerous benefits to biological approaches, with certain microorganisms reporting degradation of phenols and phenolic compounds up to 1 g/L [15, 19]. The focus on harsh conditions has grown throughout the last few decades, resulting in a pure culture being obtained of unidentified extremophilic microorganisms and their associated metabolites [20]. Such extremophilic bacteria can provide crucial knowledge about ecological and biochemical responses and can lead to biotechnology or commercial uses [21, 22]. Extreme thermophiles currently have great potential and, while utilizing a contemporary understanding of genetics of these microbes, their application in renewable feedstock production by means of metabolic engineering will further increase [23]. Thermophilic microalgae are also used to find enough enzymes that then are integrated into plant genomes to increase their output and resistance to production [15]. Micro-algae separation and selection allow high quantities of biomass and important chemicals such as lipids to be produced in an industrial way [22, 24, 25]. The capacity to extract ammonium from wastewater at temperatures of 40-42 °C and light intensities of 2,500 μmol m2/s for 5 h in a day was studied using a green microalga Chlorella sorokiniana isolated from a wastewater stabilization pond at La Paz, Baja California Sur, Mexico [15, 26]. Thermophilic microalgae may obviously be utilized as a gene pool to identify thermostable enzymes which can be employed in dry locations for improved stability and culture in such settings [27]. Thermophilic microalgae are becoming increasingly more important since they can live at high CO2 levels. This characteristic makes them attractive candidates for CO2 emissions from industrial flue gases and adds a step towards global warming reduction. Thermophilic microalgae are efficiently employed to bioremediate harmful industrial effluents and wastewater regardless of origin [15].
1.3 Status of Microalgae-Based WWT Plants
1.3.1 Conditions and Requirements (Abiotic and Biotic Requirements, Nutrients Requirement)
Wastewater remediation is required for preventing pollution and contamination of freshwater bodies as well as for effective reuse of the treated wastewater for sustainability. An ever-increasing population, reduction of freshwater availability, expanding industrialization, and growing human development index (HDI) has increased the demand for wastewater recycling and its sustainable utilization to help manage the precious potable water resources globally in the 21st century [28].
Wastewater is treated conventionally using four types of treatment methods based on the technology used or the category of inflow water. The different treatment plant types are sewage treatment plants (STPs), effluent treatment plants (ETPs), activated sludge plants (ASPs), and common and combined effluent treatment plants (CETPs). Most of the resultant treated water is used for non-potable applications after secondary treatments itself because of technological and/or logistical limitations [29, 30] and non-mandatory status of the tertiary treatment. However, this type of treated water often does not meet the minimum quality standards of water reuse and once released into water bodies it rapidly brings down the dissolved oxygen (DO) and causes pH fluctuation, resulting in the creation of dead aquatic zones and an increase in the overall toxicity [31, 32]. Moreover, these conventional wastewater treatment plants (CWWTPs) are energy intensive and require high operational and maintenance cost [33, 34]. In such a scenario, where the conventional systems are already posing challenges, an ever-increasing population will further stress the global wastewater treatment and reuse scenario as the nutrient load of nitrogen and phosphorus will increase, which will further call for a mandatory tertiary treatment [35–38]. Studies have shown that microalgae are excellent candidates for nitrogen and phosphorus removal and are better than other classes of microorganisms. Being photosynthetic and highly adaptive in their environment, microalgae are also considered the best candidates for tertiary treatment systems. The autotrophic nature of these organisms reduces the system’s energy footprint and atmospheric carbon sequestering along with N and PO4- removal, which is an added bonus to the environment [39–44].
Wastewaters are complex systems, their treatment is not as straightforward as often understood in terms of biochemical oxygen demand (BOD), chemical oxygen demand (COD) and sludge. Their temporal and spatial characteristics depend on their source, geophysical conditions, factors such as temperature and pH, effluent and nutrient load, physical and chemical impurities, biotic load and flow regime, treatment system size, treatment protocol, transformation products and treatment technology, etc. Besides the composition of the wastewater, wastewater treatment at a national/regional level also depends upon the environmental policy, water resource availability, water withdrawn and water stress [45]. Nevertheless, the present discussion is focused on microalgae-based wastewater treatment plants and only the factors that directly affect these plants will be discussed in this section. The following table shows some of the recent works on biotic and abiotic factors of microalgae-based WWT. This will help to develop more clarity on biotic-abiotic factors and growth conditions for microalgae as well as its potential as a wastewater treatment candidate. From Table 1.1 it can be clearly understood that microalgae are a good candidate for nitrogen and phosphorus removal under all different system configurations. They are even effective in untreated wastewaters and can be employed along with conventional treatment methods. It can be further observed from the literature cited in the table that the best results are obtained with natural consortia instead of using a single isolated species [39]. In addition to the use of natural consortia, a combination with aerobic bacteria seems to give better results as has been suggested in many studies in the literature cited in this table. It is also proved that aerobic bacteria support microalgal photosynthetic rates by reducing the micro-environments around the microalga and thereby help faster, better, energy smart and sustainable treatment of wastewater; whereas the conventional wastewater treatment is both oxygen and energy intensive, and thus less environmentally friendly and less sustainable [46]. Moreover, from Table 1.1, it can be further observed that if the microalgae are autotrophic there are fewer requirements on the surrounding media and the biomass produced can be further utilized or valorized, unlike the CWWTs [30, 42, 47, 48]. Microalgae has proven to be good in most of the wastewater treatment studies, except for complex wastes like phenols [49] and hydrocarbons [40, 50–52].
