Electrocoagulation in treatment of municipal wastewater- life cycle impact assessment

The purpose of this study is investigation of electrocoagulation (EC) as a treatment of municipal wastewater, integrating life cycle impact assessment (LCIA) for assessing its environmental performance of investigated treatment. The study evaluated the effectiveness of EC in removing physico-chemical and microbial parameters using aluminum (Al) and iron (Fe) electrodes in monopolar and bipolar modes. Bipolar arrangement of Al(-)/Al/Al/Al(+) electrodes achieved the highest removals: 70% COD, 72% BOD5 followed by complete elimination of total phosphorous, turbidity and microbial parameters. This treatment was subject to investigation of the influence of reaction time (t = 10-60 min) on removals at higher current density (CD = 3.33 mA/cm2). In order to reduce energy consumption, the same reaction time range was used with a reduced CD = 2.33 mA/cm2. Following removal efficiencies obtained: 47-72% COD (higher CD) and 53-78% (lower CD); 69-75% BOD5 (higher CD) and 55-74% CD (lower CD); 12-21% NH4- (higher CD) and 7-22% NH4- (lower CD). Total P, NO3- and NO2- compounds showed the same removals regardless the CD. Decrease in current density did not influence removals of total suspended matter, turbidity, salinity as well as microbial parameters. The bipolar arrangement of Al(-)/Al/Al/Al(+) electrodes, assuming a lower CD = 2.33 mA/cm2 and t = 30 min, was assessed with the Recipe 2016Midpoint (H) and USEtox v.2 LCIA methods to explore the environmental justification of using EC for wastewater treatment. The LCIA results revealed that the EC process significantly reduces water eutrophication and toxicity for freshwater and marine ecosystems, but has higher impacts in global warming, fossil fuel consumption, human toxicity, acidification, and terrestrial ecotoxicity due to high energy consumption. This can be mainly explained by the assumption in the study that the EC precipitate is dispersed to agricultural soil without any pre-treatment and material recovery, along with relatively high energy consumption during the process.

Eco-friendly nanoparticles: mechanisms and capacities for efficient removal of heavy metals and phosphate from water using definitive screening design approach

Can nano-zero-valent iron, synthesized using oak leaf extract, be the key solution for water preservation, efficiently removing heavy metal ions and phosphate anions simultaneously? This research unveils how this technology not only promises high efficiency in the remediation of water resources, but also sets new standards for environmentally friendly processes. The high antioxidant capacity and high phenol content indicate suggest the possibility of oak-nZVI synthesis using oak leaf extract as a stable material with minimal agglomeration. The simultaneous removal of Cd and phosphates, as well as and Ni and phosphates was optimized by a statistically designed experiment with a definitive screening design approach. By defining the key factors with the most significant impact, a more efficient and faster method is achieved, improving the economic sustainability of the research by minimizing the number of experiments while maximizing precision. In terms of significance, four input parameters affecting process productivity were monitored: initial metal concentration (1-9 mg L-1), initial ion concentration (1-9 mg L-1), pH value (2-10), and oak-nZVI dosage (2-16 mL). The process optimization resulted in the highest simultaneous removal efficiency of 98.99 and 87.30% for cadmium and phosphate ions, respectively. The highest efficiency for the simultaneous removal of nickel and phosphate ions was 93.44 and 96.75%, respectively. The optimization process fits within the confidence intervals, which confirms the assumption that the selected regression model well describes the process. In the context of e of the challenges and problems of environmental protection, this work has shown considerable potential and successful application for the simultaneous removal of Cd(II) and Ni(II) in the presence of phosphates from water.

Metal Nanoparticles in Dye Wastewater Treatment - Smart Solution for Clear Water

BACKGROUND

In past years, nanomaterials have been actively studied and developed and successfully used in many fields. Due to water scarcity, the application of nanomaterials in water and wastewater treatment has drawn significant attention. Due to their superior features, they represent functional materials with great potential for pollution removal and environmental applications.

OBJECTIVE

This literature review aims to summarize and present the metal nanoparticles used for dye wastewater treatment. The discussion subject is metallic nanoparticles for mentioned use, with a special focus on iron-based, bimetallic, and photocatalytic nanomaterials.

METHODS

Reference search of "metal nanoparticles in dye wastewater treatment" was conducted in detail through the Serbian Library Consortium for Coordinated Acquisition (KoBSON). Published papers search was mainly based on Web of Science and ScienceDirect database focusing on the latest research on this topic. The corresponding literature was carefully read, analyzed, and evaluated.

RESULTS

Two hundred and twenty-four scientific and review articles, thesis, and book chapters, patents were evaluated in order to summarise current trends in metal nanoparticle use in wastewater treatment. An increasing trend in scientific research regarding metal nanoparticles can be observed for the removal of different inorganic and organic pollutants. Among the most extensively tested are dye molecules, representing challenging species in terms of degradation and consequent removal. Modification, layering, combination, and green synthesis of metal nanoparticles result in materials capable of efficient and environmentally sustainable wastewater treatment.

CONCLUSION

In this paper, an extensive review of metal nanoparticles in dye wastewater treatment is presented. With rapid water demand, the development of sustainable materials and technology is necessary. The use of these materials represents eco-friendly, energy-efficient, and sustainable water purification solutions. However, the matter of usage commercialization is still to be addressed.

