A hydroponics experiment was conducted to investigate the effect of iron plaque on root surfaces and selenium (Se) on the uptake and transfer of mercury (Hg) in rice seedlings by adding in the EDTA-Fe (0, 10, 30, 50, 70 mg Fe l⁻¹) into the solution to produce a different amount of iron plaque outside rice root. After 24 h, the red-brown iron plaque was formed on the root surface, and the amount of iron plaques was positively correlated with the amount of Fe in the solution. The iron plaque deposited on the root surface has a strong adsorption effect on the inorganic Hg. The addition of Se could promote the adsorption of Hg²⁺ on the iron plaque of rice, and the introduction of Se could increase the adsorption capacity of Hg on iron plaque on average by 1.42 times. The Hg was extracted by DCB (Dithionite-citrate-bicarbonate) up to between 66.2 and 67.8% of the total Hg when the roots with iron plaque (Fe70) were incubated with the combination of 5 μmol L⁻¹ of HgCl₂ and 5 μmol L⁻¹ of Na₂SeO₃ for an hour. After 3 days, the content of Hg in the iron plaque decreased to 6.3–33.9%, indicating that part of the inorganic Hg adsorbed by the iron plaque could be reabsorbed and used. Besides that, the iron plaque allowed the Hg to stay longer in the iron plaque, which hindered the transfer of Hg to the shoot significantly. Hg adsorbed in the iron plaque can be desorbed by low-molecular-weight organic acids, which was equivalent to desorption of Hg from ferric hydroxide oxides. Hg adsorbed on the iron plaque can be moved back to the rest of the plant. These results suggest that the iron plaque and Se in the root surface might play a role as “physical buffer” in the absorption and transfer of Hg.

One of the most undesired wastes is the human excreta due to the socio-environmental pressure. Otherwise, the nutriments contained in human excreta could be used as fertilizers to enrich the soil. Familial waterless litter composting toilets (FWLCT) are an alternative for locations where a centralized sewerage network cannot be provided or where there is a lack of standard urban infrastructure including roads, electricity, and water supply. The scientific researches on the composting techniques, the methods of control of the composting processors, and the rate of produced leachate are very limited. In this research, the composting systems included a feces and urine collection device. In each passage, the litter (carbonaceous material) is added to the excreta. Regularly, the buckets were emptied into a composting device located outside the house to which an additional portion of carbonaceous materials can be added. Monitoring was carried out on five rural and one urban familial composting areas in France for 1.5 years. The physiochemical and microbiological properties of the compost and leachate have been monitored and measured in compliance with the protocols. The results show that one of the main problems of this system of human excreta treatment is that the composting process does not achieve a significant rise in temperature and does not allow reaching the optimum temperatures (> 50 °C). Otherwise, from an agronomic point of view, the obtained compost is not rich enough in nutriments to be a good compost as soil fertilizer. But it can be used as a soil conditioner. The average leachate flux from the composters is 1.79 L/day. Because of the very short stay time in the piles, the leachate is contaminated by harmful bacteria and should be treated by another sanitation system.

Chromate can be reduced by methanotrophs in a membrane biofilm reactor (MBfR). In this study, we cultivated a Cr(VI)-reducing biofilm in a methane (CH₄)-based membrane biofilm batch reactor (MBBR) under anaerobic conditions. The Cr(VI) reduction rate increased to 0.28 mg/L day when the chromate concentration was ≤ 2.2 mg/L but declined sharply to 0.01 mg/L day when the Cr(VI) concentration increased to 6 mg/L. Isotope tracing experiments showed that part of the ¹³C-labeled CH₄ was transformed to ¹³CO₂, suggesting that the biofilm may reduce Cr(VI) by anaerobic methane oxidation (AnMO). Microbial community analysis showed that a methanogen, i.e., Methanobacterium, dominated in the biofilm, suggesting that this genus is probably capable of carrying out AnMO. The abundance of Methylomonas, an aerobic methanotroph, decreased significantly, while Meiothermus, a potential chromate-reducing bacterium, was enriched in the biofilm. Overall, the results showed that the anaerobic environment inhibited the activity of aerobic methanotrophs while promoting AnMO bacterial enrichment, and high Cr(VI) loading reduced Cr(VI) flux by inhibiting the methane oxidation process.

