Iron Oxides / Hydroxides

Analyses of the costs of surface water treatment plants (WTP) in Poland show that unit capital and operating costs decline with increasing production. Costs of depreciation, electricity consumption and salaries have the largest share in the total WTP operating costs. Life cycle costing has shown that additional WTP costs may be related to maintenance of too many rapid gravity fi lters. In the case of complex water supply systems a large water manufacturer is often treated as a reserve source, but assurance of resident supply reliability increases the WTP operating costs. Water treatment plants are also charged with flood protection costs.

Groundwater is a viable alternative when access to surface water resources is limited. Iron and manganese are known ions in soil and naturally in groundwater sources. However, human activities also are responsible. To identifying the best module for removing manganese and iron in the water treatment plant (WTP) of Mazandaran, 516 samples were taken from raw and treated water. The concentration of manganese, iron, was measured by atomic absorption spectrophotometry, and turbidity was used with the nephelometry method. The water pollution index (WPI) was applied for categorizing the status of pollution in treated water. The effect of seasonal temperature and backwashing (At flow rates of 3.5, 9.2, and 15.3 m h-1) on the sand filter efficiency was also investigated. The highest concentrations of manganese, iron, and turbidity in raw water were 0.744, 6.70 mg L-1, and 41.8 NTU, and in treated water were 0.67, 1.09 mg L-1, and 5.58 NTU, respectively. The mean concentration of manganese and iron in raw and treated water were 0.24 ± 0.1, 0.93 ± 0.91, 0.105 ± 0.06 and 0.18 ± 0.14 mg L-1 respectively. The WPI statuses in drinking water were excellent for manganese and iron in 95.74 and 53.88 % of the samples and very poor in 1.16 and 12.01 % of the samples, respectively, and its classification for drinking water for manganese and iron was excellent ˃ good ˃ extremely polluted ˃ polluted and the concentration of iron was more than manganese in treated water. The study of temperature's effect on sand filters showed that the removal efficiency in warm seasons was higher than in cold seasons. Also, the turbulence in the backwash with the 9.2 m h − 1 rates, is lesser than other speeds, and in this flow, after 270 s, the turbidity decreases to less than 10 NTU. Spearman correlation comparison showed that the parameters amounts after filtration decreased significantly (p ≤ 0.0001) in comparison to raw water. The results showed that module #1 that used open-aeration and chlorine as oxidations, was most effective in removing iron and manganese. In the end, the WTP couldn't diminish the parameters completely and need subsidiary units.

The study aimed to determine Aluminum sludge composition and structure for its valorisation as an alternative natural material for heavy metals removal from wastewater for further reuse as treated water in different applications. The study was conducted to investigate the introduction of Al-bearing sludge composition. The physical and chemical properties were examined using X-ray diffraction tests (XRD), scanning electron microscope tests (SEM), Fourier-transform infrared tests (FTIR), and Brunauer-Emmett-Teller tests (BET). Furthermore, the heavy metal concentrations of synthetic wastewater were measured using the spectrophotometry method. The experimental procedure is based on testing different pH limits and amounts of aluminum sludge to find the optimum conditions for copper (Cu) and zinc (Zn) removal. The results demonstrated a high removal efficiency where its value reached up to 97.4% and 96.6% for Zn and Cu, respectively, in an acidic medium (pH = 6) using a relatively high a...

The management of the ever increasing residual sludge from our waterworks in an economical and environmentally friendly manner remains a very important issue. This has led to genuine efforts aimed at its beneficial re-use. The recovery of coagulants from ...

The work concerns the effects of the treatment of groundwater contaminated with iron and manganese compounds taken from quaternary deposits. In the treatment process, a simple reagent-free technology based on aeration and rapid filtration processes was used. The article presents an analysis of the results of the quality of treated and abstracted water in the years 2008-2020. The period analyzed covers the modernization of the WTP, which was carried out in 2012. The purpose of modernization was to increase the efficiency of the WTP. After the modernization of the station, the efficiency of iron and manganese removal was found to be very high (99%), and the sequence of technological processes used was correct. The devices operated in the WTP work effectively by treating the water directed to the distribution system, which meets the Polish and EU quality requirements for water intended for human consumption.

The purpose of pre-design technological investigations is to define the water treatment technology for a new or existing water treatment plant. The investigation is performed on model-scale equipment, making sure that the results can be extrapolated to the technological scale. The investigation should allow for the determination of unit process parameters and ensure the desired outcome i.e. treated water meeting the applicable quality standards. Indirectly, the investigation results can also be used as a basis for defining the estimated scope of the investment, the costs of its execution and the future equipment operating costs. Technological investigations are carried out on the grounds of existing or future treatment plants in order to take into account the variable composition and quality indicators of the raw water to be treated. The pilot station, being the main element of the technological investigation, should be designed, built and operated with a view to the possibility of ...

