Bioremediation of petroleum refinery wastewater using Bacillus subtilis IH-1 and assessment of its toxicity.

Environmental contamination from petroleum refinery operations has increased due to the rapid population growth and modernization of society, necessitating urgent repair. Microbial remediation of petroleum wastewater by prominent bacterial cultures holds promise in circumventing the issue of petroleum-related pollution. Herein, the bacterial culture was isolated from petroleum-contaminated sludge samples for the valorization of polyaromatic hydrocarbons and biodegradation of petroleum wastewater samples. The bacterial strain was screened and identified as Bacillus subtilis IH-1. After six days of incubation, the bacteria had degraded 25.9% of phenanthrene and 20.3% of naphthalene. The treatment of wastewater samples was assessed using physico-chemical and Fourier-transform infrared spectroscopy analysis, which revealed that the level of pollutants was elevated and above the allowed limits. Following bacterial degradation, the reduction in pollution parameters viz. EC (82.7%), BOD (87.0%), COD (80.0%), total phenols (96.3%), oil and grease (79.7%), TKN (68.8%), TOC (96.3%) and TPH (52.4%) were observed. The reduction in pH and heavy metals were also observed after bacterial treatment. V. mungo was used in the phytotoxicity test, which revealed at 50% wastewater concentration the reduction in biomass (30.3%), root length (87.7%), shoot length (93.9%), and seed germination (30.0%) was observed in comparison to control. When A. cepa root tips immersed in varying concentrations of wastewater samples, the mitotic index significantly decreased, suggesting the induction of cytotoxicity. However, following the bacterial treatment, there was a noticeable decrease in phytotoxicity and cytotoxicity. The bacterial culture produces lignin peroxidase enzyme and has the potential to degrade the toxic pollutants of petroleum wastewater. Therefore the bacterium may be immobilised or directly used at reactor scale or pilot scale study to benefit the industry and environmental safety.

Optimization and kinetic analysis of electrocoagulation-assisted adsorption for treatment of young landfill leachate.

An investigation was conducted on the electrocoagulation treatment of high-strength young landfill leachate using an electrode made of aluminium in a batch electrochemical cell reactor. An iron sheet of 1 m⨯1 m⨯1.1 m (L: B: H) was used to construct the two landfill simulating reactors, both the reactors were operated at different conditions, i.e., one without rainfall (S1) and the other with rainfall (S2). Both reactors have 51% wet and 49% dry waste, which is the typical waste composition of India, and the quantity of waste taken was 450 kg; hence, the generated leachate was treated. This work focuses on the utilization of electrocoagulation as the sole treatment method where coagulation and adsorption occur simultaneously for young landfill leachate. The study employed a central composite design (CCD) to systematically vary the initial pH, current density (CD), and reaction time to examine their impact on the removal efficiency of COD (Chemical oxygen demand), TOC (Total organic carbon), and TSS (Total Suspended Solids). The optimum conditions obtained were a pH of 7.35, a CD of 15.29 mA/cm2, and a reaction duration of 57 min. When the conditions were optimized, the COD, TSS, and TOC removal efficiencies were 83.56%, 73.12%, and 85.58%, respectively. Also, the electrodes depleted 2.78 g of Al/L. In addition, pseudo-first-order and pseudo-second-order kinetics were employed to examine the elimination of contaminants by adsorption on aluminium hydroxide, thereby confirming the adsorption process. After investigation through energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD), with the produced sludge confirmed that electrocoagulation removed a significant amount of metals from landfill leachate.

Perspectives and understanding on the occurrence, toxicity and abatement technologies of disinfection by-products in drinking water.

