Search Results (16)

In this study, the effectiveness of the Fenton process in removing natural organic matter (NOM) from groundwater was investigated. The subject of this study is groundwater characterised by increased content of NOM and iron (II) compounds. In laboratory-scale studies, the influence of the ratio of concentrations of Fe(II) ions, which are naturally occurring in groundwater, to hydrogen peroxide (H₂O₂) as well as oxidation time and pH on the removal efficiency of organic matter was determined. Indicators such as total organic carbon (TOC), dissolved organic carbon (DOC), UV absorbance at 254 nm (UV₂₅₄), UV absorbance at 272 nm (UV₂₇₂), and specific UV absorbance (SUVA₂₅₄) were used to quantitatively and qualitatively assess the organic substances present in the raw water and after oxidation with Fenton’s reagent. Analysis of the results obtained showed that the highest removal efficiency of organic substances in the deep oxidation process using the Fenton reaction was obtained for a concentration ratio of Fe(II) to H₂O₂ = 1:5. Acidification of the water samples to a pH of about 4 and extending the oxidation time to 30 min significantly increased the removal efficiency of organic substances including mainly dissolved organic substances containing aromatic rings. The organic substances containing aromatic rings, determined at a wavelength of 254 nm, were degraded to other organic intermediates. Full article

Water Treatment Residuals (WTRs) are a by-product of the addition of chemical coagulants to water during the water treatment process and are a mixture of water and organic and inorganic matter that coagulates during the treatment process. WTRs often contain metals such as iron, aluminium, and manganese that have been oxidised as part of the process or are constituents of the coagulation chemicals used. The metals within WTRs are of interest with regard to applying these sludges to agricultural land. WTRs can also contain beneficial organic matter and nutrients (primarily nitrogen). The nature of the benefits delivered is largely dependent on the quality of the raw water and these beneficial components are generally found in much smaller quantities in WTRs than are found in sewage sludge produced from wastewater. However, WTRs can still be used to enhance the physical properties of soils. As urban populations increase in size, it is anticipated that the tonnage of WTRs will increase significantly in the future. At present, the majority of WTRs are disposed of in landfills; however, landfill charges are increasing significantly, making disposal of an increasing tonnage of WTRs financially unviable. In terms of a circular economy, the procedure of reusing WTRs for alternative applications satisfies the Scottish Government’s goals in terms of waste prevention and reducing the amount of material being sent to landfill as set out in the Proposals for Legislation in 2019. Given the potential benefits in terms of cost savings and compliance with government legislation, and the complexities of understanding where and when WTRs can be used in land applications, we developed a Decision Support Tool (DST) that uses data obtained from an extensive review of approaches in other countries to assist in decision making. We also conducted a pre-application analysis and provided guidance on when and where WTRs can be used in land applications and when they are not suitable, presented in a simplified format that requires few inputs from the user in order to simplify the process and removes the requirement for a specialist operator during pre-application analyses. Full article

Low-cost and easily accessible sludge treatment technologies are necessary in low- and middle-income countries. This study aimed to evaluate the use of Moringa oleifera seed powder (MO) as a natural sludge conditioner for supernatant quality improvement prior to thickening as a result of gravity settling. The zone settling rate (ZSR) and sludge volume index (SVI) were used to evaluate the gravity settling capacity. Supernatant clarification was evaluated in terms of the capacity to remove turbidity, apparent colour, Escherichia coli, and organic matter associated with zeta potential evolution. The effects on the values of pH and electrical conductivity were also evaluated. Finally, the effects on the toxicity (chronic and acute) of the supernatant effluent were examined. A significant supernatant quality improvement was observed with the addition of MO. The ZSR (0.16 cm/min) and SVI (53 mL/g) results showed that the sludge had good sedimentability, and the addition of MO maintained these characteristics in a statistical manner. Increasing the MO dosage increased the zeta potential of the supernatant, resulting in an optimal dosage of 1.2 g/L, with a removal of 90% turbidity, 70% apparent colour, 99% E. coli, and 40% organic matter. The pH and electrical conductivity values did not change with increasing MO dosage, which is a competitive advantage of MO addition compared to iron and aluminium salt addition. A reduction in the ability to remove organic matter was observed at higher dosages of the natural coagulant due to the presence of residual MO in the final effluent. The optimal MO dosage of 1.2 g/L did not affect the acute or chronic toxicity of the supernatant. These results emphasized that M. oleifera seed powder can improve the supernatant quality and can potentially be a low-cost and easily accessible conditioner for wastewater sludge thickening. Full article

