Environmental Science and Bio/Technology

Seaweed biorefinery Abstract Seaweed offers a wide range of interesting bioactives. With over 10,000 species globally, it is of great interest to be able to extract these compounds. Hence, seaweed fractionation into a wide spectrum of valuable products using multistage cascade processes offers a sustainable approach of exploitation of this resource to produce bioactive ingredients, chemicals and biofuels. This biorefinery processing approach should be adapted to local conditions to maximize the biomass utilization and to lower the waste fractions or preventing any waste materials re-enforcing the circular economy. This review presents an overview of the potential uses of waste generated after seaweed processing for food and other uses, as well as the utilization of invasive species biomass and other invasive species. Graphical abstract

Application of alkali-activated materials for water and wastewater treatment: a review Abstract Alkali-activation (or geopolymer) technology has gained a great deal of interest for its potential applications in water and wastewater treatment during the last decade. Alkali-activated materials can be prepared via a relatively simple and low-energy process, most commonly by treating aluminosilicate precursors with concentrated alkali hydroxide and/or silicate solutions at (near) ambient conditions. The resulting materials are, in general, amorphous, have good physical and chemical stability, ion-exchange properties, and a porous structure. Several of the precursors are industrial by-products or other readily available low-cost materials, which further enhances the environmental and economic feasibility. The application areas of alkali-activated materials in water and wastewater treatment are adsorbents/ion-exchangers, photocatalysts, high-pressure membranes, filter media, anti-microbial materials, pH buffers, carrier media in bioreactors, and solidification/stabilization of water treatment residues. The purpose of this review is to present a comprehensive evaluation of the rapidly growing prospects of alkali-activation technology in water and wastewater treatment.

Removal of cesium ions from aqueous solutions using various separation technologies Abstract Cesium is the major fission product of uranium, which widely exists in radioactive wastewater. Radiocesium has potential adverse effects on human health and ecological environment. Different methods such as chemical precipitation, coagulation/co-precipitation, solvent extraction, membrane process, chemical reduction, and adsorption have been used to remove radioactive cesium from aqueous solution. However, the development of innovative technologies capable of selectively removing radioactive cesium is still imperative yet challenging. This review focused on cesium removal using various separation technologies, including chemical precipitation, solvent extraction, membrane separation, and adsorption. The key restraints for cesium removal, as well as the recent progress of these methods have also been discussed. Particular attention has been paid to the adsorption methods, which has been highlighted by introducing the latest advances in inorganic adsorbents (such as metal hexacyanoferrates, clay minerals, carbon-based-adsorbents, and ammonium molybdophosphate), organic adsorbents (such as ion exchange resin, metal–organic frameworks and supramolecular/indicator grafting adsorbents), and biosorbents (such as agroforestry wastes and microbial biomass). Adsorption-based methods are high efficient in separation of cesium ions from aqueous streams, and adsorption of cesium ions has been investigated intensively and even used in practical applications, there is still considerable scope for improvement in terms of adsorption capacity and selectivity.

Keratin based thermoplastic biocomposites: a review Abstract Fibre reinforced composites have become important materials for manufacturing a diverse range of industrial products. Keratin-rich materials including sheep wool and poultry feathers can have added value by partially substituting synthetic polymers in the production of biocomposites with improved mechanical properties. The strong intermolecular disulfides, hydrogen, ionic and hydrophobic interactions of keratin make it behave as a thermoset material which is not easy to process and thermally blend with other polymers. Therefore, different plasticizers, compatibilizers and coupling agents were investigated in order to make keratin a processable material. This review discusses recent developments in the production of thermoplastic keratin blend biocomposites. In particular, the processing and preparation conditions has been discussed, and their strengths and limitations are enumerated and critically evaluated. Graphical abstract

Polymers derived from hemicellulosic parts of lignocellulosic biomass Abstract Furfural, which is directly derived from the hemicellulosic parts of lignocellulosic biomass, is considered as one of the most promising platform chemicals to manufacture commodity chemical products such as polymers and their monomers. Its production has already been commercialized. In this review, potentially relevant methods for producing important chemicals from furfural, which are used as monomers for different polymers, and for the polymerization of furfural and its derivatives (e.g., furfuryl alcohol), have been discussed. First, the production of furfural from different lignocellulosic biomasses is presented. Next, the synthesis of various monomers and their highest available yields from furfural are discussed. The polymers that can be directly produced from furfural and its derivatives are explored. Finally, the challenges of producing furfural-based products have been highlighted.

