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Challenges and opportunities associated with wastewater treatment systems
Abstract
The untreated water may lead to an excessive disposal of wastes which may reduce the water quality of water bodies and damage water ecosystems. Wastewater treatment systems are widely implemented in industries and municipalities to decrease toxic wastewater release into aquatic ecosystems. Wastewater recycling, reclamation, recovery, and reuse can be used as tools for the control of water resources and can attract researchers and stakeholders. Currently microbial fuel cells and microalgae are intensively studied as a cost-effective technology to complete sustainable wastewater treatment. These technologies have potential benefits for energy, and environmental and economic sustainability. This chapter will review the challenges, barriers, and opportunities associated with improving wastewater treatment systems.
... For its part, energy, like water, is a fundamental resource to face the great challenges and opportunities facing the world today (Saavedra et al., 2021). The demand for water and energy has increased due to population growth and the development of cities, so the society-economy binomial depends on both available energy and available clean water (Bhat et al., 2021). Good management of both resources contributes to the sustainability of the environment. ...
... These new technologies are necessary due to the increasing demand for energy and the decrease in the availability and quality of water. The problems of scarcity and high consumption of water, coupled with the growing effects of climate change due to the excessive use of fossil fuels, make it necessary to seek innovative alternatives to remedy such problems (Santhosh et al., 2016;Bhat et al., 2021). This Research Topic Research Topic covers the synthesis and characterization of catalytic and photocatalytic materials for the removal of emerging contaminants and pathogens in water. ...
This Research Topic Research Topic covers the synthesis and
characterization of catalytic and photocatalytic materials for the
removal of emerging contaminants and pathogens in water.
Alternatives are evaluated to improve carbon-based materials for
electrochemical systems and treat industrial wastewater. Finally, the
nature and grouping of energy resources are analyzed. This Research
Topic of papers is formed of four original research articles, one brief
research report article, and one opinion article. A description of each
is given below.
... Sludge, as a derivative solid waste from flocculation and biological process in wastewater treatment, has significantly restricted the sustainability of textile (De Gisi and Notarnicola, 2017). Due to the higher production of textile sludge, landfill with no enough land and energy-intensive incineration troubled the sludge disposal (Anshassi et al., 2021;Bhat et al., 2021;Mazibuko et al., 2019;Muralikrishna and Manickam, 2017;Narani et al., 2020;Singh et al., 2020). In big cities, special attention has been drawn on the used clothes (Pensupa et al., 2017;Piribauer and Bartl, 2019;Sahuand and Pramanik, 2017;Senthil Kumar and Anbalagan, 2017;Wagner and Heinzel, 2020;Williams, 2015). ...
Due to global population growth and living standards improvements, textile production and consumption are increased. Textile solid waste has become challenging issue for waste management authority. It is reported that textile materials are discarded daily, representing approximately 1.5% of the generated waste around the world. Over the past few decades, special attention has been given to the used clothes in all regions globally, which can reduce energy costs by 80% and also represent a source of raw materials economically profitable and environmentally responsible. This review article attempted to address different topics including: source of solid textile waste, environmental impact of textile waste as a result of massive consumption of clothing, textile waste management processes such as recycling, reuse of textile waste, landfill and incineration and energy recovery from textile waste. Narrative review with collection of recent quantitative information was carried to reflect the status of textile solid waste. In this article, the possibilities of bio-ethanol production from textile waste as valuable cellulosic raw material are investigated and presented. Results show that developing countries lack of systematic waste management. On another side of the globe, some countries are trying to recover energy these days by incineration. The heat and power that recovered from this process can be used instead of other energy sources. Throughout the incineration process, flue gases (CO2, H2O, O2, N2) are generated so it should be properly designed to avoid pollution. During energy recovery, different pre-treatment methods and different enzymatic hydrolysis parameters are recommended to be implied for better results.
... However, these processes are challenging to quantify and require substantial time to yield precise results. To address these issues, scientists have explored various solutions, among which artificial intelligence models have emerged as a promising approach [20]. These models facilitate more consistent and economical monitoring of pollutant parameters at treatment plants and assist in regulating these pollution elements during processing. ...
Water pollution poses global challenges to environmental sustainability and public health, necessitating effective wastewater treatment strategies. Traditional linear models often fail to capture the complexities of pollutant removal processes. Artificial neural networks (ANNs) and adaptive neuro-fuzzy inference systems (ANFIS) have emerged as powerful tools for modeling and optimizing wastewater treatment. ANNs excel in learning complex patterns and nonlinear relationships, while ANFIS integrates neural network learning with fuzzy logic to handle uncertainties in environmental systems. Case studies demonstrate their efficacy in predicting pollutant removal efficiencies, with ANFIS consistently outperforming traditional methods. Insights into influential factors like pH and pollutant concentration guide process optimization. The review underscores ANNs and ANFIS' potential to enhance wastewater treatment efficiency, reduce costs, and ensure regulatory compliance, paving the way for sustainable water management practices. Keywords: Artificial neural networks; Adaptive neuro-fuzzy inference systems; Modelling; Wastewater
... The phenolic species in wastewater caused by the pharmaceutical or dye industries are one of the persistent organic pollutants that are resistant to decomposition/degradation and cause serious harmful effects both on human health and the environmental ecosystem . Significant interest is being shown in wastewater remediation, notably the removal and degradation of different types of organic pollutants, as well as highly sensitive and selective monitoring of even a trace amount of these pollutants, using practical and environmentally friendly methods (Sabreena et al., 2022;Bhat et al., 2021). ...
p_Aminophenol, namely 4-aminophenol (4-AP), is an aromatic compound including hydroxyl and amino groups contiguous together on the benzene ring, which are suitable chemically reactive, amphoteric, and alleviating agents in nature. Amino phenols are appropriate precursors for synthesizing oxazoles and oxazines. However, since the toxicity of aniline and phenol can harm human and herbal organs, it is essential to improve a reliable technique for the determination of even a trace amount of amino phenols, as well as elimination or (bio)degradation/photodegradation of it to protect both the environment and people's health. For this purpose, various analytical methods have been suggested up till now, including spectrophotometry, liquid chromatography, spectrofluorometric and capillary electrophoresis, etc. However, some drawbacks such as the requirement of complex instruments, high costs, not being portable, slow response time, low sensitivity, etc. prevent them to be employed in a wide range and swift in-situ applications. In this regard, besides the efforts such as (bio)degradation/photodegradation or removal of 4-AP pollutants from real samples, electroanalytical techniques have become a promising alternative for monitoring them with high sensitivity. In this review, it was aimed to emphasize and summarize the recent advances, challenges, and opportunities for removal, degradation, and electrochemical sensing 4-AP in real samples. Electroanalytical monitoring of amino phenols was reviewed in detail and explored the various types of electrochemical sensors applied for detecting and monitoring in real samples. Furthermore, the various technique of removal and degradation of 4-AP in industrial and urban wastes were also deliberated. Moreover, deep criticism of multifunctional nanomaterials to be utilized as a catalyst, adsorbent/biosorbent, and electroactive material for the fabrication of electrochemical sensors was covered along with their unique properties. Future perspectives and conclusions were also criticized to pave the way for further studies in the field of application of up-and-coming nanostructures in environmental applications.
... The release of large amounts of chemical pollutants and disinfection by-products into the environment has placed our ecosystems in an unbalanced situation and has recently caused great concern about the effects on human health and aquatic life (Deepak et al., 2021;Hayati et al., 2021;Mohamed et al., 2018;Mohammadinezhad et al., 2018;Taghavi et al., 2021). Among various organic pollutants, pharmaceutical compounds have been found to be active at extremely low concentrations in groundwater and surface water, and their use has become a major concern as they pose a threat to the environment and human health (Adityosulindro et al., 2018;Bhat et al., 2021;Ellepola et al., 2020;Jafarizadeh et al., 2021). Recently, the pandemic COVID-19 has caused significant difficulties for the national health systems of most countries Polat et al., 2021). ...
