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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. [ABSTRACT FROM AUTHOR]

Rivers are the primary source of potable water and other residential uses. Since wastewater from the nearby industries and urban areas degrades the quality of the rivers, it is essential to monitor their water quality and quantity continuously. This study determines the pollution level in a river in accordance with drinking water standards. The entropy-weighted water quality index (EWQI) indicates the level of river pollution, and the principal component analysis (PCA) and Pearson correlation matrix were used to identify pollution sources. Twenty parameters were considered for the study, which includes alkalinity, biochemical oxygen demand (BOD), calcium (Ca+2), cadmium (Cd), chloride (Cl-), copper (Cu), dissolved oxygen (DO), electrical conductivity (EC), fluoride (F-), hardness, iron (Fe), lead (Pb), magnesium (Mg+2), manganese (Mn), nitrate (NO3-), pH, potassium (K+), sodium (Na+), sulphate (SO42-), total dissolved solids (TDS) and zinc (Zn). The EWQI varied between 68.93 (good) to 259.91 (extremely poor). Post-monsoon EWQI values are higher due to the fact that monsoon-filled sewers continue to drain into the river even after the rainy or monsoon season has ended. Winter, pre-monsoon, and monsoon all produced five components (PCs) that explained 79%, 74%, and 80% of the overall variance, respectively and post-monsoon produced 6 PCs that explained 83% of the overall variance. PCA and Pearson correlation matrix indicate pollution from runoff sources during the pre-monsoon and monsoon season along with the pollution sources existing in the monsoon and post-monsoon season, domestic and metal sources. [ABSTRACT FROM AUTHOR]

To combat the persistent environmental issues resulting from eutrophication, it is necessary to scavenge excess phosphorous levels from aquatic ecosystems. In response, a cationic adsorbent was prepared by modifying agrowaste-derived natural biomacromolecule; nanofibrillated cellulose (NFC) using cetyltrimethylammonium bromide (CTAB) surfactant. Comprehensive characterization through XRD, FTIR, HR-SEM, SEM-EDX, BET and XPS demonstrated that quaternizing NFC significantly improved its surface chemistry by introducing substantial quaternary ammonium groups. This modification imparted positive ζ potential across broad pH range, underscoring a strong affinity for negatively charged phosphate ions. Enhanced roughness and improved spatial dispersion led to nearly threefold increase in phosphate removal efficiency compared to pristine NFC, attributable to a higher number of available active sites. The adsorption process followed pseudo-second-order kinetic and Sips isotherm model, with a maximum adsorption capacity of 21.78 mg P/g, reaching equilibrium within 120 min. Besides, the prepared adsorbent demonstrated pH-dependent adsorption and displayed stable adsorption capacity particularly at weakly acidic or neutral pH conditions. Furthermore, it exhibited excellent retention capacity with only 12.61 % desorption rates over three cycles. Both XPS and FTIR results revealed that electrostatic adsorption (based on Lewis acid-base principle) and hydrogen bonding were primary adsorption mechanisms. • Facile preparation of enviro-benign cationic NFC for enhanced phosphate removal. • Threefold increase in phosphate removal efficiency compared to pristine NFC. • Adsorbent exhibits maximum adsorption capacity of ∼22 mg/g. • Phosphate-loaded adsorbent's excellent stability aids to environmental applications. • The study elucidates the underlying removal mechanisms comprehensively. [ABSTRACT FROM AUTHOR]

In this study, chemometric techniques have been used in source apportionment for spatial variation of surface water quality of seven rivers (Baralia, Puthimari, Pagladia, Beki, Manas, Kolong and Kameng River) of Assam (India). The study was carried out in two phases. The first phase included the survey of the study area and the collection and analysis of water samples. In the second phase, cluster analysis (CA), discriminant analysis (DA) and principal component analysis (PCA) were applied to the observed water quality data-sets. CA grouped all the sampling sites into three clusters based on the similarities of the characteristics they possess. The result from CA was verified using DA, which helped in determining the variables that distinguish the observed groups. DA resulted in eight water quality parameters (DO, total alkalinity, K+, Ca2+, Mg2+, Cl-, SO42- and Mn) affording 100% correct assignations in spatial analysis of rivers. PCA applied to the three separate datasets obtained from CA indicated that soil leaching, organic waste and fertilizer were the major sources of water quality variation. Therefore, the present study illustrates the requisiteness and efficacy of chemometric techniques in source apportionment for variation of water quality and effective management of water resources. [ABSTRACT FROM AUTHOR]

[Display omitted] • Identification of barriers hindering large-scale biogas proliferation in India. • The public/private/academic sector experts were consulted. • Analysis of barriers was performed using AHP and Fuzzy AHP approach. • Lack of funding, profitability, & fuel competition impede growth. • Various mitigation strategies for successful adoption are proposed. This study explores why large-scale biogas plants are not widely installed in India despite the wealth of biomass resources. The methodology includes an extensive literature review and surveyed biogas experts in different sectors, such as private, public, and academic, to identify and rank key obstacles using the Analytical Hierarchy Process (AHP) and Fuzzy-AHP techniques. Overall, 27 barrier elements were identified across six different categories. As perceived by different experts, except for financial barriers, notable differences were found in the relative importance of other barrier categories. Among the different barriers, competition from other fuels, subsidies, lack of financing mechanisms, and feedstock variation are the most influential. To overcome these challenges and successfully promote the growth of the biogas sector in India, a combination of financial strategies, collaborative efforts, standardized procedures, and comprehensive resource mapping were proposed. These measures can inform effective policy development and contribute to achieving numerous Sustainable Development Goals. [ABSTRACT FROM AUTHOR]

