Biomedical subjects

Spyros K Golfinopoulos

Publications and source records attributed to Spyros K Golfinopoulos.

9 recordsLinked to original sources

PubMed2004

Modeling the formation of chlorination by-products in river waters with different quality.

Water chlorination results in formation of a variety of organic compounds, known as chlorination by-products (CBPs), mainly trihalomethanes (THMs) and haloacetic acids (HAAs). Factors affecting their concentrations have been found to be organic matter content of water, pH, temperature, chlorine dose, contact time and bromide concentration, but the mechanisms of their formation are still under investigation. Within this scope, chlorination experiments have been conducted with river waters from Lesvos island, Greece, with different water quality regarding bromide concentration and organic matter content. The factors studied were pH, time and chlorine dose. The determination of CBPs was carried out by gas chromatography techniques. Statistical analysis of the results was focused on the development of multiple regression models for predicting the concentrations of total trihalomethanes and total HAAs based on the use of pH, reaction time and chlorine dose. The developed models, although providing satisfactory estimations of the concentrations of the CBPs, showed lower correlation coefficients than the multiple regression models developed for THMs only during previous study. It seems that the different water quality characteristics of the two river waters in the present study is responsible for this phenomenon. The results indicate that under these conditions the formation of THMs and HAAs in water has a more stochastic character, which is difficult to be described by the conventional regression techniques.

Bromides↗

PubMed2003

Organochlorine pesticides in the surface waters of Northern Greece.

A survey undertaken in Northern Greece has shown that organochlorine pesticides are present in the surface waters. Surface water samples have been collected seasonally from four rivers and five lakes for a period of two years. Solid-phase extraction followed by gas chromatographic techniques with electron capture detection was used for the determination of the compounds. The most commonly encountered organochlorine pesticides in surface waters were the isomers of hexachlorocyclohexane, aldrin, dieldrin and endosulfan sulfate. In some cases the concentrations detected were higher than the qualitative target levels set by the European Union, especially for hexachlorocyclohexane and aldrin. The occurrence of these compounds in Greek surface waters can be attributed to intense agricultural activity as well as to transboundary pollution.

Agriculture↗

PubMed2003

The occurrence of disinfection by-products in the drinking water of Athens, Greece.

Application of chlorination for the disinfection of drinking water results in the formation of a wide range of organic compounds, called disinfection by-products (DBPs), which occur due to the reaction of chlorine with natural organic materials. The occurrence of DBPs was studied in samples from four drinking-water treatment plants (WTPs) and from the distribution network of Athens, Greece. Twenty-four compounds, which belong to different categories of DBPs, were monitored, including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetonitriles (HANs), haloketones (HAKs), chloral hydrate (CH) and chloropicrin (CP). Sampling was performed monthly for a period of two years, from three different points at each WTP and from eight points atthe distribution network. Samples were analyzed by GC-ECD methods, which included pretreatment with liquid-liquid extraction for volatile DBPs and acidic methanol esterification for HAAs. The results of the analyses have shown the presence of disinfection by-products belonging to all categories studied in all water samples collected after prechlorination. The major categories of DBPs detected were THMs and HAAs, while the other volatile DBPs occurred at lower concentrations. The concentrations of DBPs did not in any case exceed the maximum contaminant levels (MCL) set by USEPA and WHO. However, monitoring these compounds needs to be continued, because their levels could increase due to changes in the quality of water entering the water treatment plants. Reduction of the concentrations of DBPs could be achieved by optimization of the chlorination conditions, taking into account the effect of time. Moreover, research on alternative disinfection methods (e.g. ozone, chlorine dioxide, chloramines) and their by-products should be conducted to evaluate their applicability in the case of the drinking water of Greece.

Chlorine Compounds↗

PubMed2002

Determination of haloacetic acids in water by acidic methanol esterification-GC-ECD method.

Acidic methanol esterification followed by gas chromatography (GC) with electron capture detection (ECD) was applied for the determination of the nine haloacetic acids in water. The main advantage of this method is the use of acidic methanol as the derivatization agent instead of the hazardous diazomethane. The recoveries, estimated at concentrations ranging from 0.5 to 30 microg/l, are high for eight of the nine haloacetic acids, with the only exception being monochloroacetic acid. However, problems with this compound have been reported with diazomethane derivatization methods as well. The detection limits of the method range from 0.01 to 0.2 microg/l.

