The aim of this work was to investigate the biosorption of a cationic dye (methylene blue (MB)) by Salvinia minima. Biomass was characterized using the point of zero charge and scanning electron microscopy. The effects of pH (2–10), biosorbent dose (1–6 g/L), initial MB concentration (49.14 ± 1.03, 99.60 ± 0.67, 148.91 ± 2.00, 198.24 ± 1.91, 243.74 ± 2.32 mg/L), and time (20, 40, 60, 120, 180, 240, 300, 360 min) on MB biosorption and removal were evaluated. The MB biosorption kinetics were analyzed using pseudo-first- and pseudo-second-order kinetic models, as well as Elovich and intraparticle diffusion models, and Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms were used to analyze the equilibrium biosorption. A positive effect of pH on MB biosorption and removal was observed when pH was increased from 2 to 4 (28.18 ± 0.30 and 110 ± 0.05 mg/g, 23.20 ± 0.27 and 90.50 ± 0.01 %, respectively), while an increase in the biomass dose from 1 to 6 g/L reduced biosorbent efficiency from 157.30 ± 2.59 to 38.23 ± 0.02 mg/g. The adsorption kinetic data fit the pseudo-second-order equation, suggesting that chemisorption was the rate-determining step during MB biosorption by S. minima biomass. Equilibrium biosorption was described by the Freundlich model, implying that MB multilayers form on the heterogeneous surface of the biomass. S. minima biomass can be used as a biosorbent for the removal and adsorption of cationic dyes from water or wastewater.

The bacterial communities in the intestinal tracts of earthworm were isolated by culture-dependent approaches. In total, 72 cultures were isolated and purified from the gut of an earthworm under aerobic culture condition, out of which 25 isolates were laccase positive. Isolate 33, a good laccase producer was identified as Bacillus safensis DSKK5, using both biochemical and molecular approaches. It was found to produce maximum laccase activity at 0.75 % of wheat bran, 37 °C, and pH 6.2. Further, copper sulfate and copper chloride showed a maximum laccase production. In order to understand the affinity of binding and interaction between toxic dyes and bacterial laccase, homology models were generated. The resulted models were further validated and used for docking studies with commonly used industrial dyes. Molecular docking using CCDC GOLD software gave a good score with all the textile dyes. Further, validation using molsoft ICM software showed a good binding energy of −104.25, −106.00, −113.98, and −100.36, with commercial dyes, i.e., procion blue, procion green, procion red, and reactive yellow 86, respectively. Experimental data showed a maximum decolorization with procion green (85.66 %) and procion red (85.58 %), which validate the molsoft ICM results, i.e., −106.00 and −113.98, respectively.

Endocrine disruptor compounds (EDCs) are dangerous pollutants largely present in urban, industrial, and agricultural wastes, and through leaching and degradation from/of these matrices, they can reach and contaminate the environment. Bioremediation of polluted systems from EDCs using white rot fungi can be a valuable alternative approach with respect to conventional physical and chemical methods. These fungi have the capacity to biodegrade numerous phenolic contaminants with their unspecific extracellular ligninolytic enzymes. This study investigated the simultaneous removal of the xenoestrogens bisphenol A (BPA), ethynilestadiol (EE2), and 4-n-nonylphenol (NP), the herbicide linuron, and the insecticide dimethoate from a waste landfill leachate (LEACH) adopting a combination of adsorption and biodegradation. Trametes versicolor and Stereum hirsutum were inoculated, separately, on potato dextrose agar alone or added with different adsorbent materials of low cost and wide availability. The substrates with the fungus were superimposed on the contaminated LEACH. The control used was the LEACH overlaid by not inoculated potato dextrose agar. Both fungi showed an adequate tolerance to LEACH. In a period of 20 days, T. versicolor growing on the various substrates removed almost 100 % of BPA, EE2, NP, and linuron, and from 59 to 97 % of dimethoate. S. hirsutum showed a marked degrading activity only towards NP, which was totally removed after 20 days or less with any substrate and, to a lesser extent, linuron. Even in the absence of fungus, the methodology adopted achieved a relevant contaminant removal, with the only exception of the very hydrophilic dimethoate.

Major ion chemistry (2000–2009) from 208 lakes (342 sample dates and 600 samples) in class I and II wilderness areas of the Sierra Nevada was used in the Steady-State Water Chemistry (SSWC) model to estimate critical loads for acid deposition and investigate the current vulnerability of high elevation lakes to acid deposition. The majority of the lakes were dilute (mean specific conductance = 8.0 μS cm⁻¹) and characterized by low acid neutralizing capacity (ANC; mean = 56.8 μeq L⁻¹). Two variants of the SSWC model were employed: (1) one model used the F-factor and (2) the alternate model used empirical estimates of atmospheric deposition and mineral weathering rates. A comparison between the results from both model variants resulted in a nearly 1:1 slope and an R²value of 0.98, suggesting that the deposition and mineral weathering rates used were appropriate. Using an ANCₗᵢₘᵢₜof 10 μeq L⁻¹, both models predicted a median critical load value of 149 eq ha⁻¹ year⁻¹of H⁺for granitic catchments. Median exceedances for the empirical approach and F-factor approach were −81 and −77 eq ha⁻¹ year⁻¹, respectively. Based on the F-factor and empirical models, 36 (17 %) and 34 (16 %) lakes exceeded their critical loads for acid deposition. Our analyses suggest that high elevation lakes in the Sierra Nevada have not fully recovered from the effects of acid deposition despite substantial improvement in air quality since the 1970s.