Disinfection by-products (DBPs) are one of the significant emerging contaminants that have caught the attention of researchers worldwide due to their pervasiveness. Their presence in drinking water, even in shallow concentrations (in levels of parts per billion), poses considerable health risks. Therefore, it is crucial to understand their kinetics to understand better their formation and persistence in the water supply systems. This manuscript demonstrates different aspects of research carried out on DBPs in the past. A systematic approach was adopted for the bibliographical research that started with choosing appropriate keywords and identifying the most relevant manuscripts through the screening process. This follows a quantitative assessment of the extracted literature sample, which included the most productive and influential journal sources, the most widely used keywords, the most influential authors active in the research domain, the most cited articles, and the countries most actively engaged in the research field. Critical observations on the literature sample led to the qualitative assessment, wherein the past and current research trends were observed and reported. Finally, we identified the essential gaps in the available literature, which further led to recommending the course ahead in the research domain. This study will prove fruitful for young and established researchers who are or wish to work in this emerging field of research.

Thermal pretreatment of Lantana camara for improved biogas production: Process parameter studies for energy evaluation.

The rigid lignocellulosic structure of Lantana camara impedes the hydrolysis phase and reduces the biogas production during anaerobic digestion of Lantana camara. Hence, the current study focuses on the impact of various heating pretreatment techniques, viz., hot air oven (HAO), autoclave (ATC), hot water bath (HWB), and microwave (MCW) on L. camara to speed up hydrolysis and boost up biogas production. ATC pretreatment of L. camara was witnessed to be most efficient compared to HAO, MCW, and HWB pretreatment. ATC pretreatment enhanced the solubilization (45.44%), and an increment in volatile fatty acids (VFA) was observed (56.75%) at 110 °C for 80 min when correlated to the untreated (control). Cumulative methane production following ATC pretreatment had risen to 3656 mL in 5 weeks from 2895 mL in 7 weeks. Thermal pretreatment of Lantana camara broke down the rigid lignocellulosic structure, accelerating the hydrolysis stage and improving biogas production simultaneously. To the best of our knowledge, this is the first thermal pretreatment study conducted on Lantana camara for biogas production.

Critical review with science mapping on the latest pre-treatment technologies of landfill leachate.

The most frequent strategy for solid waste management, adopted across the globe is landfill. Through microbial decomposition municipal solid waste degrades, producing end products such as carbon dioxide, methane, volatile organic compounds, and leachate. High levels of organic waste and heavy metals content in leachate can cause pervasive damage to the ecosystem and contaminate groundwater. Leachate requires extensive treatment before being released into the environment because of its complex chemical composition and identifying the appropriate technologies for leachate treatment remains a key problem for municipal landfill operations. Given the possible harm caused by substantially contaminated leachate, it should adhere to stricter quality criteria for direct disposal of leachate and one treatment method cannot efficiently tackle all the pollutants. In order to reduce the landfill leachates high fouling power, pre-treatment of landfill leachate is necessary. The study provides a comprehensive review of pre-treatment technologies, as well as a critical assessment of strengths and limitations. Current review-based analysis was undertaken based on the filtered 395 papers published for science mapping and to evaluate the qualitative studies in the area of pre-treatment of Landfill Leachate till 2022. A three-step process was employed to conduct bibliometric analysis, qualitative valuation, and identification of influential and productive journals, countries, researchers and articles, emerging technology, and outlining some of the major research gaps in the research field.

Ecological and health risk assessment associated with translocation of heavy metals in Lycopersicum esculentum from farmland soil treated with different composts.

To meet the United Nations' Sustainable Development Goals, agricultural soil which is a non-renewable natural resource must be carefully managed. Heavy metals present in agricultural soil may imperil food security and instigate extreme risks to human health. Organic wastes have been long known for valuable amendments to soil thereby, improving overall soil health. In the present study, Echhornia crassipes, Hydrilla verticillata, and vegetable waste, was utilized to prepare compost amendments. Lycopersicum esculentum was used to metal uptake from compost amended soils. 5%, 10%, 15%, 25%, and 35% compost: soil (w/w) were studied to understand metal translocation in plants. Potential Ecological risk indices showed that while the degree of risk was medium for the natural soil, it reduced to slight for the soil amended with WHC and VWC for all compositions. The non-carcinogenic risks associated with the human health reduced on application of the composts, however, they still remained substantial for Fe, As, and Pb for WHC, HVC, and VWC composts at higher application ratios, especially among children. On the other hand, the carcinogenic health index values which were calculated to estimate the risk associated with ingestion of L. esculentum, showed a decrease in risk for all the metals studied, upon soil amendment. Soil amended with HVC compost showed an increase in carcinogenic risk for As, Pb, and Cr. Finally, we conclude that biological soil remediation is economical and a sustainable land management strategy that may lead to green and clean remediation solutions for metal contaminated soil.

