Correlation between the Results of Sequential Extraction and Effectiveness of Immobilization Treatment of Lead- and Cadmium-Contaminated Sediment

The assessment of the quality of sediment from the Great Backi Canal (Serbia), based on the pseudo-total lead (Pb) and cadmium (Cd) content according to the corresponding Dutch standards and Canadian guidelines, showed its severe contamination with these two metals. A microwave-assisted BCR (Community Bureau of Reference of the Commission of the European Union) sequential extraction procedure was employed to assess their potential mobility and risk to the aquatic environment. Comparison of the results of sequential extraction and different criteria for sediment quality assessment has led to somewhat contradictory conclusions. Namely, while the results of sequential extraction showed that Cd comes under the high-risk category, Pb shows low risk to the environment, despite its high pseudo-total content. The contaminated sediment, irrespective of the different speciation of Pb and Cd, was subjected to the same immobilization, stabilization/solidification (S/S) treatments using kaolinite, montmorillonite, kaolinite-quicklime, montmorillonite-quicklime, fly ash, zeolite, or zeolite-fly ash combination. Semi-dynamic leaching tests were conducted for Pb- and Cd-contaminated sediment in order to assess the long-term leaching behavior of these metals. In order to simulate “worst case” leaching conditions, the semi-dynamic leaching test was modified using 0.014 M acetic acid (pH = 3.25) and humic acid solutions (20 mg TOC l-1) as leachants instead of deionized water. The effectiveness of S/S treatment was evaluated by determining diffusion coefficients (De) and leachability indices (LX). The standard toxicity characteristic leaching procedure (TCLP) was applied to evaluate the extraction potential of Pb and Cd. A diffusion-based model was used to elucidate the controlling leaching mechanisms. Generally, the test results indicated that all applied S/S treatments were effective in immobilizing Pb and Cd, and the treated sediments may be considered acceptable for “controlled utilization” based on LX values, irrespective of their different availability in the untreated samples. In the majority of samples, the controlling leaching mechanism appeared to be diffusion, which indicates that a slow leaching of Cd and Pb could be expected when the above S/S agents were applied. The TCLP results showed that all S/S samples were nonhazardous

Uticaj doze ozona i UV zračenja na potencijalnu toksičnost podzemne vode nakon O3/UV unapređenog oksidacionog procesa

In this study the impact of ozonation and advanced O3/UV oxidation process on the general toxicity of the groundwater was examined by using the Allium anaphase-telophase test. Investigated oxidation treatments lead to increasing the toxicity of groundwater in comparison to raw water. Ozonation process lead to increasing of toxicity mostly as a consequence of bromate formation. On the other hand O3/UV process lead to increasing of toxicity as a result of formation of brominated organic by-products.U ovom radu ispitivan je uticaj tretmana vode ozonom i primene unapređenog O3/UV procesa na opštu toksičnost podzemne vode primenom Allium anafazno-telofaznog testa. Ispitivani oksidacioni tretmani dovode do povećanja toksičnosti podzemne vode u odnosu na sirovu vodu. Proces ozonizacije dovodi do povećanja toksičnosti vode najvećim delom kao rezultat formiranja bromata. S druge strane, primena O3/UV procesa dovodi do povećanja toksičnosti vode kao rezultat formiranja bromovanih organskih nusproizvoda

Sorption-desorption behaviour of hydrophobic organic compounds on Danube sediment

The sorption-desorption hysteresis of naphthalene and phenanthrene onto Danube sediment was investigated. Hysteresis indices (HI) are calculated for three equilibrium concentration (Ce=1%, 5% i 50% of the solubility in water). The results of sorption-desorption hysteresis indicated that it exists for both investigated sorbates on the Danube sediment. For more hydrophobic compound, phenanthrene (logKOW< 4.55) hysteresis is less pronounced in comparison with naphthalene (logKOW< 3.36). In the case of naphthalene, the existence of hysteresis may be due to irreversible pore deformation of the sorbent which causes the formation of meta-stable states in the sorbate mesopores

The influence of electrode combinations on the kinetics removal of organic substances from the printing effluent