Biogas production from agricultural residue by anaerobic digestion is the most favourable option for providing sustainable energy and reducing the environmental pollution. The experimental methane potential of co-digested rice straw and food waste were measured for different carbon to nitrogen (C/N) ratios in 1 L anaerobic reactor. Co-digesting rice straw with food waste for C/N 25, 30 and 35 almost showed the similar methane yield 294.17 ± 3.78 mL/g-VS added , with an increase of 134.53 mL/g-VS added (71.09%) than mono-digestion. After optimizing the C/N ratio for co-digestion, interactive effect of initial pH and food/microorganism (F/M) ratio were also explored in this study using central composite design – response surface methodology (CCD-RSM). Results from the optimization study showed significant interaction, and validation experiment for optimum condition (C/N 30, pH 7.32, F/M 1.87) showed a methane yield of 323.78 mL/g-VS added (94.41%), 166.54 mL/g-VS added higher than the mono-digestion (control). • Co-digestion of rice straw and food waste was studied. • 71.09% increase in methane yield from co-digestion. • CCD-RSM was used for optimization. • Validation experiment showed a methane yield of 323.78 mL/g-VS added. [ABSTRACT FROM AUTHOR]

Biochemical methane potential tests using water hyacinth (WH), pretreated water hyacinth (PWH), and Hydrilla verticillata (HV) as substrates using sewage media were explored. This study replaced the freshwater required to prepare the slurry for AD of organic solid waste with domestic sewage. Cow dung was used as the inoculum. WH (241.5 mL CH4/g VSadded), PWH (200.5 mL CH4/g VSadded), and HV (212 mL CH4/g VSadded) produced significant amounts of methane in the sewage medium. 16S-rRNA analysis showed that, in sewage, ~ 85% of the microbes were hydrolytic bacteria, and 7% were methanogens. This abundant quantity of hydrolytic microbes from sewage accelerated lignin degradation, achieving 28.32% and 38.34% degradation for WH and HV, respectively, within 14 days. Field emission-scanning electron microscopy images visually confirmed the enhanced substrate degradation in the presence of sewage. The net energy produced from the AD of WH and HV was significant (4664 J/g VSadded and 4109 J/g VSadded), but for PWH, it was negative, indicating that using sewage medium may be better than costly pretreatment techniques. This study demonstrated the potential of using sewage as an alternative to freshwater in AD, offering a sustainable solution for freshwater conservation and the possible utilisation of sewage for improved methane production, especially for substrates with lignin that are difficult to degrade. [ABSTRACT FROM AUTHOR]

• The challenges in the anaerobic digestion of lignocellulosic waste. • Management of agricultural residue in a sustainable manner. • Operational parameters and suggestion for optimized biogas yield. • Various inhibitory compounds affecting the anaerobic digestion process. Anaerobic digestion of lignocellulosic biomass has gained huge attention in current years, especially for degrading agricultural waste (i.e. rice straw, wheat straw etc.). Challenges related to anaerobic digestion of agricultural waste are low biogas yield, poor buffering capacity, low quality end products and potential variability. These inadequacies are either because of low mass transfer (high solid contents, poor nutritional structure) or can be accredited to recalcitrant nature of agricultural residues. To overcome these challenges various techniques exists like pretreatment of feedstock, co-digestion with different substrate and inoculation efficiency have been considered to increase the performance of anaerobic process. This review includes the effect of these techniques on lignocellulosic degradation, synergistic interaction with high C/N ratio feedstock and improving the buffering capacity by inoculum ratio optimization. Furthermore, key parameters influencing the anaerobic digestion are included with proposed future study. [ABSTRACT FROM AUTHOR]

• A novel two stage digester performance was investigated in continuous mode. • Untreated, pretreated and co-digested water hyacinth was used as a feedstock. • Intermittent mixing was beneficial for enhanced biogas production. • COD removal efficiency was quite good. Mixing and the separation of stages in a digester during anaerobic digestion demonstrate enhanced biodegradation efficiency of the feedstock. But two stage anaerobic digesters are difficult to operate and require huge space. Also, continuous high intensity mixing minimises biogas production. Based on these criteria, a novel type of two stage anaerobic digester was designed. The aim of this study was to evaluate the performance of this novel anaerobic digester in continuous mode utilising water hyacinth as the feedstock. Initially, untreated water hyacinth whole plant was fed in the digester followed by hot air oven pretreated water hyacinth and water hyacinth co-digested with food waste. The optimal OLR for untreated and pretreated water hyacinth was observed to be 3.75 kg COD/m3.d whereas for co-digested water hyacinth the optimal OLR was 6.7 kg COD/m3.d; illustrating an average COD removal of 72.5%, 82% and 77% for untreated, pretreated and co-digested water hyacinth respectively. [ABSTRACT FROM AUTHOR]

Rice straw is a widely existing lignocellulosic waste with high potential for methane production. However, high carbon/nitrogen (C/N) ratio of rice straw causes the poor process stability for mono-digestion. This study investigated the co-digestion of rice straw and hydrilla verticillata (nitrogen rich co-substrate) at different C/N ratios to enhance biomass degradation. Different C/N ratios revealed notably enhanced process stability and higher volumetric methane yields than mono-digestion (control). C/N-25 (Co-digestion) showed the highest methane productivity with an increase of 40% than the control. This increase was caused by the improvement of the metabolic pathway due to proper nutritional structure (C/N). C/N-15 obtained the lowest methane yield due to ammonia inhibition (315 mg/L). Biodegradation reaction kinetics parameters were also calculated during the digestion process and it showed reasonably good agreement between the experimental and predicted value (R2 > 0.98) for modified gompertz model. The average R max of C/N-25 was 2.78% less than R max observed in control. The favourable reducing environment established during the degradation stage was represented by low oxidation-reduction potential (−312.8 mV) values. Since no added energy inputs are required for this process, it is highly practicable on farm-scale in contrast to pretreatment. Schematic Sketch illustrating the experimental design for anaerobic co-digestion. Image 1 • Biomethane yield by co-digestion was higher than mono-digestion. • Hydrilla verticillata is an excellent co-substrate for co-digestion with rice straw. • The optimum C/N ratio was 25 for the anaerobic co-digestion of rice straw and hydrilla verticillata. • Co-digestion reduced the ammonia inhibition by improving process stability than mono-digestion. [ABSTRACT FROM AUTHOR]