The standard groundwater treatment technology is a simple, non-chemical reagent technology based on aeration and filtration processes. This treatment technology is resulted in the formation of groundwater treatment sludge (GWTS). Because one of the elements of sustainable development is the possibility of their reuse, that water treatment plant operators are looking for new ways of managing these sludges. At present, not all factors determining the adsorptive capacity of water treatment sludge are known. The explanation why the adsorption capacity of sludge with a similar structure and chemical composition may differ significantly will allow for their wider use as adsorbents. The information which must be known to ensure proper sludge management are the quality, chemical composition and texture characteristics of the GWTS. The sludges were characterized by X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy and N 2 adsorption/desorption isotherms. The results showed that the composition and properties of the GWTS depend primarily on the quality parameters of the raw water and the processes and reagents used in its treatment technology. GWTS contains mainly amorphous iron oxides. Sludges are characterized by a large specific surface area (145 m 2 /g). Due to composition and textural parameters, GWTS demonstrates good adsorption properties toward different compounds such as heavy metals and metalloids. In this article, the authors describe the relationship between properties of resulting sludge and the properties of groundwater, the treatment technology and backwash water treatment from rapid filters.

Iron (Fe) and manganese (Mn) are two of many substances that are causing harm to human health and various environmental contamination. This study investigates the performance of rapid sand filter as an improvement to the existing commercial filter media. Rapid sand filters were tested using groundwater collected from Kg Budi Kelantan. Groundwater collected were tested using seven velocities ranging from 0.89 to 5.04 m/hr. The concentration of Mn, Fe and turbidity of the treated groundwater were compared. It is found that the highest Mn, Fe and turbidity removal were recorded by using velocity of 4.38 m/hr followed by 2.95 m/hr and 2.4 m/hr. These three velocities represent more than 95% removal of final treated groundwater, where final Fe, Mn and turbidity ranging from 0.06 mg/L to 0.09 mg/L, 0 to 0.4 mg/L and 0.9 to 3.0 NTU, respectively. A positive trend also recorded where the initial head loss of the sand filter is directly proportional to the flow velocity. This means the filter media was still under a clean condition and no accumulation of sediment deposit occurs. The significance of this study to treat groundwater by removing the iron and manganese especially in rural areas were achieved successfully.

The management of the ever increasing residual sludge from our waterworks in an economical and environmentally friendly manner remains a very important issue. This has led to genuine efforts aimed at its beneficial re-use. The recovery of coagulants from ...

Layered double hydroxides (LDHs) based heterostructures provide an opportunity for the development of highperformance supercapacitors. Up till now, hierarchical NiCo 2 S 4 @NiFe LDH heterostructure is scarcely investigated for supercapacitor. In this work, the hierarchical NiCo 2 S 4 @NiFe LDH heterostructure nanosheet arrays on Ni-foam (NF) were synthesized by a facile hydrothermal method. As the supercapacitor electrode, it has been revealed that the incorporation of NiFe can significantly increase the capacitive performance of the heterostructure. At a current density of 1 Ag − 1 , a specific capacitance of NiCo 2 S 4 @NiFe LDH electrode was reached up to 827 Fg − 1 , outperforming that of pristine NiCo 2 S 4 and NiFe LDH. Moreover, the electrode keeps 90.2% of its preliminary capacitance after 12,000 cycles at 5 A g − 1. In addition, NiCo 2 S 4 @NiFe LDH electrode offer high energy density of 38.1 W h kg − 1 and power density of 1800 W kg − 1. According to DFT calculations, NiFe-LDH adsorption on NiCo 2 S 4 is strong and governed by large interfacial interactions with a charge transfer of 0.44 eV to NiCo 2 S 4 surface thus demonstrating the significantly improved electrochemical performance. Hence, such an outstanding electrochemical finding suggest that NiCo 2 S 4 @NiFe LDH heterostructures could be attractive electrode materials as practical supercapacitors for next generation energy storage devices.

This paper evaluates the adsorption capacity of iron-rich adsorbent to remove arsenic from groundwater in decentralised water supply treatment; a pilot-scale with a capacity of 5 m3/day has been investigated at Cu Da Nursery School in Hanoi city, in which the concentration of arsenic in groundwater is abnormally high (175-400 μg/l). The pilot system was designed to include a series of processes, such as aeration, sedimentation, sand filtration, and adsorption, using the iron-rich adsorbent and activated carbon from coconut shells. The pilot system was tested with three operated modes. The results demonstrate that the treatment efficiency of the overall treatment processes was significantly higher than that of the traditional treatment system used by local people. After aeration, sedimentation, and sand filtration, the water quality was discovered to respond substantially in reducing iron by over 96% (from 8-12 mg/l to less than 0.3 mg/l) arsenic by 55 to 60%, but after iron-rich ads...

Amino functionalized graphene oxide was synthesized (AFGO) using a chemical method in order to apply in ion flotation process as a novel nanocollector for nickel ion removal with the aim of reducing collector consumption during the process. The synthesized AFGO was investigated using various analytical analysis. To create the negative charge onto the amino functionalized graphene oxide, 2,6-diaminopyridine was used to improve the properties of amino functionalized graphene oxide for removal of nickel ions with positive charge from synthetic wastewater using ion flotation. This study introduced a new collector for ion flotation to reduce the required collector concentration during the process which had simple synthesis, economical, high efficiency and stability in a wastewater. The nickel removal percentage of approximately 100% was achieved using the nanocollector.