Thermophilic-mesophilic biodegradation: An optimized dual-stage biodegradation technique for expeditious stabilization of sewage sludge.

The present study investigated the stabilization of fresh sewage sludge through a dual-stage biodegradation process; rotary drum composting in series with vermicomposting. After thermophilic exposure in a rotary drum composter, the partially degraded feedstock was separated into S1 without vermiculture, S2 and S3 with Eudrilus eugeniae and Eisenia fetida vermi-monocultures, respectively. The S3-derived vermicompost exhibited an 80% and 88% reduction in CO2 and ammonium-nitrogen evolution rates, respectively, demonstrating the expedient stabilization of sludge. The robust, more than 85% seed germination index supported S2 and S3 derived vermicompost viability. A significant decrease in heavy metals was evinced with S2 and S3-derived vermicompost; the S1-derived end product exhibited higher Zn, Cr, and Pb levels in the absence of vermicomposting. Furthermore, soil amended with 20% vermicompost from S3 displayed 50% more plant growth than S1. Thus, the optimized thermophilic-mesophilic dual-biodegradation technique stabilizes sewage sludge quickly, has a lot of potential in sludge management facilities around the world, and produces a marketable end product.

Hydraulic performance, consolidation characteristics and shear strength analysis of bentonites in the presence of fly-ash, sewage sludge and paper-mill leachates for landfill application.

A rapid upsurge in urban and industrial developments leads to increased generations of solid wastes. The most accepted technique of waste discarding around the world is landfilling. Leaching chemicals from municipal dumping grounds can pollute the groundwater source and the surrounding environment without appropriate precautionary measures. Bentonite is a low-cost constituent used as a liner material in landfills due to its low permeability, high sealing ability, high specific surface area, and the ability to hold up the impurity migration through adsorption. However, leachate interaction with bentonite may alter its properties and reduce its usefulness as a barrier material in the long term. Also, bentonite having different chemical and mineralogical compositions will behave differently due to the leachate interaction. Therefore, it is necessary to compare the performance of various bentonites in the presence of leachates. In the present investigation, two Indian bentonites of different mineralogical compositions were studied for their change in the index properties, swelling, swelling potential, swelling pressure, hydraulic conductivity, consolidation parameters and shear strength properties in the presence of fly ash, sewage sludge and paper mill leachates. The outcomes showed that in the presence of all the leachates, liquid limit, free swell, compression index, swelling potential, swelling pressure, time to complete 90% of consolidation and shear strength dropped; whereas, hydraulic conductivity and coefficient of consolidation increased. Besides, the quality of bentonite prominently influenced the hydraulic, strength and swelling behaviour. The bentonite having a higher cation exchange capacity, liquid limit, specific surface area, and swelling capability undergoes a higher variability in the free swell (80.0, 73.8 and 76.9% decline), liquid limit (73.5, 61.7 and 69.2% decline), swelling potential (61.3, 55.7 and 51.0% decline), swelling pressure (53.3 and 56.4% decrease), and hydraulic conductivity (57.5, 8.6 and 41.1 times increase at a void ratio of 1.2) values when infused with fly ash, sewage sludge and paper mill leachates, respectively. The study also showed that the fly ash leachate interaction causes a higher variation in bentonite behaviour than sewage sludge and paper mill leachates. The study's findings would prove beneficial to design engineers for selecting bentonite types for landfill liners.

Development of function-specific indices for assessing water quality based on the proposed modifications of the expected conflicts on existing information entropy weights.