Table 1.1 Microalgae-based WWT abiotic and biotic requirements, nutrients requirement.
Abiotic factor
Biotic factor
Organism used
Treatment level/sampling
Treatment system
Findings
Reference
Lighting, pH
Species of microalgae and bacterial consortia, cell density, cell size
New isolated species
Anaerobic digested (AD) effluent sample
600-L horizontal tubular photobioreactors
- 99% removal of (TN) and Total Phosphorus (TP).
[
40
]
Temperature
CO
2
Total Nitrogen (TN)
Total Phosphorus (TP)
Franceia amphitricha
Scenedesmus
sp.
Chlorella
sp.
Chlorellaceae
Chlamydomonas
sp.
Desmodesmus
sp.
Irradiance
3 fluoroquinolones-ofloxacin, ciprofloxacin, norfloxacin;
Chlamydomonas reinhardtii
(UTEX ID 2243),
Chlorella sorokiniana
Direct toilet water
1200L Photobioreactor and a suspect screening
- Microalgae ability for macrolide biotransformation.
[
53
]
Temperature
Orbital Shaking
- 40 different TPs were identified.
COD, TSS, Total nitrogen (TN), Total Phosphorus (TP)
Interaction of several species
Leptolyngbya
sp.
Untreated influent wastewater
High-rate algal ponds (HRAPs)
- Microalgae biodiversity plays critically essential role in high productivity of HRAPs treating municipal wastewater.
[
54
]
Synechococcus
sp.
Chlorella
sp.
Parachlorella
sp.
Dictyosphaerium
sp.
pH, Temp
Scenedesmus
sp.
Total solar irradiance
Desmodesmus
sp.
Pediastrum
sp.
Zooplankton Daphnia
sp.
CO
x
, NO
x
, SO
x
, pH, Light, temperature, wind (m/s), precipitation (mm), relative humidity (%) DO
Consortium of local freshwater green algae
Chlorella
sp.,
Scenedesmus dimorphus
,
Scenedesmus quadricauda
, and
Desmodesmus armatus
,
Coelastrum microporum
Municipal untreated wastewater and CO
2
from CHP plant
Raceway pond systems
- In wastewater treatment process, the interaction between bacteria and microalgae plays a crucial role.
[
55
]
nitrogen (N), phosphorus (P), magnesium (Mg), carbonate (CO
3
) and gamma radiation
-
Chlorella vulgaris
Synthetic media
Lab-scale setup
- Biomass increase with high N and P and low Mg and CO
3
, Lipid accumulation increase with low N and P and high Mg and CO
3
.
[
56
]
- Gamma radiation has negative effect on biomass and lipid accumulation.
Autotrophic and heterotrophic growth conditions
-
Auxenochlorella protothecoides
Synthetic media
Lab-scale setup
- Hub genes defined
[
57
]
Ammonium urea, and Nitrate as nitrogen source
Algal consortium
Tetraselmis
sp. (UTEX LB 2767),
Raphidocelis subcapitata
(UTEX 1648),
Chlamydomonas reinhardtii
(UTEX 2243), and
Scenedesmus obliquus
(UTEX 393)
Navicula
sp.