[Display omitted] • Tanner diagram illustrates that MSW does not need auxiliary fuel for combustion. • Heating value of MSW and legacy waste were 37.74 and 40.43 MJ/kg, respectively. • High lignin content in MSW suggests char production suitability. • MSW has activation energy of 5.72 kJ/mol, less than legacy waste of 14.96 kJ/mol. • Legacy waste has lower energy barrier (5.42 kJ/mol) than MSW (113.86 kJ/mol). This study explores the viability of utilizing municipal solid waste (MSW) and legacy waste as a renewable energy source through pyrolysis, akin to solid fuels. The heating value of MSW and legacy waste were found to be 37737.89 and 40432.84 kJ/kg, respectively. Proximate analysis shows that MSW fits within Tanner diagram parameters, eliminating the need for auxiliary fuel in pyrolysis. With 47.6 % and 44.16 % lignin content in MSW and legacy waste were deemed suitable for char production. Thermal degradation resulted in mass losses of 68 % for MSW and 82 % for legacy waste. The kinetic and thermodynamic assessment indicates lower activation energy (E a) and Gibbs free energy (ΔG) for MSW (5.72 kJ/mol and 170.37 kJ/mol, respectively) compared to fossil fuels, suggesting faster reactions without additional energy requirement. MSW emerges as a promising alternative to fossil fuels, aligning with the United Nations' 2030 Sustainable Development Goals. [ABSTRACT FROM AUTHOR]

Abstract 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. Graphical abstract Image 1 Highlights • Carbon-rich agents found to be efficient for composting of H. verticillata. • Thermophilic phase with maximum peak of 68 °C was achieved in Run B. • Compost feedstock amended with grass clippings showed highest degradation rate. • Moisture content and bulk density were negatively correlated. [ABSTRACT FROM AUTHOR]

Graphical abstract Schematic representation of optimization of process variable for co-digestion of rice straw and hydrilla verticillata. Highlights • Anaerobic co-digestion of rice straw with hydrilla verticillata enhanced the methane yield. • CCD-RSM design was used to optimize the methane yield. • Maximum methane yield was obtained under interactive effect of C/N ration and F/M ratio. • The optimum condition for maximum methane yield was documented. Abstract Anaerobic co-digestion is a realistic approach to concurrently manage agriculture residue and harness renewable energy. To achieve the anaerobic degradation requirements and to recompense the nitrogen deficiency of rice straw, it should be digested with another nitrogen-rich co-substrate to advance its characteristics. This study exhibits the necessity of co-digestion to improve physicochemical and biochemical progression compared to mono-digestion. The individual effect of carbon/nitrogen (C/N) ratio, food/microorganisms (F/M) ratio and pH, in addition to their interaction effects on methane yield (mL CH 4 /g-VS added) were explored in this study. A central composite design – response surface methodology was used for defining the experimental design for anaerobic co-digestion of rice straw and hydrilla verticillata. Results of this study showed significant interaction of C/N ratio and F/M ratio, and individual response parameters on methane yields. The optimum condition for anaerobic co-digestion (C/N ratio 29.7, F/M ratio 2.15 and pH 7.34) showed methane yield of 287.6 mL CH 4 /g-VS added , 1.84 fold (156.32 mL CH 4 /g-VS added) higher than mono-digestion (control). Model validation proved the high adequacy of the model and methane yield is good output response variable for co-digestion study and it is necessary to optimize the transient variation in C/N ratio, F/M ratio and pH. [ABSTRACT FROM AUTHOR]

Abstract This paper reports an optimisation study for producing fired bricks using organic solid wastes used as partial substitutes to the soil. A series of experiments were carried out following Design of Experiments approach proposed by Taguchi (L25 orthogonal array with four factors and five levels). Different type of wastes (additives) were added to two different types of soils (laterite and alluvial) in various mix ratio and fired at two different temperatures (850 and 900 °C) in line with the commercial kiln practice. The effects of additives, soils, firing temperature and mix ratio on the performance characteristic were analysed using ANOVA, Signal to Noise (S/N) ratio and Random Forest regression analysis. It was inferred that (i) firing temperature of a brick is the least important parameter affecting a brick's compressive strength, water absorption or linear shrinkage, and (ii) substituting up to 15% of fertile soil by an appropriate additive (waste type) can still achieve compressive strength comparable to the normal clay brick. Graphical abstract Image 1 Highlights • Optimisation study for producing fired bricks using organic solid wastes. • Taguchi Method with Random Forest Regression alongside ANOVA was used. • Degraded municipal solid waste is the optimal additive to use with 20% mix ratio. • ANOVA revealed compressive strength of bricks primarily depends on the choice of mix ratio. [ABSTRACT FROM AUTHOR]

Invasive aquatic weed management is one of the biggest challenges in the field of solid waste management. Eichhornia crassipes , Pistia stratiotes and Hydrilla verticillata (L.f.) Royle pose some of the world's most noted aquatic weed problems. Previously reported studies on management of H. verticillata , a submersed aquatic plant, have shown that temporary removal, chemical treatment or biological control methods each have advantages and disadvantages. Removal programs that propose to compost harvested H. verticillata biomass may provide a novel technique to manage this issue. However, the properties of such compost as an agriculture resource are unclear. This study presents the different mix proportions of H. verticillata , cow dung and sawdust used for the composting of 550 L rotary drum composter. This work characterizes the biological, physicochemical, and respirometry properties of the various mixes over a 20-day composting period. The results suggest that the biomass of H. verticillata can be beneficially utilized to produce stable compost for potential use in agricultural systems. [ABSTRACT FROM AUTHOR]

Strenuous efforts are being made to make the manufacturing activities sustainable. Consequently, industries are seeking ways not only to reduce energy consumption, waste accumulation and carbon footprint but also to reduce exploitation of precious natural resources. Fertile soil is one such precious resource which is being used for brick manufacturing for centuries. Brick industry needs frugal innovations to accommodate large quantities of waste and to make the production processes sustainable. Numerous studies in the past have tried to recycle waste materials by incorporating them into the brick production cycle. This experimental feasibility study is first to demonstrate the use of aquatic weed (water hyacinth) in brick manufacturing. Using chemical-mineralogical and physical-mechanical characterization, optimal mixing ratio of water hyacinth (WH) and soil was determined for achieving the desirable mechanical properties (compressive strength and water absorption) of a fired clay brick compliant with Indian and ASTM standard codes. XRD results confirmed that addition of WH does not cause compositional changes in the phase and leads merely to an increased porosity in bricks. An optimum mix of 10% WH with soil and a firing temperature of 900 °C were found appropriate for brick production using WH as a partial substitute to the soil. Greenhouse gas (CO 2 ) emission during firing was ascertained and it was estimated that incorporation of 10% WH leads to 7% net saving in the consumption of external fuel required for firing the bricks. [ABSTRACT FROM AUTHOR]

