Bioremediation of micropollutants using living and non-living algae - Current perspectives and challenges

Design, construction and application of algae-bacteria synergistic system for treating wastewater

The wastewater treatment technology of algae-bacteria synergistic system (ABSS) is a promising technology which has the advantages of low energy consumption, good treatment effect and recyclable high-value products. In this treatment technology, the construction of an ABSS is a very important factor. At the same time, the emergence of some new technologies (such as microbial fuel cells and bio-carriers, etc.) has further enriched constructing the novel ABSS, which could improve the efficiency of wastewater treatment and the biomass harvesting rate. Thus, this review focuses on the construction of a novel ABSS in wastewater treatment in order to provide useful suggestions for the technology of wastewater treatment.

Biotransformation of the azo dye reactive orange 16 by Aspergillus flavus A5P1: Performance, genetic background, pathway, and mechanism

This study reports the strain Aspergillus flavus A5P1 (A5P1), which is with the capable of degrading the azo dye reactive orange 16 (RO16). The mechanism of RO16 degradation by A5P1 was elucidated through genomic analysis, enzymatic analysis, degradation pathway analysis and oxidative stress analysis. Strain A5P1 exhibited aerobic degradation of RO16, with optimal degradation at an initial pH of 3.0. Genomic analysis indicates that strain A5P1 possesses the potential for acid tolerance and degradation of azo dye. Enzymatic analysis, combined with degradation product analysis, demonstrated that extracellular laccase, intracellular lignin peroxidase, and intracellular quinone reductase were likely key enzymes in the RO16 degradation process. Oxidative stress analysis revealed that cell stress responses may participate in the RO16 biotransformation process. The results indicated that the biotransformation of RO16 may involves biological processes such as transmembrane transport of RO16, cometabolism of the strain with RO16, and cell stress responses. These findings shed light on the biodegradation of RO16 by A5P1, indicating A5P1's potential for environmental remediation.

Toxic heavy metal ions contamination in water and their sustainable reduction by eco-friendly methods: isotherms, thermodynamics and kinetics study

Heavy metal ions can be introduced into the water through several point and non-point sources including leather industry, coal mining, agriculture activity and domestic waste. Regrettably, these toxic heavy metals may pose a threat to both humans and animals, particularly when they infiltrate water and soil. Heavy metal poisoning can lead to many health complications, such as liver and renal dysfunction, dermatological difficulties, and potentially even malignancies. To mitigate the risk of heavy metal ion exposure to humans and animals, it is imperative to extract them from places that have been polluted. Several conventional methods such as ion exchange, reverse osmosis, ultrafiltration, membrane filtration and chemical precipitation have been used for the removal of heavy metal ions. However, these methods have high operation costs and generate secondary pollutants during water treatment. Biosorption is an alternative approach to eliminating heavy metals from water that involves employing eco-friendly and cost-effective biomass. This review is focused on the heavy metal ions contamination in the water, biosorption methods for heavy metal removal and mathematical modeling to explain the behaviour of heavy metal adsorption. This review can be helpful to the researchers to design wastewater treatment plants for sustainable wastewater treatment.

Anionic dye removal by immobilized bacteria into alginate-polyvinyl alcohol-bentonite matrix

Methyl orange (MO) is commonly used in the textile dyeing industry, posing serious health and environmental hazards due to its carcinogenic, mutagenic properties, and potential for bioaccumulation. Appropriate handling is needed to solve these problems by harnessing the capacity of living microorganisms and the adsorption properties of bentonite clay minerals. Although the conventional approach predominantly depends on free cells, recent study has developed other methods such as immobilization techniques. Therefore, this study aimed to investigate the efficiency of the immobilization matrix comprising sodium alginate (SA), polyvinyl alcohol (PVA), and bentonite by modifying Pseudomonas aeruginosa, Bacillus subtilis, and Ralstonia pickettii for MO removal of 50 mg/L. In the free cell technique, the results showed that the MO decreased to 43.13, 36.61, and 27.45% for each of the bacteria within 10 days at 35 °C. The bacterial immobilization technique, including live immobilized P. aeruginosa (LIPa), live immobilized B. subtilis (LIBs), and live immobilized R. pickettii (LIRp) beads also demonstrated significant efficiency, achieving MO removal rates up to 97.15, 95.65, and 66.63% within 10 days. These synthesized beads showed reusability, with LIPa, LIBs, and LIRp being used up to 4, 4, and 2 cycles, respectively. The external and internal surface conditions were observed using SEM instrument and the results showed that all components were agglomerated. Comparisons using dead bacterial biomass indicated that treatment with live bacteria consistently yielded significantly higher removal rates. These results showed the effectiveness of immobilized bacteria in MO removal, offering a promising potential in reducing pollutants.