Wastewater as a feedstock
Lab-scale setup
- In heterogeneous nitrogen environments, functional diversity increases with species complementarity and productivity
[
58
]
Ammonium as Nitrogen source
Bacteria derived from the AD effluents interactions with the
Chlorella
species
Chlorella vulgaris
(KCTC AG10002) and
Chlorella protothecoides
(UTEX 1806)
AD effluents from four different lab-scale anaerobic digesters
Lab-scale setup
- A viable way to treat and value-add the wastewater effluents by
Chlorella
cultured on AD effluents
[
59
]
pH, EC, TS, TDS, TSS, DO, COD, Ammonia, Nitrate, Phosphate
Varying concentrations of same algal species at different HRT
Chlorella vulgaris
Raw domestic wastewater
Lab-scale setup
- Addition of microalgae to CWWTs can be a solution for pollution control
[
32
]
pH
Microalgae consortia
Different naturally occurring sewage algal species
Comparative study on wastewater and artificial media
Lab-scale setup
- Microalgae consortia has effectively removed phosphate and nitrogen with real wastewater instead of from synthetic media
[
44
]
Nitrogen and phosphorus
1.3.2 Microalgae-Based WWT System –Photobioreactor System in Suspension and Immobilized Model
Microalgae culture systems are vast. In wastewater treatment, local consortia of microalgae is preferably cultured in open raceway ponds or high-rate algal ponds (HRAPs). However, algae cultivation is done in a photobioreactor (PBR) either for culture valorization, biomaterial production or for high lipid production as well as to study the finer nuances of R&D on a specific species or an improved strain [60–62]. Nevertheless, the use of a photobioreactor for treatment of wastewater could undermine the overall cost and energy efficiency [63].
Microalgae is adventitious over filamentous as well as macroalgae in terms of its feasibility of culture in suspension as well as in immobilized forms [64]. With the advancement of information technology, control and feedback loops, automation, etc., PBR has gone from lab scale to pilot scale in the last two decades. Although giving a complete overview of the two decades of PBR algal cultivation is difficult and beyond the scope here, a few suspensions and immobilized algal culture studies are presented in Table 1.2.
1.3.3 Evaluation of Treatment Performance
Performance evaluation (PE) of a system is important for optimization of a process and is extensively applied in wastewater treatment processes. It is reported that the PE data do not provide suitable operational information for the optimization of individual units involved in a WWTP; however, they are important indicators for the overall performance of the system [78]. A good system performance can significantly reduce the operation and maintenance cost of the running plants. Furthermore, performance modeling and cost evaluation of processes are essential for designing, constructing, and predicting future economic requirements. The future economic requirements may have the labor requirement, project construction, consistence maintenance, material and energy requirements, and amortization costs of a WWTPs [79, 80]. Nonetheless, since wastewater treatment plants are associated with pollution control and the environment, it is obligatory for these plants to comply with the local/global regulatory authority [81]. In this case, PE becomes very important for all aspects, viz. technological, management, economic, environmental, social, and compliance, of running a WWTP [82, 83]. Table 1.3 shows some of the recent studies on PE of WWTPs.
Table 1.2 Microalgae growth systems –suspension and immobilization in PBRs.
Aim
Culture type
PBR scale
Organism
Output
Reference
Anaerobic food processing wastewater for biodiesel production and wastewater purification
Suspension
Pilot scale
Chlorella pyrenoidosa
- Effective pollutants purification
[
65
]
Primarily treated pulp and paper wastewater
Suspension
Membrane photobioreactor (MPBR)
Chlorella vulgaris
- Moderate purification
[
66
]
Testing and comparison of 2-system MFC-PBR with a control MFC
Suspension
MFC-PBR (photobioreactor)
Chlorella
sp.
- ηCOD values up to 99%
[
67
]
Study on hydrodynamic conditions using computational fluid dynamics (CFD)
Suspension
Hybrid tubular photobioreactor
Mixed filamentous and smaller microalgae
- Importance of CFD simulations for scale-up in production of microalgae
[
68
]
Advanced pH control
Suspension
Raceway and thin-layer open photobioreactors
Scenedesmus
- With lower CO
2
consumption, improvement in system performance
[
69
]
Phosphate and nitrate recovery from wastewater
Immobilized
Design and operation of twin-layer photobioreactor for culturing green alga
Halochlorella rubescens
on vertical sheet-like surfaces
Halochlorella rubescens
- 70–99% removal of Nitrogen and Phosphorus
[
70
]
Treatment of dairy effluents with high organic load
Immobilized
2-stage treatment –the first one consisting of a 1L PBR with immobilized
Chlorella pyrenoidosa,
whereas later includes two column sand bed filtration
Chlorella pyrenoidosa
- Within 96 hour of 2-stage purification process, complete removal of NH
4
+
-N and 98% removal of PO
4
3-
-P
[
71
]
Treatment of effluents from aquaculture
Immobilized
Synthetic textile used as a support medium for immobilized/packed bed bioreactor
Picochlorum
sp.
- C and N removal rates up to 95%
[
72
]
Treatment of untreated palm oil mill effluent (POME)
Immobilized
3L capacity flat bioreactor
Chlorella
sp.
