Enterobacter sp. HIT-SHJ4 isolated from wetland with carbon, nitrogen and sulfur co-metabolism and its implication for bioremediation.

Both autotrophic and heterotrophic denitrification are known as important bioprocesses of microbe-mediated nitrogen cycle in natural ecosystems. Actually, mixotrophic denitrification co-driven by organic matter and reduced sulfur substances are also common, especially in hypoxic environments such as estuarine sediments. However, carbon, nitrogen and sulfur co-metabolism during mixotrophic denitrification in natural water ecosystems has rarely been reported in detail. Therefore, this study investigated the co-metabolism of carbon, nitrogen and sulfur using samples collected from four distinct natural water ecosystems. Results demonstrated that samples from various sources all exhibited the ability for co-metabolism of carbon, nitrogen and sulfur. Microbial community analysis showed that Pseudomonas and Paracoccus were dominant bacteria ranging from 65.6% to 75.5% in mixotrophic environment. Enterobacter sp. HIT-SHJ4, a mixotrophic denitrifying strain which owned the capacity for co-metabolism of carbon, nitrogen and sulfur, was isolated and reported here for the first time. The strain preferred methanol as its carbon source and demonstrated remarkable efficiency for removing sulfide and nitrate with below 100 mg/L sulfide. Under weak acid conditions (pH 6.5-7.0), it exhibited enhanced capability in converting sulfide to elemental sulfur. Its bioactivity was evident within a temperature from 25 °C to 40 °C and C/N ratios from 0.75 to 3. This study confirmed the widespread presence of microbial-mediated synergistic carbon, nitrogen and sulfur metabolism in natural aquatic ecosystems. HIT-SHJ4 emerges as a novel strain, shedding light on carbon, nitrogen and sulfur co-metabolism in natural water bodies. Furthermore, it also serves as a promising candidate microorganism for in-situ ecological remediation, particularly in dealing with contamination posed by nitrate, sulfide, and organic matter.

Identifying the optimal type and locations of natural water retention measures using spatial modeling and cost-benefit analysis.

Water management has shifted from solely technical and engineering approaches towards nature-based solutions (NBS), like natural water retention measures (NWRM), offering benefits beyond hydrology, such as improved well-being and biodiversity conservation. Determining the best type and location of these measures is challenging due to diverse options with varying benefits and effects depending on measure type and location characteristics. While most studies regarding the optimal allocation and implementation of NBS focus on the urban environment, this study presents a methodology for decision-makers focusing on inter-urban regions with limited data on NWRM implementation. Through hydrological modeling and cost-benefit analysis (CBA), we identify Pareto optimal NWRM sites and types, considering water quantity and quality alongside economic, environmental, and social objectives. We defined optimal locations that seek the most significant reduction of runoff, sediment, and pollutants, whilst optimal NWRM types are defined to seek the most cost-effective measures based on hydrological, ecological, and social criteria. Using the Open Non-point Source Pollution and Erosion Comparison Tool (OpenNSPECT), we simulated increased infiltration in different inter-urban areas and identified the optimal placement. The criteria for selecting suitable NWRM types for the identified areas are derived from the EU Directorate General for the Environment (DG-ENV) NWRM database. The results show different effective areas for reducing runoff, sediment, and pollutants. While one NWRM (natural bank stabilization) was identified as most beneficial for reducing sediment, several measures were selected for runoff reduction. Interestingly, measures with high potential for pollutant reduction seem to offer limited social and biodiversity benefits, suggesting conflicting objectives and highlighting the importance of accounting for multiple criteria. By employing simplified models and qualitative benefit assessments, this paper presents a practical decision-making approach to facilitate NWRM implementation in data-scarce areas.

Reinvestigation on the Mechanism for Algae Inactivation by the Ultraviolet/Peracetic Acid Process: Role of Reactive Species and Performance in Natural Water.

