Fotis Rigas

Adsorption of humic acid on acid-activated Greek bentonite.

The adsorption of humic acid on bentonite from Milos Island (Greece) acid-treated with dilute H(2)SO(4) solutions over a concentration range between 0.25 and 13M has been studied. Bentonite activated with 3M sulfuric acid (AAS) showed a higher efficiency in removing humic acid from aqueous solutions and was selected for further investigation. The specific surface area of acid-activated bentonite was estimated using the methylene blue adsorption method. The morphology of untreated, activated, and HA-sorbed bentonite was studied under scanning electron microscope (SEM). The effects of contact time, adsorbate concentration, adsorbent dose, and temperature on the adsorption of humic acid onto bentonite activated with 3M H(2)SO(4) were studied using a batch adsorption technique. Acidic pH and high ionic strength proved to be favorable for the adsorption efficiency. Pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used to describe the kinetic data and the rate constants were evaluated. The experimental isotherm data were analyzed using Langmuir, Freundlich, and Temkin equations and the isotherm constants were determined. Thermodynamic parameters (DeltaH(o), DeltaS(o), and DeltaG(o)) of adsorption of humic acid onto acid-activated bentonite with 3M sulfuric acid were also evaluated.

Risk and consequence analyses of hazardous chemicals in marshalling yards and warehouses at Ikonio/Piraeus harbour, Greece

Abstract The risk and the consequences of possible accidents at Ikonio (Piraeus harbour, Greece) are investigated and analyzed in this paper. At this harbour large cargoes of dangerous chemicals (toxic or flammable) are unloaded and stored in warehouses or in marshalling yards. Houses and a school are located near the plant and are directly exposed to danger in the case of an accident. The results were obtained by Breeze Hazard Professional software package, which contains several models for performing consequence modeling through quantitative risk assessment.

Removal of amino acids from water by adsorption on polystyrene resins

The adsorption of eight amino acids, L-asparagine, D,L-threonine, L-lysine, L-leucine D,L-methionine, L-tyrosine, L-phenylalanine and D,L-tryptophan, on the non-polar macroporous adsorbents Amberlite XAD-2 and XAD-4 (polystyrene–divinylbenzene copolymers) was studied. Equilibrium adsorption experiments were conducted to estimate the types of isotherm and their parameters. The effect the chemical composition and structure of the amino acids on the efficiency of adsorption was evaluated. The influence of pH and ionic strength was also studied. The data of adsorption isotherms of the examined amino acids seemed generally to approach the Freundlich isotherm model. Tryptophan isotherm adsorption data could match in some cases the Langmuir model. The majority of the adsorption isotherms were almost linear. In terms of adsorbed amino acid on both resin surfaces, the amino acids can be ranked thus: D,L-tryptophan > L-phenylalanine > D,L-methionine, L-tyrosine > L-leucine > L-lysine > D,L-threonine > L-asparagine. In low pH solution, adsorption was generally higher than that at intermediate and high pH values. Generally, as the ionic strength increases, the adsorption of the amino acids increases. © 2001 Society of Chemical Industry

The Use of Bacteriophages for Monitoring the Microbiological Quality of Sewage Sludge

The use of bacteriophages as potential indicators of faecal pollution has recently been studied. The correlation of the number of bacterial indicators and the presence of three groups of bacteriophages, namely somatic coliphages (SOMCPH), F-RNA specific phages (FRNAPH) and phages of Bacteroides fragilis (BFRPH), in raw and treated sludge is presented in this study. Raw and anaerobically digested sewage sludge samples from two wastewater treatment plants in Athens were collected on a monthly basis, over a 2-year period, and analyzed for total coliforms, E. coli, intestinal enterococci and the three groups of bacteriophages. A clear correlation between the number of bacterial indicators and the presence of bacteriophages was observed. E. coli concentrations of ≥103 cfus g−1 and <103 cfus g−1 comprise a threshold for the presence of FRNAPH and BFRPH, respectively. Likewise, intestinal enterococci concentrations of ≥104 cfus g−1 and <103 cfus g−1 comprise a threshold for the presence of FRNAPH and BFRPH, respectively. In the case of SOMCPH, it was not possible to define a threshold, since they were detected with the lowest observed indicator concentrations in all samples.

Safety analysis and risk assessment in a new pesticide production line

Abstract In this work, the safety analysis of a new production line in a pesticide factory in Northern Italy is presented. The analysis was based on four different methods in a way that every part of the new line was investigated. The eventual incidents identified by this analysis were further examined with regard to their consequences using three different simulation models for the release and dispersion of the resultant toxic cloud. This analysis has proven that the risk level for the personnel of the factory and the surroundings is acceptable.