The first ultrasonic synthesis of [Cu(L)4(SCN)2] (L = 1-methylimidazole) nanocomplex was carried out under ultrasonic irradiation, and its photocatalytic performance for the degradation of remdesivir (RS) under sunlight irradiation was comprehensively investigated for the first time in this study. The physicochemical properties of the synthesized photocatalyst were examined by Fourier-transform infrared (FT-IR), field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), diffuse reflectance spectroscopy (DRS), and thermogravimetric analysis (TGA) techniques. The band gap of the synthesized [Cu(L)4(SCN)2] nanocomplex was determined to be 2.60 eV by the diffuse reflectance spectroscopy method using Kubelka-Munk formula. The photocatalytic performance of nanocomplex was examined for the removal of remdesivir under sunlight from water for which the results indicated that an amount of 0.5 gL-1 of the [Cu(L)4(SCN)2] nanocomplex was sufficient to remove more than 96% remdesivir from its 2 mg L-1 concentration within 20 min, at pH = 6. The kinetic data showed that the photodegradation onto the [Cu(L)4(SCN)2] nanocomplex has a high correlation (0.98) with the pseudo-second-order kinetic model. The decrease in chemical oxygen demand (COD) (from 70.5 mg L-1 to 36.4 mg L-1) under optimal conditions clearly confirmed the mineralization of the RS drug. The values of ΔS° (-0.131 kJ mol-1 K-1) and ΔH° (-49.750 kJ mol-1) were negative, indicating that the adsorption process was spontaneous and more favorable in lower temperatures. Moreover, the RS structure in the open shell state and the high HOMO and LUMO gaps based on the M06/6-31 + G (d) level of theory may be a confirmation of this fact. In addition, the Hirshfeld surface analysis (HSA) of the crystal packing of the prepared complex was discussed in detail to evaluate the interactions between the crystal packings. The results of this study confirm that the [Cu(L)4(SCN)2] nanocomplex can be successfully used for the photodegradation of pharmaceutical contaminants.
... It is essential to discover effective solutions to the crucial environmental issue of water pollution brought on by rapid industrialization (Ameen et al., 2022;Alahdal et al., 2021;Karimi et al., 2022;Al Sharabati et al., 2021;Bhat et al., 2021;Korfali and Karaki, 2018). Chlorophenols, one of the most frequently used organic industrial chemicals, are among the greatest threats to the environment and human health due to their high stability, toxic effects, and carcinogenicity (Michalowicz and Duda, 2007). ...
A crucial problem that needs to be resolved is the sensitive and selective monitoring of chlorophenol compounds, specifically 4-chlorophenol (4-CP), one of the most frequently used organic industrial chemicals. In light of this, the goal of this study was to synthesize Fe3O4 incorporated cellulose nanofiber composite (Fe3O4/CNF) as an amplifier in the development of a modified carbon paste electrode (CPE) for 4-CP detection. Transmission electron microscopy (TEM) was used to evaluate the morphology of the synthesized nanocatalyst, while differential pulse voltammetry (DPV), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV) techniques were implemented to illuminate the electrochemical characteristics of the fabricated sensor. The ultimate electrochemical sensor (Fe3O4/CNF/CPE) was used as a potent electrochemical sensor for monitoring 4-CP in the concentration range of 1.0 nM-170 μM with a limit of detection value of 0.5 nM. As a result of optimization studies, 8.0 mg Fe3O4/CNF was found to be the ideal catalyst concentration, whereas pH = 6.0 was chosen as the ideal pH. The 4-CP's oxidation current was found to be over 1.67 times greater at ideal operating conditions than it was at the surface of bare CPE, and its oxidation potential decreased by about 120 mV. By using the standard addition procedure on samples of drinking water and wastewater, the suggested capability of Fe3O4/CNF/CPE to detect 4-CP was further investigated. The recovery range was found to be 98.52-103.66%. This study paves the way for the customization of advanced nanostructure for the application in electrochemical sensors resulting in beneficial environmental impact and enhancing human health.
There is evidence that human activity causes pollution that contributes to an enhanced selection of bacterial pathogens in the environment. In this review, we consider how environmental pollution can favour the selection of bacterial pathogens in the environment. We specifically discuss pollutants released into the environment by human activities (mainly human waste) that are associated with the selection for genetic features in environmental bacterial populations that lead to the emergence of bacterial pathogens.
Finally, we also identify key pollutants that are associated with antibiotic resistance and discuss possibilities of how to prevent their release into the environment.
The amount of agricultural and industrial wastes is increasing due to increase in industrial and agricultural activities in the world. Therefore, sustainable management of wastes, which is a major challenge being faced by both agricultural and industrial sectors in the world, is required. Composting, which is one of the valorization methods used to accelerate decomposition and stabilization of organic wastes, is well known and getting widespread. This study covers design and instrumentation of a pilot scale aerated static pile composting systems based on engineering principles. With this system, basic scientific data (decomposition rates of composting materials, optimum temperature and moisture values) which are required for construction of large-scale composting facilities and operation of composting process will be obtained. The system consists of (1) aeration system, (2) control, data acquisition and recording unit, and (3) measurement system (temperature, instant CO 2 /O 2 concentrations, airflow, and energy consumption by aeration). In this study, each components of this system will be introduced. This study has been conducted under the program of 1007 of the scientific and technological research council of Turkey.
Huge quantities of apple orchard waste (AOW) generated could be regarded as a promising alternative energy source for fuel and material production. Conventional and traditional processes for disposal of these wastes are neither economical nor environment friendly. Hence, sustainable technologies are required to be developed to solve this long-term existence and continuous growing problem. In light of these issues, this review pays attention towards sustainable and renewable systems, various value-added products from an economic and environmental perspective. Refined bio-product derived from AOW contributes to resource and energy demand comprising of biomethane, bioethanol, biofuels, bio-fertilizers, biochar, and biochemicals, such as organic acid, and enzymes. However, the market implementation of biological recovery requires reliable process technology integrated with an eco-friendly and economic production chain, classified management.
Flavonoids are the secondary metabolites synthesized by microalgae and have diverse applications in various fields. The present study compares among two microalgal strains, Chlorella vulgaris (CV) and Chlorella pyrenoidosa (CP), for the production of flavonoids and lipids, which were cultivated in mixotrophic as well as autotrophic modes. This study also focuses on the role of l-phenylalanine as a supplement to enhance flavonoids. The current work establishes the relation between nitrates, external carbon, and l-phenylalanine for enhanced production of flavonoids and lipids. The extracted flavonoids were found to be maximum in CP-autotrophic mode followed by CV-mixotrophic mode with 138 μg/ml and 118 μg/ml, respectively. The common flavonoids observed with both the microalgal strains were quercetin, catechin, and p-coumaric acid. In comparison, the production of the maximum lipid of 23.7% was reported with mixotrophic operation in CV, followed by CP (19.4%). The scavenging activity of the extracted flavonoids was determined using a hydrogen peroxide assay and was found to be in the range of 63–73% at all experimental conditions. CP was found to produce more flavonoids in autotrophic mode, whereas mixotrophic mode showed maximum production of lipids and flavonoids in the CV. The simultaneous production of high value-added products, viz., flavonoids and lipids, not only paves a pathway for the biorefinery approach but also elevates the commercial potential during scale-up.