Using wastewater as a cultivation alternative for microalga Dunaliella salina: Potentials and challenges

Untreated or poorly treated wastewater still represents environmental issues world-widely. Wastewater, especially saline wastewater treatment, is still primarily associated with high costs from physical and chemical processes, as high salinity hinders biological treatment. One favourable way is to find the suitable biological pathways and organisms to improve the biological treatment efficiency. In this context, halophilic microorganisms could be strong candidates to address the economics and effectiveness of the saline wastewater treatment process. Dunaliella salina is a photoautotrophic microalga that grows in saline environments. It is known for producing marketable bio-compounds such as carotenoids, lipids, and proteins. A biological treatment based on D. salina cultivation offers the opportunity to treat saline wastewater, reducing the threat of possible eutrophication from inappropriate discharge. At the same time, D. salina cultivation could yield compounds of industrial relevance to turn saline wastewater treatment into a profitable and sustainable process. Most research on D. salina has primarily focused on bioproduct generation, leaving thorough reviews of its application in wastewater treatment inadequate. This paper discusses the future challenges and opportunities of using D. salina to treat wastewater from different sources. The main conclusions are (1) D. salina effectively recovers some heavy metals (driven by metal binding capacity and exposure time) and nutrients (driven by pH, their bioavailability, and functional groups in the cell); (2) salinity plays a significant role in bioproducts generation, and (3) wastewater can be combined with the generation of bioproducts.

A fungal-algal self-flocculation system and its application to treat filter sludge leachate in the sugar industry

The efficient and economical treatment of wastewater using microalgae has attracted much attention. However, harvesting microalgae cells from treated wastewater remains challenging. In the present study, a Chlorella vulgaris suspension containing filamentous fungi Aspergillus niger and Chaetomium gracile was successfully used to construct a self-flocculating system, with a microalgae flocculation efficiency of 99.6% achieved by gravity sedimentation within 4 h. The diameter of fungi played an important role in determining flocculation efficiency, and the optimal particle size was 10 mm. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) results indicated that the sweeping action of fungal mycelia and the interaction between the functional groups of fungi and the C. vulgaris surface contributed to improve flocculation. Co-cultivation of C. vulgaris and fungi could effectively remove 83.53%, 94.45% and 76.88% of total phosphorus, total nitrogen and chemical oxygen demand, respectively, from the sludge leachate from a sugar mill. The fungal-algal biomass reached 5.75 g/L. Herein, the constructed self-flocculation system had coupled efficient flocculation of C. vulgaris with removal of pollutants from wastewater in a short period of time, and providing a green, pollution-free, low-cost method for simultaneous wastewater treatment and the production of high quality biomass.

Modified polymer membranes for the removal of pharmaceutical active compounds in wastewater and its mechanism-A review

Membrane technology can play a suitable role in removing pharmaceutical active compounds since it requires low energy and simple operation. Even though membrane technology has progressed for wastewater applications nowadays, modifying membranes to achieve the strong desired membrane performance is still needed. Thus, this study overviews a comprehensive insight into the application of modified polymer membranes to remove pharmaceutical active compounds from wastewater. Biotoxicity of pharmaceutical active compounds is first prescribed to gain deep insight into how membranes can remove pharmaceutical active compounds from wastewater. Then, the behavior of the diffusion mechanism can be concisely determined using mass transfer factor model that represented by β and B with value up to 2.004 g h mg-1 and 1.833 mg g-1 for organic compounds including pharmaceutical active compounds. The model refers to the adsorption of solute to attach onto acceptor sites of the membrane surface, external mass transport of solute materials from the bulk liquid to the membrane surface, and internal mass transfer to diffuse a solute toward acceptor sites of the membrane surface with evidenced up to 0.999. Different pharmaceutical compounds have different solubility and relates to the membrane hydrophilicity properties and mechanisms. Ultimately, challenges and future recommendations have been presented to view the future need to enhance membrane performance regarding fouling mitigation and recovering compounds. Afterwards, the discussion of this study is projected to play a critical role in advance of better-quality membrane technologies for removing pharmaceutical active compounds from wastewater in an eco-friendly strategy and without damaging the ecosystem.