In view of the problem of Fe³⁺ pollution in an iron sulfur mine, different layers of loess soil in the Bijie area were used for adsorption to alleviate the mine wastewater pollution by natural treatment. The effects of the initial concentration of Fe³⁺, adsorption time and pH value on the adsorption performance of top, core and subsoil layers of loess soils were studied by the oscillatory equilibrium method, and the adsorption mechanism of these three soils was analyzed through a kinetic adsorption experiment and infrared spectroscopy. The results showed that the adsorption capacity of Fe³⁺ was improved by increasing the initial concentration and reaction time, but the adsorption rate of the adsorption capacity of Fe³⁺ was reduced. The adsorption rate of Fe³⁺ in the subsoil layer was faster than that in the other two layers. The higher the pH, the higher the adsorption capacity. After the pH was higher than 3.06, it had little effect on the adsorption capacity, but the adsorption rate increased. The first-order kinetic equation, second-order kinetic equation and Elovich equation were suitable for iron adsorption kinetics of three soils. The fitting correlation coefficient of the second-order kinetic equation was close to one, indicating the main role of chemical adsorption. The adsorption rate constant of the subsoil layer was about two times and three times that of the core soil layer and the topsoil layer. The Langmuir model can better fit the isothermal adsorption process. The results of infrared spectroscopy of soil showed that the content of soil organic matter played an important role in the adsorption capacity of Fe³⁺. The subsoil layer had a higher concentration of organic matter and more abundant functional groups, so the adsorption capacity of Fe³⁺ was the highest. The results could provide a theoretical basis for the removal of iron in acid mine wastewater. Full article

In this study, chalcopyrite (CuFeS₂), a natural mineral with a bimetallic structure, was used as the activator to generate radicals for removing organic pollutants from aqueous solutions via the activation of peroxymonosulfate (PMS). Sulfisoxazole (SIX), a sulfonamide antibiotic, was selected as the model pollutant. The results showed that chalcopyrite was highly reactive toward the activation of PMS; under the conditions of 50 µM PMS and 1 g/L chalcopyrite, approximately 95.7% of the SIX was degraded after reaction for only 5 min. An increase in the loading of chalcopyrite (0.25–2 g/L) promoted the degradation of SIX, while elevated levels of PMS (0.05–0.5 mM) slightly retarded the degradation kinetics. Although the best performance was observed under acidic conditions (pHs 3 and 4), near complete degradation of SIX was also achieved at pH 5.5. Identification of reactive species revealed that both a hydroxyl radical and a sulfate radical were formed in chalcopyrite–PMS oxidation, and they were responsible for the degradation of SIX. Trace amounts of copper and iron were leached out from chalcopyrite during the activation, and both the heterogeneous and homogeneous activation of PMS contributed to the generation of oxidizing radicals. Common water constituents including Cl⁻, ${{\mathrm{HCO}}_3}^{-}$, and natural organic matter at their environmentally relevant levels showed a limited effect on the degradation of SIX, which suggests that chalcopyrite–PMS oxidation has high reactivity and stability in the degradation of organic pollutants and shows great practical application potential. Full article