- Removal of total nitrogen ranged between 11 to 62.46% along with COD removal between 23 to 63.1% using beads made from 8% Na-alginate concentration
[
73
]
Removal of heavy metal ion (Copper (Cu
2+
)
Suspended and Immobilized
30-L photobioreactor
Oven-dried mixed microalgae of
Chlorella sorokiniana, Monoraphidium
sp. and
Scenedesmus obliquus
bound in Na-Alginate is used as biosorbent
- 96.4% removal efficiency
[
74
]
Treatment of ADE with highly concentrated organic matter
Suspended and Immobilized
Two-sequencing batch PBRs to compare suspension/immobilization effect
Microcystis aeruginosa
- Microalgae immobilization is better than suspension for the ADE treatment
[
75
]
Optimization of PBR with respect to light and CO
2
for algal biomass
Immobilized
Twin-layer photobioreactors (TL-PBRs), a type of porous substrate bioreactor (PSBR)
Halochlorella rubescens
- Surface productivity of 31.2 g/m
2
/d of dry biomass obtained using a combination of 1023 μmol photons per m
2
/s and 3% of CO
2
[
76
]
Scale-up feasibility studies for production of Astaxanthin
Suspended and Immobilized
Small-scale angled twin-layer porous substrate photobioreactor (TL-PSBR)
Haematococcus pluvialis
- 6.5 g/m
−2
of optimal initial biomass density
[
77
]
Table 1.3 Performance evaluation of WWTPs.
Source/plant
Method/technique for PE
Result/conclusion
Reference
Wastewater treatment plant with extended aeration sludge process
BOD, COD, TSS & PO
4
- Performance of WWTP, w.r.t. to various physicochemical properties was evaluated along with effluent discharge characteristics in a water body (Yamuna River).
[
81
]
Constructed wetlands
Analytic hierarchy process (AHP) entropy weight method Preference ranking organization method
- 48% organic matter removal by a vertical-flow wetland process, and 31.2% of NH
3
-N, and 32.4% of TN removals by an integrated-flow wetland process.
[
82
]
Extended aeration plant and Trickling filter plant
BOD and COD estimation before and after treatment
- BOD removal of 79.5% and 90.7% was reported through trickling filter, and trickling filter with extended aeration processes, respectively.
[
84
]
- The removal efficiency of COD was 60% and 86% through trickling filter, and trickling filter with extended aeration processes, respectively.
Discharge water treatment plant
Physicochemical and biological parameters
- Data verified against atomic adsorption spectroscopy, bacteriological analysis, photometer and flame photometer, and turbidity meter.
[
85
]
Sewage treatment plant
pH, BOD, COD, TSS
- The treated effluents met the discharge standards.
[
86
]
WWTPs of several metropolitan municipalities
Stepwise weight assessment ratio analysis (SWARA) method Output-oriented data envelopment analysis (DEA)
- Improvement in total, technical, and scale efficiencies was shown in multiple metropolitan municipalities.
[
87
]
Industrial WWTP
STOAT software used for modeling and PE
- Removal efficiency of WWTP: BOD, 90%; COD, 93.02%, and TSS, 96.12%.
[
88
]
Wastewater treatment plant in Souss-Massa region
Physicochemical and microbiological studies
- Removal of impurities between 97.5% and 100%.
[
89
]
Sewage water treatment plant
Evaluation of physicochemical indicators and fecal coliform prevalence
- WWTP performance was reported in accordance with the prescribed general limits.
[
90
]
Mashhad wastewater treatment plant
Optimized NN model using genetic algorithm
- The most important factors affecting the performance of Mashhad treatment plant were inlet flow rate, TCODin/TBODin ratio, temperature and load of organic matter.
[
91
]
Membrane bioreactor WWTP
Influent and effluent sample analysis
- The average BOD and COD removal efficiencies were reported as 97.6% and 96.5%, respectively.
[
92
]
Tabriz WWTP
Support vector machine (SVM) and ANN model
- Efficient results using ensemble methods in predicting the performance of Tabriz WWTP.
[
93
]
Municipal WWTPs
Multi-criteria decision-making technique for order of preference by similarity to ideal solution
- In environmental monitoring systems, a field base approach, w.r.t. suitability of the weight allocation method and fuzzy approach is proposed.