Assessment of Fenton's reagent and ozonation as pre-treatments for increasing the biodegradability of aqueous diethanolamine solutions from an oil refinery gas sweetening process

The aim of this work was to evaluate the efficiency of three chemical oxidation processes for increasing the biodegradability of aqueous diethanolamine solutions (aqueous DEA solutions), to be used as pre-treatments before a biological process. The raw aqueous DEA solution, sourced from a sour gas sweetening plant at a Mexican oil refinery, was first characterized by standardized physico-chemical methods. Then experiments were conducted on diluted aqueous DEA solutions to test the effects of Fentons reagent, ozone and ozone-hydrogen peroxide on the removal of some physicochemical parameters of these solutions. Lastly, biodegradability tests based on Dissolved Organic Carbon Die Away OECD301-A, were carried out on a dilution of the raw aqueous DEA solution and on the treated aqueous DEA solutions, produced by applying the best experimental conditions determined during the aforementioned oxidation tests. Experimental results showed that for aqueous DEA solutions treated with Fentons reagent, the best degradation rate (70%) was obtained at pH 2.8, with Fe(2+) and H(2)O(2) at doses of 1000 and 10,000 mg/L respectively. In the ozone process, the best degradation (60%) was observed in aqueous DEA solution (100 mg COD/L), using 100 mg O(3)/L at pH 5. In the ozone-hydrogen peroxide process, no COD or DOC removals were observed. The diluted spent diethanolamine solution showed its greatest increase in biodegradability after a reaction period of 28 days when treated with Fentons reagent, but after only 15 days in the case of ozonation.

Pseudomonas, Pantoea and Cupriavidus isolates induce calcium carbonate precipitation for biorestoration of ornamental stone

Bacterially induced calcium carbonate precipitation from various isolates was investigated aiming at developing an environmentally friendly technique for ornamental stone protection and restoration.

Multiparametric investigation of mould‐free shelf life of bread via factorial design

Abstract The investigation of a complex process, such as the bread making process, can be greatly favored by the approach of statistical design of experiments. Using simple first order factorial designs, reliable models were constructed investigating the effects of salt, sugar, sorbic acid, calcium propionate, vegetable fibers, fat and emulsifier on the shelf life of bread (optimization parameter). These effects were in general linear. An exception was observed in the case of use of calcium propionate where an interaction between salt and sugar was determined. The effects of all significant factors on optimization parameter were reasonable. Sorbic acid and calcium propionate proved to be more effective preservatives than salt and sugar by an order of magnitude. Antifungal efficiency of sorbic acid was found to be about three times that of calcium propionate. Prolongation of shelf life reached 117% for sorbic acid and 63 % for calcium propionate, when salt and sugar were fixed to their basic levels. Vegetable fibers had a detrimental effect on shelf life greatly decreasing it by as much as 65 % of the control samples (without fibers). Addition of fat and emulsifier in the dough showed a slightly negative effect on the mould‐free shelf life of bread.

Safety of Buried Pressurized Gas Pipelines near Explosion Sources

Accidental explosions in process industries, explosives factories, open pit mines, quarries, public works or even intentional explosions near a pipeline (sabotage) may endanger buried pressurized gas pipelines. Risk estimation is very complicated due to a great deal of phenomena participating in the final output, namely, explosion, energy transfer to the soil and air, soil pipeline interaction and response of the pipeline. The explosion source analysis was based on theoretical, semi-empirical or complicated computer codes. Stresses on the pipeline were directly related to the peak particle velocity of the ground in contact with the pipeline. The cube root scaling model of the shock wave propagation through soil was used for estimating the attenuation of particle velocity. The relative stiffness of the liner compared to the medium in which it is embedded was also taken into account. A one-step estimation method was developed for the prediction of either safety distance, or maximum allowable quantity of explosives, or pipe equivalent stress induced by ground shock waves generated by the explosion. The method is based on a relationship of attenuation of peak particle velocity with distance pipeline stress models and an experimentally determined relationship between circumferential and longitudinal strains derived from experimental results. The Huber-Hencky-Mises stresses approach was used in the models. The method takes into account the parameters related to explosion source, explosive-to-soil coupling effect, shock wave propagation in the ground, attenuation of ground waves with distance, soil-to-pipe coupling effect, dynamic nature of impact wave and construction characteristics of the pipeline in single solvable formulas for each of the above cases. Scientific calculators can be used to solve these formulas, but estimations can be greatly facilitated by the constructed nomographs or by use of a worksheet prepared in Ms-Excel environment.

Cupriavidus metallidurans biomineralization ability and its application as a bioconsolidation enhancer for ornamental marble stone

Bacterially induced calcium carbonate precipitation of a Cupriavidus metallidurans isolate was investigated to develop an environmentally friendly method for restoration and preservation of ornamental stones. Biomineralization performance was carried out in a growth medium via a Design of Experiments (DoE) approach using, as design factors, the temperature, growth medium concentration, and inoculum concentration. The optimum conditions were determined with the aid of consecutive experiments based on response surface methodology (RSM) and were successfully validated thereafter. Statistical analysis can be utilized as a tool for screening bacterial bioprecipitation as it considerably reduced the experimental time and effort needed for bacterial evaluation. Analytical methods provided an insight to the biomineral characteristics, and sonication tests proved that our isolate could create a solid new layer of vaterite on marble substrate withstanding sonication forces. C. metallidurans ACA-DC 4073 provided a compact vaterite layer on the marble substrate with morphological characteristics that assisted in its differentiation. The latter proved valuable during spraying minimum amount of inoculated media on marble substrate under conditions close to an in situ application. A sufficient and clearly distinguishable layer was identified.