Evangelos A. Voudrias

Sorption–desorption behaviour of 2,4-dichlorophenol by marine sediments

Batch kinetic and isotherm experiments were conducted to determine the sorption-desorption behavior of 2,4-dichlorophenol from seawater solutions by marine sediments containing various amounts of organic carbon (from 1.02% to 12.72% dry weight). The results indicated linear type isotherms for sorption and desorption in all marine sediments studied. The observed difference in linear sorption coefficients between sorption and desorption was indicative of sorption hysteresis. The kinetic experiments showed that equilibrium was established in less than 20 h. The study is significant with respect to sediment remediation in contaminated harbors and coastal areas.

Laboratory scale bioremediation of petroleum-contaminated soil by indigenous microorganisms and added Pseudomonas aeruginosa strain Spet.

The bioremediation of petroleum-contaminated soil was investigated at laboratory scale, using three different approaches. The first approach comprised biostimulation of indigenous microorganisms. The second approach involved combination of biostimulation of indigenous microorganisms and bioaugmentation by inoculation with free cells of petroleum degrading Pseudomonas aeruginosa strain Spet. The third was a variation of the second, in which inoculation with encapsulated cells in starch and sodium alginate of P. aeruginosa strain Spet was applied. The bioremediation of the original hydrocarbon-contaminated soil (3.5% dry weight) and that of diluted with clean natural soil at 1:1 w/w were investigated. By providing sufficient moisture, nutrients and aeration by stirring in the original contaminated soil, total concentration of n-alkanes was reduced by 94% after 191 days of treatment and total concentration of 16 polycyclic aromatic compounds by 79%, while for the 1:1 diluted soils biodegradation reached 89% and 79%, respectively. The results showed that bioaugmentation with free or encapsulated P. aeruginosa cells and/or soil dilution had no significant effect on biodegradation.

Modeling of Contaminant Transport Resulting from Dissolution of Nonaqueous Phase Liquid Pools in Saturated Porous Media

A mathematical model for transient contaminant transport resulting from the dissolution of a single component nonaqueous phase liquid (NAPL) pool in two-dimensional, saturated, homogeneous porous media was developed. An analytical solution was derived for a semi-infinite medium under local equilibrium conditions accounting for solvent decay. The solution was obtained by taking Laplace transforms to the equations with respect to time and Fourier transforms with respect to the longitudinal spatial coordinate. The analytical solution is given in terms of a single integral which is easily determined by numerical integration techniques. The model is applicable to both denser and lighter than water NAPL pools. The model successfully simulated responses of a 1,1,2-trichloroethane (TCA) pool at the bottom of a two-dimensional porous medium under controlled laboratory conditions.

Reactivities of hypochlorous and hypobromous acid, chlorine monoxide, hypobromous acidium ion, chlorine, bromine, and bromine chloride in electrophilic aromatic substitution reactions with p-xylene in water

Introduction Hypohalous acids HOX (X = C1 or Br) are relatively weak electrophiles which react only with aromatic substrates having activated rings (1,2). However, protons and some anions, such as OC1-, C1-, or Br-, may convert HOX into highly reactive species and, thus, may catalyze halogenations of relatively nonreactive substrates (1-6). The reactive species X-Y may be a permanent dipole consisting of partially positively charged X6+ attached to a partially negatively charged carrier Yh. X may be Br or C1, and Y may be H20, HO, Br, Cl, or OC1. In homoatomic species (Cl,, Br2) X6+-X6is formed by dipole induction (1). In acidic aqueous HOCl solutions, possible chlorinating agents are HOC1, Cl2O, H20C1+ (1,6), and, if C1-is present, Clz (2, 7,8). In acidic aqueous HOBr solutions possible brominating agents are HOBr and H20Br+ and, if Bror C1is present, Br, and BrC1, respectively (1,3,5). Chlorinating and brominating agents may coexist in mixed systems, which contain HOCl and Br-. In such system bromination and chlorination may be competing reactions as will be shown in the following paper (9). These systems are of public health interest because chlorine disinfection of water containing organic compounds and Brmay lead to the formation of chlorinated and brominated aromatic byproducts (7, 9, 10). The mechanism of aromatic electrophilic substitution reactions is thought to proceed through Wheland intermediates (also termed CT complexes or arenium ions) according to Scheme I (11). Formation of a Wheland intermediate is generally preceded by rapid bimolecular formation of an encounter or a a-complex [X-Y, RH], where RH is the aromatic compound. The encounter complex of phenol and C12 [Clz, CGH50H], for example, is formed at a rate of (2.3 f 0.5) X lo4 M-l s-l (8).

Behavior and fate of linear alkylbenzene sulfonate in different soils

Abstract To investigate the behavior of surfactants in soil ecosystems, the sorption of linear alkylbenzenesulfonate on soils from three different areas of Northern Greece and with different organic matter content was studied. LAS sorption on these soils decreased with increasing pH and correlated positively with the organic matter content of the soils.

DNAPL pool dissolution in saturated porous media: procedure development and preliminary results

Abstract In order to study dissolution kinetics of dense non-aqueous-phase liquids (DNAPLs), a procedure was developed to create a DNAPL pool at the bottom of a specially designed experimental aquifer. The aquifer was housed in an all glass rectangular tank with internal dimensions 75 cm × 21.1 cm × 36.8 cm. The tank was equipped with sampling ports, inlet and outlet wells, constant-head reservoirs, and pumps for full hydraulic control. The pool was formed inside a 27.9 cm × 18 cm × 4.7 cm internal dimensions glass pan containing a gravel layer 1.6 cm thick at the bottom and the remainder filled with aquifer sand. The pools formed had a distinct, but not perfectly flat upper surface. The fraction of sand penetrated by DNAPL was larger at elevations closer to the bottom of the tank. Dissolution experiments, using TCA and mixture of TCE and TCA pools, resulted in aqueous concentrations much lower than the respective solubility. Pulsed pumping increased the respective aqueous concentrations by a factor of ≈ 6.