The low-alkalinity stabilization/solidification (S/S) treatment of the soil containing high concentrations of geogenic As by physical encapsulation is considered as a proper management before land development; however, the choice of an effective binder and the leaching potential of As remain uncertain. In this study, the influence of S/S binders (cement blended with fuel ash (FA), furnace bottom ash (FBA), or ground granulated blast furnace slag (GGBS)) on the speciation and leaching characteristics of geogenic As was studied. The results of X-ray diffractometer (XRD) and X-ray photoelectron spectroscopy (XPS) showed the reduced amount of calcium silicate hydrate phase and the decrease in oxidation state of As(V)-O on the surface of Fe(III) oxides/hydroxides in the low-alkalinity S/S treated soils. This might be due to the binder incorporation and change in pH conditions, which slightly affected the As-Fe interaction and increased the non-specifically sorbed species of As. Therefore...

The Dutch drinking water sector is actively investigating methods to reduce arsenic (As) to < 1 μg/L in drinking water supply. We investigated (1) the effectiveness of sequential permanganate (MnO 4¯) eferric (Fe(III)) dosing during aerationerapid sand filtration to achieve < 1 μg/L As (2) the influence of MnO 4¯e Fe(III) dosing on preestablished removal patterns of As(III), Fe(II), Mn(II) and NH 4 + in rapid sand filters and (3) the influence of MnO 4¯e Fe(III) dosing on the settling and molecular-scale structural properties of the filter backwash solids. We report that MnO 4¯e Fe(III) dosing is an effective technique to improve arsenite [As(III)] removal at groundwater treatment plants. At a typical aeration-rapid sand filtration facility in the Netherlands effluent As concentrations of < 1 μg/L were achieved with 1.2 mg/L MnO 4¯e and 1.8 mg/L Fe(III). The optimized combination of MnO 4¯e and Fe(III) doses did not affect the removal efficiency of Fe(II), Mn(II) and NH 4 + in rapid sand filters, however, the removal patterns of Fe(II) and Mn(II) in rapid sand filter were altered, as well as the settling behaviour of backwash solids. The characterization of backwash solids by Fe K-edge X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) showed that the changed settling velocity of backwash solids with MnO 4¯e Fe(III) in place was not due to changes in the molecular-scale structure of Fe-precipitates that constitute the major portion of the backwash solids.

Producing clean water from wastewater is a major issue due to environmental pollution. There is in particular a need for cheap sorbents to filter water. Here we developed a method to produce sorbing nanoparticles from water treatment residues using high-energy ball milling. Results show that 75 min of milling of residues yields particles sized lower than 100 nm, according to scanning and transmission electron microscopy. The sorption capacity of nanoparticles, of 50.0 mg Pg-1 , is 30 times higher than the sorption maxima of unmilled residues, of 1.7 mg Pg-1. Our method is therefore simple, efficient, and cheap, and enhances highly the adsorption capacity of treatment residues.

The aim of this paper is to investigate the performance of hematite nanoparticles in coagulation process in turbidity removal from naturally and artificially turbid raw surface water. Alum is widely used as coagulant in drinking water treatment processes in Egypt. To avoid residual aluminum problems, hematite nanoparticles have been used as coagulant. In this study, the prepared hematite nanoparticles before and after agglutination are characterized by using electron microscope (TEM, SEM). In addition to quality tests of treated water by hematite nanoparticle after coagulation process, tests were also conducted in comparison to alum. Effect of hematite nanoparticles dosage on the coagulation ability was studied to determine the highest turbidity removal. The results show the highest turbidity removal by hematite nanoparticles of values up to 93.8%.

The possibility of using the process of coagulation for purifying the filter backwash water from a swimming pool water system has been presented. The assessment of the process efficiency based on the physicochemical parameters was extended by a phytotoxicity analysis of products (sludges and supernatant liquids) obtained from the coagulation processes. The phytotoxicity of sludges was examined with respect to garden cress (Lepidium sativum) and white mustard (Sinapis alba), while duckweed (Lemna minor) was used for studying liquids. Coagulation process was highly effective in purifying backwash water when the lowest of the studied aluminum coagulant doses (from 7 to 20 mg/dm 3) was used. Moreover, the phytotoxicity assessment of backwash water allowed the determination of the hazard toward plants, which would be posed by using the backwash water for plant irrigation. The high stimulation of the growth of plant indices, observed in samples with raw backwash water, was caused by nutritive nitrogen and phosphorus. Their removal, in the case of postcoagulation solutions, significantly contributed to the inhibition of plant growth. In turn, sludges derived from both raw washings and coagulation exhibited phytotoxicity.

The possibility of using the process of coagulation for purifying the filter backwash water from a swimming pool water system has been presented. The assessment of the process efficiency based on the physicochemical parameters was extended by a phytotoxicity analysis of products (sludges and supernatant liquids) obtained from the coagulation processes. The phytotoxicity of sludges was examined with respect to garden cress (Lepidium sativum) and white mustard (Sinapis alba), while duckweed (Lemna minor) was used for studying liquids. Coagulation process was highly effective in purifying backwash water when the lowest of the studied aluminum coagulant doses (from 7 to 20 mg/dm 3) was used. Moreover, the phytotoxicity assessment of backwash water allowed the determination of the hazard toward plants, which would be posed by using the backwash water for plant irrigation. The high stimulation of the growth of plant indices, observed in samples with raw backwash water, was caused by nutritive nitrogen and phosphorus. Their removal, in the case of postcoagulation solutions, significantly contributed to the inhibition of plant growth. In turn, sludges derived from both raw washings and coagulation exhibited phytotoxicity.