Water hyacinth is a deadly weed in an aquatic environment but a potential feedstock for the generation of renewable biogas through anaerobic digestion. Biochemical methane potential (BMP) was examined for fresh water hyacinth whole plant after microbial pretreatment to determine the ideal food to microorganism (F/M) ratio. The study revealed that after microbial pretreatment of water hyacinth the F/M ratio 1.5 showed the highest methane yield of 156 ± 19 mL CH 4 /g VS on the 20th day. It was observed that the microbial pretreated water hyacinth illustrated enhanced biogas production within a short time period when compared to the untreated water hyacinth. The ideal F/M ratio played a significant role alongwith the microbial pretreatment process to accelerate the hydrolysis period and increasing biogas generation. [ABSTRACT FROM AUTHOR]

Pulp and paper industry is one of the most polluting, energy and water intensive industries in the world. Produced pulp and paper mill sludge (PPMS) faces a major problem for handling and its management. An anaerobic digestion has become an alternative source. This review provides a detailed summary of anaerobic digestion of PPMS – An overview of the developments and improvement opportunities. This paper explores the different pretreatment methods to enhance biogas production from the PPMS. First, the paper gives an overview of PPMS production, and then it reviews PPMS as a substrate for anaerobic digestion with or without pretreatment. Finally, it discuss the optimal condition and concentration of organic and inorganic compounds required for the anaerobic metabolic activity. Future research should focus on the combination of different pretreatment technologies, relationship between sludge composition, reactor design and its operation, and microbial community dynamics. [ABSTRACT FROM AUTHOR]

Different heating processes were applied to pretreat the pulp and paper mill sludge to enhance the hydrolysis stage. Hot air oven, autoclave, microwave and water bath were used for comparison. Chemical analyses exposed that all the pretreatment methods have shown improvement in solubilisation of organic matter. Among the pretreatments studied, heat transfer through hot air (80 °C for 90 min) mode had the highest impact on sludge solubilisation. There was an increase in cellulose (P = 0.0096), acid soluble (P = 0.0053) and insoluble lignin (P = 0.0012), but decrease in hemicellulose (P = 0.0009) content after pretreatment. The XRD and FT-IR spectroscopic characterisation shows the development of aliphatic, unsaturated and carbonyl carbon functionalities in the pretreated samples at higher severities. FESEM picture also confirms the change in structure after pretreatment. Thus, pretreatments contribute to disruption of the lignocellulosic structure making the cellulose easily accessible to acidogenic microorganisms. [ABSTRACT FROM AUTHOR]

As a potential pathway to sustainable construction, this novel study demonstrates the feasibility of incorporating degraded municipal solid waste (MSW) as one of the constituents for production of fired bricks. The raw materials, degraded MSW and two different soils, i.e. laterite soil and alluvial soil, were mixed together in different proportions ranging from 5 to 20%. Specimens of these mixtures were then fired at 850 and 900 °C respectively. Various properties such as bulk density, linear shrinkage, loss on ignition, water absorption, compressive strength, and modulus of elasticity on light of the respective Indian and ASTM standard codes were studied and compared. An optimum constituent mix of 20% degraded MSW with (laterite or alluvial) soil fired at temperature of 900 °C was found to be most appropriate for brick production. The ultimate uptake of this study is 8% net saving in the energy consumption of external fuel by mixing 20% degraded MSW. [ABSTRACT FROM AUTHOR]

Water hyacinth is capable of miraculously concealing an entire freshwater body within two weeks by forming thick mats. These thick mats of water hyacinth causes nuisance to both aquatic organisms and human beings. As it intimidates the existence of aquatic organisms and bothers the livelihood and recreational activities of human beings. Therefore this weed is used for biochemical methane potential test in order to check it's prospective for producing biogas. Biochemical methane potential (BMP) was examined for both untreated as well as hot air oven pretreated water hyacinth whole plant (i.e., leaves, stem and roots) to determine the ideal food to microorganism (F/M) ratio. A comparative study conducted between untreated and hot air oven pretreated water hyacinth revealed that the F/M ratio 2 of the untreated water hyacinth, showed the highest methane yield of 143 ± 14 mL CH 4 /g VS on the 32nd day whereas for hot air oven pretreated water hyacinth F/M ratio 1.5 showed the highest methane yield of 193 ± 22 mL CH 4 /g VS on the 14th day itself. It was observed that the hot air oven pretreated water hyacinth showed enhanced biogas production within a very short duration. Also, the ideal F/M ratio was determined for both untreated and pretreated water hyacinth through BMP study. [ABSTRACT FROM AUTHOR]

As a potential pathway to sustainable construction, this novel study demonstrates the feasibility of incorporating degraded municipal solid waste (MSW) as one of the constituents for production of fired bricks. The raw materials, degraded MSW and two different soils, i.e. laterite soil and alluvial soil, were mixed together in different proportions ranging from 5 to 20%. Specimens of these mixtures were then fired at 850 and 900 °C respectively. Various properties such as bulk density, linear shrinkage, loss on ignition, water absorption, compressive strength, and modulus of elasticity on light of the respective Indian and ASTM standard codes were studied and compared. An optimum constituent mix of 20% degraded MSW with (laterite or alluvial) soil fired at temperature of 900 °C was found to be most appropriate for brick production. The ultimate uptake of this study is 8% net saving in the energy consumption of external fuel by mixing 20% degraded MSW. [ABSTRACT FROM AUTHOR]

The objective of the study was to assess the effect of substrate concentration by specific methanogenic activity (SMA) of thermally pretreated pulp and paper mill sludge. Different substrate concentration through food to microorganism ratio varied from 1.0 to 3.0 was carried out in a mesophilic condition as biochemical methane potential assay. Experimental results offered that cellulose removal rate spikes up to 60.2%. The specific methane gas production and biodegradability were increased up to 303 mL of CH 4 /g VS and 73% respectively. By increasing the substrate concentration, SMA was significantly improved in a linear manner. The net energy of 8735 kJ was gained after thermal pretreatment. In addition to that three kinetics model were used, among that the modified Gompertz and logistic function models represent and reproduce the experimental data, while the earlier has the better fit. [ABSTRACT FROM AUTHOR]