With more and more emerging organic contaminants (EOCs) detected in the soil and groundwater, researches on interactions between these pollutants and soils or aquifer materials have attracted greater concerns. In this study, the removal of chlorpheniramine maleate (CP), an antihistamine drug used to treat rhinitis and urticaria, by birnessite, which is a common layered manganese oxide, in aqueous solution was investigated by batch studies, X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analyses, and molecular simulations. The quantum mechanics simulation showed that the final energy of the interaction between CP and the (010) edge surfaces under a strong alkaline condition was much smaller than that under a neutral to slightly alkaline condition. A higher CP adsorption were achieved from neutral to weak alkaline solution, as the broken bond effect of birnessite was strongly influenced by solution pH by protonation and deprotonation of birnessite edges.

The aim of the present study is to investigate the effects of operating conditions and establish the mechanism of xanthene dye removal from aqueous solutions by electrocoagulation (EC) using a batch-stirred cell operated under galvanostatic regime. The influence of the operating parameters such as: initial pH and dye concentration, electrolysis time, current density, electrode configuration, and electrical current type on the EC performances was investigated. EC tests were performed at current density values ranging from 45 to 109 A/m, initial dye concentrations ranged between 0.1 and 1 g/L, and initial pH values adjusted in the range from 3 to 9. The effects of several electrode configurations (aluminum–aluminum, mild steel–mild steel, and aluminum–mild steel) and current regimes (direct current and alternating pulsed current) on the removal efficiency and energy and material consumption are also discussed. Total organic carbon (TOC) analysis, UV–vis spectroscopy, Fourier transform infrared spectroscopy (FTIR), and cyclic voltammetry (CV) were employed in order to elucidate the decolorization mechanism of Rhodamine 6G (R6G) dye by EC in aqueous solutions. With this aim in view, chemical coagulation tests were also carried out. The best performance was obtained when the EC process was conducted with iron-based electrode configuration in alternative pulse current (APC) mode. It was found that the removal of R6G is due to the co-precipitation of polymeric iron flocs with the phenyl-xanthene radicals remained in the bulk solution after the demethylation and deamination processes. Furthermore, the flocs are separated by flotation with the support of the molecular hydrogen generated at the cathode (in particular at relatively high values of current density) or by sedimentation.

Biochar produced from malt spent rootlets was employed for the removal of Hg(II) from pure aqueous solutions. Batch experiments were conducted at 25 °C. The optimum pH value for Hg(II) sorption onto biochar was 5. Biomass dose and contact time were examined to determine sorption kinetics and equilibrium capacity constants. The increase of biochar dose resulted in higher sorption efficiency. After a 24-h contact time at biochar concentrations of 0.3 and 1 g/L, the Hg(II) removal was 71 and 100 %, respectively. Based on the sorption kinetic data, the biochar sorption capacity for mercury reached its maximum after 2 h; 33 % of Hg(II) was removed within the first 5 min. Based on the isotherm data, the maximum biochar sorption capacity for Hg(II) was 103 mg/g. Finally, HCl, EDTA, NaCl, HNO₃, H₂SO₄, and distilled water leaching solutions were tested for Hg(II) desorption with HCl being the most effective.

A simple strategy and method is presented to monitor NO₂ health standards in busy streets of middle large South East Asian cities.

Drinking water network is vulnerable to toxic chemicals. Anomaly detection-based event detection can provide reliable indication of contamination by analyzing the real-time water quality data, collected by online-distributed sensors in water network. This article reviews the water quality event detection methodologies based on the correlation of water quality parameters and contaminants. Further, we review how to reduce the impact of contamination in water distribution network, including sensor placement optimization and contamination source determination.

A soil core collected in a tidal freshwater marsh in the Waccamaw National Wildlife Refuge (Georgetown, SC) exuded a particularly strong odor of cow manure upon extrusion. In order to test for manure and determine its provenance, we carried out microbial source tracking using DNA markers for Bacteroides, a noncoliform, anaerobic bacterial group that represents a large proportion spectrum of the fecal population. Three core sections from 0–3 cm, 9–12 cm, and 30–33 cm were analyzed for the presence of Bacteroides. The ages of core sediments were estimated using²¹⁰Pb and¹³⁷Cs dating. All three core sections tested positive for Bacteroides DNA markers related to cow or deer feces. Because cow manure is stockpiled, used as fertilizer, and a source of direct contamination in the Great Pee Dee River/Winyah Bay watershed, it is very likely the source of the Bacteroides that was deposited on the marsh. The mid-points of the core sections were dated as follows: 0–3 cm, 2009; 9–12 cm, 1999, and 30–33 cm, 1961. The presence of Bacteroides at different depths/ages in the soil profile indicates that soils in tidal freshwater marshes are, at the least, capable of being short-term sinks for Bacteroides and, may have the potential to be long-term sinks of stable, naturalized populations.