[
94
]
1.4 IoT and Edge Computing-Based Monitoring and Modeling of Integrated Microalgae-Based WWT Plant
In recent years, environmental IoT sensors have been receiving attention as an important tool for monitoring and modeling of the environmental processes, including wastewater treatment. The IoT-based technology is being extensively used to connect everyday objects with sensors for network-based cost-effective data collection and transfer. It is noteworthy that IoT-based smart sensors and devices can be used efficiently in a monitoring system to send alerts to prevent accidents and also reduce the workload by reducing the physical monitoring of infrastructure. In addition, the cloud computing technology facilitates the cost-effective data transfer to server and processing units without latency in processing. Thus, the integrated IoT and edge cutting technology can be effectively used for data collection and processing from a wastewater treatment plant associated with algal pond technology [95, 96]. Nowadays, the open pond algal cultivation system is receiving attention for large-scale algae cultivation due to its advantages of low capital cost and easy operational processes [95]. However, the cultivation process parameters, viz. light intensity, temperature, nutrient concentration, and other physicochemical parameters affect the algal growth yield, and real-time monitoring using advanced IoT-based sensors is needed [97].
The algae-based bioprocess and biorefineries are integrated with Industry 4.0 approaches to facilitate the simultaneous production of growth-associated products and co-products with the advantages of low residual quantity and optimal downstream capital investment [98]. This involves an automated algal growth and harvesting system with integrated supervisory system via a network of IoT plug-and-play sensors with advantages of cost-effective operational costs and real-time monitoring. The idea of Industry 4.0 takes a step forward with Industry 5.0 with an emphasis on the restorations of human hands, brains and intuitions in the manufacturing senses, with smart IoT facilities-based transformation of a production system connected via cloud servers. The industry 5.0 approach consists of both the capabilities of humans and machines, which are integrated together to enhance the process performance and manufacturing capacity. This industrial revolution can help in sound decision-making, resulting in a collective community commitment and the willingness of civic influences, thereby reducing the market risk and improving financial strength [98].
Industry 4.0 can manage the value-added products (e.g., biodiesel, biopolymers, bioethanol etc.), business strategies, and control of integrated algae-associated WWTPs. It can overcome the gaps associated with algal-based innovative manufacturing, which exploited intelligent devices for disperse manufacturing processes. However, the latest development in analytical data methods, including sensors and hyper spectral cameras, led to a paradigm shift towards application of Industry 4.0 to Industry 5.0 through machine learning-based support vector machines (SVMs) and convoluted neural networks (CNNs) [98–100]. The integrated algal pond with wastewater treatment has been reported progressively worldwide in many countries located from polar areas (North America and Europe) to the equator (Africa and South Asia) [95]. Regardless of the global presence of this technology, this cost-effective technology is facing challenges of being upgraded with advanced monitoring and control technologies to meet the standard regulations on effluent discharge. In the recent past, activated sludge-based WWTPs incorporated innovative design and controlling processes, including instrumentation, control and automation (ICA).
1.4.1 Machine Learning Approaches for Data Acquisition, Monitoring and Analysis System
The machine learning and deep learning-based artificial intelligence approach has produced tremendously powerful tools for solving complex problems in real-world applications in recent years [96]. It is noteworthy that the advanced wastewater treatment process, including microalgae-based WWTP, are complex processes and affected by diverse physical, chemical, and microbiological factors. Besides which, the stochastic perturbations and uncertainties in these processes require appropriate operational control of the system. Secondary treatment-associated microalgae cultivation is considered a tertiary treatment for nutrient recovery and is complex under natural environmental conditions. The integrated microalgae-based WWTP faces diverse environmental conditions, viz. temperature, solar radiation, nutrients availability, and culture characteristics [101]. These environmental variables are nonlinear in nature and exhibit complex relationships in this integrated system, promising nutrient uptake and bio-product formations. Thus, these systems can employ machine learning and deep learning-based AI techniques to understand the complex system. Table 1.4 shows the recent applications of artificial intelligence approaches in these processes.
Table 1.4 Some recent applications of machine learning (ML) approaches used to understand the complex wastewater and algal cultivation systems.
S. no.
AI approach
Process studied
Findings
References
1.
ANN
Techno-economic evaluation of algae-based tertiary treatment of WWTP
- ANN-based techno-economic feasibility analysis of nutrient supplemented secondary-treated (ST) wastewater effluents integrated with pilot-scale microalgal cultivation was performed.
[
101
]
- The study concluded with a shorter payback period of integrated wastewater-algal cultivation system than the project’s lifetime.
2.
ML technique using decision tree (DT) algorithm
Exploration of significant factors of algal biomass and lipid accumulation
- The technique utilized to determine the optimum conditions of variables leading to high biomass and lipid accumulation.
[
102
]
- Association rule mining was used to find the specific conditions leading to very high biomass and lipid levels.