Graphical abstract
Recovering resources from wastewater systems is increasingly being emphasised. Many technologies exist or are under development for recycling nutrients such as nitrogen and phosphorus from wastewater to agriculture. Planning and design methodologies are needed to identify and deploy the most sustainable solutions in given contexts. For the environmental sustainability dimension, life cycle assessment (LCA) can be used to assess environmental impact potentials of wastewater-based nutrient recycling alternatives, especially nitrogen and phosphorus recycling. This review aims to evaluate how well the LCA methodology has been adapted and applied for assessing opportunities of wastewater-based nutrient recycling in the form of monomineral, multimineral, nutrient solution and organic solid. We reviewed 65 LCA studies that considered nutrient recycling from wastewater for agricultural land application. We synthesised some of their insights and methodological practices, and discussed the future outlook of using LCA for wastewater-based nutrient recycling. In general, more studies suggested positive environmental outcomes from wastewater-based nutrient recycling, especially when chemical inputs are minimised, and source separation of human excreta is achieved. The review shows the need to improve methodological consistency (e.g., multifunctionality, fertiliser offset accounting, contaminant accounting), ensure transparency of inventory and methods, consider uncertainty in comparative LCA context, integrate up-to-date cross-disciplinary knowledge (e.g., agriculture science, soil science) into LCA models, and consider the localised impacts of recycled nutrient products. Many opportunities exist for applying LCA at various scales to support decisions on wastewater-based nutrient recycling - for instance, performing "product perspective" LCA on recycled nutrient products, integrating "process perspective" LCA with other systems approaches for selecting and optimising individual recovery processes, assessing emerging nutrient recovery technologies and integrated resource recovery systems, and conducting systems analysis at city, national and global level.
In this study, two different organic fractions of municipal solid waste (OFMSW) served as raw material in a novel treatment process that combines thermal hydrolysis (TH) pretreatment at different times, followed by anaerobic digestion of the solid fraction and photo-fermentation of the liquid fraction. The results indicate that both wastes performed similarly, and no statistically relevant differences stand out on the overall performance regarding TH times. The thermal pretreatment improves the biodegradability of the solid fraction during anaerobic digestion compensating the loss of the organic matter in the liquid fraction. The produced biogas may feed a combined heat and power (CHP) system, making the process energetically positive in all studied scenarios. In addition, the combination of TH and anaerobic digestion decreased the volume of the waste to be disposed by 59-61%, which is 5-11% higher than that obtained with the traditional treatment of anaerobic digestion process. Specific phototrophic activity tests were performed on the liquid phase using a mixed culture of purple phototrophic bacteria (PPB) that consumed up to 80% of the soluble organics. The assays yielded an average 52% efficiency on specific phototrophic activity (kM) and 62% on biomass yield (YX/S), compared to an optimized growth medium. PPB was also capable of producing polyhydroxyalkanoates, bioH2 and single-cell protein without optimization. Apart from methane, the overall mass balances showed yields up to 150 g of high added-value products per Kg of initial total solids on this proof-of-concept platform.
In management of helminth infections and transmission, the correct prediction of sludge accumulation patterns in waste stabilization ponds (WSP) is important as sedimented eggs are associated with sludge depth. However, sedimentation in WSP is complicated by the non-stationary nature of the inputs and environmental factors such as weather variables, that are mostly site specific. This paper investigates sludge accumulation patterns in the Buguruni WSP (in Dar es Salaam, Tanzania) and the role that wind and increased run-off during rainy season play. Sludge depths were measured twice; in January 2017 and January 2018. Higher sludge depths were observed close to the inlet, indicating that more helminth eggs may be recovered in the sludge around this area. A sedimentation model set in Delft3D successfully reproduced the sludge accumulation pattern near the inlet, with wind and inflow characteristics as the major driving factors. The pond inlet receives more solids and water during the rain season as a result of defective pipes and manholes, and simulations show that this has significant impacts on sludge accumulation. Improved sludge depth measurement and wind and discharge data will improve modeled sludge accumulation patterns to capture those away from the inlet. Our research has shown that neglecting maintenance of the pond, as well as the sewer system has potential severe health and environmental effects, impacting communities downstream of the WSP. This research also shows the important role that numerical modeling can play in sustainable management of WSP.
A lab-scale system consisting of a methanogenic and an aerobic moving bed biofilm reactor (MBBR) was operated for seven months to investigate major pollutants’ and polar organic micropollutants’ removal from domestic wastewater under three different organic loading rates (OLRs). For all OLR values tested, the system achieved efficient COD (>84%) and NH4-N removal (>96%); both reactors contributed to the decrease of organic loading, while the aerobic bioreactor was exclusively responsible for the removal of ammonium nitrogen. The increase of OLR from 0.20 ± 0.10 to 2.10 ± 0.20 kg COD m-3 d-1 resulted to increase of the detected volatile fatty acids in the anaerobic reactor and increase of the produced biogas to 172.7 ± 25.3 mL L reactor-1 d-1. All target micropollutants were partially removed during different experimental phases; their removal ranged between 31% (5-methyl-1H-benzotriazole, 5TTR) and 97% (2-hydroxybenzothiazole, OH-BTH). Except benzotriazole (BTR) and OH-BTH, both reactors contributed significantly to the removal of target micropollutants, while the addition of extra aerobic MBBR as a final polishing step enhanced only OH-BTH removal. Use of experimental and literature data showed that the increase of organic loading enhanced the removal of three out of five target micropollutants, while the key factor responsible for this effect was COD concentration in influent wastewater. The modelling of micropollutants’ removal efficiency using biodegradation kinetics calculated in batch experiments showed satisfactory correlation between predicted and measured values for most target compounds.
The present study aimed to assess the possibility of integrating natural attenuation (NA) and chemical oxidation (O) with the bio-electrocatalytic remediation (BET) process to remediate petroleum hydrocarbons contaminated soil. Six different reactors were operated, wherein in the first reactor was a NA system, and the second condition to the NA was supplemented with a chemical oxidant (NAO). These systems were compared with BET systems which were differentiated based on the position and distance between the electrodes. The study was performed by considering NA as a common condition in all the six different reactors viz., NA, NAO, NA + BET with 0.5 cm space amid electrodes (BETH-0.5), NAO + BET with 0.5 cm space amid electrodes (BETOH-0.5), NAO + BET with 1.0 cm space amid electrodes (BETOH-1.0), and NAO + BET with vertical electrodes at 1.0 cm distance (BETOV-1.0). The highest total petroleum hydrocarbons (TPH) degradation efficiency was observed with BETOH-0.5 (67 ± 0.8%) followed by BETOH-1.0 (62 ± 0.6%), BETH-0.5 (60%), BETOV-1.0 (56 ± 0.5%), NAO (46.6%), and NA (27.7%). In NA, the indigenous microorganisms remediate the organic contaminants. In the NAO system, KMnO4 actively breakdown the carbon-carbon double bond functional group. Further, in BETOH-0.5, an anodophilic bacteria enriched around the electrode reported enhanced treatment efficiency along with a maximum of 260 mV (1.65 mA). BET systems integrated with chemical oxidation processes were much more effective in the TPH removal process than an individual process. The BET method adopted here thus provides a good opportunity for bio-electrocatalytic remediation of TPH and resource recovery in the form of bioelectricity.
Macronutrient-enriched biochars have potential for nutrient recycling from waste, enhance soil fertility, reduce consumption of fertilizers, and thereby promoting sustainable agriculture. The focus of the recent research studies has been on exploring different methods for production of macronutrients (nitrogen [N], phosphorus [P], and potassium [K]) enriched biochar fertilizers. There is now an urgent need to comprehend the work carried out on biochar fertilizers for a proper scientific understanding and advancement. This review provides crucial information about nutrients enriched biochars production and the underlying mechanisms toward its use in agriculture. The production methods, nutrient characteristics, potential major challenges and future perspectives of using these nutrients enriched biochars have also been dealt in the present review. Among primary macronutrients, the main focus of nutrients enriched biochar are on N and P. Total N, P, and K enriched up to 10%, 15.32%, 25.85% in biochar through controlled (primarily temperature) pyrolysis and utilization of specific feedstock. Although total macronutrients content in nutrients enriched biochar were thoroughly studied, but the bio-labile and plant available fractions of these nutrients are yet to be extensively researched. Nutrients transformation in biochars revealed about comparatively higher bio-available K fraction due to formation of water soluble kalicinite (KHCO3) minerals. The efficacy of biochars toward soil fertility and plant growth was widely studied (mainly as pot experiments) and there results varied. Overall, the prospects of nutrients enriched biochars toward sustainable agriculture has gained momentum with time and further engineered biochars hold great potential to cater for specific soil-plant-environment system.