Heavy metal contamination is one of the most important environmental issues. Therefore, appropriate steps need to be taken to reduce heavy metals and metalloids in water to acceptable levels. Several treatment methods have been developed recently to adsorb these pollutants. This paper reviews the ability of residuals generated as a by-product from the water treatment plants to adsorb heavy metals and metalloids from water. Water treatment residuals have great sorption capacities due to their large specific surface area and chemical composition. Sorption capacity is also affected by sorption conditions. A survey of the literature shows that water treatment residuals may be a suitable material for developing an efficient adsorbent for the removal of heavy metals and metalloids from water.

The standard groundwater treatment technology is a simple, non-chemical reagent technology based on aeration and filtration processes. This treatment technology is resulted in the formation of groundwater treatment sludge (GWTS). Because one of the elements of sustainable development is the possibility of their reuse, that water treatment plant operators are looking for new ways of managing these sludges. At present, not all factors determining the adsorptive capacity of water treatment sludge are known. The explanation why the adsorption capacity of sludge with a similar structure and chemical composition may differ significantly will allow for their wider use as adsorbents. The information which must be known to ensure proper sludge management are the quality, chemical composition and texture characteristics of the GWTS. The sludges were characterized by X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy and N 2 adsorption/desorption isotherms. The results showed that the composition and properties of the GWTS depend primarily on the quality parameters of the raw water and the processes and reagents used in its treatment technology. GWTS contains mainly amorphous iron oxides. Sludges are characterized by a large specific surface area (145 m 2 /g). Due to composition and textural parameters, GWTS demonstrates good adsorption properties toward different compounds such as heavy metals and metalloids. In this article, the authors describe the relationship between properties of resulting sludge and the properties of groundwater, the treatment technology and backwash water treatment from rapid filters.

Iron-impregnated food waste biochar (Fe-FWB) was synthesized for Se(Ⅵ) removal from aqueous solution. The effect and interactive effects of different parameters including pyrolysis time, temperature, and Fe concentration were explored using response surface methodology (RSM) to enhance conditions to achieve the highest Se(Ⅵ) removal using Fe-FWB. Pyrolysis time was not significant for Se(Ⅵ) adsorption capacity of Fe-FWB, but temperature and Fe concentration were found to be significant. The highest adsorption was achieved at 3.47 h and 495.0 °C with an Fe concentration of 0.44 M. Fe-FWB synthesized under optimum conditions were used to investigate the kinetic, equilibrium, and thermodynamic adsorption of Se(Ⅵ). Se(Ⅵ) adsorption reached equilibrium within 6 h, and both pseudo-second order and pseudo-first order models were suitable for describing kinetic Se(Ⅵ) adsorption. The Freundlich model was found to suitably fit the equilibrium adsorption data than the Langmuir model. The highest adsorption capacity of Fe-FWB for Se(Ⅵ) was 11.7 mg g-1. Se(Ⅵ) adsorption on Fe-FWB was endothermic and spontaneous. The enthalpy change for Se(Ⅵ) adsorption was 54.4 kJ mol-1, and the entropy change was negative at 15-35 °C. The increment of solution pH from 3 to 11 decreased the Se(Ⅵ) adsorption from 19.2 to 7.4 mg g-1. The impact of interfering anions on Se(Ⅵ) adsorption followed the lineup: HCO3- &gt; HPO42- &gt; SO42- &gt; NO3-. When compared to some adsorbents, the adsorption capacity of Se(Ⅵ) onto Fe-FWB was comparable even at neutral pH and the Fe-FWB was granular. These results indicate that Fe-FWB has prospective application in the removal of Se(Ⅵ) from aqueous solutions.

The Dutch drinking water sector is actively investigating methods to reduce arsenic (As) to < 1 μg/L in drinking water supply. We investigated (1) the effectiveness of sequential permanganate (MnO 4¯) eferric (Fe(III)) dosing during aerationerapid sand filtration to achieve < 1 μg/L As (2) the influence of MnO 4¯e Fe(III) dosing on preestablished removal patterns of As(III), Fe(II), Mn(II) and NH 4 + in rapid sand filters and (3) the influence of MnO 4¯e Fe(III) dosing on the settling and molecular-scale structural properties of the filter backwash solids. We report that MnO 4¯e Fe(III) dosing is an effective technique to improve arsenite [As(III)] removal at groundwater treatment plants. At a typical aeration-rapid sand filtration facility in the Netherlands effluent As concentrations of < 1 μg/L were achieved with 1.2 mg/L MnO 4¯e and 1.8 mg/L Fe(III). The optimized combination of MnO 4¯e and Fe(III) doses did not affect the removal efficiency of Fe(II), Mn(II) and NH 4 + in rapid sand filters, however, the removal patterns of Fe(II) and Mn(II) in rapid sand filter were altered, as well as the settling behaviour of backwash solids. The characterization of backwash solids by Fe K-edge X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) showed that the changed settling velocity of backwash solids with MnO 4¯e Fe(III) in place was not due to changes in the molecular-scale structure of Fe-precipitates that constitute the major portion of the backwash solids.

