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Pure water will become a golden resource in the context of the rising pollution, climate change and the recycling economy, calling for advanced purification methods such as the use of nanostructured adsorbents. However, coming up with an ideal nanoadsorbent for micropollutant removal is a real challenge because nanoadsorbents, which demonstrate very good performances at laboratory scale, do not necessarily have suitable properties in in full-scale water purification and wastewater treatment systems. Here, magnetic nanoadsorbents appear promising because they can be easily separated from the slurry phase into a denser sludge phase by applying a magnetic field. Yet, there are only few examples of large-scale use of magnetic adsorbents for water purification and wastewater treatment. Here, we review magnetic nanoadsorbents for the removal of micropollutants, and we explain the integration of magnetic separation in the existing treatment plants. We found that the use of magnetic nanoadsorbents is an effective option in water treatment, but lacks maturity in full-scale water treatment facilities. The concentrations of magnetic nanoadsorbents in final effluents can be controlled by using magnetic separation, thus minimizing the ecotoxicicological impact. Academia and the water industry should better collaborate to integrate magnetic separation in full-scale water purification and wastewater treatment plants.

Biohydrogen production from various organic wastes, wastewaters and biomass has been widely studied due to the higher production rates and fundamentals and technologies have also been well developed and heavily documented through diverse laboratory-scale bioreactors. Recently, research has been geared to the concomitant production of biohydrogen and methane which is so called “biohythane”. One-stage and two-stage (bio-H2 + bio-CH4) methods are the main biohythane production methods and this field of research for probing into green biofuels is gradually gaining ground. In this paper, the salient aspects of biohythane research at the present time are revisited and the research success and latent promise of biohythane are highlighted based on the findings of the relatively few publications in this area.

The green approach of the one-pot enzyme-assisted biomass deconstruction for the production of biofuels and high-value added chemicals in the presence of combined ionic liquids with metal nanoparticles (CILMNPs) process is receiving more interest in biomass-to-energy research. This paper gives a succinct overview of the recent applications of CILMNPs in the pretreatment of lignin-based biomass for macrocellular deconstruction at the one-pot scale and then holistically addresses the multifarious research hurdles, challenges and prospects which have to be addressed to achieve the green merits on a larger scale of processing. Once the one-pot green metrics will be matched by their corresponding process metrics, the potential for pilot-scale production and eventually industrial utilization of CILMNPS will take good shape. Furthermore, such process scale-up campaigns using CILMNPS for biomass depolymerization will have to be robustly designed for an effective and efficient application by selecting bioprocesses involving enzymatic hydrolysis, saccharification and deoxygenation/hydrodeoxygenation routes operated under continuous regimes. These tasks will demand considerable applied research efforts in the form of process intensification and optimization both at the one-pot scale and for prospective large-scale bioprocessing units.

Biohydrogen production from lignocellulosic biomass (LCB) is an active research area. Several workers have tested a number of substrates under different operational conditions and brought forward the many positive process performance features and identified the main sources of inhibition. This review analyzes selected fermentative biohydrogen production processes by revisiting the core biohydrogen production performances in terms of gas production rates and yields and equally addresses the options for process enhancement by the application of through pretreatment methods and detoxification of process inhibitors. In addition, the issues related to continuous biohydrogen operation in different reactor configurations are highlighted. Lastly, future avenues of research which may be engendered and engineered to enhance the biohydrogen generation and process biokinetics are discussed. This review intends to provide the fundamental understanding of biohydrogen production and provides a perspective on future developments in this area of applied research.

This review summarizes the recent essential aspects of subcritical and supercritical water technology applied tothe extraction, hydrolysis, carbonization, and gasification processes. These are clean and fast technologies which do not need pretreatment, require less reaction time, generate less corrosion and residues, do not usetoxic solvents, and reduce the synthesis of degradation byproducts. The equipment design, process parameters, and types of biomass used for subcritical and supercritical water process are presented. The benefits of catalysis to improve process efficiency are addressed. Bioactive compounds, reducing sugars, hydrogen, biodiesel, and hydrothermal char are the final products of subcritical and supercritical water processes. The present review also revisits advances of the research trends in the development of subcriticaland supercritical water process technologies.