In this research, the electrocoagulation/flotation (ECF) reaction kinetics of organic substances removal from the waste fountain solution was investigated. The ECF reaction kinetics of the organic substances removal from the printing effluent can be described by a pseudo-second rate equation. Obtained results have shown that the trend of decrease in pseudo-second order constant for organic substances removal follows the trend of decrease in the efficiency of electrode combinations (Fe(-)/Al(+) > Al(-)/Fe(+) > Al(-)/Al(+) > Fe(-)/Fe(+)) and current density (8 > 4 > 2 mA cm-2 ) of the ECF treatment

The combined electrocoagulation/flotation and adsorption processes for organic substances regeneration of waste printing developer

This paper investigates the possibility of reducing the content of organic substances in waste printing developer using a combination of electrocoagulation/flotation (ECF) and adsorption (AD) processes. The content of organic substances in waste printing developer was monitored by analysis of total organic carbon (TOC), chemical oxygen demand (COD) and biological oxygen demand (BOD5) before and after the ECF and AD processes, respectively. When combining the two processes, a removal of 99.4, 92.9 and 96.0% of the TOC, COD and BOD5 was achieved, respectively. Obtained results confirm the improvement in the printing industrial effluent quality and height removal of organic substances by the combined ECF and AD treatments

Enhanced coagulation with pre-oxidation for the removal of arsenic from groundwater

One of the most wide-spread problems with current drinking water resources globally is the natural presence of arsenic in groundwaters. The aim of this work was to investigate the removal of arsenic by a variety of combined oxidation/coagulation processes, in order to identify and optimise the most critical process parameters. The most significant gains made by both preoxidation steps were observed in the techniques which combined aluminum and ferric chloride based coagulation. The most efficient coagulation treatment investigated involved application of preozonation at a dose of 7.5 mg O3/l with subsequent combined coagulation with PACl–FeCl3 (30 mg Al/l and 10 mg FeCl3/l)

Experimental design of photo-Fenton process decolorization of Reactive Red 120 by using mathematical statistics models

A statistical design of experiments was used to evaluate the potential use of clay catalyst (CuOFeB) during photo-Fenton process in which the concentration of hydrogen peroxide (H2O2), catalyst loading and pH values were selected as effective experimental factors in the process of dye decolorization. The photo-Fenton oxidation of Reactive Red 120 (RR120) has been investigated using a concentrating solar parabolic reactor with constant solar radiation of 950 W/m2 during summer period of the year. Under the optimal reaction conditions catalyst showed good catalytic activity in the processes with dye removal over 90%. Also, experiment confirmed that decolorization efficiency depends on the pH and concentration of H2O2 , wherein better results were achieved under lower pH values and higher concentration of H2O2

Optimization of homogenous fenton process using definitive screening design applied for flexographic printing wastewater

The treatment of flexographic cyan dye synthetic solution and real printing effluent has been studied by using homogeneous Fenton process with the addition of FeSO4*7H2O as a catalyst. The study demonstrate that applied treatment could significantly reduce dye concentration in the examined aqueous solutions. Operating parameters, such as initial dye concentration, iron dosage, hydrogen peroxide concentration and pH were varied to investigate their influence on decolorization efficiency, as well as their mutual interactions. The optimal conditions, found with definitive screening design (DSD) statistical method, were: dye concentration = 123 mgL-1 , Fe concentration = 60 mgL-1 , H2O2 concentration = 5.44 mM and a pH value = 2. Under these conditions decolorization efficiency resulted with 87% and 37% for cyan synthetic solution and real printing effluent, respectively

Characterization and kinetic study of magenta printing effluent after homogeneous fenton treatment

The objectives of this study were to determine the physico-chemical characterization of Magenta printing effluent treated with homogeneous Fenton process, as well as kinetic model that best describes degradation process of organic pollutant. Physico-chemical characterization of printing effluent before and after homogeneous Fenton treatment included measurements of pH, electrical conductivity, temperature, turbidity, chemical oxygen demand, biochemical oxygen demand, total organic carbon and toxicity test. Three kinetic models (first-order, second-order, and Behnajady-Modirshahla-Ghanbary) were evaluated in order to best describe Magenta degradation process. Results indicated that dye degradation process is followed with the increase of conductivity and biological oxygen demand due to the formation of various by-products and release of inorganic ions. The obtained results are in accordance with the established dye mineralization degree on the basis of chemical oxygen demand and total organic carbon content. However, treated printing effluent is characterized as nontoxic due to the Vibrio fischeri inhibition of 18.16%