This study provided an in-depth understanding of enhanced algae inactivation by combining ultraviolet and peracetic acid (UV/PAA) and selecting Microcystis aeruginosa as the target algae species. The electron paramagnetic resonance (EPR) tests and scavenging experiments provided direct evidence on the formed reactive species (RSs) and indicated the dominant role of RSs including singlet oxygen (1O2) and hydroxyl (HO•) and organic (RO•) radicals in algae inactivation. Based on the algae inactivation kinetic model and the determined steady-state concentration of RSs, the contribution of RSs was quantitatively assessed with the second-order rate constants for the inactivation of algae by HO•, RO•, and 1O2 of 2.67 × 109, 3.44 × 1010, and 1.72 × 109 M-1 s-1, respectively. Afterward, the coexisting bi/carbonate, acting as a shuttle, that promotes the transformation from HO• to RO• was evidenced to account for the better performance of the UV/PAA system in algae inactivation under the natural water background. Subsequently, along with the evaluation of the UV/PAA preoxidation to modify coagulation-sedimentation, the possible application of the UV/PAA process for algae removal was advanced.

Oxygen micro-nanobubbles for mitigating eutrophication induced sediment pollution in freshwater bodies.

Sediment hypoxia is a growing problem and has negative ecological impacts on the aquatic ecosystem. Hypoxia can disturb the biodiversity and biogeochemical cycles of both phosphorus (P) and nitrogen (N) in water columns and sediments. Anthropogenic eutrophication and internal nutrient release from lakebed sediment accelerate hypoxia to form a dead zone. Thus, sediment hypoxia mitigation is necessary for ecological restoration and sustainable development. Conventional aeration practices to control sediment hypoxia, are not effective due to high cost, sediment disturbance and less sustainability. Owing to high solubility and stability, micro-nanobubbles (MNBs) offer several advantages over conventional water and wastewater treatment practices. Clay loaded oxygen micro-nanobubbles (OMNBs) can be delivered into deep water sediment by gravity and settling. Nanobubble technology provides a promising route for cost-effective oxygen delivery in large natural water systems. OMNBs also have the immense potential to manipulate biochemical pathways and microbial processes for remediating sediment pollution in natural waters. This review article aims to analyze recent trends employing OMNBs loaded materials to mitigate sediment hypoxia and subsequent pollution. The first part of the review highlights various minerals/materials used for the delivery of OMNBs into benthic sediments of freshwater bodies. Release of OMNBs at hypoxic sediment water interphase (SWI) can provide significant dissolved oxygen (DO) to remediate hypoxia induced sediment pollution Second part of the manuscript unveils the impacts of OMNBs on sediment pollutants (e.g., methylmercury, arsenic, and greenhouse gases) remediation and microbial processes for improved biogeochemical cycles. The review article will facilitate environmental engineers and ecologists to control sediment pollution along with ecological restoration.

A Low-Cost Colorimetric Assay for the Analytical Determination of Copper Ions with Consumer Electronic Imaging Devices in Natural Water Samples.

This study reports a new approach for the determination of copper ions in water samples that exploits the complexation reaction with diethyldithiocarbamate (DDTC) and uses widely available imaging devices (i.e., flatbed scanners or smartphones) as detectors. Specifically, the proposed approach is based on the ability of DDTC to bind to copper ions and form a stable Cu-DDTC complex with a distinctive yellow color detected with the camera of a smartphone in a 96-well plate. The color intensity of the formed complex is linearly proportional to the concentration of copper ions, resulting in its accurate colorimetric determination. The proposed analytical procedure for the determination of Cu2+ was easy to perform, rapid, and applicable with inexpensive and commercially available materials and reagents. Many parameters related to such an analytical determination were optimized, and a study of interfering ions present in the water samples was also carried out. Additionally, even low copper levels could be noticed by the naked eye. The assay performed was successfully applied to the determination of Cu2+ in river, tap, and bottled water samples with detection limits as low as 1.4 µM, good recoveries (89.0-109.6%), adequate reproducibility (0.6-6.1%), and high selectivity over other ions present in the water samples.

Natural Zeolites for the Sorption of Ammonium: Breakthrough Curve Evaluation and Modeling.