Water serves numerous purposes besides drinking, such as irrigation and industrial usage. Most water quality indices developed have primarily focused on drinking water quality. However, assessing other functionalities of water bodies is also equally essential. The present study proposes a novel technique to measure water quality for two highly specific water use, i.e., assessing heavy metal contamination and irrigation suitability. The ambiguities in the current practice of entropy weights were identified, and a novel method was proposed, considering a three-dimensional approach instead of the conventional two-dimensional procedure. Weights to different parameters were assigned based on the probability estimates obtained from the frequency of observed values within acceptable limits. The proposed method's reliability, correctness, and applicability were tested using Deepor Beel's water quality dataset. Results were highly consistent with the experimental values and correlated well with other established methods. The efficacy of the method was determined by employing sensitivity analyses. Both indices showed high reliability and correctness, as no single parameter was found to be highly sensitive compared to others. Therefore, the proposed methodology proved to be the most reasonable, incorporating all the factors required for a reliable water quality monitoring program.

Interrelationships among critical success factors for the planning of municipal solid waste management PPP projects in India using structural equation modelling.

This research aims at investigating the interrelationships between critical success factors (CSFs) in municipal solid waste management (MSWM) projects taken up in public-private partnership (PPP) mode in India and studies the extent to which they can affect project success. A three-step procedure was followed to identify the CSFs in MSWM. A conceptual structural equation model (SEM) was developed using cluster groupings of the identified CSFs to show their interrelationships. Data collection from the public sector and private sector waste management managers was done through a questionnaire survey. The respondents' data were analysed in analysis of moment structures (AMOS) using structural equation modelling. The SEM analysis of the respondents' data gives the most exemplary fitting measurement model with the 17 CSFs taken as components of five latent variables: external environment, financial characteristics, project planning and procurement, project operation and management and project stakeholders. The model shows the relationships between the constructs of CSFs for project success. This study contributes to current ideas by empirically identifying the interrelationships between the MSWM CSFs, which can help waste management professionals handle the CSFs rationally. Furthermore, the study shows that all the groups have a direct and positive impact on project success. The findings may only portray the opinion of solid waste management managers in India.

Optimization of electrokinetic pretreatment for enhanced methane production and toxicity reduction from petroleum refinery sludge.

This study examined the effect of electrokinetic pretreatment on petroleum sludge (PS) released from the wastewater treatment plants of petrochemical industries for enhanced biodegradation and contaminant removal. The application of electric field on PS through direct current is optimized with the combined variation of applied voltage (40-80 V), exposure duration (20-120 min) and distance between graphite electrodes (8-16 cm) using central composite design-response surface methodology (CCD-RSM). The optimization study revealed significant interaction among the response variables to obtain an optimum condition (60 V, 83.5 min, 11.6 spacing) for maximization of solubilization in terms of soluble chemical oxygen demand (230% increment against untreated) and volatile fatty acids (172% increment against untreated) concentrations for accelerated hydrolysis of complex PS. BMP batch assays were performed at different inoculum and sludge ratios (0.3, 0.4, 0.5 and 0.7) based on volatile solids content after pretreatment at the optimized condition which resulted in accumulated methane ranging from 5.16 to 6.61 L/gVSadded (untreated - 3.9 L/gVSadded). The mixing ratio of 0.4 showed the maximum methane enhancement of 69.2% compared to untreated. The maximum removal of organic content (62.8%), oil and grease (71.74%), and total petroleum hydrocarbon (52.9%) were also observed for the mixing ratio of 0.4. The FTIR study showed the efficacy in hydrocarbon dissociation and decomposition after pretreatment of PS. The net energy gain (3508 kJ) and phytotoxicity reduction of batch digestate after the anaerobic digestion suggest the economic feasibility and decontamination efficiency of the electrokinetic pretreatment technique respectively. Further research could be performed to evaluate the viability of this pretreatment for enhanced methane recovery at field-scale levels to relate to these lab-scale postulations.