To identify the enzymes potentially useful for the decolorization of azo dyes, the secretome of the ascomycetous fungus Myrothecium roridum IM6482 was studied by using a bottom-up proteomic approach. Among the identified proteins, the most promising for dye removal was laccase, which decolorized respectively, 66, 91, 79, and 80% of Acid Blue 113 (AB 113), Acid Red 27 (AR 27), Direct Blue 14 (DB 14), and Acid Orange 7 (AO 7). The degradation of dyes was enhanced at the wide range of pH from 4 to 8. The addition of redox mediators allowed eliminating AB 113 in concentrations up to 400 mg/L and decolorization of the simulated textile effluent. Microbial toxicity and phytotoxicity tests indicated that dyes are converted into low-toxicity metabolites. This is the first insight into the M. roridum secretome, its identification and its application for removal of select azo dyes. Obtained results extended knowledge concerning biodegradative potential of ascomycetous, ligninolytic fungi and will contribute to the improvement of dye removal by fungi.

Giardia and Cryptosporidium have caused numerous outbreaks of diarrhea as a result of the ingestion of water contaminated with sewage. In Brazil, the efficiency of Giardia and Cryptosporidium removal by combined fixed-film systems has rarely been studied. The aims of the present study were therefore to verify the removal efficiency of Giardia and Cryptosporidium by a combined system (anaerobic/anoxic filter and aerated submerged biofilter) and to perform the genetic characterization of these parasites. The (oo)cysts were detected by centrifuge concentration and membrane filtration from raw sewage, effluents, adhered biomass, and sludge samples. Immunofluorescence assay and differential interference contrast microscopy were used for the visualization of the (oo)cysts. Nested PCR was applied to confirm Giardia and Cryptosporidium. Giardia and Cryptosporidium were detected in 27% and 5.5% of the 144 analyzed samples of raw sewage and effluents, respectively. A total of 33,000 cysts/L were recovered in the adhered biomass samples (n = 25) from different points of the aerated submerged biofilter, while 6000 oocysts/L were registered in a single point. An average of 11,800 cysts/L were found in the sludge samples (n = 5). The combined system exhibited a removal efficiency of Giardia cysts of 1.8 ± 1.0 log removal. The C and BIV assemblages of Giardia were identified in the raw sewage while AII was found in the treated effluent sample. It was not possible to calculate the removal efficiency of Cryptosporidium oocysts by the combined system. The combined system exhibited some potential as a suitable treatment for the removal of parasites from sewage.

Accurate prediction of suspended sediment concentration (SSC) carried by a river or watershed basin is essential for understanding the hydrology of basin in terms of water quality, river bed sustainability and aquatic habitats. In this study, four heuristic methods, namely, radial basis neural network (RBNN), self-organizing map neural network (SOMNN), least square support vector regression (LSSVR), and multivariate adaptive regression spline (MARS) were employed for daily SSC modeling at Ashti, Bamini, and Tekra stations located in Godavari River basin, Andhra Pradesh, India. The Gamma test (GT) was utilized for identifying the most significant input variables for the applied heuristic approaches. The results obtained by RBNN, SOMNN, LSSVR, and MARS models were compared with those of the traditional sediment rating curve (SRC). The performance of the models was evaluated based on the root mean square error (RMSE), coefficient of efficiency (COE), Pearson correlation coefficient (PCC), Willmott index (WI), and pooled average relative error (PARE) indices, as well as the visual inspection using line diagram, scatter diagram, and Taylor diagram (TD). The results of comparison revealed that the four heuristic methods gave higher accuracy than the SRC model. Among the heuristic models, the RBNN-3 (RMSE = 0.045, 0.062, 0.131 g/l; COE = 0.884, 0.883, 0.914; PCC = 0.955, 0.961, 0.958; and WI = 0.970, 0.963, 0.976) outperformed the other models in simulating daily SSC records in the studied stations.

Effectiveness of steam explosion (SE) pretreatment for deconstructing the complex structural carbohydrates (SC) and lignin recalcitrance properties of rice straw (RS) for conjunctive improvement of biofuel yield and waste valorization was evaluated. This work exhibited successful pretreatment of RS at a different pressure (1.2, 1.5, and 1.8 MPa) and retention (3, 6, 9, and 12 min) for enhancement of SC contribution to biomethane production. Regression analysis demonstrated that SE pretreatment efficiency improved at high-temperature and short-retention time for biodegradation of RS. Maximum cumulative methane yield (EMY) achieved 254.8 mL/gvs at 1.2 MPa (3 min) of SE-treated RS with 62.7% of very significant improvement compared with untreated RS (156.6 mL/gvs). Furthermore, solid fraction of xylose, arabinose, cellobiose, glucose, and acid-soluble lignin in SE-treated RS of 1.2 MPa (3 min) were biodegraded by 27.4%, 46.4%, 100%, 48.8%, and 14.1%, respectively, after anaerobic digestion. Therefore, SE pretreatment was an encouraging approach for enhancing SC conversion to biomethane and waste resource to circular economy.