Dark fermentation is a technically feasible technology for achieving carbon dioxide-free hydrogen production. This review presents the current findings on continuous hydrogen production using dark fermentation. Several operational strategies and reactor configurations have been suggested. The formation of attached mixed-culture microorganisms is a typical prerequisite for achieving high production rate, hydrogen yield, and resilience. To date, fixed-bed reactors and dynamic membrane bioreactors yielded higher biohydrogen performance than other configurations. The symbiosis between H2-producing bacteria and biofilm-forming bacteria was essential to avoid washout and maintain the high loading rates and hydrogenic metabolic flux. Recent research has initiated a more in-depth comparison of microbial community changes during dark fermentation, primarily with computational science techniques based on 16S rRNA gene sequencing investigations. Future techno-economic analysis of dark fermentative biohydrogen production and perspectives on unraveling mitigation mechanisms induced by attached microorganisms in dark fermentation processes are further discussed.
Date biomass is a renewable natural resource since it can be substituted in a comparatively shorter period. Hence it is considered as a possible feedstock for bioenergy motivations through anaerobic digestion (AD). Despite the fact AD is a fully demonstrated technology, the use of new feedstock necessitates detailed investigation. Worldwide several researchers are evaluating methane yield short of paying much consideration to the source type and structural and elemental composition of biomass. Hence, the current study was intended to relate methane yield to those two structural and chemical composition of biomass. In this sense, biochemical methane potential (BMP) for different date biomass, namely Pedicels, Fibrilium, Petiole, Fruit bunch, Spath, Palm, and a mixture of all biomass samples was tested for 30 days. Among all the experimental variations, higher productivity was observed with Palm as 72.60 mL CH 4 /g VS/days, followed by Spath (66.61 mL CH 4 /g VS/days), Mixed biomass (64.57 mL CH 4 /g VS/days), Fruit bunch (64.34 mL CH 4 /g VS/days), Pedicels (59.06 mL CH 4 /g VS/days), Fibrilium (57.42 mL CH 4 /g VS/days), and Petiole (41.17 mL CH 4 /g VS/days). From the experimental results, it can be concluded that among all the biomass samples, Palm is the best substrate for higher methane production. However, the remaining experimental conditions produced methane yield was comparatively low. This might be due to the composite nature of the substrate with lignin as an insoluble fraction. Hence, Pedicels, Fibrilium, and Petiole biomasses cannot be recommended as a substrate for biogas production without appropriate pretreatment.
In recent years, bioelectrochemical hybrid technology has emerged as an alternative energy conversion device for bioelectricity generation with concurrent waste remediation. The major attractions of this bioelectrochemical technology are eco-friendly nature, energy-saving, and energy transformation with reduced sludge generation. A wide variety of substrates, including complex wastewater, can be employed as a potential substrate to operate the bioelectrochemical cells (BEC). Hence, microbial electro-remediation technologies are aimed towards the enhancement of the metabolic activity of electrochemically active biocatalyst by supplying organic/inorganic nutrients, electron acceptors, or donors, thus stimulating oxidation or reduction of contaminants. In this regard, BEC has gained much attention, in which the control environment is feasible by means of electrical current/voltage that serves as a donor or acceptor for hazardous waste remediation. In the present review, we mainly emphasize the developments and advancements of microbial electro-remediation technologies in the direction of complex hazardous waste remediation. We reviewed and discussed various BEC mediated complex pollutants remediation (ex: aromatics, dye, nitrogen compounds, heavy metals etc.) and its limitations. In conclusion, the future perspectives in the BEC for bioenergy generation with concurrent waste remediation are proposed through numerous aspects and approaches to afford clean energy and the environment.
Metal(loid)s are used in various industrial activities and widely spread across the environmental settings in various forms and concentrations. Extended releases of metal(loid)s above the regulatory levels cause environmental and health hazards disturbing the ecological balance. Innovative processes for treating the metal(loid)-contaminated sites and recovery of metal(loid)s from disposed waste streams employing biotechnological routes provide a sustainable way forward. Conventional metal recovery technologies demand high energy and/or resource inputs, which are either uneconomic or unsustainable. Microbial electrochemical systems are promising for removal and recovery of metal(loid)s from metal(loid)-laden wastewaters. In this communication, a bioelectrochemical system (BES) was designed and operated with selenium (Se) oxyanion at varied concentrations as terminal electron acceptor (TEA) for reduction of selenite (Se⁴⁺) to elemental selenium (Se°) in the abiotic cathode chamber. The influence of varied concentrations of Se⁴⁺ towards Se° recovery at the cathode was also evaluated for its regulatory role on the electrometabolism of anode-respiring bacteria. This study observed 26.4% Se° recovery (cathode; selenite removal efficiency: 73.6%) along with organic substrate degradation of 74% (anode). With increase in the initial selenite concentration, there was a proportional increase in the dehydrogenase activity. Bioelectrochemical characterization depicted increased anodic electrogenic performance with the influence of varied Se⁴⁺ concentrations as TEA and resulted in a maximum power density of 0.034 W/m². The selenite reduction (cathode) was evaluated through spectroscopic, compositional and structural analysis. X-ray diffraction and Raman spectroscopy showed the amorphous nature, while Energy Dispersive X-ray spectroscopy confirmed precipitates of the deposited Se° recovered from the cathode chamber. Scanning Electron Microscopic images clearly depicted the Se° depositions (spherical shaped; sized approximately 200 nm in diameter) on the electrode and cathode chamber. This study showed the potential of BES in converting soluble Se⁴⁺ to insoluble Se° at the abiotic cathode for metal recovery.
This study focused on treatment of sulfate-rich wastewater using microbial fuel cell (MFC) with biotic anode (bAC) and abiotic cathode (aCC) separated by a cation exchange membrane (CEM) under batch operation. MFC was operated under varied circuitry modes-open circuit (OC-without resistance) and closed circuit (CC-applied resistance (1KΩ)) to evaluate and assess the removal of sulfates and salts with simultaneous organic carbon utilization. The results of OC and CC depicted sulfates removal efficiency of 38% and 56%, salinity of 12% and 21% and COD removal of 47% and 58%, respectively. Both OC and CC showed K± decrement in bAC and increment in aCC with a comparatively higher efficiency of ionic mobilities in CC. Bioelectrochemical data showed maximum open circuit voltage (OCV) of 498mV with redox catalytic peak currents [Anode/cathode, 3.5/-4.9mA (OC); 6.9/-7.9mA (CC)]. Microbial communities showed dominance of Proteobacteria and Actinobacteria with specific enrichment of sulfate reducing bacteria (SRB) and halophiles.
Solid waste containing heavy metals, halogens and other hazardous substances can cause harm to humans and environment. It is a central issue that how to treat solid waste effectively and harmlessly. Hydrothermal technology is a prominent method to treat solid waste and has attracting worldwide attentions. In the hydrothermal reaction, water acts as a reaction medium, which is clean and environmentally friendly. The high temperature and high pressure environment prompt various reactions occurring quickly and efficiently. The closed environment of the hydrothermal reactor is conducive to avoid secondary pollution. In this paper, the concept and principle of hydrothermal technology are introduced, and the applications on the treatment of solid waste are summarized from three angles of reduction, detoxification, and recycling. At the end of the paper, we look forward to the future development of the hydrothermal technology applied on the solid waste treatment.