Enhancement of soil physico-chemical properties post compost application: Optimization using Response Surface Methodology comprehending Central Composite Design.

The application of compost has been recognized as one of the most promising approaches for preserving soil quality and crop production. The present study exhaustively investigates the impact of Water Hyacinth Compost (WHC), Hydrilla verticillata Compost (HVC) and Vegetable Waste Compost (VWC) on soil nutrient quality and engineering properties [Bulk Density (BD), water retention and specific gravity]. For the study, six different proportions constituting 5, 10, 15, 25, 35 and 45% of the composts by weight of the soil were taken. The soil compost mixtures were evaluated at different periods (0, 15, 30, 45, 60 and 120 days) for various nutrients [Na, Mg, P, K, Ca, Total Organic Carbon (TOC), Total Kjeldahl Nitrogen (TKN)], BD, water retention capacity, change in specific gravity and Cation Exchange Capacity (CEC) values. It was observed that when the percentage of compost was increased to 15-45%, it resulted in enhanced nutrient value of the soil. Also, for WHC, HVC and VWC 60 days was sufficient to improve the soil quality to its maximum extend. Based on the optimized physico-chemical properties generated from the Response Surface Methodology (RSM) model, it was found that compared to WHC and HVC, the VWC performed better results viz., generating low BD (0.87 g/cm3), high water retention capacity (45.63%) and degree of saturation (77.49%) of the soil. While WHC, HVC and VWC can be used to improve soil nutrient content and overall physico-chemical parameters in long terms, VWC could be more efficient and beneficial to degraded soil for restoring soil health.

Impact of real and simulated municipal solid waste leachates on the hydraulic and swelling behaviour of bentonites for landfill application.

For the efficient functioning of a landfill, compacted bentonite is an acclaimed liner element due to its excellent adsorption capability, minimal hydraulic conductivity, and superior specific surface area (SSA). However, the leachate generation within the landfill worsens the liner material's quality, causing migration of the leachates, contaminating groundwater, and causing pollution of surrounding environment. With this perspective, a comparative assessment of the influence of real and simulated municipal solid waste (MSW) leachate on two different bentonites has been carried out in the present investigation. The two bentonites, differing precisely by their cation exchange capacity (CEC), liquid limit (LL), and swelling capability, were examined for variation in their LL, free swell (FS), and hydraulic behaviour concerning their interaction with both leachates. Results depicted that in both the leachates, LL and FS, swelling potential (SP) and pressure declined, whereas hydraulic conductivity (HC) rose. Furthermore, the bentonite quality greatly influenced the LL, FS, SP, swelling pressure, and hydraulic behaviour. Bentonite having higher CEC, SSA, and swelling ability experienced a higher variability in the LL (55.5 and 65.2% decrease), free swelling (76.9 and 83.1% decrease), SP, swelling pressure (53.3 and 56.4% decrease), and HC (13.1 and 49.4 times increase) values when permeated with simulated and real MSW leachates, respectively. The study also showed that the real MSW leachate interaction causes a higher variation in bentonite behaviour than its simulated counterpart. The study's findings would prove beneficial to design engineers for selecting bentonite types for landfill liners.

Bio-inherent attributes of water hyacinth procured from contaminated water body-effect of its compost on seed germination and radicle growth.

Compost is generally used for soil conditioning, growing plants and remediation of pollution. It is imperative to evaluate compost standard and toxicity test is a salient parameter for determining compost quality. Seed germination test is an essential method to discern the phytotoxicity of compost. Ecotoxicity of water hyacinth compost was inspected for the denouement of the compost quintessence and its concentration on seed germination indices. The aim of this paper was to assess seed emergence rate index, germination velocity coefficient and rate of germination of L. esculentum and B. oleracea at discrete concentrations of water hyacinth compost. The highest germination percentage achieved was 95% (L. esculentum) at 100 g/L and 100% (B. oleracea) at 32 g/L of the compost extract. The probability of inadvertent ceasing of germination was found to be < 0.0001 for either of the test species. Consequently, the water hyacinth compost aid plant growth and is recommended for substantially ameliorating languishing ecological idiosyncrasy.