The methane production rate increases with a decrease in moisture content up to the optimum threshold level and diminish in a batch reactor fed with the lignocellulosic material in solid state anaerobic digestion. The interpretation on two-faceted effect of moisture content could not be elucidated by the conventional anaerobic digestion model no 1. This study proposed that the decreased moisture content causes augmented mass diffusion resistance by the accumulation of hydrolytic product. This could lead to the reduced production of methane gas. Based on the hypothesis, a new solid state anaerobic digestion model was developed based on mass diffusion limitation and hydrolysis inhibition. The better degree of agreement between model simulation and the literature as well as experimental data verified that the deterioration in the volumetric rate of methane production. This could be attributed to hydrolysis inhibition as a result of limited mass diffusion in solid state anaerobic digestion. [ABSTRACT FROM AUTHOR]

This paper reports the results of an exploratory experimental study to manufacture eco-friendly lightweight bricks through binary mix of paper mill sludge (PMS) and soil. The pre-manufacture activities include mineralogical, chemical, thermal and index properties characterisation of two kinds of soils (laterite and alluvial) and PMS. The mix ratio between PMS and soil was varied (0%, 5%, 10%, 15% and 20%) and two firing temperatures 850 °C and 900 °C were tested in order to emulate the typical conditions of a kiln. The performance of incorporating PMS into the mix was tested by evaluating properties such as linear shrinkage, compressive strength, water absorption, mass loss on ignition, and bulk density of bricks as recommended by the relevant Indian and ASTM standard codes. X ray diffraction results confirmed that the addition of PMS does not show any phase transformation and only enhances the porosity thereby leading to weight reduction. Based on the results, an optimum mix of 10% PMS with both soil types was found suitable for brick production at a firing temperature of 900 °C. Results obtained in this study will be helpful to brick industry for commercial production of PMS incorporated bricks leading to sustainable use of resources. [ABSTRACT FROM AUTHOR]

The aim of this work was to study the effect of four different types of thermal pretreatment techniques i.e., hot air oven, microwave, autoclave and hot water bath on the hydrolysis, compositional analysis and characterization of water hyacinth. To determine the most efficient thermal pretreatment technique exhibiting enhanced solubilisation. Highest solubilisation was achieved by hot air oven (55.5%), followed by microwave, hot water bath and autoclave. Bio-chemical methane potential (BMP) test of hot air oven pretreated and untreated water hyacinth was conducted. Cumulative methane production of 3039 ± 32 mL CH 4 /g VS was achieved by hot air oven pretreated water hyacinth at 90 °C for 1 h which was way higher than the cumulative methane production of untreated water hyacinth 2396 ± 19 mL CH 4 /g VS on the 35th day. Compositional analysis and characterization of water hyacinth were also investigated to study the changes in the pretreated samples. [ABSTRACT FROM AUTHOR]

The application of anaerobic digestion is mounting worldwide because of its economic and environmental benefits. As a concern, the rate and extent of the anaerobic digestion of pulp and paper mill sludge was tested using the biochemical methane potential (BMP) with different food/microorganisms (F/M) ratio. The study was evaluated at five different F/M ratios (i.e. 0.5, 1.0, 1.5, 2.0, 2.5). In addition to that reaction kinetics and the influence of biodegradability were also evaluated for the biomethane potential of substrates. The highest cumulative methane yield was obtained in F/M ratio 2.0 with 3.4 L followed by F/M ratio 1.5 and 2.5 with 3.3 L and 2.9 L, respectively. The maximum methane production rate 3.66 L CH 4 was perceived as per kinetics. The biomass activity may be affected due to the high substrate concentration during BMP test of lower F/M ratios. On the other hand, F/M ratio greater than 2.0, methane yield was decreased due to increased volatile fatty acid production reduces the reactor pH and inhibits methanogens activity. [ABSTRACT FROM AUTHOR]

Water hyacinth is well known for accumulating heavy metals from the water bodies and its uncontrolled growth; due to which it is posing serious threat to the water bodies and the environment. Therefore, the present paper aimed at the safe treatment and recycling of nutrients by vermicomposting of water hyacinth. Three different earthworm species E. fetida , E. eugeniae , P. excavatus were compared for its higher biomass growth, organic matter degradation and heavy metal changes during the study. The nutrient concentration and stability parameters (OUR and CO 2 evolution) were evaluated during the degradation of water hyacinth in five different trials. Results showed that nutrients (Na, K, Ca, Mg, total Nitrogen (TN) and available Phosphorous (AP)) were increased and the stability parameters were reduced significantly at the end of vermicomposting. It was observed that E. eugeniae accumulated higher concentration of heavy metals in its body tissue during transit of waste through worm’s gut. On an overall, E. fetida proved to be the best on account of biomass increment as well as juveniles hatched when compared with the other earthworm species during the treatment. [ABSTRACT FROM AUTHOR]

Studies were conducted to undertake a physico-chemical analysis and to examine the bioavailability as well as the leachability of potential toxic elements during the rotary drum reactor composting of water fern with rice husk and cattle manure in different combinations. The highest temperature (54.2 °C) was measured in trial 3 (water fern, cattle manure and rice husk at a ratio of 6:3:1) during the process. The highest reductions of the moisture content and volatile solids were observed approximately 31.4 and 32.9%, respectively, in trial 3. The soluble biochemical oxygen demand (BOD) and the oxygen uptake rate of the compost in trial 3 indicated that the compost was stable after the process. The total concentrations of potential toxic elements (Zn, Cu, Mn, Fe, Ni} Pb, Cd and Cr) were increased in the process of composting. The total concentrations of the macronutrients in the final composts of different trials were increased by 1.4-2.0% for K, 1.1-1.3% for Ca and 0.76-0.82%. The highest reduction in the soluble BOD was found to be 82.4% in trial 3. Composting of water fern biomass with the appropriate ratio of cattle manure decreased the bioavailable and leachable forms of the potential toxic elements greatly. [ABSTRACT FROM AUTHOR]