Advances, challenges, and prospects in microalgal-bacterial symbiosis system treating heavy metal wastewater

Heavy metal (HM) pollution, particularly in its ionic form in water bodies, is a chronic issue threatening environmental security and human health. The microalgal-bacterial symbiosis (MABS) system, as the basis of water ecosystems, has the potential to treat HM wastewater in a sustainable manner, with the advantages of environmental friendliness and carbon sequestration. However, the differences between laboratory studies and engineering practices, including the complexity of pollutant compositions and extreme environmental conditions, limit the applications of the MABS system. Additionally, the biomass from the MABS system containing HMs requires further disposal or recycling. This review summarized the recent advances of the MABS system treating HM wastewater, including key mechanisms, influence factors related to HM removal, and the tolerance threshold values of the MABS system to HM toxicity. Furthermore, the challenges and prospects of the MABS system in treating actual HM wastewater are analyzed and discussed, and suggestions for biochar preparation from the MABS biomass containing HMs are provided. This review provides a reference point for the MABS system treating HM wastewater and the corresponding challenges faced by future engineering practices.

A critical review on remediation of microplastics using microalgae from aqueous system

Microplastics (MPs) are deemed to be a global concern due to their harmful negative effects on the aquatic environment and human beings. MPs have a significant impact on both fresh and marine water ecosystems. In many countries, there is concern about the deleterious consequences of MPs on human health due to the presence of MPs in aquatic life for higher intake of marine food (fish and shellfish). Exposure to MPs causes fish to suffer from growth retardation, neurotoxicity, and behavioural abnormalities and it affects human as well. It causes oxidative stress, neurotoxicity, cytotoxicity, and immune system disruption after being ingested to these contaminated fish in human body. Due to these reasons, it has become imperative to find ways to resolve this problem. This review paper represents a pioneering endeavor by consolidating comprehensive information on microplastic-polluted Indian riverine ecosystems and effective MPs removal methods into a single, cohesive document. It meticulously evaluates the principles, removal efficiency, benefits, and drawbacks of various techniques, aiming to identify the most optimal solution. Furthermore, this paper provides a comprehensive exploration of the interesting interactions between MPs and microalgae, delving into the intricate processes of hetero-aggregation. Additionally, it shines a spotlight on the latest advancements in understanding the efficacy of microalgae in removing MPs, showcasing recent breakthroughs in this field of research. Moreover, the work goes beyond conventional assessments by elucidating the characteristics of MPs and exploring diverse influencing parameters that impact MPs removal by microalgae and also addresses the potential future aspects. This thorough investigation uncovers important factors that could significantly contribute to the development of more efficient and sustainable remediation strategies.

Pollutants in aquatic system: a frontier perspective of emerging threat and strategies to solve the crisis for safe drinking water

Water is an indispensable natural resource and is the most vital substance for the existence of life on earth. However, due to anthropogenic activities, it is being polluted at an alarming rate which has led to serious concern about water shortage across the world. Moreover, toxic contaminants released into water bodies from various industrial and domestic activities negatively affect aquatic and terrestrial organisms and cause serious diseases such as cancer, renal problems, gastroenteritis, diarrhea, and nausea in humans. Therefore, water treatments that can eliminate toxins are very crucial. Unfortunately, pollution treatment remains a difficulty when four broad considerations are taken into account: effectiveness, reusability, environmental friendliness, and affordability. In this situation, protecting water from contamination or creating affordable remedial techniques has become a serious issue. Although traditional wastewater treatment technologies have existed since antiquity, they are both expensive and inefficient. Nowadays, advanced sustainable technical approaches are being created to replace traditional wastewater treatment processes. The present study reviews the sources, toxicity, and possible remediation techniques of the water contaminants.

Phycoremediation of heavy metals and production of biofuel from generated algal biomass: a review

Due to human activity and natural processes, heavy metal contamination frequently affects the earth's water resources. The pollution can be categorized as resistant and persistent since it poses a significant risk to terrestrial and marine biological systems and human health. Because of this, several appeals and demands have been made worldwide to try and clean up these contaminants. Through bioremediation, algal cells are frequently employed to adsorb and eliminate heavy metals from the environment. Bioremediation is seen as a desirable strategy with few adverse effects and low cost. Activities and procedures for bioremediation involving algal cells depend on various environmental factors, including salinity, pH, temperature, the concentration of heavy metals, the amount of alga biomass, and food availability. Additionally, the effectiveness of removing heavy metals from the environment by assessing how environmental circumstances affect algal activities. The main issues discussed are (1) heavy metal pollution of water bodies, the role of algal cells in heavy metal removal, the methods by which algae cells take up and store heavy metals, and the process of turning the algae biomass produced into biofuel. (2) To overcome the environmental factors and improve heavy metals bioremediation, many strategies are applied, such as immobilizing the cells, consortium culture, and using dry mass rather than living cells. (3) The processes for converting produced algal biomass into biofuels like biodiesel and biomethanol. The present study discusses the life cycle assessment and the limitations of biofuel products from algae biomass.