A novel continuous and flexible electroflotocoagulation (EFC) reactor was built using concentric cylindrical Al and Fe electrodes, which can be operated either as anodes or cathodes linked to a DC connection. The reactor was operationally assessed related to various cell configurations that assured the required stages of coagulant dosage, mixing, reaction, and settling or flotation. The effects of several design variables and operational parameters (such as the electrode position that determines the reactor configuration, current density (i), flow rate (F), and the electrode area-treated volume ratio (Sel/V)) on the specific energy consumption versus the aluminum dose and charge loading rate were investigated. The most energy-efficient cell configuration using an aluminum anode and iron cathode was tested for the treatment of surface water (Bega river, Timisoara city, Romania) rich in hydrophobic natural organic matter (8.3 mg C∙L⁻¹ and specific UV absorbance parameter of 3.9 L∙m⁻¹∙mg⁻¹) and with a high turbidity of 92 NTU, under flood conditions. The best results that assured 97% turbidity removal, 87% for absorbance recorded at 254 nm, and 60% for DOC removal, through enhanced electroflotocoagulation, were achieved for an operational current density of 10 A∙m⁻² with specific energy and electrode consumption of 0.1 kW h∙m⁻³ and 0.017 kg Al∙m⁻³, respectively. Full article

Cr(VI) is toxic and carcinogenic, which fuels discussions on reducing existing standards for maximum Cr concentrations in drinking water. Fe(II) reductive precipitation is a common and economical method for achieving very low Cr(tot) concentrations (<5 µg/L). While Cr(VI) is reduced to Cr(III), Fe(II) is oxidized to Fe(III). The resulting Cr(III) and Fe(III) have low solubilities at neutral pH, precipitate as hydroxides, and can be removed by conventional media filtration. The presence of natural organic matter (NOM) in the raw water source can, depending on pH, concentration, type of NOM, and contact time, affect this process in various ways, from promoting Cr(VI) reduction, to re-reducing Fe(III), to forming stable complexes with Cr and Fe, thus, impairing chromium removal. The presented data showed that NOM, whether dominated by terrestrial humic acid, or of aquatic origin, could substantially impair chromium removal at neutral pH conditions. In particular, the ultimate removal of Cr(III) was affected. Soluble complexes and/or colloids of Cr(III), Fe(III) and NOM in the size range of 10 kDa–0.1 µm were formed, that could not be removed by conventional media filtration. Presence of iron sludge (>50 mg/L Fe(III)) mitigated the negative impacts of NOM on Cr(VI) reduction and Cr(III) removal. However, even 100 mg/L Fe(III), the highest applied sludge concentration, did not lead to a decrease in Fe(II) dosing requirements under the given conditions. A molar ratio higher than the given stochiometric ratio of [Fe(II)]:[Cr(VI)] = 3 was necessary for sufficient Cr(VI) removal. Full article

Water supply and water treatment are of major concern all around the world. In this respect, membrane processes are increasingly used and reported for a large range of applications. Desalination processes by membranes are well-established technologies with many desalination plants implemented in coastal areas. Natural water treatment is also well implemented to provide purified water for growing population. This review covers various aspects of desalination: membranes and modules, plants, fouling (scaling, biofouling, algal blooms), cleaning, pretreatment (conventional and membrane treatments), energy and environmental issues, renewable energies, boron removal and brine disposal. Treatment of natural water focuses on removal of natural organic matter, arsenic, iron, nitrate, fluoride, pesticides and herbicides, pharmaceutical and personal care products. This review underlines that desalination and natural water treatment require identical knowledge of membrane fouling, construction of large plants, cleaning procedures, energy and environmental issues, and that these two different fields can learn from each other. Full article

Effluent organic matter (EfOM) is present in different domestic and industrial effluents, and its capacity to hold metallic ions can interfere in the wastewater treatment process. Due to the low quality of water, new sustainable technologies for this purpose have become extremely important, with the development of renewable-source nanomaterials standing out in the literature. Nanocellulose (NC) deserves to be highlighted in this context due to its physicochemical characteristics and its natural and abundant origin. In this context, the interactions between NC extracted from cotton linter, organic matter fraction (humic substances) and metal ions have been evaluated. Free metal ions (Ca, Fe, Mg and Mn) were separated by ultrafiltration and quantified by atomic absorption spectrometry. The nanomaterial obtained showed potential for the treatment of effluents containing iron even in the presence of organic matter. The probable interaction of organic matter with NC prevents the efficient removal of calcium, magnesium and manganese. For these elements, it is desirable to increase the interaction between metal and NC by modifying the surface of the nanomaterial. Full article