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 CO 2 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. [Display omitted] • An optimized dual-stage biodegradation technique for expeditious stabilization of sewage sludge. • Marketable products and potential in global management facilities are derived by recycling sludge. • The biodegradation process was coherent in lowering the heavy metal contamination. • The end products applied to the soil evinced a positive role in plant growth. [ABSTRACT FROM AUTHOR]

• The study involved science-mapping technique for scientific reviewing of published literature. • Productive and influential journals, scholars, and countries dynamic in ecological modelling were synopsized. • Current topics of research were examined. • Gaps in current research were recognized. • Future research prospects were discussed through a scientific structure. The present study provides a scientific investigation of a detailed review of the published works in the domain of eutrophication-based ecological modelling till the year 2020. A total of 399 articles were extracted for final analyses, which were subjected to a three-step hierarchical procedure; Bibliographic examination, scientometric investigation, and qualitative assessment. The bibliographic test filtered 320 samples, based on which the article samples were subjected to several scientometric analyses, such as identifying the most influential and productive journals, researchers, articles, and countries. Keyword analysis revealed the most frequently used keywords in the research domain and amongst scholars around the world. The scientometric studies were followed by a qualitative assessment wherein the current trends in research were discussed. This was followed by identifying the critical gaps in research to provide future direction. Thus, this research offers a more comprehensive and holistic approach towards the critical review of the published literature, thereby providing essential insights to the researchers regarding the existing practices of developing eutrophication-based ecological models and the future prospects lying ahead. [ABSTRACT FROM AUTHOR]

Behaviour of heavy metals in the environment is widely acknowledged to be assessed by different physicochemical forms of presence rather than their overall concentration. In this study, Tessier 5-step sequential extraction technique was used to measure the trace metal (Mn, Cu, Zn, Fe, Pb, Co, Cd) fractions in surficial sediments in different seasons, in turn, analyse the risk posed by different fractions to the aquatic ecosystem. The findings reveal that residual fraction (F5) is in highest proportion (~44%) among the trace metals analysed. However, the proportion of carbonate and exchangeable fractions was comparatively higher (~24%), posing amajor risk to the aquatic ecosystem. Particle size v/s metal fraction scatter-plots showed that in the case of Cu, Fe and Mn, there is some form of both anthropogenic and natural pollution during the studied period, whereas, in rest of the metals, pollution is due to natural sources. Principal component analysis (PCA) led to the generation of 2 principal components (PCs), which accounted for approximately 80% of the total variance. PC1 and PC2 accounted for 45% and 35% of the total variance, respectively, which helped identify the pollution source as anthropogenic. Then, risk assessment code (RAC) revealed, Zn (41%), Mn (35%), Cu (35%), and Pb (27%) posed ahigher threat in drier months. In contrast, Co (40%) and Cd (48%) pose a higher threat with monsoon onset, showing variation of mobility of different metals in different seasons. Fe is the least mobile among the metals analysed, posing very little to the aquatic environment. Then, comparison with sediment quality guidelines (SQGs) reveals, although their potential hazard is high, they never surpass the SQGs. Thus, trace metal sediment contamination does not pose any risk to the river's aquatic environment in the present study but calls for stringent measures employment in river pollution abatement. [ABSTRACT FROM AUTHOR]

Highlights: [•] Pile composting of phumdi biomass with rice husks and cattle manure. [•] Low temperature profile as compared to water hyacinth composting. [•] Phumdi composting without addition of cattle manure is not effective. [•] Stable compost obtained after 30 days composting period. [ABSTRACT FROM AUTHOR]

The bioavailability and leachability of heavy metals play a major role in the toxicity of heavy metals in the compost applied for soil conditioning. A rotary drum composter was used for the study of heavy metal bioavailability and leachability during water hyacinth composting with a mixture of cattle manure, sawdust and lime. Lime was added in 1, 2 and 3% to the mixture of water hyacinth, cattle manure and sawdust at a ratio of 6:3:1 respectively. Influences of physico-chemical parameters on heavy metal bioavailability and leachability were studied during the process. The bioavailability of heavy metals solubility and diethylene triamine penta-acetic acid extractability was examined. The toxicity characteristics leaching procedure (TCLP) test was performed for assessing the hazardous properties of compost. The nutrients and the total concentration of heavy metals were increased during the composting process. The lime was very effective in reducing water solubility, plant availability and leachability of the selected heavy metals (Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr) during the process. The addition of lime provided a buffer against the decrease in pH and a sufficient amount of Ca that would improve the metabolic activity during composting. The addition of an excess amount of lime slowed the metabolic activity of the microbes due to its high alkalinity. The TCLP test confirms that the heavy metals concentrations in the control and in the lime-amended compost were below the threshold limits. [ABSTRACT FROM AUTHOR]

The presence of heavy metals in water hyacinth compost is the main limiting factor for its land application. Water hyacinth can accumulate heavy metals in its tissues. Application of natural zeolites (clinoptilolite) during water hyacinth composting may be helpful to immobilise heavy metals. The present study was carried out on the speciation of heavy metals (Zn, Cu, Mn, Fe, Pb, Ni, Cd and Cr) during rotary drum composting of water hyacinth mixed with cattle manure, sawdust and natural zeolite. The Tessier sequential extraction method was used for heavy metal speciation determination. The water hyacinth, cattle manure and sawdust at a ratio of 6:3:1 ratio was mixed with 5, 10 and 15% natural zeolite by weight. Influences of physicochemical parameters such as temperature, pH and organic matter degradation on speciation of heavy metals were studied during the process. A rotary drum composter has been shown to be highly efficient for organic matter degradation. The most bioavailable fractions (exchangeable and carbonate fractions) were reduced significantly due to the combined effects of zeolite addition and metal complexing with stabilised organic matter as a result of the high degradation of organic matter in a rotary drum. Ni, Pb and Cd were not found in the reducible and oxidisable fractions. Overall, the addition of an optimum quantity of natural zeolite significantly reduced the bioavailability fractions of heavy metals during rotary drum composting of the water hyacinth. [ABSTRACT FROM AUTHOR]