Hydrogen production from lignocellulosic biomass (LCB) using dark fermentation is an interesting research niche being developed over the last decade. This review analyses the relevant studies which focused on biohydrogen production from LCB using dark fermentation techniques in terms of substrate characterization, bottlenecks associated with the pretreatment and its subsequent utilization, possible remedies for the scale-up of the most adapted processes and finally the prospects and suggestions which may be envisaged. Studies dealing primarily with the utilization of raw and pretreated LCB have been assessed in terms of biohydrogen production performance for production rate and yield. Energy production analysis and prospecting of suitable cellulosic biomass and efficient cellulolytic microbes have been elucidated towards better cellulose hydrolysis and efficient conversion of LCB to H2 in addition to process economics.

The persistence and bioaccumulation of environmental pollutants in water bodies, soils and living tissues remain alarmingly related to environmental protection and ecosystem restoration. Adsorption-based techniques appear highly competent in sequestering several environmental pollutants. In this review, the recent research findings reported on the assessments of composts and compost-amended soils as adsorbents of heavy metal ions, dye molecules and xenobiotics have been appraised. This review demonstrates clearly the high adsorption capacities of composts for umpteen environmental pollutants at the lab-scale. The main inferences from this review are that utilization of composts for the removal of heavy metal ions, dye molecules and xenobiotics from aqueous environments and soils is particularly worthwhile and efficient at the laboratory scale, and the adsorption behaviors and effectiveness of compost-type adsorbents for agrochemicals (e.g. herbicides and insecticides) vary considerably because of variabilities in structure, topology, bond connectivity, distribution of functional groups and interactions of xenobiotics with the active humic substances in composts. Compost-based field-scale remediation of environmental pollutants is still sparse and arguably much challenging to implement if, furthermore, real-world soil and water contamination issues are to be addressed effectively. Hence, significant research and process development efforts should be promptly geared and intensified in this direction by extrapolating the lab-scale findings in a cost-effective manner.

Over the last couple of decades, academic research on adsorbents has been flourishing. The preparation, functionalization, and adsorption performance evaluation have grown explosively. Novel adsorbents have demonstrated excellent capabilities to remove metal ions and organic contaminants from aqueous environments having different physicochemical conditions. This article presents gaps and potential research possibilities related to economic assessment, benchmarking of synthetic real wastewaters, adsorptive (component) additivity, constraints of process scale-up, process intensification, and modeling, simulation and optimization of large-scale adsorption-based water remediation systems. These discussions foster fresh ideas and investigations in the cognate science and engineering disciplines so that industrial applications of novel adsorbents for innovative water treatment matures both technically and cost-effectively.

The aim of the study was to investigate the effects of carton in the composting process of mixed vegetable wastes using an experimental composter of capacity 80L. Three different mixes were set-up (Mixes 1, 2 and 3) which consisted of vegetable wastes, 2.0kg paper and bulking agents, vegetable wastes, 1.5kg carton and bulking agents, vegetable wastes, 4.5kg carton and bulking agents, respectively. Temperature evolution, pH trends, moisture levels, respiration rates, percentage volatile solids and electrical conductivity were monitored for a period of 50days. The system remained under thermophilic conditions for a very short period due to the small size of the reactor. The three mixes did not exceed a temperature of 55°C, where sanitization takes place by the destruction of pathogens. The highest peak of CO2 evolution was observed in Mix 2 indicating that maximum microbial degradation took place in that mix.

International audience; This review provides the alternative routes towards the valorization of dark H-2 fermentation effluents that are mainly rich in volatile fatty acids such as acetate and butyrate. Various enhancement and alternative routes such as photo fermentation, anaerobic digestion, utilization of microbial electrochemical systems, and algal system towards the generation of bioenergy and electricity and also for efficient organic matter utilization are highlighted. What is more, various integration schemes and two-stage fermentation for the possible scale up are reviewed. Moreover, recent progress for enhanced performance towards waste stabilization and overall utilization of useful and higher COD present in the organic source into value-added products are extensively discussed.

The implementation of cleaner waste treatment technologies in developing countries is accompanied by myriads of limitations and obstacles. This study reports that greenhouse gas (GHG) emission reductions that would not have happened with business-as-usual scenarios are achievable in the waste management system under the Clean Development Mechanism (CDM). The grounds for CDM failures and successes were reviewed by reflecting on the past and current episodes in developing countries. It was found that economic development was directly proportional to increase in waste generation rate and influenced waste composition. The need to decouple waste production from Gross Domestic Product (GDP) and linking the prevalence of more low-carbon emissions waste treatment options were found essential to ensure sustainable development and mitigate climate change. Based on the present evaluation, Brazil and Thailand have had the largest number of CDM projects and mostly small-scale projects with the highest maximum emission reductions in Brazil (751, 148 Mt CO2e) followed by Vietnam (158, 727 Mt CO2e) and India (158, 077 Mt CO2e). It was found that small-scale projects were more feasible as technology transfer and financial status were hindering the implementation of large-scale CDM projects. Moreover, emissions trading through CDM were accompanied by technical obstructions in terms of carbon leakage, permit allowances and unfair carbon price with irregular international policies and regulations to control GHGs. This study highlights the potential of a carbon trading scheme through CDM waste management projects designed to aid highly polluting developed countries achieve their target baselines for carbon emissions. The increasing GHG emissions in developing and least developed countries could be tackled at the early stages of economic growth through financial and technological assistance from industrialized countries.