This work presents the first use of Cofalit® (vitrified asbestos-containing waste) as a solid filler in pilot-scale thermocline thermal energy storage (TES). The thermocline size is 4 m³ connected to the MicroSol-R installation at the PROMES research facility in Odeillo, France. The study compares the thermal performance of the thermocline filled with Cofalit® to the reference case of alumina spheres for typical charge and discharge operations. It evaluates the actual thermal behavior of thermocline considering three leading performance indicators: process duration, thermocline thickness, and process efficiency. The investigation shows a 22% shorter charge duration in Cofalit® compared to alumina and 16% shorter discharge duration. Cofalit® exhibits about 16% lower thermocline thickness during both charge and discharge compared to alumina. The charge efficiency is slightly better in Cofalit® than alumina with an efficiency of 82% and 78%, respectively. Also, Cofalit® has a better discharge efficiency, 90% with respect to 84% for alumina. These results confim a good thermal performance of Cofalit® as filler material in thermocline TES. Considering the cost-saving and positive environmental impact of using Cofalit® as well as the good thermal performance of the thermocline filled with it, Cofalit® appears a very good filler material in TES. The obtained temperatures from radial positions indicate no significant variation during charge and discharge, and this confirms the one-dimensional thermal behavior of this setup. A parametric analysis is performed using a 1D continuous solid (C-S) model to investigate the influence of particle diameter, porosity, thermal conductivity, and volumetric heat capacity on the thermal performance of the thermocline. The analysis confirms the experimental findings, and it indicates that about a 10.9% longer process duration is associated with a 10% larger volumetric heat capacity and less affected with other parameters. Thermocline thickness is mainly affected by the diameter as well as the volumetric heat capacity of the solid filler; it grows 2.2% for each 10% diameter increase and around 3.23% for doubling the volumetric heat capacity. Charge efficiency demonstrates independency from evaluated properties. While discharge efficiency increases sharply at a tiny particle diameter before an optimum diameter value is reached, then it starts to decrease by 1.4% to each 10% bigger diameter.
The interest in implementing waste-to-energy (WtE) solutions for municipal solid waste (MSW) is increasing on a global scale motivated by the environmental concerns that arise from an inadequate disposal. The evaluation of the environmental impacts associated with WtE technologies has been widely addressed through the life-cycle assessment (LCA) methodology. However, a robust analysis of the environmental consequences of implementing WtE solutions requires the consideration of the entire MSW management system. In this review, we delve into published LCA studies on MSW management systems with the aim of identifying WtE solutions and their impact on the system's environmental performance. We found a consensus amongst the case studies reviewed on the favourable environmental consequences of both the diversion of organic waste from composting to anaerobic digestion and the implementation of a landfill gas collection system to produce electricity. There was also a consensus that the diversion of MSW from landfilling to incineration would generally reduce the global warming impact, but with uncertain human health consequences. Discrepancies were observed with respect to the environmental consequences of both the diversion of organic waste from incineration to anaerobic digestion and the diversion of waste from incineration to mechanical-biological treatment plants. Overall, this review can help decision-makers pre-identify environmentally sound WtE solutions. However, a subsequent LCA specific to the new context is imperative in order to identify the environmentally preferred option.
Anaerobic digestion is one of the most effective and environment-friendly waste management techniques. It not only treats the organic fraction of municipal solid waste, but at the same time it can be considered as one of the potent renewable energy sources due to generation of methane during digestion process. The technology is not new and has been commercialised from early 1980s. But, the data suggests that it is not still widely applied for energy recovery from organic wastes at centralised level. The reason may be poor methane yield due to operational issues and process instability. There were numerous studies already done at the lab scale, now it is the time to replicate the outcomes of lab-scale studies to the full scale plant. Further studies are required to make the anaerobic digestion techno-economically sustainable. This paper presents a detailed review of essential process parameters and identifies gaps and solutions for effective implementation of the anaerobic digestion of organic fraction of municipal solid waste. The paper also presents the effect of co-digestion, pre-treatments and inhibition on the performance of anaerobic digestion. The paper will help the readers in understanding the process, operation and control of anaerobic digestion technology.
Solid wastes including phosphate tailings (PT) and fly ash (FA) are by-products with large quantities and deposited in surface impoundment without treatment, which can easily trigger environment issues. The comprehensive utilization of industrial solid wastes has received intensive attention. In present work, the recycling of industrial solid wastes was studied to explore the probability of utilizing PT and FA as fillers for fabrication of polymer materials with low fire hazards. The micro-sized PT and FA powders were firstly treated with silane coupling agents and then introduced into thermoplastic polyurethane (TPU) through solvent blending method. The influences of solid wastes on the thermal degradation behavior, as well as the fire hazards of TPU were explored. The thermogravimetric analysis results illustrated that due to the introduction of PT and FA, the thermal degradation rate was reduced while the thermal degradation temperature and char yields were increased, in contrast to pristine TPU. The cone calorimetry test results demonstrated the introduction of PT and FA obviously reduced the heat release rate (HRR), total heat release (THR), smoke production rate (SPR), total smoke release (TSR), carbon monoxide (CO) and carbon dioxide (CO2) emission rate of TPU composites. Therefore, the PT and FA might be promising fillers for fabrication of polymeric materials with controllable properties and provide a novel solution for effective recycling of industrial solid wastes.
A safe operation of a wastewater collection and transport system must consider the probability of overflow events in and off the industry limits. In this paper the reliability of the collection and wastewater transport system of a refinery is assessed by using Cox reliability models. These models were adjusted to take into account the complex nature of the system. Rainfall is considered a model covariable since we are dealing with an open system. The probabilities of overflow from one retention tank either to another or to the water body were evaluated. The results indicate that through the creation of two scenarios, with different rainfall indices, in which it was possible to verify that the higher the index, the lower the reliability of the system. In conditions of rain, non-pumping, and in a one-day retention time, the reliability of the system did not exceed 76 % with a probability of overflow of 24 %. Nevertheless, after 4-day retention, the estimated reliability of the system dropped to 11.6 % and the probability of overflow increased to 88.4 %. And the system gets even more chaotic, if in the presence of rain, the activation of the pumps does not occur. The presence of rain is a factor that accelerates the occurrence of overflow.
The growing presence of pharmaceutical compounds in aqueous systems leads to the search for new efficient and eco-friendly solutions to this problem. Although pharmaceutical products are widely found in the aqueous environments, there is limited understanding of their ecological effects. To augment the removal of pharmaceuticals, a bench reactor was inoculated with activated sludge and fed with a synthetic medium. Two pharmaceuticals of widespread usage, ibuprofen (IBU) and paracetamol (PARA) in the range 0.4–1 mg L⁻¹ were used. The uptake values increased from 0.192 to 0.660 mg g⁻¹ for IBU and from 0.104 to 0.341 mg g⁻¹ for PARA. The removal efficiency reached values from 99.1–99.5 % and is independent of the initial IBU concentration. For PARA the removal percentage ranged from 93.3–98.8 decreasing with the increase on the initial concentration. The removal mechanism is well described by pseudo-first order and pseudo-second order kinetic models for all concentrations tested. At same time, batch assays were performed in order to assess the toxicity of both pharmaceuticals into the activated sludge using quantitative image analysis (QIA). For IBU experiments, QIA studies showed that this compound favors the growth of aggregated biomass rather than filamentous bacteria. A comparison between this biological technology and adsorption by a commercial porous ceramic material and Pinus bark was also performed. The results showed that the biological technology allowed better results (99.5 % against 19.4 and 9.3 %, respectively for the ceramic material and Pinus bark) for IBU. The results obtained for PARA showed comparable results for the biological technology and for adsorption by the ceramic material. The activated sludge system presented here appears to be a promising treatment for pharmaceutical contaminated effluents and the biomass present in the activated sludge seems do not be negatively affected by the presence of high concentrations of both pharmaceuticals.