Contamination of drinking water by arsenic and fluoride is a global problem, as more than 300 million people in more than 100 countries have been affected by their presence. These elements are considered the most serious contaminants in drinking water and their removal is a worldwide concern. Therefore, the evaluation of three alternative approaches—electrocoagulation, adsorption by biomaterials, and adsorption by metal oxide magnetic nanoparticles (MNPs)—was performed for arsenic and fluoride removal from groundwater. Arsenic removal from synthetic and groundwater (well water) was accomplished with the three processes; meanwhile, fluoride removal from groundwater was only reported by two methods. The results indicate that an electrocoagulation process is a good option for As (&gt;97%) and F (&gt;90%) removal in co-occurrence; however, the operational conditions for the removal of both pollutants must be driven by those used for fluoride removal. As (80–83%) and F (&gt;90%) removal ...

The synthesized ultra-microporous zirconium-magnesium bimetal oxide was adroitly synthesized via the use of sol-gel technique. The synthesized composite was applied in the adsorption of copper, nickel and zinc cations from aqueous solutions. The composite properties were characterized by X-ray diffraction (XRD), Surface area (BET) by nitrogen adsorption-desorption, Thermo-gravimetric measurement (TG/DTG) and Fourier transformed infra-red (FTIR). The surface morphology of the synthesized composite was studied via the use of scanning electron microscopy (SEM) and fractal dimension concept. The influence of initial pH on sorption of copper, nickel and zinc cations in terms of removal efficiency was studied and deduced that the removal increases significantly with increasing the pH from 3 to 11. The intra-particle kinetic diffusion model confirmed that the adsorption mechanism controlled by multi-diffusion steps, comprising both film and intra-particle diffusion. The Toth isotherm model was elected to represent equilibrium of the concerned cations adsorption onto the composite. The thermodynamic parameters were calculated via the use of Flory-Huggins model.

The management of the ever increasing residual sludge from our waterworks in an economical and environmentally friendly manner remains a very important issue. This has led to genuine efforts aimed at its beneficial re-use. The recovery of coagulants from water works sludge have been studied for several years, because of the toxic nature of free and complexed aluminum species to aquatic life, cost benefit of the recovery and the stringent environmental regulations on disposal of these sludge on land or into water bodies. This paper presents a review of the available reports of the researches on the various methods of recovery of coagulant from water works sludge.

water supply for villages and small towns is provided mainly from groundwater resources. In spite of good physicochemical and bacteriological properties for groundwater, in most cases it is required to remove iron and manganese, which influences the applied treatment technologies. The processes of potable water treatment result in the emergence of certain by-products, i.e. technological wastewater (mainly spent filter backwash water) and sediments that contain the pollutants removed from water. The study presents the results of the Authors' tests of particle size and quantity distribution in spent filter backwash water from the groundwater treatment plant in Kąty Wrocławskie. The paper also contains an analysis of the changeability of iron and manganese content and turbidity in different phases of filter backwashing (initial backwashing, air backwashing, second backwashing). The research consisted of four series of tests conducted during the period from July 2013 to May 2014. Spent filter backwash water samples were collected during backwashing of two filters. Test results have shown that the quality of spent filter backwash water changed on subsequent stages of backwashing. Suspension particles of a size ranging from 10÷20 µm accounted for the highest volume percentage share in the analysed samples of spent filter backwash water from both filters, while the quantitative distribution of particles of the given diameters was heterogeneous and it depended on the stage of filter backwashing.

Natural organic matter (NOM) found in natural waters, is a heterogeneous mixture of compounds, still undiscovered from a chemical point of view. Standard water quality indicators, such as chemical oxygen demand (COD), dissolved organic carbon (DOC), UV254, pH and others, do not provide information about the nature of NOM, such as molar mass or hydrophobicity. UV absorbance at different wavelengths is becoming more and more useful for characterizing NOM. UV absorption is a popular and relatively simple indicator determining the content of organic pollutants in water. The functional groups of organic compounds absorbing UV and VIS radiation are chromophores. It is believed that different chromophores are identified by different wavelengths. The UV The Possibility of Using UV Absorbance Measurements... 341 absorbance at 220 nm is associated with both carboxylic and aromatic chromophores, while UV absorption at 254 nm is typical of aromatic groups with different degrees of activity. Fro...

Mining effluents can often contain heavy metals such as Lead (Pb), Zinc (Zn), Iron (Fe), Manganese (Mn), Cadmium (Cd), Arsenic (As) and if left untreated can cause damage to the local aquatic environment. In this study we demonstrate the operation of a 9 m 3 /h pilot unit (PU) installed in Greece. It consists of a pH regulation and oxidation stage, followed by filtration to a catalytic multimedia filter, activated carbon filter and a reverse osmosis (RO) unit. PU is fed by the existing pretreatment installation outlet. Our results prove that PU installing improved the water quality of water discharge, so that the final concentrations of dissolved metals to be even lower than the legislation limits for potable water. The removal of Fe, Mn and Zn was 97-100 %, As, Cd and Pb was 80-93 %. Operational data demonstrated very good removal efficiency of the Filtration Stage so that RO stage can be omitted. PU successful application enables design to be applied covering the complete installation needs. The operation of PU is simple, automatic, and constant. It is environmentally friendly and economically viable in terms of fixed and operational cost.