Higher concentrations of disinfection byproducts (DBPs) in small water systems have been a challenge. Adsorption by tailored activated carbon (AC), developed from waste materials of a pulp and paper company using optimization of chemical activation by nitric acid followed by physical activation and metal coating, was tested for the removal of natural organic matter from water using synthetic and natural water. AC was coated with aluminum and iron salts in a ratio of 0.25 to 10.0% of metal: AC (wt:wt%). The optimization of dosage, pH, and time was performed to achieve the highest adsorption capacity. The modified AC of 0.75% Fe-AC and 1.0% Al-AC showed 35–44% improvement in DOC removal from natural water. An enhancement of 40.7% in THMs removal and 77.1% in HAAs removal, compared to non-modified, AC were achieved. The pseudo-second order was the best fitted kinetic model for DOC removal, representing a physiochemical mechanism of adsorption. Full article

The research on selenium presence in water resources has revealed the need to determine the respective aquatic species. As selenium oxyanions SeO₃²⁻ (Se^IV) and SeO₄²⁻ (Se^VI) predominate in natural waters, their determination is essential, mainly due to different ecotoxicity properties, as well as to different removal options from relevant-polluted waters. This study focuses on the SeO₃²⁻/SeO₄²⁻ speciation/separation and determination through the selective adsorption of SeO₃²⁻ only onto specific iron oxy-hydroxides (FeOOHs). For this purpose, the laboratory prepared FeOOHs examined along with the commercially available relevant material (Bayoxide), which was found to present optimum results for the speciation of selenium oxyanions, at the low concentration range 10–100 μg/L, using a dose of 0.5 g/L of adsorbent and gently stirring for 30 min at the usually encountered pH value of 7.3 ± 0.2. Moreover, the relevant experiments showed that the other major ions Cl⁻, HCO₃⁻, NO₃⁻, SO₄²⁻, Ca²⁺, Mg²⁺, Na⁺, possibly found in most natural waters at the concentration range 0–200 mg/L, as well as silicon, total organic carbon (TOC) of natural organic matter (NOM) and iron at the concentration range 0–50 mg/L, 0–5 mg/L and 0–1 mg/L, respectively, did not interfere with the selective adsorption of Se(IV). Furthermore, the most important advantage of this selective speciation method is its implementation/combination with all commonly applied analytical methods for the determination of total selenium. Full article

This paper describes work to assess the possibility of a modified Fenton process being used to remove the hard-to-degrade plasticizer di(2-ethylhexyl) phthalate (DEHP) from the bottom sediments of a reservoir. The modifications in question entail iron(II) ions being replaced by iron(III), as well as facilitation of the process using a chelating agent. Analysis further revolved around the impact of such factors as amounts of reagents, reaction of the environment, initial contents of the contaminant, and the presence of other “competing” contaminants also of a hard-to-decompose nature. As the maximum efficiency of DEHP removal obtained did not exceed 30%, the low susceptibility to degradation is made clear, as is the need for earlier desorption of the contaminant from the matrix. The effect of the modified Fenton process on the content of organic matter and dissolved organic carbon was also considered, as was the tendency to cause selected metals and plant nutrients to leach from bottom sediments. Full article