Shotgun Metagenomic Analyses of Microbial Assemblages in the Aquatic Ecosystem of Winam Gulf of Lake Victoria, Kenya Reveals Multiclass Pollution

Lake Victoria, the second-largest freshwater lake in the world, provides an important source of food and income, particularly fish for both domestic consumption and for export market. In recent years, Lake Victoria has suffered massive pollution from both industrial and wastewater discharge. Microplastic biomes, pharmaceutical residues, drugs of abuse, heavy metals, agrochemicals, and personal care products are ubiquitous in the aquatic ecosystem of Winam Gulf. These pollutants are known to alter microbial assemblages in aquatic ecosystems with far-reaching ramification including a calamitous consequence to human health. Indeed, some of these pollutants have been associated with human cancers and antimicrobial resistance. There is a paucity of data on the microbial profiles of this important but heavily polluted aquatic ecosystem. The current study sought to investigate the metagenomic profiles of microbial assemblages in the Winam Gulf ecosystem. Water and sediment samples were collected from several locations within the study sites. Total genomic DNA pooled from all sampling sites was extracted and analyzed by whole-genome shotgun sequencing. Analyses revealed three major kingdoms: bacteria, archaea and eukaryotes belonging to 3 phyla, 13 classes, 14 families, 9 orders, 14 genera, and 10 species. Proteobacteria, Betaproteobacteria, Comamonadaceae, Burkholdariales, and Arcobacter were the dominated phyla, class, family, order, genera, and species, respectively. The Kyoto Encyclopedia of Genes and Genomes indicated the highest number of genes involved in metabolism. The presence of carbohydrate metabolism genes and enzymes was used to infer organic pollutions from sewage and agricultural runoffs. Similarly, the presence of xylene and nutrotoluene degradation genes and enzyme was used to infer industrial pollution into the lake. Drug metabolism genes lend credence to the possibility of pharmaceutical pollutants in water. Taken together, there is a clear indication of massive pollution. In addition, carbohydrate-active enzymes were the most abundant and included genes in glycoside hydrolases. Shotgun metagenomic analyses conveyed an understanding of the microbial communities of the massively polluted aquatic ecosystem of Winam Gulf, Lake Vicoria, Kenya. The current study documents the presence of multiclass pollutants in Lake Victoria and reveals information that might be useful for a potential bioremediation strategy using the native microbial communities.

A review on algae biosorption for the removal of hazardous pollutants from wastewater: Limiting factors, prospects and recommendations

Heavy metals, dyes and pharmaceutical pollutants in water environment are considered as serious threat to the human and animal health globally. Rapid development of industrialization and agricultural activities are the major source for eliminating the toxic pollutants into the aquatic environment. Several conventional treatment methods have been suggested for the removal of emerging contaminants from wastewater. Algal biosorption, among other strategies and techniques, is demonstrating to be a limited technical remedy that is more focused and inherently more efficient and helps remove dangerous contaminants from water sources. The different environmental effects of harmful contaminants, including heavy metals, dyes, and pharmaceutical chemicals, as well as their sources, were briefly compiled in the current review. This paper provides a comprehensive definition of the future possibilities in heavy compound decomposition by using algal technology, from aggregation to numerous biosorption procedures. Functionalized materials produced from algal sources were clearly proposed. This review further highlights the limiting factors of algal biosorption to eliminate the hazardous material. Finally, this study showed how the existence of algae indicates a potential, effective, affordable, and sustainable sorbent biomaterial for minimizing environmental pollution.