Highlights: [ • ] Vermicomposting of water hyacinth using Eisenia fetida. [•] Determination of physico-chemical parameters. [•] Evaluation of bioavailability factor and speciation of heavy metals. [ABSTRACT FROM AUTHOR]

Highlights: [•] Composting of water hyacinth with cattle manure, sawdust and lime. [•] Lime could enhance the composting temperature and organic matter degradation. [•] Lime can reduce the bioavailability and leachability of heavy metals. [•] The amount of lime should not be more than 2% in the composting. [•] Utilization of lime sludge in composting can help in waste minimization. [ABSTRACT FROM AUTHOR]

Abstract: Studies were carried out on bioavailability and leachability of heavy metals (Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr) during rotary drum composting of water hyacinth (Eichhornia crassipes) for 20 days. This study investigates the influence of physic-chemical parameters such as pH, temperature and organic matter content on distribution of heavy metal bioavailability and leachability during water hyacinth composting. The bioavailability was investigated in the form of water soluble and diethylenetriamine penta-acetic acid (DTPA) extractable. Results show that during composting, the total metal concentration was increased. Water soluble Ni, Cd and Pb and DTPA extractable Cd and Pb were not detected but all metal concentration were observed by TCLP test during the composting process. Leachability of Cd was very low among all the eight metals analyzed. The optimum proportion of cattle manure can enhance organic matter degradation and humification process; consequently it reduced the toxicity of metals during rotary drum composting. [Copyright &y& Elsevier]

The bioavailability and leachability of heavy metals is important role when considering their toxicity during composting following land application. Therefore, studies were carried out on Zn, Cu, Mn, Fe, Ni, Pb, Cd and Cr during 30 days agitated-pile composting of water hyacinth (Eichhornia crassipes). This study investigated the influence of parameters such as pH, temperature and organic matter content on the distribution of heavy metal bioavailability and leachability during composting of water hyacinth. Results showed that the contents of total metal concentration increased during the composting process. The bioavailability of heavy metals was investigated in the form of water soluble and diethylene triamine pentaacetic acid (DTPA) extractable. In the water soluble, DTPA and leachable Zn, Cu, Mn, Ni and Cr reduced but there was a gradual increase in the Fe concentration during the composting process. Furthermore, in water soluble and leachable Ni, Cd and Pb were not detected and in DTPA extractable Cd and Pb were also not detected during 30 days of composting. [ABSTRACT FROM AUTHOR]

Abstract: The Tessier sequential extraction method was employed to investigate the changes in heavy metals speciation (Zn, Cu, Mn, Fe, Pb, Ni, Cd and Cr) during water hyacinth (Eichhornia crassipes) composting. Results showed that, the contents of total metals concentration were increased during the composting process. The largest proportion of metals was found in the residual fraction which was in more stable form and is consequently considered unavailable for plant uptake. Reducible and oxidizable fractions of Ni, Pb and Cd were not found in all trials during water hyacinth composting. The concentrations of Cu and Cd were very low comparative to the other metals, but the percentage of exchangeable and carbonate fractions were similar as other metals. From this study it can be concluded that the appropriate proportion of cattle manure addition (Trial 4) significantly reduced the mobile and easily available fractions (exchangeable and carbonate fractions) during the composting process. [Copyright &y& Elsevier]

Abstract: High rate composting studies on institutional waste, i.e. vegetable wastes, tree leaves, etc., were conducted on a demonstration-scale (3.5m3) rotary drum composter by evaluating changes in some physico-chemical and biological parameters. During composting, higher temperature (60–70°C) at inlet zone and (50–60°C) at middle zone were achieved which resulted in high degradation in the drum. As a result, all parameters including TOC, C/N ratio, CO2 evolution and coliforms were decreased significantly within few days of composting. Within a week period, quality compost with total nitrogen (2.6%) and final total phosphorus (6g/kg) was achieved; but relatively higher final values of fecal coliforms and CO2 evolution, suggested further maturation. Thus, two conventional composting methods namely windrow (M1) and vermicomposting (M2) tried for maturation of primary stabilized compost. By examining these methods, it was suggested that M2 was found suitable in delivering fine grained, better quality matured compost within 20days of maturation period. [Copyright &y& Elsevier]

Effect of turning frequency on quality, namely some chemical characteristics (temperature, moisture content, pH, electrical conductivity, total organic matter, nitrogen dynamics, phosphorus and trace elements) and stability of compost (biochemical oxygen demand, chemical oxygen demand, rate of oxygen consumption and carbon dioxide evolution) in a rotary drum were studied. Composting was stimulated by three turns of rotary drum at different time intervals i.e. at the gap of 6h (Run A), 12h (Run B), 18h (Run C) and 24h (Run D) for 15d. It was observed that Run D (24h turning frequency) caused longer thermophilic phase (4d) with a higher rise at temperature 58°C; consequently, peak of maximum temperature was shifted along with the increase of turning frequency. Around 23% of available carbon in Run D was utilized by micro-organisms and contained lower final electrical conductivity (1.32dSm−1) possibly causing lesser phytotoxicity effects on the growth of plants. The percentage increase in total nitrogen and total phosphorus (organic and inorganic) in Run D was found to be 45% and 37% as compared to 7% and 17%, 6% and 32% and 18% and 30% in Run A, B, and C, respectively, indicating higher mineralization. The final values of respiration rates (CO2 evolution and oxygen uptake rate) for Run D was found to be the lowest, nevertheless, other runs also provided relatively stable compost. [Copyright &y& Elsevier]

Paper industry wastewater is considered a severe polluter of the environment because it contains various toxic pollutants that critically impact the aquatic and terrestrial ecosystems. The current study aimed to assess the bioremediation perspective of Pseudomonas putida strain to eliminate the hazardous pollutants of paper industry wastewater. The physico-chemical analysis of the treated wastewater showed that the Pseudomonas putida MTCC 7525, which secreted laccase enzyme, significantly reduced the pollution parameters such as EC, TDS, COD, phenols, TKN, TOC, lignin and color by 69, 87, 68, 97, 75, 85, 57 and 72%, respectively in comparison to the control. The organic pollutants in the wastewater samples were characterized and identified by GC-MS and FTIR analysis, which also showed that most of the toxic compounds were reduced following the bacterial treatment. The toxicity assessment of the wastewater was performed in terms of cyto-genotoxicity and phytotoxicity assay using onion and mung bean plants. The result of the toxicity study demonstrated that the toxic effect of the wastewater samples declined after the bacterial treatment. These results showed that Pseudomonas putida MTCC 7525 could be used effectively in the paper industry for bioremediation applications, thus minimizing the undesirable effects on the environment. [Display omitted] [ABSTRACT FROM AUTHOR]