The present fossil fuel-based energy sector has led to significant industrial growth. On the other hand, the dependence on fossil fuels leads to adverse impact on the environment through releases of greenhouse gases. In this scenario, one possible substitute is biohydrogen, an eco-friendly energy carrier as high-energy produces. The substrates rich in organic compounds like organic waste/wastewater are very useful for improved hydrogen generation through the dark fermentation. Thus, this review article, initially, the status of biohydrogen production from organic waste and various strategies to enhance the process efficiency are concisely discussed. Then, the practical confines of biohydrogen processes are thoroughly discussed. Also, alternate routes such as multiple process integration approach by adopting biorefinery concept to increase overall process efficacy are considered to address industrial-level applications. To conclude, future perspectives besides with possible ways of transforming dark fermentation effluent to biofuels and biochemicals, which leads to circular bioeconomy, are discussed.
Chlorine is a common element in the environment where it mostly exists in an inorganic ionic state that is highly mobile and non-degradable. It is important to investigate the potential release of chlorine into the environment from mineralized waste (MW) for stable landfill reclamation. In this study, inorganic chlorine in the MW migration process was explored during thermal treatment for chlorine pollution control. The temperature and chlorine greatly affected the distribution of inorganic chlorine in the thermally treated products. Below 800 °C, more than 60% of the inorganic chlorine remained in the bottom slag. Above 900 °C, volatilization caused the release of chlorine from the MW and more than 75% of the inorganic chlorine was deposited inside the furnace. The mass of inorganic chlorine deposited in the thermal treatment furnace was significantly correlated with the actual temperature. At 1000 °C, the masses of inorganic chlorine deposited under pyrolysis, incineration, and gasification atmospheres were 7.69, 5.81, and 5.68 mg, respectively. The greatest deposition of inorganic chlorine inside the furnace occurred during pyrolysis. The chlorine migration process must gain more sight during MW thermal processing.
With the rapid increase of municipal solid waste landfill，air pollution caused by landfill gases draws more attention． A lot of research has been carried out on landfill gases emission，which concentrated on greenhouse gases and volatile organic compounds． This paper summarizes the recent research progress of three kinds of greenhouse gases and volatile organic compounds in municipal solid waste landfill． The emission estimate，generation models，advantages and disadvantages of monitoring methods，and volatile organic compounds treatment and reutilization，of the solid wastes and landfill gases，both in China and overseas，are introduced． The necessity of research on the correlation among the appropriate landfill gases and secondary pollutants， and meteorological conditions concerning landfill gas emissions monitoring should also been strengthened．
Thermal treatment could effectively realize the detoxification of heavy metals in municipal solid waste incineration (MSWI) fly ash through the approach of removal or stabilization process. To lower the operating temperature and suppress the evaporation of heavy metals, a molten salts (NaCl-CaCl2) thermal treatment method was proposed for the detoxification of heavy metals from MSWI fly ash at a relatively mild condition (600/800 °C). The fate of heavy metals during the heating process and their stabilization properties in the remained ash slag after molten salts thermal treatment were investigated. The results showed that, compared with the traditional thermal treatment, heavy metals were more easily chlorinated by the means of molten salts thermal treatment. The well distributed chloride in molten salts facilitated the direct chlorination of PbO/CdO. Furthermore, Al2O3 in ash enhanced the indirect chlorination of CuO/PbO/CdO, except for ZnO. In contrast, SiO2 showed better performance in promoting the indirect chlorination of heavy metal oxides. Meanwhile, some Zn2+ was precipitated from molten salts as Si/Al-Zn composite oxides through the interactions with ash containing Si/Al oxides. On the other hand, the dissolved heavy metals in molten salts showed a good thermal stability during the thermal treatment. The volatilization fractions of all detected heavy metals were less than 5%. After the molten salts thermal treatment, heavy metals in the ash slag were well stabilized and the amount of heavy metals leached was significantly lower than that from the raw fly ash.
With the inevitable rise in human population, resource recovery from waste stream is becoming important for a sustainable economy, conservation of the ecosystem as well as for reducing the dependence on the finite natural resources. In this regard, a bio-based circular economy considers organic wastes and residues as potential resources that can be utilized to supply chemicals, nutrients, and fuels needed by mankind. This review explored the role of aerobic and anaerobic digestion technologies for the advancement of a bio-based circular society. The developed routes within the anaerobic digestion domain, such as the production of biogas and other high-value chemicals (volatile fatty acids) were discussed. The potential to recover important nutrients, such as nitrogen through composting, was also addressed. An emphasis was made on the innovative models for improved economics and process performance, which include co-digestion of various organic solid wastes, recovery of multiple bio-products, and integrated bioprocesses.
Life cycle assessment (LCA) has been recognized as a sophisticated approach to evaluate the overall impact of a process and related by-products through its life cycle from an environmental viewpoint. LCA is being performed in different sectors for an optimal evaluation and comparison purposes. Herein, we signify the LCA in wastewater treatment technology, recent advances in LCA, and their effective deployment to know the fate of hazardous pollutants. The available literature revealed that the generation of numerous contaminants is the hotspot in the life cycle of various industrial processes. The synergies of different industrial sectors coupled with LCA strategies deliver highly efficient, precise, reliable, and sustainable production processes with a minimal environmental load. A properly designed LCA procedure also provides comprehensive information to producers, consumers, and policymakers or legislative authorities to further broaden the practical applications of LCA, minimize the environmental insecurity, and lower/reduce the related human health risks.
The high content of tetracycline in municipal sludge may result in vermicomposting products carrying a high abundance of antibiotic resistance genes, thus lowering the utilization value of the vermicompost. Hence, this study aimed to reveal the underlying effects of tetracycline concentrations on the resistance genes involved in vermicomposting systems for sludge recycling. For this purpose, fresh sludge substrates with different concentrations of tetracycline (100, 500, and 1000 mg·kg-1) were vermicomposted for 60 days using Eisenia foetida. In parallel, sludge treatment without the addition of the tetracycline was used as a control. During the experiment, changes in bacterial communities, tetracycline resistance genes (tetC, tetG, tetM, tetW, and tetX), and class 1 integron (intI1) were detected using high-throughput sequencing and qualitative PCR, respectively. The results showed that the addition of tetracycline reduced the abundance of Proteobacteria but increased the abundance of Bacteroidetes in the sludge vermicompost. Furthermore, the concentrations of tetracycline had a significant negative correlation with Shannon and Pielou indexes of bacterial diversity. In addition, tetracycline increased intI1 genes and tetracycline resistance genes in the sludge by 4.25 times and 4.7-186.9 times, respectively. Moreover, there was a significantly positive correlation between the abundance of tetM genes and tetracycline concentration. This study suggests that higher concentration of tetracycline in sludge can modify the microbial community structure of vermicompost, enhancing the abundance of antibiotic resistance genes and their associated dissemination risks.
This article outlines the prospects and challenges of hydrogen production from biomass and residual wastes, such as municipal solid waste. Recent advances in gasification and pyrolysis followed by reforming are discussed. The review finds that the thermal efficiency of hydrogen from gasification is ~50%. The levelized cost of hydrogen (LCOH) from biomass varies from ~2.3–5.2 USD/kg at feedstock processing scales of 10 MWth to ~2.8–3.4 USD/kg at scales above 250 MWth. Preliminary estimates are that the LCOH from residual wastes could be in the range of ~1.4–4.8 USD/kg, depending upon the waste gate fee and project scale. The main barriers to development of waste to hydrogen projects include: waste pre-treatment, technology maturity, syngas conditioning, the market for clean hydrogen, policies to incentivize pioneer projects and technology competitiveness.
The main opportunity is to produce low cost clean hydrogen, which is competitive with alternative production routes.