The standard groundwater treatment technology is a simple, non-chemical reagent technology based on aeration and filtration processes. This treatment technology is resulted in the formation of groundwater treatment sludge (GWTS). Because one of the elements of sustainable development is the possibility of their reuse, that water treatment plant operators are looking for new ways of managing these sludges. At present, not all factors determining the adsorptive capacity of water treatment sludge are known. The explanation why the adsorption capacity of sludge with a similar structure and chemical composition may differ significantly will allow for their wider use as adsorbents. The information which must be known to ensure proper sludge management are the quality, chemical composition and texture characteristics of the GWTS. The sludges were characterized by X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy and N 2 adsorption/desorption isotherms. The results showed that the composition and properties of the GWTS depend primarily on the quality parameters of the raw water and the processes and reagents used in its treatment technology. GWTS contains mainly amorphous iron oxides. Sludges are characterized by a large specific surface area (145 m 2 /g). Due to composition and textural parameters, GWTS demonstrates good adsorption properties toward different compounds such as heavy metals and metalloids. In this article, the authors describe the relationship between properties of resulting sludge and the properties of groundwater, the treatment technology and backwash water treatment from rapid filters.

The paper presents the results of analyzes of the granulometric composition of suspended solids in backwash water from biological activated carbon (BAC) filters and its changes during sedimentation. Backwash water samples were taken during backwashing of two pilot filters after different filtration time. It was found that regardless of the concentration of suspended solids in the collected backwash water, particle sizes vs. their percentage volume contributions for all samples were similar. Particle sizes were in the range of 2-100 m. However, the two-hour sedimentation for most of the samples proved to be effective (total suspended solids removal up to 93%), which is caused by selfcoagulation of the sample.

The management of the ever increasing residual sludge from our waterworks in an economical and environmentally friendly manner remains a very important issue. This has led to genuine efforts aimed at its beneficial re-use. The recovery of coagulants from ...

Arsenic (As) and chromate (Cr(VI)) contamination of ground and surface waters is a major problem worldwide. Given that a new drinking water limit is anticipated for Cr(VI) and that the limit of arsenic in drinking water is quite low (10 μg/L), there is an urgent need for evaluating technologies that could be efficient for removal of both contaminants simultaneously. In this work, the use of Fe(II) redox assisted coagulation was investigated to simultaneously remove the contaminants of interest. The basic principle of this technology is that Fe(II) could react with Cr(VI) and form Fe(III)-hydroxides and insoluble Cr(III) species, while the freshly formed Fe(III) hydroxides are very efficient adsorbents for As(V). The effect of pH, the water matrix composition, Fe(II) dose, initial contaminant concentrations, NOM presence and phosphate concentration were the examined parameters. The results revealed that with a dose of 2 mg/L Fe(II), residual As(V) and Cr(VI) concentrations were both ...

Two laboratory tests were carried out to verify the suitability of an Italian commercial biochar as an adsorbing material. The chosen contaminant, considered dissolved in groundwater, was As. The circular economic concept demands the use of such waste material. Its use has been studied in recent years on several contaminants. The possibility of using an efficient material at low cost could help the use of low-impact technologies like permeable reactive barriers (PRBs). A numerical model was used to derive the kinetic constant for two of the most used isotherms. The results are aligned with others derived from the literature, but they also indicate that the use of a large amount of biochar does not improve the efficiency of the removal. The particular origin of the biochar, together with its grain size, causes a decrease in contact time required for the adsorption. Furthermore, it is possible that a strong local decrease in the hydraulic conductibility does not allow for a correct di...

The aim of the study was to select an appropriate technology for the treatment of groundwater with particular emphasis on the effectiveness of organic matter removal. The technological research was carried out on a pilot scale for 6 weeks. The pilot station was supplied with groundwater taken from two wells with different physical and chemical composition and mixtures of the two waters. The installation of the pilot station enabled different configuration of technological processes and continuous water sampling past each device. The following parameters were determined for the water samples: temperature, pH, alkalinity, colour, turbidity, COD KMnO4, TOC and dissolved oxygen, total and bivalent iron and manganese. On the basis of the analysis of the test results, it was found that the treatment technology based on natural aeration and rapid filtration processes was effective for water from well no. 2 and the mixtures of waters from well no. 1 and well no. 2, and the quality of treate...

Heavy metal ions have deadly effects on all forms of life, and through the disposal of industrial wastewater, they enter water resources and, eventually, the food chain. Advanced oxidation processes can remove hazardous and non-degradable organic pollutants in aqueous solutions. Variables examined were initial concentrations of calcium peroxide and heavy metals, contact time, pH, and ozonation rate. Maximum removal rate of heavy metals by ozonation with calcium peroxide under optimal conditions (contact time = 90 min, pH = 3, heavy metal concentration = 25 mg/L, calcium peroxide concentration = 0.025 mg/L and ozonation rate = 1 g/min) in synthetic and real samples were respectively 89.8% and 64.6% for Pb, 92.1% and 73.9% for Cu, 90.4% and 69.7% for Ni, 86.9% and 59.1% for Cd, and 93.4% and 78.8% for Zn. Maximum COD removal rates in synthetic and real samples were 88.1% and 69.9%, respectively. Removal rates of heavy metals and COD under optimal conditions on wastewater from the Isfahan electroplating industry and steel company were determined. The use of the ozonation process with calcium peroxide can be recommended as a good, coefficient method for the removal of heavy metals in wastewater treatment.