The excessive use of ammonium fertilizer and its associated leakage threatens aquatic environments around the world. With a focus on the treatment of drinking water, the scope of this study was to evaluate and model the breakthrough curves for NH4+ in zeolite-filled, fixed-bed columns. Breakthrough experiments were performed in single- and multi-sorbate systems with the initial K+ and NH4+ concentrations set to 0.7 mmol/L. Breakthrough curves were successfully modeled by applying the linear driving force (LDF) and Thomas models. Batch experiments revealed that a good description of NH4+ sorption was provided by the Freundlich sorption model (R2 = 0.99), while unfavorable sorption was determined for K+ (nF = 2.19). Intraparticle diffusion was identified as the rate limiting step for NH4+ and K+ during breakthrough. Compared to ultrapure water, the use of tap, river, and groundwater matrices decreased the treated bed volumes by between 25% and 69%-as measured at a NH4+ breakthrough level of 50%. The concentrations of K+ and of dissolved organic carbon (DOC) were identified as the main parameters that determine NH4+ sorption in zeolite-filled, fixed-bed columns. Based on our results, the LDF and Thomas models are promising tools to predict the breakthrough curves of NH4+ in zeolite-filled, fixed-bed columns.

Selective Detection of Mg2+ for Sensing Applications in Drinking Water.

A new series of ligands containing the 2-(2-hydroxy-3- naphthyl)-4-methylbenzoxazole (HNBO) fluorophore showed selectivity for Mg2+ ions, without the interference of Ca2+ . The most promising representative L3 resulted the best performing sensor for Mg2+ both in solution and embedded in an all-solid-state optode, especially towards real samples of drinkable water.

Propylimidazole Functionalized Coumarin Derivative as Dual Responsive Fluorescent Chemoprobe for Picric Acid and Fe3+ Recognition: DFT and Natural Spring Water Applications.

A propylimidazole functionalized coumarin derivative (IPC) was fabricated for the first time and applied as a dual responsive fluorescent chemoprobe for sensitive and selective recognition of picric acid (PA) and Fe3+. Strong fluorescence quenching phenomena of the IPC were observed in H2O/ACN (5/95, v/v) medium (λem=408 nm) upon the additions of Fe3+or PA. The fabricated dual responsive IPC offered good selectivity and sensitivity with the low limit of detection values (0.92 µM for PA and 0.22 µM for Fe3+) lower than the acceptable amounts of Fe3+ and PA by the international official authorities. The validation study for the chemoprobe IPC for PA and Fe3+ was also performed. The interaction phenomena of IPC with PA and Fe3+ based on the findings of a range of experiments were considered and DFT computations were done to verify their recognition mechanisms. The sensing phenomena of IPC towards PA (1:1) and Fe3+ (3:1) were confirmed by the MALDI TOF-MS, FT-IR, 1H-NMR titration and Job's methods. Furthermore, the compound IPC was effectively applied as a fluorescent sensor for Fe3+ and PA detection in real natural spring water samples.

In-situ rapid monitoring of nitrate in urban water bodies using Fourier transform infrared attenuated total reflectance spectroscopy (FTIR-ATR) coupled with deconvolution algorithm.

Urban river and lake systems show important ecological function, and eutrophication frequently occurs and results from human activities due to the limited self-regulating ability. Since nitrate (NO3-) is one of the key factors causing water eutrophication, its rapid qualification plays critical role in the eutrophication control and management. In this study, water samples were collected from typical water bodies from Nanjing in different seasons, and Fourier transform infrared attenuated total reflectance spectroscopy (FTIR-ATR) was employed for the quantitative determination of NO3- coupled with algorithms of deconvolution and partial least squares regression (PLSR). Results indicated that the typical absorption band of NO3- at 1500-1200 cm-1 was observed and the intensity of the band around 1360 cm-1 was positively correlated with the concentration of NO3- through spectra deconvolution. PLSR models were established based on the deconvolution spectra, which were excellent with the correlation coefficients (R2) of more than 0.8886 and the ratio of prediction to deviation (RPD) of more than 2.76; it was found that the carbonate in water might impact the prediction due to its absorption around 1450 cm-1, but the prediction model performed well in condition that the carbonate content in a low level with less than 10 mg L-1. Significant temporal and spatial variations of NO3- were observed in the typical water bodies, and the Qinhuai River having the highest NO3- content, which mainly was influenced by human activities, and the impact of water pH and temperature were not significantly observed. Therefore, FTIR-ATR combined with deconvolution and PLSR, allowed a rapid determination of NO3- in urban water bodies, providing an alternative option for the monitoring of nitrate in natural water body, which will benefit the prevention and control of eutrophication.