Anaerobic digestion (AD) of waste activated sludge (WAS) is an important bio-energy strategy that has been hindered by low conversion efficiency. This paper presents a comprehensive review of research on the sludge’s property and enhancing AD of WAS, and proposes two perspectives of material structure and microbial activity on improving AD efficiency. In the first part of this review, the key principle problems for hindering AD efficiency are identified based on the concept of AD. Then, the possibility that the complex microstructure and composition of WAS are responsible for poor biodegradability is considered and main methods for enhancing AD are summarized. In the third part, according to the published works, the main knowledge gaps in research are recognized as the identification and specific activity adjustment of functional microbes, the understanding of key constituents of WAS and their interactions, the deciphering of complex structure of sludge organic substance, and the revealing of relationships between complex nature of WAS and biodegradability. Further discussions reveal that to enhance AD more studies should be centered on the sludge’s structure and properties in future. However, this review is expected to provide the clear and accurate research directions for enhancing AD efficiency of WAS.
Anaerobic digestion (AD) is an effective process for waste management, pollution mitigation, renewable energy utilization, and greenhouse gas emissions reduction. However, low temperature is one of the most limiting factors for the application of AD in many cold regions. To expand the applications of AD to larger areas in the world, many studies have been conducted to explore its potential under low-temperature conditions. The purpose of this article is to present a comprehensive review on recent progresses and findings in this field. The generation and management of manure in cold regions are summarized to demonstrate the potential capacity of AD. Advancements in theories and technologies that can improve the performance of anaerobic digestion in cold regions are thoroughly reviewed. The benefits of AD applications in terms of emission reduction are evaluated at global scale.
Sludge composting is increasingly adopted due to its end product for application as a soil nourishment amendment. Although the ratio of C/N is significant in the quality and process of composting, little information has been obtained from the effects of nutritional energy (carbon and nitrogen) on the fate of antibiotic resistance genes (ARGs) during sludge composting. Dynamic variations of ARGs, microbial community as well as functional characteristics during composting of sludge were investigated in this study. Three levels of carbon to nitrogen (20:1, 25:1 and 30:1) were developed for the composting of sludge with fermented straw plus a control which was just sewage sludge (C/N = 9.5:1). A novel finding of this work is that the highest initial C/N ratio (30:1) could prolong the thermophilic period, which was helpful to reduce some target ARGs. Some ARGs (sul1, sul2, and aadA1) had negative correlation with multiple metabolic pathways, which were difficult to remove.
Enhanced coagulation and adsorption were investigated in separate and combined processes to alleviate problems created by high levels of NOM (15 mg L−1) and ammonia (2.5 mg L−1 NH4-N) in dam water. Raw water acidification to pH 6.2 with optimised enhanced coagulation in jar tests achieved effective (68%) DOC reduction and satisfactory residual turbidity, aluminium, and colour, however removed only 5% ammonia. Adsorption on the nano-adsorbent (termed ACZ) led to 45% DOC reduction and excellent 58% ammonia removal in 30 min. Concurrent enhanced coagulation and complementary adsorption using only 80 mg L−1 alum and 150 mg L−1 ACZ doses showed high performance with 76% ammonia, 90% DOC, and 95% trihalomethanes formation potential (THMFP) reduction in 20 min time. Concurrent treatment can be simply implemented utilising readily available rapid mixers and flocculators, and operated on demand. Pre-adsorption and consecutive enhanced coagulation using the same alum and ACZ doses resulted in slightly better DOC but reduced (61%) ammonia removal. The results showed that concurrent treatment could safely resolve a challenging operational problem. ACZ combines the distinct advantages of zeolite and activated carbon in a single product, and may find additional uses in removing taste and odour, heavy metals, and synthetic organic matter from ground and surface waters.
Demand for hot water treatment has opened up broad new areas of research for fabricating thermally stable polymer membranes. In multiple industrial applications, the contaminated process water must be treated at high temperatures to maintain a sustainable and energy-efficient water recycling process. The present article reviews recent efforts made to develop thermally stable thin film composite membranes and provides insights on polymer material selection rationale, characterization techniques, promising progresses, major challenges, and potential future trends. Thin film composite membranes are the most commonly used polymeric membranes for desalination and water treatment, primarily due to their outstanding permeation properties. However, commercially available thin film composite membranes suffer from limited thermal resilience at temperatures above 45 °C, resulting in a short working lifetime. This limitation has motivated researchers to improve the thermal stability of thin film composite membranes through three primary approaches: (i) tuning the chemistry of the selective layer, (ii) enhancing the thermal properties of the porous sublayer, and (iii) incorporating nanomaterials into both the selective and support layers of thin film nanocomposite membranes. Among different approaches, efforts on modifying the selective layer have gained momentum due to the critical role it plays on the overall separation performance. Synthesis parameters were modified to develop new polyamide layers with higher cross-linking degree and rigidity. Furthermore, employing other strategies, such as using novel sublayers or well-dispersed nanoparticles was also found to increase the thermal tolerance of thin film composite membranes. The major challenges for the development of robust thin film composite and nanocomposite membranes are yet to: (i) overcome the trade-off relation between thermal stability and permselectivity of membranes, primarily caused by low reactivity of new monomers with stabilized resonance structure and severe aggregation of nanoparticles, and (ii) explore reliable methods to characterize the individual layers of composite membranes. This review explains how to select appropriate materials and preparation methods to produce thermally stable thin film composite membranes. The possible future directions of research in this field also discussed.
This work dealt with the determination of the suitability of sorption of Volatile Organic Compounds (VOCs) on biochars prepared from neem, sugarcane and bamboo feedstocks. Six different VOCs namely benzene, toluene, methyl chloride, xylene, chloroform and carbon tetrachloride were used in a laboratory-scale set-up on non-activated biochars prepared via slow pyrolysis (350-550 °C). Although all the chars showed considerable sorption but amongst them N3 (neem-based biochar) showed the maximum removal efficiency (65.5 mg g-1 for toluene). Variation in pyrolysis temperature and feedstock type showed significant change in the porosity and specific surface area of the biochar, which is favorable for VOC sorption efficiency. With higher surface area and contact time, the sorption capacity of char enhanced. However, the extent of sorption capacity of biochars differed with changing VOC type. Pseudo-Second-Order model fitted well with the results obtained from VOC sorption kinetics.
This study used a metagenomic approach to investigate the effects of earthworms on ARGs and HPB during the vermicomposting of dewatered sludge. Results showed that 139 types of ARGs were found in sludge vermicompost, affiliated to 30 classes. Compared with the control, the total abundance of ARGs in sludge vermicompost decreased by 41.5%. Moreover, the types and sequences of plasmids and integrons were also decreased by vermicomposting. Proteobacteria and Actinobacteria were the most dominant hosts of ARGs in sludge vermicompost. In addition, earthworms reduced the total HPB abundance and modified their diversity, thus leading to higher abundance of Enterobacteriaceae in sludge vermicompost. However, the sludge vermicompost was still ARG and HPB enriched, indicating a remaining environmental risk for agricultural purpose. The observed change of microbial community and the reduction of mobile genetic elements caused by earthworm activity are the main reasons for the alleviation of ARG pollution during vermicomposting.
Membrane separation is an environmentally friendly process with low energy consumption and high separation efficiency. Energy can be retrenched by in-situ treating high temperature aqueous streams without heat exchange. Unfortunately, dealing with such streams, most commercial organic membranes are restricted by low thermal stability. Therefore, scientists turned to thermally stable polymers and inorganic materials. Numerous materials have been studied to develop thermally stable membranes for separating high temperature aqueous streams. However, difficulties were faced in elevating the flux of inorganic membranes and balancing the structure rigidity and flux of polymer membranes. This review aims at collecting the researches focusing on applications of thermal stable materials in treating high temperature streams, as well as the accompanied challenges. Firstly, the effect of temperature on the structure and performance of membranes are interpreted by mathematic models. Sequentially, the structure change of membranes at elevated temperature are discussed in terms of movement of polymer chains. Classified discussion is held according to the components of thermal stable membranes. The key points discussed include fabrication process, relationship between structure and performance in practical applications. The objective of this review is to summarize the recent developments and challenges in thermally stable membranes for water treatment, offer some advice for designing new materials and modifying existent materials, and emphasize the significance for researches in this area. The future direction for fully exploiting the potential of thermally stable membranes for water treatment is also presented.