Heavy metals released from industrial activities pose a significant threat to the environment and public health due to their reported toxicity even at trace levels. Although there are several available methods to treat or remove heavy metals from water and wastewater, the research focuses on development of technological solutions which sound environmental friendly and economically feasible, able to reduce the costs and maximize the efficiency. In this framework, the biosorption process, which uses cheap and non-pollutant materials, may be considered as an alternative, viable and promising, technology for heavy metal and metalloid ions sequestration and ultimately removal technology in the waste water treatment. However, there is as yet little data on full-scale applications for the design and testing of adsorption units using single biosorbents and their combinations to sequester heavy metal ions from multi-metal systems. Immediate research and development is hence earnestly required in this specific direction to further make progress this blooming technology and widen its scope of application to real situations needing heavy metal pollution remediation. This review provides a comprehensive appraisal of the equilibrium modeling of a number of biosorption processes as well as the structural, chemical and morphological modifications and activation of biosorbents. Further the relative merits of the methods used to recover sequestered heavy metal ions and regenerate biosorbents through desorption routes and their future applications are discussed.

In this study, estimates of greenhouse gas (GHG) emissions (for methane, carbon monoxide and nitrous oxide) following the potential installation of an aerated bioreactor landfill system at the Mare Chicose landfill in Mauritius have been determined based on procedures outlined in the Approved Baseline and Monitoring Methodology AM0083, "Avoidance of landfill gas emissions by in-situ aeration of landfills" from the UNFCCC/CCNUCC CDM, and compared to the baseline emissions (flaring method) for a credit period of 10 years to compute emissions reductions (ERs). The second part of this study has employed a combined multi-parameter sensitivity analysis (MPSA) and response surface methodology (RSM) approach to assess the relative importance of 5 selected parameters in influencing the amount of ERs. This technique of data analysis is reportedly novel in this field of research in environmental engineering for GHG emissions quantification. The parameters tested were the monitored methane content in venting well/header k during in-situ aeration in the year y (MC CH4,v,k.q ), monitored methane content from surface emissions during in-situ aeration in zone i in the quarter q (MC CH4,s,i,q ), total volume of surface emissions in zone i in quarter q (SG s,i,q ), potential methane generation capacity (L o,i ) of the waste in landfill zone i as determined by sampling and lab analysis and fraction of degradable waste (f dg , i ) in landfill zone i. Results from the MPSA and mesh plots from the RSM showed that L o , i had the most influence on the ERs. The largest ERs amounted to 835,104.61 tCO 2e obtained from the variations in L o,i whereas 189,343.30 tCO 2e was the lowest predicted ERs. The best working values for the five parameters with respect to a better environmental performance for minimal GHG emissions and maximum ERs were: 0.077-0.134 ton CH 4 /ton waste for L o,i , 0.713-0.8 for f dg,i , 688,829.30-972,916.67 m 3 for SG s,i,q , 1.01 × 10 - 5 to 1.75 × 10 ―5 tCH 4/ m 3 for MC CH4,v,k,q and 6.70× 10 ―8 to 5.16 × 10 ―7 tCH 4 /m 3 for MC CH4,s,i,q . The results of this study present a novel tool of optimized parameter values and ERs data which can be used to decide on how to better design and operate the landfill in Mauritius under the Clean Development Mechanism.

The Port Louis Harbour is the sole port in Mauritius and handles 99% of cargo entering the island. The port area is subject to a wide range of port installations handling, processing and storing a wide range of cargo ranging from petroleum products, coal, cement, edible oil, heavy oil, molasses, wheat, bitumen to fertiliser manufacturing. This study integrated procedures of ISO14001 and was carried out in the context of the UNEP GEF WIO–Lab Solid Wastes Demo Project during the period April 2009 to May 2010. An inventory of the wastes generation and flow from ships and within the industrial port area was conducted, and on basis of the results obtained, an environmental pollution prevention and protection program was developed to eventually assist in the setting up of a Port Waste Management System (PWMS) at the Port Louis Harbour. The PWMS identified the significant environmental aspects and impacts, structure of the organisation, distribution of responsibilities, needs for training, objectives and targets as well as the operational control measures. At the end of the study, suggestions on how to improve the port’s environmental performance with regards to waste management were recommended.