A cost effective method for immobilization of Cu and Ni polluted river sediment with nZVI synthesized from leaf extract

This study investigates the performance of oak (OL) and mulberry (ML) leaves for synthesized of nanoscale zero-valent iron (nZVI), in immobilizing Cu and Ni in contaminated sediment. Characterization of synthesized Fe nanoparticles from oak and mulberry leaf extracts demonstrated that they are nontoxic and stabile nanomaterials for application in the sediment remediation. Effectiveness of stabilization process was performed by microwave-assisted sequential extraction procedure (MWSE) and single-step leaching tests which have been applied to evaluate the metal extraction potential. This research showed that OL-nZVI and ML-nZVI were effective in transforming available Cu and Ni to stable fraction. The maximum residual percentage of Cu increased by 76% and 73%, and for Ni 81% and 80%, respectively, with addition of 5% OL-nZVI and 5% ML-nZVI. Used single-step leaching tests (Toxicity Characteristic Leaching Procedure-TCLP and German standard test- DIN) indicated that all stabilized samples can be considered as non-hazardous waste, as all leached metal concentrations met the appropriate set criteria. Cost analysis showed that the operating cost for contaminated sediment treatment with green synthesized nZVI are 50.37 €/m3/per year. This work provides a new insight into the immobilization mechanism and environmental impact of Cu and Ni in contaminated sediment and potential way of treatment with OL-nZVI and ML-nZVI. Generally, nZVI can be an effective and versatile tool for stabilization of sediment polluted with toxic metals.

Leachability and Microstructural Analysis of Clay and Lime Stabilized/Solidified Polluted Sediment – Long-Term Performance

The objective of this study is to enable a better understanding of the effectiveness of solidification/stabilization (S/S) technique in treating polluted sediment, and provide the much needed validation of the longevity of the technology. In this research kaolinite and montmorillonite, with a certain proportion of lime, were used for S/S treatment of sediment polluted with metals. Leachability of metals was examined using the toxicity characteristic leaching procedure (TCLP) and the German standard leaching test (DIN 3841-4 S4) prescribed in national legislative. Results indicated successful S/S treatment using both clays and lime, from the aspect of all leached metals even with pH variations over time and slight changes in structural integrity of specimens. X-ray diffraction (XRD), scanning electron microscope (SEM) analyses and porosity measurement were also performed on the prepared monolithic matrices. XRD qualitative and semi-quantitative analysis proved hydration and pozzolanic product formation with increase in their content and finer crystallites formation over time. SEM analysis confirmed the presence of morphologically dense and stable structures while pore size distribution indicated on mesoporous matrices with ongoing compaction over time. Generally, structural microanalysis indicated the formation of hardened matrices over time and hydration process has been fully completed and further carbonation took place. Unconfined compressive strength measurement gave the satisfying results and matured monolite with 30 % of montmorillonite and 10 % of lime can be considered potentially applicable as non-load-bearing material. In summary, all results indicated that this kind of S/S treatment can achieve satisfactory durability and represent reliable and economically feasible technique for long-term remediation of metal polluted sediment.

Remediation of Toxic Metal Contaminated Sediment Using Three Types of nZVI Supported Materials

Due to nZVI effectiveness in the removal of toxic metals as well as low-cost regarding its production, kaolinite, bentonite and carboxymethyl cellulose supported nZVI were chosen for in-situ remediation of river sediment. Small-scale laboratory studies have shown that the percentage of removed metal (Ni, Zn and Pb) ranged up to 80% depending on the nanomaterial used. The metal mobility in sediments was investigated using single extraction, which is proved to be better for quick estimation of metal mobility, and for highly contaminated sites both single and sequential extraction needs to be used. Risk assessment code indicated medium risk for Ni and high risk for Pb and Zn in untreated sediment. In-situ treatment in laboratory proved to be very effective, providing the choice of optimal doses of three different nanomaterials used towards the concentration of toxic metals in the sediment.

Organic and inorganic priority substances in sediments of Ludaš Lake, a cross-border natural resource on the Ramsar list

For the first time, long-term monitoring (from 2002 to 2014) was carried out of surface sediments in Ludaš Lake, a Ramsar site in northern Serbia. Organic (16 EPA PAHs, mineral oils, selected pesticides and polychlorinated biphenyls (PCBs)) and inorganic substances (eight heavy metals: Ni, Zn, Cd, Cr, Cu, Pb, As and Hg) were continually investigated. Dibenzo[a,h]anthracene (DahA) and fluorene (Flo) were found at levels indicative of causing adverse effects to biota. Diagnostic ratios of specific PAHs were dominated by high molecular weight components, particularly DahA, which contributed 81.78 % of the total high carcinogens, benzo[b]fluoranthene (BbF) and Flo. Potential ecological risk factors (ERi) and the high relative standard deviations (RSD) obtained (up to 245 %) for the parameters monitored confirm the high periodical anthropogenic impact from industry, municipal wastewater and agriculture. The highest concentration of inorganic pollution found was for Cd (440-831 mg/kg) at all sites, Cu (439 mg/kg) in the eastern part of the lake and Cu (388 mg/kg) and Hg (771 mg/kg) in the northern part of the lake. Based on factor analysis of principal component analysis (PCA/FA), As and phenanthrene (Phe) had significant loadings (0.808 and 0.907, respectively). This association of As with organic anthropogenic sources was also confirmed with the sum of PAHs, pyrene (Pyr) and mineral oil by 3D factor plot, corroborating the theory of As mobilization from metal-reducing microbes as organic (methylated) forms, accelerated by phenanthrene. According to EU national and regional data results, this research suggests that Cu, As, dibenzo[a,h]anthracene and Flo should be added to the list of priority pollutants within the context of applying the European Water Framework Directive (WFD).