Solid Waste Management (SWM) in high altitude regions is critically phased because of the non-availability of suitable facilities for the treatment and handling of large quantities of Municipal Solid Waste (MSW). Open burning practices at hill slopes were noticed which affect the surrounding environment. Hence, it became essential to measure the
environmental components around the dumpsites to examine the impacts and suggest
new technological solutions. The pollution parameters were monitored in and around the dumpsites, and the data was analysed using statistical tools. The assessment of air quality indicated maximum fine suspended particulate matter (PM2.5) concentration of 206.66 μg/m3 followed by respairable particulate matter (PM10), oxides of nitrogen (NOx) and sulphur dioxide (SO2). Among the gaseous emissions, methane (CH4) concentration was very high (38.53 mg/L) followed by carbon monoxide (CO) concentration (0.96 mg/L). Volatile organic compounds (VOCs) were also detected at few dumpsites with highest observed benzene (C6H6) concentration of 157.53 μg/m3. The soil sample analysis indicated that iron (Fe) concentration dominates followed by manganese (Mn), zinc (Zn), chromium (Cr), copper (Cu), and nickel (Ni). For evaluation of different alternatives for the SWM system, Rapid Impact Assessment Matrix (RIAM) was applied.
Landfill owners, governmental institutions, technology providers, academia and local communities are important stakeholders involved in Enhanced Landfill Mining (ELFM). This concept of excavating and processing historical waste streams to higher added values can be seen as a continuation of traditional landfill mining (LFM) and seems to be an innovative and promising idea for potential environmental and societal benefits. However, ELFM’s profitability is still under debate, and environmental as well as societal impacts have to be further investigated. This study provides a first step towards an anticipatory approach, assessing ELFM through stakeholder integration. In the study, semi-structured interviews were conducted with various stakeholders, involved in a case study in Flanders, Belgium. Participants were selected across a quadruple helix (QH) framework, i.e. industrial, governmental, scientific, and local community actors. The research comprises 13 interviews conducted with an aim to elicit stakeholder needs for ELFM implementation using a general inductive approach. In total 18 different stakeholder needs were identified. The paper explains how the stakeholder needs refer to the different dimensions of sustainability, which groups of stakeholders they primarily affect, and what types of uncertainty could be influenced by their implementation. The stakeholder needs are structured into societal, environmental, regulatory and techno-economic needs. Results show additional economic, environmental, and societal aspects of ELFM to be integrated into ELFM research, as well as a need for the dynamic modeling of impacts.
Waste activated sludge treated with an alkaline solution was used as external carbon substrates to improve the performance of enhanced biological phosphorus removal (EBPR) in a pilot plant. Supplementation of the alkali-treated sludge significantly enhanced the phosphorus removal of the pilot plant from 81.6 to 98.7%. Microscopic observations revealed that alkali treatment was effective in killing bacterial cells in the sludge, and deconstructed its morphology into a reticular form. The change in cell viability and morphology facilitated organic matter release, mostly in the form of proteins. Furthermore, supplementation of the alkali-treated sludge changed the major phosphorus accumulating organisms (PAOs) from Accumulibacter to Tetrasphaera. Enrichment of PAOs within the Tetrasphaera was due to specific carbon substrates (i.e. proteins) released by the alkali-treated sludge. Taken together, this study strongly suggests that supplementation of alkali-treated sludge was an efficient method for improving EBPR performance by enrichment of Tetrasphaera PAOs.
Fermentation is an attractive field in the area of bioprocess engineering where it represents a promising and environmentally friendly option to find an alternative for the well-established chemical process which is being used currently. With the various fermentation techniques available, various microorganisms are utilized to an extent in producing a wide range of products which range from the production of biofuels from various sources of algae, bacteria, yeasts, etc. Apart from the various renewable sources, microorganisms are even capable to synthesize a wide range of fermented food products from various biological sources. In this chapter, we have discussed various advantages of fermented products as well as explained the various renewable energy sources which are the most needed for the survival of mankind.
Sulfide-oxidizing autotrophic denitrification (SOAD) implemented in a moving-bed biofilm reactor (MBBR) is a promising alternative to conventional heterotrophic denitrification in mainstream biological nitrogen removal. The sulfide-oxidation intermediate - elemental sulfur - is crucial for the kinetic and microbial properties of the sulfur-oxidizing bacterial communities, but its role is yet to be studied in depth. Hence, to investigate the performance and microbial communities of the aforementioned new biosystem, we operated for a long term a laboratory-scale (700 d) SOAD MBBR to treat synthetic saline domestic sewage, with an increase of the surface loading rate from 8 to 50 mg N/(m2·h) achieved by shortening the hydraulic retention time from 12 h to 2 h. The specific reaction rates of the reactor were eventually increased up to 0.37 kg N/(m3·d) and 0.73 kg S/(m3·d) for nitrate reduction and sulfide oxidation with no significant sulfur elemental accumulation. Two sulfur-oxidizing bacterial (SOB) clades, Sox-independent SOB (SOBI) and Sox-dependent SOB (SOBII), were responsible for indirect two-step sulfur oxidation (S2-→S0→SO42-) and direct one-step sulfur oxidation (S2-→SO42-), respectively. The SOBII biomass-specific electron transfer capacity could be around 2.5 times greater than that of SOBI (38 mmol e-/(gSOBII·d) versus 15 mmol e-/(gSOBI·d)), possibly resulting in the selection of SOBII over SOBI under stress conditions (such as a shorter HRT). Further studies on the methods and mechanism of selecting of SOBII over SOBI in biofilm reactors are recommended. Overall, the findings shed light on the design and operation of MBBR-based SOAD processes for mainstream biological denitrification.
Proper management of municipal solid waste (MSW) has been a crucial aspect of every society due to its social, environmental, and economic impacts. Operations research techniques have frequently focused on cost minimization objectives in locational planning of municipal solid waste management (MSWM) systems. However, transportation constitutes an integral part of this system producing a considerable amount of greenhouse gas (GHG) emissions. Therefore, sustainable management of this system with GHG emissions minimization considerations is necessary to preserve the resources and protect the environment. In this study, a bi-objective optimization model is proposed to minimize system cost and carbon dioxide (CO2) emission resulting from transportation activities in locational planning of MSWM systems. The proposed model is applied to MSWM system of Ankara to introduce transfer stations (TSs). Two extensions of the current system are examined, namely, the extended and hybrid systems, where MSW is only transported through TSs in the former, while direct shipments are also allowed in the latter. For both extensions, it is observed that with no or little increase in cost, considerable savings in emission can be achieved. Simulation analyses show that CO2 emission and cost are not subject to a considerable change due to speed variations of vehicles.
This study evaluated the correlation between the amount of mercury (Hg) compounds in waste phosphor powder from spent UV curing lamps and their leaching characteristics. The appropriate thermal treatment conditions and Hg content in the residue necessary to satisfy the leaching criteria for classification as non-hazardous waste were identified. The decomposition of Hg compounds by thermal treatment was also evaluated by comparing sequential extraction results based on thermal stability and leaching potential of Hg compounds. Before the thermal treatment, the Hg content in waste phosphor powder and concentration in the leaching extract were 108.7 mg-Hg/kg and 0.56 mg-Hg/L, respectively. Hg compounds with low thermal stability were removed rapidly during the initial stage of thermal treatment at temperatures between 400 °C and 600 °C. After thermal treatment, Hg in the form of an intermetallic compound, such as Sr-Hg, was expected to be remained mainly, and the Hg content was reduced to 13 mg-Hg/kg in the waste phosphor powder, at that point the residue satisfied the leaching standard limit (5 μg-Hg/L) for non-hazardous waste stipulated in the legislation of Republic of Korea.