In pursuit of a green and sustainable world, wastewater remediation and sludge treatment have equally become a growing global environmental concern. Several innovative treatment processes have been designed throughout the last few decades for treating wastewaters and sludges but many of them are very costly and operate at low efficiencies. In view to find novel treatment processes, active research is being conducted globally. Microwave irradiation technology is gradually making a modest but promising mark of its own in enhancing to significant extents the ease, fastness, and efficiency of certain treatment processes involved in wastewater and sludge management. The authors focus on and appraise the budding use and application of microwave irradiation in chemical research undertaken for sludge and wastewater treatment. The related aspects of microwave-assisted heavy metal stabilization, pathogen inactivation, wastewater parameter analysis, and wastewater treatment polymers synthesis are also discussed.

Arsenic is a toxic element and has been responsible for many accidental, occupational, deliberate, and therapeutic poisonings since its discovery in 1250. It occurs in natural waters as the arsenite (As3+) and arsenate (As5+) ions. The solubility of arsenite and arsenate compounds is relatively high so that these ions are readily transported through aqueous routes into the environment. Arsenic can be transferred from soils to crops and accumulates in various food crops and aquatic plants. The fascinating chemistry and toxicity potential make arsenic and its compounds of particular scientific interest and environmental concern. The conventional removal of heavy metals from wastewater, natural waters, and drinking water has only limited effects on arsenic removal. In this review, the main engineering and medical applications, salient health and environmental concerns, novel research on treatment for arsenic poisoning, and removal technologies for arsenic and their derivatives are discussed and enumerated wi...

This paper provides an overview of the recent advances and trends in research in the biological production of hydrogen (biohydrogen). Hydrogen from both fossil and renewable biomass resources is a sustainable source of energy that is not limited and of different applications. The most commonly used techniques of biohydrogen production, including direct biophotolysis, indirect biophotolysis, photo-fermentation and dark-fermentation, conventional or "modern" techniques are examined in this review. The main limitations inherent to biochemical reactions for hydrogen production and design are the constraints in reactor configuration which influence biohydrogen production, and these have been identified. Thereafter, physical pretreatments, modifications in the design of reactors, and biochemical and genetic manipulation techniques that are being developed to enhance the overall rates and yields of biohydrogen generation are revisited.

Sustainable development requires the development and promotion of environmental management and a constant search for green technologies to treat a wide range of aquatic and terrestrial habitats contaminated by increasing anthropogenic activities. Bioremediation is an increasingly popular alternative to conventional methods for treating waste compounds and media with the possibility to degrade contaminants using natural microbial activity mediated by different consortia of microbial strains. Many studies about bioremediation have been reported and the scientific literature has revealed the progressive emergence of various bioremediation techniques. In this review, we discuss the various in situ and ex situ bioremediation techniques and elaborate on the anaerobic digestion technology, phytoremediation, hyperaccumulation, composting and biosorption for their effectiveness in the biotreatment, stabilization and eventually overall remediation of contaminated strata and environments. The review ends with a note on the recent advances genetic engineering and nanotechnology have had in improving bioremediation. Case studies have also been extensively revisited to support the discussions on biosorption of heavy metals, gene probes used in molecular diagnostics, bioremediation studies of contaminants in vadose soils, bioremediation of oil contaminated soils, bioremediation of contaminants from mining sites, air sparging, slurry phase bioremediation, phytoremediation studies for pollutants and heavy metal hyperaccumulators, and vermicomposting.

In recent years, due to an advance in knowledge of landfill behaviour and decomposition processes of municipal solid waste, there has been a strong thrust to upgrade existing landfill technologies for optimizing these degradation processes and thereafter harness a maximum of the useful bioavailable matter in the form of higher landfill gas generation rates. Operating landfills as bioreactors for enhancing the stabilization of wastes is one such technology option that has been recently investigated and has already been in use in many countries. A few full-scale implementations of this novel technology are gaining momentum in landfill research and development activities. The publication of bioreactor landfill research has resulted in a wide pool of knowledge and useful engineering data. This review covers leachate recirculation and stabilization, nitrogen transformation and corresponding extensive laboratory- and pilot-scale research, the bioreactor landfill concept, the benefits to be derived from this bioreactor landfill technology, and the design and operational issues and research trends that form the basis of applied landfill research.