A review on simultaneous heavy metal removal and organo-contaminants degradation by potential microbes: Current findings and future outlook

Industrial processes result in the production of heavy metals, dyes, pesticides, polyaromatic hydrocarbons (PAHs), pharmaceuticals, micropollutants, and PFAS (per- and polyfluorinated substances). Heavy metals are currently a significant problem in drinking water and other natural water bodies, including soil, which has an adverse impact on the environment as a whole. The heavy metal is highly poisonous, carcinogenic, mutagenic, and teratogenic to humans as well as other animals. Multiple polluted sites, including terrestrial and aquatic ecosystems, have been observed to co-occur with heavy metals and organo-pollutants. Pesticides and heavy metals can be degraded and removed concurrently from various metals and pesticide-contaminated matrixes due to microbial processes that include a variety of bacteria, both aerobic and anaerobic, as well as fungi. Numerous studies have examined the removal of heavy metals and organic-pollutants from different types of systems, but none of them have addressed the removal of these co-occurring heavy metals and organic pollutants and the use of microbes to do so. Therefore, the main focus of this review is on the recent developments in the concurrent microbial degradation of organo-pollutants and heavy metal removal. The limitations related to the simultaneous removal and degradation of heavy metals and organo-pollutant pollutants have also been taken into account.

Recent innovations and challenges in the eradication of emerging contaminants from aquatic systems

Presence of emerging pollutants (EPs), aka Micropollutants (MPs) in the freshwater environments is a severe threat to the environment and human beings. They include pharmaceuticals, insecticides, industrial chemicals, natural hormones, and personal care items and the pollutants are mostly present in wastewater generated from urbanization and increased industrial growth. Even concentrations as low as ngL^-1 or mgL^-1 have proven ecologically lethal to aquatic biota. For several years, the biodegradation of various Micropollutants (MPs) in aquatic ecosystems has been a significant area of research worldwide, with many chemical compounds being discovered in various water bodies. As aquatic biota spends most of their formative phases in polluted water, the impacts on aquatic biota are obvious, indicating that the environmental danger is substantial. In contrast, the impact of these contaminants on aquatic creatures and freshwater consumption is more subtle and manifests directly when disrupting the endocrine system. Research and development activities are expected to enable the development of ecologically sustainable, cost-effective, and efficient treatments for practical systems in the near future. Therefore, this review aims to understand recent emerging pollutants discovered and the available treatment technologies and suggest an innovative and cost-effective method to treat these EPs, which is sustainable and follows the circular bioeconomy.

Environmental occurrence, toxicity and remediation of perchlorate - A review

Perchlorate (ClO4-) comes under the class of contaminants called the emerging contaminants that will impact environment in the near future. A strong oxidizer by nature, perchlorate has received significant observation due to its occurrence, reactive nature, and persistence in varied environments such as surface water, groundwater, soil, and food. Perchlorate finds its use in number of industrial products ranging from missile fuel, fertilizers, and fireworks. Perchlorate exposure occurs when naturally occurring or manmade perchlorate in water or food is ingested. Perchlorate ingestion affects iodide absorption into the thyroid, thereby causing a decrease in the synthesis of thyroid hormone, a very crucial component needed for metabolism, neural development, and a number of other physiological functions in the body. Perchlorate remediation from ground water and drinking water is carried out through a series of physical-chemical techniques like ion (particle) transfer and reverse osmosis. However, the generation of waste through these processes are difficult to manage, so the need for alternative treatment methods occur. This review talks about the hybrid technologies that are currently researched and gaining momentum in the treatment of emerging contaminants, namely perchlorate.

Microalgae, a current option for the bioremediation of pharmaceuticals: a review

In this review, research on the use of microalgae as an option for bioremediation purposes of pharmaceutical compounds is reported and discussed thoroughly. Pharmaceuticals have been detected in water bodies around the world, attracting attention towards the increasing potential risks to humans and aquatic biota. Unfortunately, pharmaceuticals have no regulatory standards for safe disposal in many countries. Despite the advances in new analytical techniques, the current wastewater treatment facilities in many countries are ineffective to remove the whole presence of pharmaceutical compounds and their metabolites. Though new methods are substantially effective, removal rates of drugs from wastewater make the cost-effectiveness ratio a not viable option. Therefore, the necessity for investigating and developing more adequate removal treatments with a higher efficiency rate and at a lower cost is mandatory. The present review highlights the algae-based removal strategies for bioremediation purposes, considering their pathway as well as the removal rate and efficiency of the microalgae species used in assays. We have critically reviewed both application of living and non-living microalgae biomass for bioremediation purposes considering the most commonly used microalgae species. In addition, the use of modified and immobilized microalgae biomass for the removal of pharmaceutical compounds from water was discussed. Furthermore, research considering various microalgal species and their potential use to detoxify organic and inorganic toxic compounds were well evaluated in the review. Further research is required to exploit the potential use of microalgae species as an option for the bioremediation of pharmaceuticals in water.