3.
Modeling and process optimization using artificial neural network
Biodiesel production from
Nannochloropsis salina
- Using RSM and ANN, optimization of process parameters for biodiesel production was studied.
[
103
]
- Maximum 86.1% of biodiesel conversion for the synthesized nanocatalyst CaO was reported under optimum process conditions.
4.
ML-based multi-objective optimization
Improved biomass and bioactive phycobiliproteins (PBPs) production by
Nostoc
sp. CCC-403
- Using hybrid ML approach, 90% and 61.76% increase in cell biomass and total PBPs production, respectively, were predicted.
[
104
]
5.
ML-based classification models
Classification of microalgae
- Using FlowCAM tool, two ANN models were developed for identification and classification of microalgae samples composed by
Chlorella vulgaris
and
Scenedesmus almeriensis
using microalgae cells as input data images.
[
105
]
6.
ANN- multilayer perception
ANN model used to predict the biomass of microalgae species under different environmental conditions
- Using ANN model, it is predicted that the CO
2
and nitrogen have effects on the biomass concentration with a varying range of input parameters for different microalgae species in different environment condition.
[
106
]
7.
ANN
Discrimination of monoalgal and mixed algal cultures
- ANN was used to discriminate monoalgal and mixed algal cultures.
[
107
]
- Identification of different microalgae species in the monoalgal cultures.
- Estimation of approximate composition of mixed algal cultures.
8.
Backpropagation neural network
Production of microalgal biomass along with the growth estimate of polyculture micro-algae in raceway pond
- Estimation of polyculture microalgae growth in a semi-continuous open raceway pond (ORP) using trained ANN model.
[
108
]
- The structure of trained model included: eight input parameters, one hidden layer, and one output parameter with multilayer backpropagation NN algorithm.
9.
Multivariate timing-random deep belief net (MT-RDBN) modeling
MT-RDBN model for algal bloom
- Fine-tuned network parameters using back propagation NN algorithm.
[
109
]
- The MT-RDBN model utilized time series data for improved algal bloom prediction.
- A nonlinear time series model was developed for the characterization factor such as chlorophyll concentration with interaction factors (pH, water, and temperature).
10.
Artificial intelligence (ANN & genetic algorithm (GA)) driven process optimization
Cleaner biomass production with co-valorization of flue gas and wastewater
- Hybrid GA-ANN used for optimization and prediction of ideal process conditions for enhanced biomass of
Scenedesmus
sp. using domestic wastewater as substrate.
[
110
]
Hence, these recent studies have employed artificial intelligence techniques to understand the behavior of complex algal-based systems and wastewater systems. Thus, it can be concluded that the integration of these modern intelligence approaches with integration of population-based algorithms, such as particle swarm optimization (PSO), ant colony optimization, genetic algorithm (GA), ANN and their hybrid approaches, can integrate the economic cultivation of microalgae with safe discharge of treated wastewater into the environment.
1.5 Techno-Economic Analysis of Integrated Microalgae-Based Wastewater Treatment (WWT) System
From the above discussion, it is obvious that microalgae-associated biomass is considered a promising cost-effective renewable source, since cultivation is associated with municipal wastewater treatment. Microalgae-based wastewater treatment technology requires improvement in terms of process sustainability in addition to process optimization to be considered an economic and sustainable viable option of green bioenergy. Thus, the integrated microalgae-based wastewater treatment needs to be evaluated with life cycle assessment (LCA), process input and output analysis, and material flow analysis under current perspectives. The mitigation of climate change through cleaner sustainable industrial practices with industrial energy efficiency is a global priority [111]. Although microalgae-based WWTPs have not been a major concern in relation to industrial energy use, efforts are being made to reduce energy use in integrated microalgae-WWTPs through utilizing the concept of industrial ecology [112]. The cleaner best practices and novel technologies for energy reduction in municipal WWTPs are described by Crawford and Sandino [113]. In addition, economic transparency, incentives, and accountability to stakeholders play an important role in adaptation and implementation of this novel technology. Quantitative modeling techniques, such as the material flow cost accounting (MFCA)-based economic evaluation process, which are associated with the analysis of hidden cost and material loss related to environmental impacts are extensively used [114]. In MFCA, the material and cost balance are calculated in terms of “quantity center (QC)” and the steps in the process, viz. production, recycling, and other systems are illustrated by visual models of QCs [115]. The procedure of MFCA methods has been recognized by the standardization of ISO145051 (International Organization of Standardization, 2011); however, several studies have been reported on the improvement of this method through incorporation and integration of energy flow, life cycle analysis, management control system and environmental management accounting, supply chain analysis, and “4R” circular economy principle [114].