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/gVS added (untreated - 3.9 L/gVS added). 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. • Electrokinetic pretreatment conditions optimized using CCD-RSM for improved biodegradability of petroleum refinery sludge. • The methane yield was enhanced by 69.2% after pretreatment. • O&G and TPH removal were 71% and 53% respectively after the anaerobic digestion process. • Net energy recovered was 10.9 folds higher than the expended energy. • The pretreatment technology illustrated superiority and potential for large-scale application. [ABSTRACT FROM AUTHOR]

• This study employed science-mapping approach for scientific reviewing of published literature. • Productive and influential journals, scholars, and countries active in water quality indexing were summarized. • Current topics of research were discussed. • Gaps in current research were identified. • Future research directions were proposed through a framework. Water quality has always remained paramount when it comes to sustainable development. The most convenient method of determining the health of a particular water body is through water quality indexing. Based on the filtered 2049 articles published, the present review-based study was conducted for a science-based mapping to evaluate the research in the domain of water quality indexing until 2020. A three-stage sequential process; bibliometric examination, scientometric investigation, and qualitative valuation resulted in the identification of the most influential and productive journals, researchers, articles, and countries dynamic in the research field. Keyword analysis further revealed that groundwater quality assessment for drinking water has been the key focus of research among scholars. The scientometric analysis was followed by a qualitative discussion on the current topics of research; mainly categorized into four classes, i.e., specific indices, human intervention, performance assessment and emerging technologies, and also highlighting some of the significant research gaps. This was followed by presenting a research framework wherein, plausible future directives were proposed. This study thus provides a more comprehensive picture on the existing researches carried out in the domain of water quality indexing, identifying the primary gaps and thereby providing multi-disciplinary guidance for various researchers and practitioners linked to the current research to the future. [ABSTRACT FROM AUTHOR]

• Kinetic study of plug flow anaerobic digestion of corn silage was studied. • Biogas generation rate and its yield increased first and then diminished. • Maximum biogas yield and k were obtained as 0.716 m3/kg and 0.0689 per day. • Developed kinetic model can be used to design the industrial plug flow reactor. Kinetic study of plug flow reactor digesting corn silage was studied under the mesophilic condition (37 ± 2 °C). The effect of organic loading rate (OLR) on biogas yield and its production was tested in a long-term experimental study. Both the biogas yield (0.68–0.39 m3/kg) and methane content in the biogas (66–58%) were reduced with the increase in OLR (3.5–8.5 kg VS /m3٠d). In this study, the maximum biogas yield (y m) as 0.716 m3/kg and first-order reaction rate constant (k) values as 0.0689 per day was obtained. The developed kinetic model could be used to design the dimension for a plug flow reactor digesting different organic wastes such as agricultural residue, animal manures, and biogas crops. [ABSTRACT FROM AUTHOR]

[Display omitted] • The RV technique was persistent in producing nutrient rich vermicompost in 27 days. • Initial thermophilic phase of RV degraded significant percentage of AIL. • RV technique was proven potential in management of lignocellulosic terrestrial weeds. • 20% vermicompost (w/w) amendment to soil has higher influence in over all plant growth. The present study investigates the biodegradation of two potentially toxic terrestrial weeds Parthenium hysterophorus and Lantana camara , implementing a novel two-stage biodegradation technique; Rotary drum composting followed by vermicomposting (RV). The RV approach was refined for a 7-day thermophilic degradation in an in-vessel rotary drum composter, followed by a 20-day mesophilic degradation utilizing Eisenia fetida and Eudrilus eugeniae vermi-monocultures. However, rotary drum composting (RDC) was performed for both the weeds (for 27 days), facilitating only initial thermophilic degradation to compare the efficacy of the RV technique. Lignocelluloses analysis revealed that cellulose degradation doubled during RV technique, indicating efficient biodegradation in reactors administered with E. fetida vermiculture compared to RDC (19.60 to 42.80% and 26.80 to 66.50% in P. hysterophorus and L. camara feedstocks). Further, these results also correlated with the X-Ray diffractograms of all trials showing the degradation of crystalline cellulose at 2θ: 20–50° for RV. Moreover, to ensure product safety, the analyzed total heavy metals content also unveiled the advantage of RV over RDC as validated by the accumulation of higher concentrations of zinc (45% and 33% in P. hysterophorus and L. camara feedstocks) and lead (55% and 45% in P. hysterophorus and L. camara feedstocks) in reactors with E. fetida. The material's seed germination index increased to 80% in the final product of all trials in the RV technique, indicating the diminishing of the phytotoxic nature. Subsequently, pot studies also indicated that the RV technique was coherent in managing noxious weeds. [ABSTRACT FROM AUTHOR]

The present study is aimed at investigating the change in surface morphology, hydraulic behaviour and sorption capability of two locally available Indian bentonites in the presence of different lead (Pb2+) concentrations. FESEM, FTIR, and EDX studies were conducted to analyse the change in surface morphology, alteration in FTIR pattern and decrease in exchangeable cation in both the bentonites before and after sorption of Pb2+. The tests were conducted in a batch mode to optimise operation parameters; pH, initial concentration, adsorbent dosage, and contact time. Equilibrium isotherm and sorption kinetics of both the bentonites were studied using various isotherm as well as kinetic models. The equilibrium data for both the bentonites were found to be the best fit for the Freundlich model. Both the bentonites followed Pseudo-second order equation. Hydraulic conductivity analysis illustrates that with the rise in Pb2+ concentration, the hydraulic conductivity increased for both the bentonite. The experimental evidence revealed that bentonite having high cation exchange capacity (CEC), swelling behaviour and high specific surface area (SSA) exhibits higher adsorption and heavy metal removal at 2000 mg/L of initial concentration of Pb2+ solution. [ABSTRACT FROM AUTHOR]