Influence of C/N ratios on treatment performance and biomass production during co-culture of microalgae and activated sludge

Novel phycosphere associated bacteria processes are being regarded as a potential and cost-effective strategy for controlling anthropogenic contaminants in wastewater treatment. However, the underlying concern with the process is its vulnerability to improper organic or nutrient intake. This study established a synergistic interaction between microalgae and activated sludge in a three-photobioreactor system (without external aeration) to understand how pollutants could be mitigated whilst simultaneously yielding biomass under different C/N ratios of 1:1, 5:1 and 10:1. The result showed that the superior biomass productivity was facilitated at a C/N ratio of 5:1 (106 mg L^-1 d^-1), and the high degradation rate constants (k_COD = 0.25 d^-1, k_TN = 0.29 d^-1, k_TP = 0.35 d^-1) was approximated using a first-order kinetic model. The removal of pollutants was remarkably high, exceeding 90% (COD), 93% (TN), and 96% (TP). Nevertheless, the C/N ratio of 1:1 resulted in a threefold drop in biomass-specific growth rate (μ = 0.07 d^-1). Microalgal assimilation, followed by bacterial denitrification, is the major pathway of removing total nitrogen when the C/N ratio exceeds 5:1. Activated sludge plays an important role in improving microalgae tolerance to high concentration of ammonia nitrogen and boosting nitrification (light phase) and denitrification (dark phase). The use of phycosphere associated bacteria could be a promising strategy for controlling nutrients pollution and other environmental considerations in wastewater.

Removal of toxic heavy metals using genetically engineered microbes: Molecular tools, risk assessment and management strategies

The direct release of industrial effluent into the water and other anthropogenic activities causes water pollution. Heavy metal ions are the primary contaminant in the industrial effluents which are exceptionally toxic at low concentrations, terribly disturb the endurance equilibrium of activities in the eco-system and be remarkably hazardous to human health. Different conventional treatment methodologies were utilized for the removal of toxic pollutants from the contaminated water which has several drawbacks such as cost-ineffective and lower efficiency. Recently, genetically modified micro-organisms (GMMs) stand-out for the removal of toxic heavy metals are viewed as an economically plausible and environmentally safe technique. GMMs are microorganisms whose genetic material has been changed utilizing genetic engineering techniques that exhibit enhanced removal efficiency in comparison with the other treatment methodologies. The present review comments the GMMs such as bacteria, algae and fungi and their potential for the removal of toxic heavy metals. This review provides current aspects of different advanced molecular tools which have been used to manipulate micro-organisms through genetic expression for the breakdown of metal compounds in polluted areas. The strategies, major limitations and challenges for genetic engineering of micro-organisms have been reviewed. The current review investigates the approaches working on utilizing genetically modified micro-organisms and effective removal techniques.

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

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

Mixed Contaminants: Occurrence, Interactions, Toxicity, Detection, and Remediation

The ever-increasing rate of pollution has attracted considerable interest in research. Several anthropogenic activities have diminished soil, air, and water quality and have led to complex chemical pollutants. This review aims to provide a clear idea about the latest and most prevalent pollutants such as heavy metals, PAHs, pesticides, hydrocarbons, and pharmaceuticals—their occurrence in various complex mixtures and how several environmental factors influence their interaction. The mechanism adopted by these contaminants to form the complex mixtures leading to the rise of a new class of contaminants, and thus resulting in severe threats to human health and the environment, has also been exhibited. Additionally, this review provides an in-depth idea of various in vivo, in vitro, and trending biomarkers used for risk assessment and identifies the occurrence of mixed contaminants even at very minute concentrations. Much importance has been given to remediation technologies to understand our current position in handling these contaminants and how the technologies can be improved. This paper aims to create awareness among readers about the most ubiquitous contaminants and how simple ways can be adopted to tackle the same.

Sustainability Assessment for Wastewater Treatment Systems in Developing Countries

As the assessment of the economic, environmental, institutional, and social sustainability of wastewater treatment systems may have several conceivable goals and intended recipients, there are numerous different approaches. This paper surveys certain aspects of sustainability assessment that may be of interest to the planners of wastewater treatment systems. Here, the key criteria assess the system’s costs and financing, including its affordability for the users, the environmental impact, the benefits for health and hygiene, the cultural acceptance of the system and its recycled products, the technical functioning, and the administrative, political, and legal framework for its construction and operation. A multi-criteria approach may then be used to analyze possible trade-offs and identify the most suitable system for a certain location.