The Dutch drinking water sector is actively investigating methods to reduce arsenic (As) to < 1 μg/L in drinking water supply. We investigated (1) the effectiveness of sequential permanganate (MnO 4¯) eferric (Fe(III)) dosing during aerationerapid sand filtration to achieve < 1 μg/L As (2) the influence of MnO 4¯e Fe(III) dosing on preestablished removal patterns of As(III), Fe(II), Mn(II) and NH 4 + in rapid sand filters and (3) the influence of MnO 4¯e Fe(III) dosing on the settling and molecular-scale structural properties of the filter backwash solids. We report that MnO 4¯e Fe(III) dosing is an effective technique to improve arsenite [As(III)] removal at groundwater treatment plants. At a typical aeration-rapid sand filtration facility in the Netherlands effluent As concentrations of < 1 μg/L were achieved with 1.2 mg/L MnO 4¯e and 1.8 mg/L Fe(III). The optimized combination of MnO 4¯e and Fe(III) doses did not affect the removal efficiency of Fe(II), Mn(II) and NH 4 + in rapid sand filters, however, the removal patterns of Fe(II) and Mn(II) in rapid sand filter were altered, as well as the settling behaviour of backwash solids. The characterization of backwash solids by Fe K-edge X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD) showed that the changed settling velocity of backwash solids with MnO 4¯e Fe(III) in place was not due to changes in the molecular-scale structure of Fe-precipitates that constitute the major portion of the backwash solids.

A new nanocomposite consisting of activated carbon (AC) from the Cortaderia selloana flower and copper-based metal-organic framework (HKUST-1) was synthesized through a single-step solvothermal method and applied for the removal of lead ions from aqueous solution through adsorption. The nanocomposite, AC/HKUST-1, was characterized by Scanning Electron Microscopy (SEM), X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), and Energy-Dispersive X-ray Spectroscopy (EDX) methods. The SEM images of both HKUST-1 and AC/HKUST-1 contain octahedral crystals. Different factors affecting adsorption processes, such as solution pH, contact time, adsorbent dose, and initial metal pollution concentration, were studied. The adsorption isotherm was evaluated with Freundlich and Langmuir models, and the latter was fitted with the experimental data on adsorption of lead ion. The adsorption capacity was 249.4 mg g−1 for 15 min at pH 6.1, which is an excellent result rivalling previously reported...

The aim of the study was to select an appropriate technology for the treatment of groundwater with particular emphasis on the effectiveness of organic matter removal. The technological research was carried out on a pilot scale for 6 weeks. The pilot station was supplied with groundwater taken from two wells with different physical and chemical composition and mixtures of the two waters. The installation of the pilot station enabled different configuration of technological processes and continuous water sampling past each device. The following parameters were determined for the water samples: temperature, pH, alkalinity, colour, turbidity, COD KMnO4, TOC and dissolved oxygen, total and bivalent iron and manganese. On the basis of the analysis of the test results, it was found that the treatment technology based on natural aeration and rapid filtration processes was effective for water from well no. 2 and the mixtures of waters from well no. 1 and well no. 2, and the quality of treate...

The presence of toxic metals in surface and natural waters, even at trace levels, poses a great danger to humans and the ecosystem. Although the combination of adsorption and coagulation techniques has the potential to eradicate this problem, the use of inappropriate media remains a major drawback. This study reports on the application of NaNO2/NaHCO3 modified sawdust-based cellulose nanocrystals (MCNC) as both coagulant and adsorbent for the removal of Cu, Fe and Pb from aqueous solution. The surface modified coagulants, prepared by electrostatic interactions, were characterized using Fourier transform infrared, X-ray diffraction (XRD), and scanning electron microscopy/energy-dispersive spectrometry (SEM/EDS). The amount of coagulated/adsorbed trace metals was then analysed using inductively coupled plasma atomic emission spectroscopy (ICP-AES). SEM analysis revealed the patchy and distributed floccules on Fe-flocs, which was an indication of multiple mechanisms responsible for Fe ...

The purpose of pre-design technological investigations is to define the water treatment technology for a new or existing water treatment plant. The investigation is performed on model-scale equipment, making sure that the results can be extrapolated to the technological scale. The investigation should allow for the determination of unit process parameters and ensure the desired outcome i.e. treated water meeting the applicable quality standards. Indirectly, the investigation results can also be used as a basis for defining the estimated scope of the investment, the costs of its execution and the future equipment operating costs. Technological investigations are carried out on the grounds of existing or future treatment plants in order to take into account the variable composition and quality indicators of the raw water to be treated. The pilot station, being the main element of the technological investigation, should be designed, built and operated with a view to the possibility of ...

Heavy metal contamination is one of the most important environmental issues. Therefore, appropriate steps need to be taken to reduce heavy metals and metalloids in water to acceptable levels. Several treatment methods have been developed recently to adsorb these pollutants. This paper reviews the ability of residuals generated as a by-product from the water treatment plants to adsorb heavy metals and metalloids from water. Water treatment residuals have great sorption capacities due to their large specific surface area and chemical composition. Sorption capacity is also affected by sorption conditions. A survey of the literature shows that water treatment residuals may be a suitable material for developing an efficient adsorbent for the removal of heavy metals and metalloids from water.