Effects of activated carbon on the reactions of free chlorine with phenols.

The use of prechlorination in drinking water treatment results in contact of free chlorine with activated carbon which has been added to remove organic compounds from water. The chlorine then reacts with the carbon and adsorbed compounds. Free chlorine reacts readily with a group of phenolic compounds (phenol, guaiacol, catechol, 2,6-dimethoxyphenol, and p-chlorophenol) in dilute aqueous solutions (10/sup -5/ M) to produce mono-, di-, or trichloro derivatives, but when it reacts with phenols adsorbed on granular activated carbon (GAC), many additional products are formed. GAC exposed to chlorine becomes capable of promoting reactions such as hydroxylations of the aromatic ring, oxidation to quinones, chlorine substitution, carboxylation, and oxidative coupling (dimer formation). The formation of chlorohydroxybiphenyls (hydroxylated PCBs) (in vivo metabolites of PCBs) is particularly important because of their potential toxicity. Such compounds are the main reaction products from chlorophenols, but they are also formed in smaller amounts from nonchlorinated phenols (phenol and guaiacol).

Composition and production rate of medical waste from a small producer in Greece

The objective of this work was to determine the composition and production rate of medical waste from the health care facility of social insurance institute, a small waste producer in Xanthi, Greece. Specifically, produced medical waste from the clinical pathology (medical microbiology) laboratory, the X-ray laboratory and the surgery and injection therapy departments of the health facility was monitored for six working weeks. A total of 240 kg medical solid waste was manually separated and weighed and 330 L of liquid medical waste was measured and classified. The hazardous waste fraction (%w/w) of the medical solid waste was 91.6% for the clinical pathology laboratory, 12.9% for the X-ray laboratory, 24.2% for the surgery departments and 17.6% for the injection therapy department. The infectious waste fraction (%w/w) of the hazardous medical solid waste was 75.6% for the clinical pathology laboratory, 0% for the X-ray laboratory, 100% for the surgery departments and 75.6% for the injection therapy department. The total hazardous medical solid waste production rate was 64+/-15 g/patient/d for the clinical pathology laboratory, 7.2+/-1.6 g/patient/d for the X-ray laboratory, 8.3+/-5.1 g/patient/d for the surgery departments and 24+/-9 g/patient/d for the injection therapy department. Liquid waste was produced by the clinical pathology laboratory (infectious-and-toxic) and the X-ray laboratory (toxic). The production rate for the clinical pathology laboratory was 0.03+/-0.003 L/patient/d and for the X-ray laboratory was 0.06+/-0.006 L/patient/d. Due to the small amount produced, it was suggested that the most suitable management scheme would be to transport the hazardous medical waste, after source-separation, to the Prefectural Hospital of Xanthi to be treated with the hospital waste. Assuming this data is representative of other small medical facilities, medical waste production can be estimated for such facilities distributed around Greece.

The concept of a sorption chemical barrier for improving effectiveness of landfill liners

In this work, we apply the concept of a “sorption chemical barrier”, as a means of improving landfill liner effectiveness. The sorption barrier is formed by addition of the organoclay hexadecyltrimethylammoniummontmorillonite (HDTMA-montmorillonite) to a fine sand-bentonite liner. Using previously published experimental data and mathematical model simulations, we demonstrate that such a liner retards significantly the transport of landfill leachate components, thus, increasing the useful life of the liner by a factor of 5 to 10, for the cases calculated. The superior HDTMA-liner performance is maintained even when the sorption extent is significantly decreased, as in the case of leachate containing methanol, a cosolvent miscible with water, found in some industrial and hazardous waste sites. The increase of the useful life of the liner results in smaller liner thickness, required to provide equivalent protection, from the point of view of contaminant transport, as compared to the liner containing no organoclay. Clay liner design based on hydraulic conductivity alone neglects the early breakthrough due to hydrodynamic dispersion and, therefore, is not a conservative one.

Removal of chlorite and chlorate ions from water using granular activated carbon

Abstract Bench scale column experiments were performed to determine the ability of granular activated carbon (GAC) to remove chlorite ion (ClO2−, the major by-product of chlorine dioxide, and chlorate ion (ClO3−, with or without natural organic matter, and under various operational conditions. Operational variances included the effect of pH, hydraulic loading, influent concentration and GAC particle size. Initially, all influent ClO2− was reduced to ClO− by GAC, but later carbon capacity for ClO2− reduction was decreased and ClO2− breakthrough was observed. Chlorite ion reduction was improved by decreasing the natural organic matter concentration, decreasing pH, decreasing hydraulic loading, decreasing GAC particle size and increasing temperature. All other parameters were maintained constant, the most effective chlorite ion removal occurred at pH 5. The results may be of interest to many water utilities, which use activated carbon for removal of organic compounds and in filter adsorbers replacing anthracite coal. There was no formation of chlorate ion in the GAC-chlorite system in the dark. Chlorate ion was not reduced by GAC, but was only physically and reversibly sorbed.