Nowadays, sustainable environment management (SEM) is considered as a primary assessment criterion for the services provided by natural as well as man-made (industrial) processes. Life cycle assessment (LCA) has become a central instrument for SEM and has provided an international standard (IS) for modeling, assessment, and evaluation of impacts of a product/process throughout its life cycle. The aim of LCA is to evaluate the impacts on ecosystems, natural resources, and human health [116]. The LCA process accounts for the evaluation of impacts of production systems on natural ecosystem throughout the different life cycle stages (e.g., extraction of resources, incorporation into processes, and end-of-life disposal) along with the social and economic impacts. In order to minimize the amount of energy consumption and the negative impacts and cost associated with microalgae-based WWTPs; LCA can play an important role in terms of quantification and exploration of social, economic, and environmental impacts. Several studies have been reported on the LCA studies for microalgae cultivation and their various forms of energy recovery (Table 1.5). These studies not only explored the environmental impacts associated with the microalgae biomass, but also the benefits associated with microalgae cultivation (e.g., CO2 sequestration) [117]. It is reported that incorporation of a high-rate algal pond system (in replacement of conventional activated sludge system) increased the environmental performances of WWTP [118]. Thus, the microalgae-based WWTP allows efficient recovery of pollutants (e.g., nutrients) from the effluent and can enhance economic and environmental sustainability of integrated microalgae WWTPs.
The studies mentioned in Table 1.5 show that LCA is extensively utilized as an efficient tool for feasibility analysis of microalgae-associated biofuel production with simultaneous assessment of environmental impacts in integrated WWTPs. Besides which, LCA is also able to determine the economic feasibility of microalgae cultivation integrated with different WWTPs for biofuel production. The GHG emissions from these integrated process technologies can be analyzed and modeled through LCA using suitable software tools such as SimaPro, GaBi, and OpenLCA [126].
In addition, life cycle costing (LCC) can also be performed to assess the feasibility and sensitivity of the microalgae-associated WWTPs-based biorefinery process [127]. It includes the estimations of costs associated with aggregated energy, installation, operation, downstream process, maintenance, and environmental and decommissioning over the complete lifetime of the microalgae-associated WWTP biorefinery. The details of various LCC models based on operating cost, salvage value, capital and maintenance costs are discussed by different researchers in their studies [127, 128–131].
The emergy analysis of an innovative process is also useful to evaluate its environmental sustainability in terms of availability of internal as well as external resources required for system maintenance and stability. Emergy is defined as the amount of energy consumed both directly and indirectly to produce a product or service [132]. The concept of emergy analysis was introduced by Odum as a method for assessing different system-based energy consumption [133]. It is widely used to evaluate the sustainability of different industrial systems related to first, second and third generation biofuel production [134], microalgae as a feedstock of bioethanol [135], oil production from microalgae [136], and supply chain related to food and agriculture production [137]. Thus, emergy analysis can be used for evaluation of sustainability of microalgae-associated WWTPs based on its energy efficiency.
Table 1.5 Recent LCA studies associated with application of microalgae and WWTPs.
S. no.
LCA approach
Process studied
Findings
References
1.
LCA - using SimaPro 9.0; Inventories - Ecoinvent v3.5
LCA for recovery of energy using briquette from microalgae biomass associated with wastewater
- Cradle-to-gate approach was used for LCA of cultivation and valorization of microalgae biomass growth in two scenarios: (i) a high-rate algal pond (HRAP), and (ii) a hybrid HRAP–biofilm reactor (BR).
[
117
]
- LCA study focused on electric power mix and revealed about 60% improvement in total environmental impacts in both scenarios.
- The environmental gains are associated with the use of wastewater for microalgae growth.
2.
LCA- life cycle inventory (LCI) for scale-up of process
Treatment, profit evaluation, and scale-up studies of microphytes growth in wastewater
- Evaluation of algal growth in wastewater for significant management of freshwater ecosystems along with wastewater treatment.
[
119
]
- This LCA analysis elucidated the system potentiality of large-scale production of value-added product from algal associated WWTPs.
3.
LCA - ISO14044 guidelines; Inventories - ecoinvent v3.4
Integrated side-stream microalgae process with municipal WWTP
- Improvement in environmental impacts due to integration of microalgae unit with WWTP were reported.
[
120
]
- The proposed solution improved the overall sustainability of WWTPs through resource recovery in terms of nutrients and solar energy.
4.
Life cycle inventory (LCI) analysis
Microalgae-associated biofuels production –a concept of industrial plant
- LCI analysis compiled the real pilot-scale process data, which was used for scale-up of microalgae-associated biofuel production in an industrial plant.