Detection of Atrazine and Its Metabolites in Natural Water Samples Using Photonic Molecularly Imprinted Sensors.

In a previous study, photonic-based molecularly imprinted polymers (MIPs) were fabricated using atrazine (ATZ) and its metabolites, desethylatrazine (DEA) and desisopropylatrazine (DIA), as templates in separate matrices. For the purposes of monitoring the abovementioned molecules in natural waters, the effect of natural waters-featuring ionic strength and natural organic matter (NOM) on atrazine MIP-were studied in this work, and the photonic MIP was implemented for monitoring the target molecules in natural water samples collected from land in nearby farms in northeast of Columbia MO. Non-imprinted polymers (NIP) were also fabricated and applied in the experiments as a control test. In presence of NaCl, CaCl2, and NOM, MIPs presented lower responses by 26%, higher responses by 23%, and higher responses by 35%, respectively. NIPs response in terms of an increase or decrease was consistent with those of MIPs, but only for a lower percentage. MIPs response in natural waters-which were characterized for their physicochemical characteristics such as conductivity, total organic carbon content, etc.-provided a good approximation of the real concentrations obtained from the LCMS instrument; in general, they showed a good concordance, although large discrepancies occurred for some samples, which can be related to reproducibility issues in the manufacturing process or the presence of unknown interfering compounds in the real samples.

Statistical model applied in the qualitative and quantitative analysis of the relationships between environmental variables and cyanotoxin concentrations in tropical reservoirs.

This article presents the use of generalized additive model for location scale and shape (GAMLSS) in the qualitative and quantitative analysis of the relationships between environmental parameters and cyanotoxins in the tropical reservoirs of Colombia. The physicochemical parameters were evaluated on each of the cyanotoxins detected with levels high by ultra-high-performance liquid chromatography coupled to triple quadrupole mass spectrometry. The models showed a relation between cyanotoxins and the nutrients as soluble total Kjeldahl nitrogen (NTK), soluble phosphorus (soluble P), total phosphorus (total P), and nitrates (NO3-), among other nutrients that are necessary for the growth of organisms that produce toxins. This model confirms that the NTK and soluble P variables favor an increase in the concentration of MC-LR and MC-YR cyanotoxins in the Abreo Malpaso reservoir. The variables NO3- and dissolved O2 contribute to a higher concentration of MC-LR, MC-YR, and MC-ADRR cyanotoxins in the Peñol reservoir. Finally, the variable total P favors the increase in the concentration of MC-LR cyanotoxin and the variable dissolved O2 favors the increase in the concentration of cyanotoxin [D-Asp3, (E)-Dhb7] -MC-RR in the Playas reservoir.

Long-Term Toxicity of Gadolinium to the Freshwater Crustacean Daphnia magna.

The lanthanides are considered emerging contaminants but information on their long-term toxicity to aquatic species under environmentally relevant conditions is scarce. We aimed to fill this gap by evaluating the long-term adverse effects of gadolinium on the freshwater model-crustacean Daphnia magna. The exposure of D. magna for up to 39 days to 0.1 mg Gd/L (a 21-days chronic toxicity NOEC value derived by us formerly) in the lake water had no negative effect (p > 0.05) on vitality, size and reproduction of parent animals as well as their offspring. Thus, assumingly the current Gd contamination levels of surface waters pose no hazard to aquatic crustaceans that in general are very sensitive to various pollutants. Moreover, presence of 0.1 mg Gd/L in the lake water even mitigated the long-term toxic effect of 0.2 mg Ni/L (studied as a model co-contaminant) to D. magna's vitality and productivity.

Dithizone-functionalized C18 online solid-phase extraction-HPLC-ICP-MS for speciation of ultra-trace organic and inorganic mercury in cereals and environmental samples.