Particulate-bound poly-aromatic hydrocarbons (PAHs) are of great concern due to their mutagenicity and carcinogenicity effect on human health. In this context, identification, quantification and inhalation cancer risk (ICR) assessment due to PM₁₀- and PM₂.₅-bound PAHs has been carried out at six monitoring stations in a critically polluted Jharia coalfield/Dhanbad City. Identification of pollution sources at study area has been performed by using PCA statistical methods. Air quality index (AQI) and air quality health index (AQHI) were calculated based on the concentration levels of PM₁₀. Location-wise direct comparison between AQI, AQHI and ICR was performed to analyse the risk levels. Consequently, maximum concentration levels of particulate (PM₂.₅ and PM₁₀)-bound total PAHs (400 and 482 ng/m³) were recorded at the monitoring station Lodna Thana, followed by Bank More and Sijua Stadium, respectively. It was also observed that mine fire-affected station Lodna Thana was exaggerated with presence of PAHs due to wood and open coal burning activities. Moreover, about 1000 and 889 cases of inhalation cancer risk were estimated due to direct exposure of PM₁₀- and PM₂.₅-bound PAHs in the study area, respectively. Active mine fire-affected station Lodna Thana was recorded with maximum probability of lung tumour due to inhalation cancer risk. This study has reported higher AQHI at station Dugdha Basti, Lodna Thana and Bank More, which results increased number of tumours due to ICR. This result concludes that Jharia coalfield/Dhanbad City are not only critically polluted area but it is also an inhalation cancer prone area due to direct exposure of active mine fire.

In the present work, the composite MgAl-LDH/biochar using activated carbon from bovine bone as support for the layered double hydroxide particles was successfully synthesised and used as an alternative adsorbent for caffeine removal from water. Kinetic studies showed that the equilibrium was achieved in only 20 min of contact between the adsorbent and the adsorbate. The pseudo-first-order model represented the experimental data more satisfactorily (R² = 0.95), suggesting a physical adsorption process. The isotherms were performed at three temperatures, in which it was observed the decrease in the adsorption in higher temperatures. It was obtained a maximum adsorption capacity of 26.219 mg/g at 40 °C, and the experimental data were better adjusted by Redlich–Peterson, R² > 0.9942. In short, the study demonstrated that the composite was satisfactorily synthesised and its use in the caffeine removal was quite attractive, being a potential adsorbent for water treatment applications.

Bioelectrochemical systems (BESs) including microbial electrolysis cells (MECs) and microbial fuel cells (MFCs) are promising for hexavalent chromium [Cr(VI)] reduction and total chromium (Cr) removal from wastewater. This study assessed the performance of simple, inexpensive, and continuous flow BESs with neither cathode catalyst nor proton exchange membrane for Cr(VI) reduction and total Cr removal. The effect of bioreactor configuration and wastewater feed mode on the performance of the BESs was investigated. Biological Cr(VI) reduction in the MEC followed a first-order kinetics with a rate constant of 0.103 d⁻¹, significantly higher than that of the control (0.033 d⁻¹). For comparison, the first-order reduction rate constants in the MFCs with the Cr(VI) fed to the anodic and the cathodic zones were 0.072 and 0.064 d⁻¹, respectively. The BESs improved total Cr removal through coprecipitating Cr(III) and phosphors as evidenced from the scanning electron microscopy energy-dispersive X-ray spectroscopy analysis. The total Cr removal efficiencies in the control, MFCs, and MEC were 26.1%, 56.7%, and 66.2%, respectively. Only 25.1% to 26.7% of total Cr was present intracellularly in the BESs (both MFCs and MEC), whereas 31.8% ± 1.4% and 38.0% ± 0.9% of total Cr in the anodic and cathodic zones of the control were present intracellularly. Overall, the BESs demonstrated a great potential to reduce Cr(VI) and remove total Cr with the MEC having the fastest Cr(VI) reduction and most efficient total Cr removal. Furthermore, the BESs significantly reduced the intracellular total Cr content.