Biodegradable kinetics and behavior of bio-based polyblends under simulated aerobic composting conditions.

The current study evaluates aerobic biodegradation of melt extruded poly(lactic acid) PLA based blends under composting conditions. Samples of neat PLA (NPLA) and bio-based polyblend composites of PLA/LLDPE (linear low-density polyethylene) having different concentration of MCC (microcrystalline cellulose crystal) were analyzed to understand the biodegradation behavior of these blends under simulated composting conditions. Biodegradation kinetics revealed that higher content of MCC and PLA accelerated the biodegradation process of the polymeric blends. Increase in the spherulite growth size and decrease in the spherulite density of the biodegraded samples confirmed the decline in amorphous portion of the test samples due to microbial assimilation, leaving behind the crystalline portion. Surface morphological analysis revealed that the samples of PLA/LLDPE/MCC blends underwent surface erosion prior to bulk biodegradation (50-80%) until the 90th day and the PLA formed fibril-like structures after degradation. This study would help in the design and preparation of biodegradable bio-based commercial blends in the future.

Microbes involved in arsenic mobilization and respiration: a review on isolation, identification, isolates and implications.

Microorganisms play an important role in arsenic (As) cycling in the environment. Microbes mobilize As directly or indirectly, and natural/geochemical processes such as sulphate and iron reduction, oxidative sulphide mineral dissolution, arsenite (AsO33-) oxidation and arsenate (AsO43-) respiration further aid in As cycle in the environment. Arsenate serves as an electron donor for the microbes during anaerobic conditions in the sediment. The present work reviews the recent development in As contamination, various As-metabolizing microbes and their phylogenetic diversity, to understand the role of microbial communities in As respiration and mobilization. It also summarizes the contemporary understanding of the intricate biochemistry and molecular biology of natural As metabolisms. Some successful examples of engineered microbes by harnessing these natural mechanisms for effective remediation are also discussed. The study indicates that there is an exigent need to have a clear understanding of environmental aspects of As mobilization and subsequent oxidation-reduction by a suitable microbial consortium.

Statistical modelling and assessment of landfill leachate emission from fresh municipal solid waste: A laboratory-scale anaerobic landfill simulation reactor study.

Quantification, measurement of quality, post-treatment, and leachate control has been a significant problem due to the dumping of waste in an unscientific manner across the globe, and especially in developing countries like India. In this context, the objective of this study was to investigate the degradation of fresh mixed municipal solid waste (MSW) in an anaerobic landfill reactor operated with rainfall addition in laboratory conditions. Experiments were carried out in a landfill reactor of 1 m length × 1 m width × 1.1 m height. The reactor was simulated with 50 years weighted average actual rainfall rate of India. It contained the waste composition of 73% wet waste (food and kitchen) and 27% dry waste (paper, plastic, wood, textiles, and others). The leachate parameters were continually monitored for 39 weeks. In the fresh MSW landfill reactor it was evident that concentrations of leachate parameters were high initially, and there was a significant decrease in BOD5 (7041-39310 mg L-1), COD (15692-71630 mg L-1) and TS (9077-33200 mg L-1) in leachate. Therefore, rainfall had a direct influence on leachate quality. The developed first-order decay models were used for BOD5, COD, and total solids with adjusted R2 of 0.83, 0.92, and 0.96, respectively. Therefore, this model can be applied for leachate strength estimation at any given time from the period of deposition of waste under similar rainfall and waste compositions, and is largely applicable in India and tropical areas. This study is expected to be a good simulation for cities with the waste composition of high wet waste (>70%) as the estimations of important design parameters such as BOD5, COD, VFA, and NH4+-N were studied in this research. As the importance of moisture (precipitation) has been established in this study, some moisture additions can be designed in areas with low rainfall, such as arid zones.

Drum composting of nitrogen-rich Hydrilla Verticillata with carbon-rich agents: Effects on composting physics and kinetics.