Current research trends on microplastic pollution from wastewater systems: a critical review Abstract Microplastics have been widely considered as contaminants for the environment and biota. Till now, most previous studies have focused on the identification and characterization of microplastics in freshwater, sea water, and the terrestrial environment. Although microplastics have been extensively detected in the wastewater, research in this area is still lacking and not thoroughly understood. To fill this knowledge gap, the current review article covers the analytical methods of microplastics originating from wastewater streams and describes their sources and occurrences in wastewater treatment plants (WWTPs). Studies indicated that microplastic pollution caused by domestic washing of synthetic fibers could be detected in the effluent; however, most microplastics from personal care and cosmetic products (PCCPs) can be efficiently removed during wastewater treatment. Moreover, various techniques for sampling and analyzing microplastics from wastewater systems are reviewed; while, the implementation of standardized protocols for microplastics is required. Finally, the fate of microplastics during wastewater treatments and the environmental contamination of effluent to environment are presented. Previous studies reported that the advanced wastewater treatment (e.g., membrane bioreactor) is needed for improving the removal efficiency of small-sized microplastics (< 100 µm). Although the role of microplastics as transport vectors for persistent organic pollutants (POPs) is still under debate, they have demonstrated abilities to absorb harmful agents like pharmaceuticals.

Anaerobic ammonium oxidation in marine environments: contribution to biogeochemical cycles and biotechnological developments for wastewater treatment Abstract Microbial processes are responsible for most reactions involved in the nitrogen cycle in the oceans, which determine the fluxes of this crucial nutrient in these environments. The present review provides an overview of the contribution of anaerobic ammonium oxidation (Anammox) to marine biogeochemical processes. Besides the conventional Anammox process, anaerobic ammonium oxidation coupled to the microbial reduction of alternative electron acceptors, such as sulfate (Sulfammox), ferric iron (Feammox), and natural organic matter (NOM-dependent Anammox) is also described in the context of global marine biogeochemical cycles. Also, the complex interactions among the oceanic biogeochemical cycles of N, S and Fe are discussed at the light of the new findings available in the literature. The review also underlines the important role of the microbial processes performing the Anammox reaction in the development of wastewater treatment systems for the removal of nitrogen from saline effluents. Strategies to enrich and immobilize Anammox bacteria in different reactor configurations for the treatment of saline wastewaters are also described as well as future directions for novel biotechnological developments based on Anammox.

A review on emulsion liquid membrane (ELM) for the treatment of various industrial effluent streams Abstract The excessive release of toxic metal ions by the several industrial effluent streams into the environment has imposed a serious threat to the ecological system. Therefore, the removal of these toxic metal ions from the wastewater of various industrial effluent streams has received a considerable amount of interest and also currently becoming an imperative area of research. Since last few decades, ELM based separation processes have been become an attractive and efficient way for the removal of toxic metal ions, organic and inorganic acids, and industrial pollutants of the various aqueous waste effluent streams. ELM is an emerging alternative technique to the conventional solvent extraction processes with an additive advantage of low solvent inventory and energy requirements. Moreover, it also preconcentrates the solute by performing both extraction and stripping operations simultaneously in a single unit. The main aim of this review paper is to elucidate the comprehensive review on the ELM (its pertinent properties/characteristics), its membrane phase compositions, its stability, and its process parameters respectively and also to delineate the applications of this technique for the removal of various low concentrated solutes.

The effects of electric, magnetic and electromagnetic fields on microorganisms in the perspective of bioremediation Abstract Some studies show how exposure to fields can enhance or reduce cell activity, with possible applicative consequences in the field of biotechnology, including biological techniques for depollution. In order to identify full-scale conditions that are suitable and potentially applicable for use in electromagnetic fields to stimulate and accelerate bioremediation processes, this paper offers an examination of the scientific literature that is available on the effects of fields on microorganisms, and a critical analysis of it. The biological effects at times contrast with each other.

A review on greywater reuse: quality, risks, barriers and global scenarios Abstract Greywater is wastewater collected from household sources without input from toilet or commode streams. Greywater represent ca. 65% of total household wastewaters globally. Different aspects of greywater, including its production sources, its characteristics, the barriers and the global scenarios of its reuse, have been critically reviewed in this paper. Given the current projections on acute water scarcity in many regions of the world, the importance of water management cannot be overlooked and a decentralized approach, segregating wastewater streams of a household with proper sanitation is a potential option for recycling greywater. This paper aims to explore the improvements achieved in the reuse of greywater. Therefore, reutilization rates were estimated, hazards and risks associated with the use of untreated greywater were analyzed were summarized. Guidelines for greywater treatment were established and barriers for successful implementation of reuse strategies were identified. Global scenarios of successful implementations of greywater reuse were presented.