A simple and efficient dithizone-functionalized solid-phase extraction (SPE) procedure, online coupled with high-performance liquid chromatography (HPLC)-inductively coupled plasma mass spectrometry, was developed for the first time for enrichment and determination of ultra-trace mercury (Hg) species (inorganic divalent Hg (Hg(II)), methylmercury (CH3Hg(II)) and ethylmercury (C2H5Hg(II)) in cereals and environmental samples. In the proposed method, functionalization of the commercial C18 column with dithizone, enrichment, and elution of the above Hg species can be completed online with the developed SPE device. A simple solution of 2-mercaptoethanol (1% (V/V)) could be used as an eluent for both the SPE and HPLC separation of Hg species, significantly simplifying the method and instrumentation. The online SPE method was optimized by varying dithizone dose, 2-mercaptoethanol concentration, and sample volume. In addition, the effect of pH, coexisting interfering ions, and salt effect on the enrichment was also discussed. Under the optimized conditions, the detection limits of Hg species for 5 mL water sample were 0.15 ng/L for Hg(II), 0.07 ng/L for CH3Hg(II), and 0.04 ng/L for C2H5Hg(II) with recoveries in the range of 85%-100%. The developed dithizone-functionalized C18 SPE column can be reused after a single functionalization, which significantly simplifies the enrichment step. Moreover, the stability of Hg species enriched on the SPE column demonstrated its suitability for field sampling of Hg species for later laboratory analysis. This environment-friendly method offers a robust tool to detect ultra-trace Hg species in cereals and environmental samples.

UV-254 degradation of nicotine in natural waters and leachates produced from cigarette butts and heat-not-burn tobacco products.

Nicotine is an important emerging contaminant widely detected in water resources. The main nicotine sources are human excretions from users and leaching from discarded tobacco product waste, which represents the most commonly littered item in urban areas and coasts. In this study, the UV254 photolytical fate of nicotine in natural water and leachates produced from conventional cigarettes (CCs) and the new generation heat-not-burn (HnBs) tobacco products is examined for the first time. The effect of UV254 irradiation on nicotine depletion in ultrapure water was initially studied. The reaction was pseudo first-order with respect to nicotine concentration at low concentrations and shifted to lower order at higher concentrations, an effect associated to absorption saturation. Although nicotine removal was fast, only 9.5% of the total organic carbon was removed after irradiation due to the formation of by-products. The chemical structures of six photo-products were derived by means of liquid and gas chromatography coupled to mass spectrometry. The photodegradation kinetics was found to depend on pH and faster kinetics were recorded when the monoprotonated form of nicotine was dominant (pH = 5-8). The presence of humic acids was found to slightly delay kinetics as they competed with nicotine for lamp irradiance, whereas the presence of salt had no effect on the direct photolysis of nicotine. Direct photolysis studies were also performed using natural waters. Compared to ultra-pure water, photodegradation was found to proceed slightly slower in river water, in similar kinetics in seawater, and relatively faster in rain water. The later was assumed to be due to the lower pH compared to the rest of the natural water tested. Leachates from used HnBs and smoked CCs were also submitted to UV254 irradiation and direct photolysis was found to proceed fast despite the high complexity of these matrices. Nonetheless, the total organic carbon in the system remained the same after irradiation due to the abundance of organics and photo-products formed. We take advantage of the present investigations and report the leaching behavior of nicotine from HnBs and CCs. Among others, we found that in HnBs ~70% of the total and bioavailable nicotine content remains in the tobacco sticks after operation and this percentage drops to 15% in CCs due to the reduction in mass after smoking. This finding demonstrated the importance of properly disposing tobacco product waste to prevent nicotine leaching in water bodies.

A thin-layer solid-phase extraction-liquid film elution technique used for the enrichment of polycyclic aromatic hydrocarbons in water.

In this article, we propose a novel microsolid-phase extraction and elution technique, which we called the thin-layer solid-phase extraction-liquid film elution technique. The thin-layer solid-phase extraction phase is an octadecylsilylated sol gel- coated porous silica thin film prepared on the outer wall of a test tube, which has a larger surface area for the extraction of the target compounds compared to a conventional solid-phase microextraction phase. After optimization of the extraction procedure for five types of polycyclic aromatic hydrocarbons, the liquid film elution technique was investigated. Liquid film elution is an elution technique wherein the compounds extracted into the thin-layer solid-phase extraction phase are eluted using a small volume of solvent film formed around the extraction phase. The results show that the elution can be carried out using 150 µL of eluent. Enrichment factors between 20 and 34 were obtained for polycyclic aromatic hydrocarbons containing more than four aromatic rings in 10 mL aliquots of aqueous samples. Finally, recoveries of 85-112% were obtained for polycyclic aromatic hydrocarbons containing more than four aromatic rings from spiked natural water samples using the thin-layer solid-phase extraction-liquid film elution technique.