Composting of the Hydrilla verticillata, an invasive aquatic weed, signifies aquatic waste management as a safe and hygienic method that produces a nutrient-rich end product, i.e., compost. However, its higher moisture content, higher N-losses, and lower degradation rate have shown negative impacts on the composting process. Therefore the primary objective of this study was to assess the composting physics and the degradation kinetics after addition of three different carbon-rich agents with Hydrilla verticillata. To pursue this objective, three carbon-rich agents (viz. dry leaves in Run A, grass clippings in Run B and wood chips in Run C) each were mixed (10% w/w) to the optimized control mixture of Hydrilla verticillata, cow dung and sawdust (8:1:1) as reported in the earlier study. The composting experiments were performed in 550L rotary drum composter for 20 days to evaluate variation in physical, chemical, nutritional properties as well as degradation kinetics. The Run A and Run B were the only two mixtures that attained the temperature (55-70 °C) that indicates standard sterilization capacity in both with maximum moisture reduction (17%) and total Kjeldahl N increment (48%) in the latter. Organic matter losses throughout the process followed a first-order kinetic equation in all the Run (A-C) and control with the higher loss in Run B whereas least in control. Nevertheless, the addition of all carbon-rich agents is found to be beneficial to improve composting physics. Amongst all Runs (A-C), Run B achieved maximum reduction in the initial value of bulk density (64%) and increment in the initial value of free air space (20%). The study also concluded that all the carbon-rich agents have produced compost with the nutritional concentration suitable for agricultural proposes.

Enhanced methane potential of rice straw with microwave assisted pretreatment and its kinetic analysis.

Biogas has become an alternative clean source of energy. Agricultural residues being renewable and abundant resources could be efficiently used as a feed for methane production. The recalcitrant behaviour of rice straw marks pretreatment an important step to facilitate the transformation into renewable (methane) energy source. Microwave pretreatment has been considered as one of the most effective method, as it can directly (thermal and nonthermal effects) react with the feedstock and destroy its complex matrix. The present study considered the different temperature and exposure time (i.e., 130-230 °C, 2-5 min). Biochemical methane potential was assessed corresponding to the maximum solubilization rate; specific methane yield was obtained as 325.76 mL/g/VS. The total net energy gain of 3288.576 J/g/VS was obtained. The performance parameters were calculated by using different kinetic models. It followed the trend as modified Gompertz > transference function > logistic function models. Field Emission Scanning Electron Microscopy (FESEM) and Fourier Transform Infrared (FTIR) analysis confirmed the breakdown of lignocellulose structure resulting from the rupture of cuticular surface.

Recalcitrant carbon for composting of fibrous aquatic waste: Degradation kinetics, spectroscopic study and effect on physico-chemical and nutritional properties.

Biochar, a recalcitrant carbon, is known to enhance organic matter degradation and improve physical properties. The objective of the study is to examine the probable effect of biochar addition during composting of a fibrous aquatic waste, i.e., water hyacinth though degradation kinetics and spectroscopic (FTIR and PXRD) analysis. Four dosages of biochar (0, 2.5, 5, and 10% w/w) were mixed to a mixture of water hyacinth, cow-dung and saw-dust comprising a total weight of 150 kg and composted using rotary drum composter for 20 days in batch mode. The study outcomes indicated that the amendment of biochar prolonged the duration of the thermophilic temperatures, reduced salinity, and promoted nutritional quality of compost. Moreover, biochar amendment enhanced the organic matter degradation with a rate constant of 0.029 day-1 and increased the total Kjeldahl nitrogen content up to 1.75% from an initial value of 1.10% in the reactor with 2.5% biochar amendment. Concurrently, biochar amendment aided in reducing Cu and Cr in the final product inferring 2.5% biochar is best suited for composting of water hyacinth. However, future studies are encouraged to decipher the microbial shifts and bioavailability of metals due to biochar dosage during composting for mitigating and managing the menace of such fibrous waste like water hyacinth by converting it to a soil conditioner.