Groundwater (GW) is one of the main potable water sources worldwide. However, the presence of undesirable compounds and particularly manganese (Mn) and iron (Fe) (mainly co-existing in GWs) are considered as objectionable components of potable water for both health and aesthetic issues. As such, individual dwellings supplied by domestic wells are especially threatened by these issues. Current domestic treatment technologies are complicated to operate and even dangerous if improperly maintained (e.g., catalytic filtration) or consume salts and produce spent brine which pollutes the environment (i.e., ion exchange resins). Therefore, it is of prime importance to design a simple and compact, yet robust, system for Mn and Fe control of the domestic GW sources, which can reliably guarantee the desired Mn limit in the finished water ( $20\mathsf{\mu }$ g/L). In the course of this study, we demonstrated, for the first time, that a hybrid hollow fiber nanofiltration (HFNF)–calcite contactor process is a promising alternative for treating domestic GWs with elevated levels of Mn, Fe, natural organic matter (NOM) and hardness. The efficacy of the HFNF membranes in terms of removal of Mn, Fe, NOM and fouling was compared with commercially available NF270 and NF90 membranes. The results revealed that HFNF (100–200 Da) and NF90 maintained considerably high rejection of Mn, Fe and NOM due to their dominant sieving effect. In contrary, the rejections of the above-mentioned components were decreased in the presence of high hardness for the looser HFNF (200–300 Da) and NF270 membranes. No membrane fouling was detected and the permeate flux was stable when the hard GW was filtered with the HFNF membranes, regardless of their molecular weight cut-off and transmembrane pressure, while the permeability of the NF270 and NF90 membranes steadily decline during the filtration. Integrating a calcite contactor, as a post filtration step, to the HFNF process yielded further Mn, Fe and NOM removals from the HFNF permeate and adjustment of its hardness level. The best performance was achieved when a blend of Calcite–CorosexTM ( $90/10\mathrm{wt}.\%$ ) was used as a post-treatment to the tight HFNF (100–200 Da). Full article

The most important advances in sustainability in the water industry are focused on the reuse of water treatment sludge. The Antaviliai Water Supply Plant, which is located in Lithuania, treats groundwater by removing iron and manganese from it. This technology does not produce water waste, as the iron sludge is used for recycling. In this study, iron sludge received from groundwater treatment is used to remove natural organic matter from river Neris water, which can be used as drinking water. Twelve doses (from 1 to 6 g/L and from 0.1 g/L to 0.9 g/L) of iron sludge powder, with acid and without it, were used. The most effective removal of organic compounds (55.51%) and reduction in water colour (53.12%) were observed when 0.3 g of iron sludge powder and 8 ml of 0.95% H₂SO₄ solution were added to the tested water. It was found that the use of a conventional coagulant (Al₂(SO₄)₃*17H₂O), with and without iron sludge powder, decreased the concentration of organic compounds and water colour from 2.8 to 28.2% compared with the use of a pure coagulant (Al₂(SO₄)₃*17H₂O) alone.. Full article

The use of iron-coated pumice (ICP) in heterogeneous catalytic ozonation significantly enhanced the removal efficiency of natural organic matters (NOMs) in water, due to the synergistic effect of hybrid processes when compared to sole ozonation and adsorption. Multiple characterization analyses (BET, TEM, XRD, DLS, FT-IR, and pH_PZC) were employed for a systematic investigation of the catalyst surface properties. This analysis indicated that the ICP crystal structure was α-FeOOH, the surface hydroxyl group of ICP was significantly increased after coating, the particle size of ICP was about 200–250 nm, the BET surface area of ICP was about 10.56 m² g⁻¹, the pH_PZC value of ICP was about 7.13, and that enhancement by iron loading was observed in the FT-IR spectra. The contribution of surface adsorption, hydroxyl radicals, and sole ozonation to catalytic ozonation was determined as 21.29%, 66.22%, and 12.49%, respectively. The reaction kinetic analysis with tert-Butyl alcohol (TBA) was used as a radical scavenger, confirming that surface ferrous iron loading promoted the role of the hydroxyl radicals. The phosphate was used as an inorganic probe, and significantly inhibited the removal efficiency of catalytic NOM ozonation. This is an indication that the reactions which occur are more dominant in the solution phase. Full article