The standard groundwater treatment technology is a simple, non-chemical reagent technology based on aeration and filtration processes. This treatment technology is resulted in the formation of groundwater treatment sludge (GWTS). Because one of the elements of sustainable development is the possibility of their reuse, that water treatment plant operators are looking for new ways of managing these sludges. At present, not all factors determining the adsorptive capacity of water treatment sludge are known. The explanation why the adsorption capacity of sludge with a similar structure and chemical composition may differ significantly will allow for their wider use as adsorbents. The information which must be known to ensure proper sludge management are the quality, chemical composition and texture characteristics of the GWTS. The sludges were characterized by X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy and N 2 adsorption/desorption isotherms. The results showed that the composition and properties of the GWTS depend primarily on the quality parameters of the raw water and the processes and reagents used in its treatment technology. GWTS contains mainly amorphous iron oxides. Sludges are characterized by a large specific surface area (145 m 2 /g). Due to composition and textural parameters, GWTS demonstrates good adsorption properties toward different compounds such as heavy metals and metalloids. In this article, the authors describe the relationship between properties of resulting sludge and the properties of groundwater, the treatment technology and backwash water treatment from rapid filters.

Heavy metal contamination is one of the most important environmental issues. Therefore, appropriate steps need to be taken to reduce heavy metals and metalloids in water to acceptable levels. Several treatment methods have been developed recently to adsorb these pollutants. This paper reviews the ability of residuals generated as a by-product from the water treatment plants to adsorb heavy metals and metalloids from water. Water treatment residuals have great sorption capacities due to their large specific surface area and chemical composition. Sorption capacity is also affected by sorption conditions. A survey of the literature shows that water treatment residuals may be a suitable material for developing an efficient adsorbent for the removal of heavy metals and metalloids from water.

The standard groundwater treatment technology is a simple, non-chemical reagent technology based on aeration and filtration processes. This treatment technology is resulted in the formation of groundwater treatment sludge (GWTS). Because one of the elements of sustainable development is the possibility of their reuse, that water treatment plant operators are looking for new ways of managing these sludges. At present, not all factors determining the adsorptive capacity of water treatment sludge are known. The explanation why the adsorption capacity of sludge with a similar structure and chemical composition may differ significantly will allow for their wider use as adsorbents. The information which must be known to ensure proper sludge management are the quality, chemical composition and texture characteristics of the GWTS. The sludges were characterized by X-ray diffraction, X-ray fluorescence, Fourier transform infrared spectroscopy and N 2 adsorption/desorption isotherms. The results showed that the composition and properties of the GWTS depend primarily on the quality parameters of the raw water and the processes and reagents used in its treatment technology. GWTS contains mainly amorphous iron oxides. Sludges are characterized by a large specific surface area (145 m 2 /g). Due to composition and textural parameters, GWTS demonstrates good adsorption properties toward different compounds such as heavy metals and metalloids. In this article, the authors describe the relationship between properties of resulting sludge and the properties of groundwater, the treatment technology and backwash water treatment from rapid filters.

The synthesized ultra-microporous zirconium–magnesium bimetal oxide was adroitly synthesized via the use of sol-gel technique. The synthesized composite was applied in the adsorption of copper, nickel and zinc cations from aqueous solutions. The composite properties were characterized by X-ray diffraction (XRD), Surface area (BET) by nitrogen adsorption–desorption, Thermo-gravimetric measurement (TG/DTG) and Fourier transformed infra-red (FTIR). The surface morphology of the synthesized composite was studied via the use of scanning electron microscopy (SEM) and fractal dimension concept. The influence of initial pH on sorption of copper, nickel and zinc cations in terms of removal efficiency was studied and deduced that the removal increases significantly with increasing the pH from 3 to 11. The intra-particle kinetic diffusion model confirmed that the adsorption mechanism controlled by multi-diffusion steps, comprising both film and intra-particle diffusion. The Toth isotherm model was elected to represent equilibrium of the concerned cations adsorption onto the composite. The thermodynamic parameters were calculated via the use of Flo-ry-Huggins model.

The surface interactions of Cd(II) and Hg(II) ions of Unwana new site Ogwuta (Isi Ogo) clay were studied using a column system technique. The effect of pH, dosage (bed height), particle size, anion type, time and influent concentration of Cd(II) and Hg(II) ions in the solution were investigated. The results showed that adsorption of metal ions increased with optimum pH of 5, contact time of 60 min, dosage of 14 g and mesh size of 63 µm. It was observed that the amount of Cd(II) and Hg(II) ions removed by the sample clay varied as the synergistic effects of the anions matrix varied. The presence of CO 3 2-brought about the highest percentage removal of 99.85% followed by Cl-, with 98.12% and SO 4 2-with 97.07%. The order is as follows: CO 3 2->Cl-> SO 4 2-. Results obtained were analyzed using Langmiur and Freundlich isotherm models and Largergren's pseudo-second other kinetic model. The data fitted well to the Freundlich isotherm and Largergren models with correlation coefficient (R 2) of 0.989 and 0.999 respectively. The maximum adsorption capacity was found to be 0.481mg/g for Cd(II) ion and 0.490 mg/g for Hg(II) ion. The clay sample showed great potential as an adsorbent for the removal of Cd(II) and Hg(II) ions from aqueous solutions.

The management of the ever increasing residual sludge from our waterworks in an economical and environmentally friendly manner remains a very important issue. This has led to genuine efforts aimed at its beneficial re-use. The recovery of coagulants from water works sludge have been studied for several years, because of the toxic nature of free and complexed aluminum species to aquatic life, cost benefit of the recovery and the stringent environmental regulations on disposal of these sludge on land or into water bodies. This paper presents a review of the available reports of the researches on the various methods of recovery of coagulant from water works sludge.