The feasibility of recycling drinking water treatment residue as suspended substrate for the removal of excess P and N from natural water.

Eutrophication of natural water commonly involves the pollution of both P and N. Here, we developed a new application of drinking water treatment residuals (DWTRs) for suspensions that permits the simultaneous removal of excess P and N from natural water and demonstrates that DWTRs recycling can provide a means for eutrophication control. Based on 364-day continuous flow tests, the suspension application of DWTRs effectively adsorbed P from overlying water under various conditions, decreasing total P concentrations from 0.0739 ± 0.0462 to 0.0111 ± 0.0079-0.0149 ± 0.0106 mg L-1, which achieved a class Ⅱ level of the China surface water quality standards during the tests. The total N concentrations were also reduced from 1.46 ± 0.63-1.52 ± 0.63 to 0.435 ± 0.185-0.495 ± 0.198 mg L-1, which achieved a class Ⅲ level during the stable stage of the tests. N removal was closely related to doses of DWTRs and aeration intensities. Effective N removal was mediated by the enriched microbial communities in the suspended DWTRs with simple, stable, and resilient networks, including many taxa associated with the N cycle (e.g., Rhodoplanes, Brevibacillus, and Pseudomonas). Further analysis indicated that both effective P adsorption and functional microbial community construction were closely related to Fe and Al in DWTRs. Suspension application prevented the burial effect of solids sinking from overlying water, which aided the ability of DWTRs to control pollution, and is potentially applicable to other materials for natural water remediation.

Occurrence and fate of antibiotics, antimicrobial resistance determinants and potential human pathogens in a wastewater treatment plant and their effects on receiving waters in Nanjing, China.

Antibiotics, antimicrobial resistance determinants and human pathogens are new types of environmental pollutants that pose a great threat to human health. Wastewater treatment plants (WWTPs) are important sources of novel pollutants; however, few studies have investigated their impact on surrounding natural water. Therefore, this study used a WWTP as the entry point to explore WWTP removal efficiency of antibiotics, antimicrobial resistance determinants and human pathogens and further analyze the impact of WWTP effluent on receiving waters. The investigated WWTP had a good removal effect on fluoroquinolones, macrolides, lincomycin, sulfanilamide, tetracycline and chloramphenicol antibiotics in wastewater, and the concentration of antibiotics in the WWTP's effluent was reduced by >80% relative to the influent. In addition to cmlA, the effect of the WWTP on antimicrobial resistance determinants removal was poor, although the effluent from the WWTP had no effect on the abundance of antimicrobial resistance determinants in the receiving water. However, with the dilution of receiving water, the abundance of antimicrobial resistance determinants gradually decreased. The WWTP could reduce the abundance of bacteria by 1000 times from influent water to effluent water. The major bacteria in the influent and effluent were Bacteroidetes and Proteobacteria. After effluent is discharged into receiving water, Cyanobacteria proliferate in large quantities, which can affect the microbial structure in the environment.The abundance of Acinetobacter, which was the predominant potential human pathogen in local wastewater, decreased dramatically after wastewater treatment. We also conducted an ecological risk assessment of the antibiotics identified and found that the ecological risk AZM and CLR posed to aquatic organisms was high. Overall, we identified the efficiency of WWTP control of antibiotics, antimicrobial resistance determinants and potential human pathogens and the impact of WWTP effluent on receiving water and provided data to support the control of the investigated pollutants.

Assessment of heavy metal contamination in natural waters of Dereli, Giresun: an area containing mineral deposits in northeastern Turkey.