In this study, biochemical methane potential assays of mixed municipal solid wastes and other types of waste such as, cellulosic, vegetable and food wastes were performed over 60 days with two different volatile solid amendments, namely domestic sewage sludge and leachate. With sewage sludge, cumulative methane (CH4) production from cellulose, food and vegetable wastes and municipal solid wastes varied from 0.23-1.51, 0.25-0.92, 0.14-0.55 and 0.07-0.21 L/g volatile solids, respectively. With leachate, the corresponding cumulative CH4 generations were 0.93-3.50, 0.97-1.81, 0.24-1.05 and 0.10-0.57 L/g VS, respectively. The individual cumulative CH4 production data fitted very well with the modified Gompertz equation and maximum methane production rates, methane production potential and lag phase time were estimated using the SigmaPlot® 11 software and this was validated by the algorithms of the Grofit software. Results showed that cumulative methane production with leachate were twice as high as with sewage slsudge. The cumulative CH4 production after 60 days varied in the order cellulose wastes>food wastes>vegetable wastes> municipal solid wastes.

Dioxins and furans are persistent, highly hazardous and ubiquitous compounds that have become the focus of many investigations due to the contamination of food and the ecosystem. Dioxins and furans refer to a class of polyhalogenated aromatic hydrocarbons generated by various chemical processes occurring often at high temperature. The main sources of dioxins and furans have been classified into four categories, namely: incineration, combustion, industrial processes and natural processes such as volcanic eruptions. Dioxins and furans are present in flue gas and fly ash from combustion, in contaminated soils, sediments and water bodies. The expression toxic equivalency (TEQ) factor has been defined to assess their toxicity. Dioxins and furans have adverse effects on human health because they are bioaccumulated in tissues and cells. They are carcinogenic and cause reproductive alterations. They are a threat to the ecosystem because they persist in nature, affecting marine and terrestrial living organisms, and subsequently ending up in the food chain. We review remediation techniques of dioxins and furans. The most common techniques are landfill cap system and deep well injections, high temperature incineration and cement kilns. This chapter focuses on the principal destruction, removal and remediation techniques based on flue gas, fly ash and soil treatment. Basic techniques are selective catalyst reduction technologies, adsorption by means of activated carbon, base catalysed reactions, photolytic degradation processes, thermal desorption processes, alkaline polyethylene glycolate (APEG) process, bioslurry treatment and vitrification.

Viewing the increase in energy demand and bearing in consideration the associated pollution issues, a shift in energy paradigm from a monopolized conventional energy regime of fossil fuels to a non-conventional renewable energy mix is necessary in the Mauritian context. Besides achieving considerable waste reduction, the incineration and fermentation of renewable biomass feedstock can also generate revenues from energy production, known as waste-to-energy (WtE) and anaerobic digestion technology (ADT), respectively. In Mauritius, municipal solid wastes (MSW) typically include food and garden wastes, other green wastes and organic residues, different grades of paper and plastics, textiles, rubber, glass, metals, wood, process sludges and inerts. This chapter provides a succinct review of research studies and large-scale applications of the WtE sector and ADT in Mauritius.

Radiation technology is regarded to be a promising “green” alternative for its high efficiency in organic pollutants remediation. To date, microwave energy has been widely used in several domestic, industrial, and medical applications. In line with the need for environmental sustainability through the application of green chemistry and green engineering practices, the potential application of microwave energy irradiation as a major source of energy and/or pretreatment for the degradation of various types of organic pollutants found in wastewaters and other contaminated water bodies has been a growing research interest. This chapter will give an account of (1) the environmental issues related to the contamination of water by organic pollutants such as industrial/textile dyes, pesticides, herbicides, xenobiotics, PAHs, PCBs, and other persistent organic pollutants, and (2) research on the application of ultrasound and mainly microwave power irradiation for the degradation these organic pollutants.

The paper reviews the state-of-the-art technologies on sludge conditioning and stabilisation. Radiation technology, best contextualised within the concept of Green Chemistry, is yet another developing area of sludge pretreatment. Besides revisiting some important aspects of sludge treatment by composting, this review paper also appraises the application of gamma ray and ultrasound irradiations particularly in sludge pretreatment and sludge composting for monitoring, and to some extent improving, the degradation and subsequent stabilisation of sludge constituents. The scientific principle of each type of radiation and selected research work are discussed, and future needs for applied research are eventually outlined.