[
121
]
- Inventories for input and output were created using data of energy, nutrients, water, and materials consumption for biomass cultivation and biodiesel production for future LCA modeling.
- A decision support system based on LCI inventory data was created to promote the development of sustainable pilot and large-scale algae-based industry for biofuel production.
5.
LCA - using SimaPro 9.0.0.29; Inventories - ReCiPe 2016 Endpoint v1.02
Geospatial and LCA analyses of an integrating microalgae cultivation system
- For three different process designs, consequential LCA was used to compare four different feeds (sewage sludge, municipal biowaste, cattle and swine manure).
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122
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- To identify the integration potential for microalgal cultivation system, a geospatial analysis of substrate availability was also conducted.
- A significant reduction in the environmental burden of microalgae cultivation system was reported due to the uses of sewage sludge, cattle and swine manure.
- The feasibility of integration of urban wastewater treatment plants to microalgae cultivation into regional economies was reported.
6.
LCA - ISO 14044 guidelines
Bioethanol production from microalgae
- Scenario analyses based on CO
2
emission and energy balance in a microalgae-associated bioethanol production system at industrial scale were conducted.
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123
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- The commercialization of microalgae-bioethanol plant along with wastewater treatments is suggested to fuel industries for CO
2
sequestration.
7.
LCA
LCA of a microalgae-based WWTP with energy balance
- Using LCA and mass and energy balances, techno-environmental performance of WWTP integrated into a high-rate algal pond were evaluated.
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124
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- LCA-based performance system for microalgae-based WWTP was developed as a tool for decision-makers for biogas production under different techno-environmental aspects.
8.
LCA - using Umberto NXT software; Inventories - Ecoinvent database v3.0
Comparative assessment of microalgae-associated biodiesel production using freshwater and wastewater as resource
- LCA-based comparative evaluation of biodiesel production in two processes, viz. algae grown in wastewater and freshwater, were performed.
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125
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- Wastewater-based biodiesel production was identified as a viable sustainable solution to freshwater-based production system.
1.6 Brief Case Studies of Commercially Available Microalgae-Based Wastewater Treatment (WWT) Plants
In the past decade, numerous firms have focused on algal biomass production, especially in the USA, UK, and Australia using wastewater as feedstock sources [138]. Algae Enterprises in Australia established an algae-based wastewater treatment facility which focused on the full spectrum of municipal, industrial and agricultural wastewater resources. The primary energy source of local algae type is produced in a closed PBR system through photosynthetically active radiation. The produced algal biomass is anaerobically digested to produce a methane-rich biogas which is further transformed into enriched energy (CH4) [138, 139].
An Advanced Integrated Wastewater Pond System (AIWPS®) has been created by Oswald Green Technologies, also called Energy Ponds™, which works with a symbiotic bacterial algal consortium to be grown on organic and inorganic municipal wastewater contaminants [140, 141]. In this process, anaerobic ponds or gravity settlers are used to remove the wastewater solids in an initial pretreated stage, followed by the assimilation of microalgae into high-rate algal pools utilizing organic and inorganic material. The collected algal biomass from the Energy Ponds is processed as a fertilizer, animal feed and plastic and biofuel raw material [138]. The US company AlgaeSystems has developed a cost-efficient, floating, offshore PBR system, which is used to take nutrients from its original source under environmental and CO2, conditions downstream [142]. It has been reported that 50,000 gal/day of raw urban wastewater was removed with an efficiency of 75% (total N), 93% (total P), or 93% (total P) (BOD). The objective of the HydroMentia Algal Turf Scrubber® (ATS), which consists of a stream pulsed in waves, is to clean wastewater [143, 144]. The removals rates of N and P were 125 mg N/m/d and 25 mg/m/d for an agricultural drainage ditch [145] with the maximum flow and continuous running of ATS. The algal biomass generated by ATS serves as compost and cattle feed to improve soil, but also can be used as a resource for the generation of biofuels [138, 144]. The approach of OneWater and Gross-Wen Technologies is based on an immobilized cell system integrated as spinning portions of the wastewater treatment system. The bacterial source and solid settling of polysaccharides are generated by the photosynthesis in this system. The bacteria may then utilize photosynthesized oxygen and create a stable ecological wastewater treatment and self-regulating system [146]. Gross-Wen Technologies’ rotating algal biofilm (RAB) system is a biofilm alga connected to vertical rotating conveyor belts. The connected microalgae fix N and P of the rich liquid nutrient, while conducting photoautotrophic growth in the gaseous stage [144, 147].