The concentration of heavy metals in the natural waters of the area surrounding Dereli (Giresun), a mineralized area, was determined. In addition, the physicochemical parameters (such as pH, Eh, and HCO3-) influencing the concentration of dissolved metals in waters were evaluated. Samples were collected from stream, spring, and main river waters, some of which are used by local residents for drinking, fish farming, and animal husbandry. The present data indicate that the water-rock interaction is the main process controlling the chemical composition of waters in the area. The waters are predominantly CaMgHCO3-type waters with alkaline pH values. Heavy metal concentrations (Pb, Zn, Cu, Fe, Mn, U, Cd, As, Hg, Sb, Ni, Co, and Ba) in waters were generally low. Relatively high values of certain metals were determined in waters of the Kotana and Kurtulmus sites of Dereli. The levels of Pb in the river, stream, and spring water samples in these sites were somewhat higher than the Pb values reported in the literature for natural waters. However, these values only slightly exceeded the Pb water limit values proposed by the USEPA and the WHO. In addition, the concentrations of other heavy metals, except Pb, were fairly similar to those of other natural waters and these values were also under the drinking water limits set by the WHO and the USEPA. This study shows that waters in the area of Dereli were not significantly affected by mineralization. This is most likely caused by the bicarbonate-rich waters affecting the dissolved metal concentrations.

Synthesis of novel adsorbent by intercalation of biopolymer in LDH for the removal of arsenic from synthetic and natural water.

This study focuses on the synthesis of nanocomposites named CCA and CZA that were prepared by the incorporation of cellulose (CL) in the Ca/Al and Zn/Al layered double hydroxide (LDH), respectively. These materials were then used for the uptake of As(III) and As(V) from aqueous medium. Characterization of both nanocomposites (CCA and CZA) was done using FTIR and Raman analysis to identify the functional groups, N2 adsorption-desorption isotherms to determine the specific surface area and pore geometry and XPS analysis to obtain the surface atomic composition. Some other characters were investigated using simultaneous TGA and DTA and elemental chemical analysis (CHNS/O). The crystallinity of the prepared nanocomposites was displayed by XRD patterns. Furthermore, the sheet-like structure of the LDHs and the irregularity of surface morphology with porous structure were observed by TEM and SEM microphotographs. Optimization of maximum adsorption capacity was adjusted using different parameters including pH, contact time and adsorbent dosage. The pseudo-second-order model was in good fitting with kinetics results. The adsorption isotherm results showed that CZA exhibits better adsorption capacity for As(III) than CCA and the Langmuir isotherm model described the data well for both nanocomposites. Thermodynamic studies illustrated the endothermic nature of CCA and exothermic nature on CZA, as well as the fact that the adsorption process is spontaneous. A real water sample collected from well located in Gabes (Tunisia), has also been treated. The obtained experimental results were confirmed that these sorbents are efficient for the treatment of hazardous toxic species such as.

UV-induced transformation of 2,3-dibromo-5,6-dimethyl-1,4-benzoquinone in water and treated wastewater.

In this work, we investigate the photolysis behavior of 2,3-dibromo-5,6-dimethyl-1,4-benzoquinone (DDBQ), the only dibrominated benzoquinone detected in treated water so far. DDBQ solutions prepared in ultra-pure water were exposed to UV radiation centered at 254 nm (UV254), and the photolysis of the parent compound was monitored together with by-product formation. The DDBQ pseudo-first order photolysis rate constants decreased when increasing the initial DDBQ concentration, and this behavior was caused by saturation of absorption. The photodegradation kinetics was found not to depend on pH and 1-butanol addition, but was affected by humic acids and components that occur in both natural waters and treated wastewater. For the first time with this class of compounds, photolysis studies were also performed using natural and treated wastewater matrices, where photodegradation was always found to proceed significantly slower than in ultra-pure water. The implications for the radiation dose that is required to reach a given treatment target are discussed, and a numerical approach by which to foresee the extent of degradation inhibition is provided that should be taken into account when planning the UV254 treatment of DDBQ. The phototransformation of DDBQ yielded hydroxyderivatives, most likely via a debromination-hydroxylation pathway. In-silico toxicity screening suggested that the transformation of DDBQ into the detected hydroxyderivatives would not eliminate toxicity. Although the monohydroxylated derivative underwent relatively fast transformation, the dihydroxylated compound was found to accumulate during irradiation. As a compromise, the irradiation conditions that produce over 90% degradation of DDBQ in the studied samples, and at the same time keep by-product formation low are discussed.