Acetates↗

PubMed2002

Determination of volatile organic compounds in surface waters and treated wastewater in Greece.

The occurrence of volatile organic compounds (VOCs) was studied in river water, lake water, seawater and treated wastewater in Greece from October 1998 to September 1999. The determination of 41 VOCs was performed with a Purge and Trap-Gas Chromatography-Mass Spectrometry method. Samples were collected seasonally from 10 rivers, seven lakes, three gulfs and four wastewater treatment plants. In surface water samples, 15 VOCs were detected. In wastewater samples, occurrence of 31 VOCs was observed. The results suggest that not only agricultural and industrial activity within the Greek territory, but also transboundary pollution deriving from neighbouring countries consist important sources of VOCs in surface waters of Greece. However, the measured concentrations did not in any case exceed the guideline values proposed by the EC.

Environmental Monitoring↗

PubMed2002

Quantitative assessment of trihalomethane formation using simulations of reaction kinetics.

A modelling procedure with a time discretisation of 1 min is developed in order to study and simulate the kinetics of formation of total trihalomethanes (TTHM) in water treatment plants. This methodology was applied on two significant processing units of Athens (Galatsi Treatment Plant-GTP, Menidi Treatment Plant-MTP). The fundamental concept of the model was based on the representation of the water treatment plant as a mixed flow reactor, where the formation of TTHM was predicated on a generalised reaction of total halogens with an organic precursor. Differential rates of reactants and products were expressed in terms of the reaction stoichiometry. Volatilisation, flocculation, coagulation and sedimentation processes were also incorporated in the model in order to assess their distinct role. The most appropriate coefficient set was sought and it was found that a stoichiometric ratio of 0.5 for total halogen, 0.6 for organic substrate and 0.2 for TTHM (or 2.5:3:1) resulted in the best fit between simulated and experimental data. The present modelling approach should be considered as a promising methodological basis towards the realistic reproduction of the dynamics of water treatment plants and the development of reliable numerical tools for the accurate prediction of THM formation.

Disinfectants↗

PubMed2002

Multiple regression models: a methodology for evaluating trihalomethane concentrations in drinking water from raw water characteristics.

The presence of trihalomethanes (THMs) in drinking water has attracted the attention of both researchers and professionals, because of the harmful effects of these substances on human health. A multiple regression model was developed to estimate THM concentrations in finished drinking water, using data from the Menidi Treatment Plant of Athens. A number of routinely measured characteristics--including chlorine dose, chlorophyll a, temperature, pH and bromide--of raw water, were used to generate a reliable methodology for predicting both total THM and individual species concentrations. Seasonality effects were also considered during the analysis. In general, these models were found to give acceptable fits, estimating accurately lows and highs over the annual cycle.

Forecasting↗

PubMed2002

Formation of organic by-products during chlorination of natural waters.

Natural water from six sources in Mytilene, Greece, was chlorinated in order to identify and quantify some of the organic by-products formed. The compounds examined were trihalomethanes, haloacetic acids, haloacetonitriles, haloketones, chloral hydrate and chloropicrin. The factors tested were time and chlorine dose. The presence of bromide ion in some of the waters studied resulted in significant changes in the by-product speciation, with enhanced brominated species formation. In addition, UV absorbance, measured at three wavelengths, led to correlation of organic matter content with the concentrations of by-products produced. The species formed, varying among different water sources, increased with increasing chlorine dose. Most of the species also increased with increasing contact time, although there were some exceptions due to hydrolysis reactions.

Chlorine Compounds↗

PubMedDate not supplied

DBP levels in chlorinated drinking water: effect of humic substances.

Chlorination is the most widely used technique for disinfection of drinking water. A consequence of chlorination is the formation of Disinfection By-Products (DBPs). The formation of DBPs in drinking water results from the reaction of chlorine with naturally occurring organic materials, principally humic and fulvic acids. This paper focuses on the effect of humic substances on the formation of twenty-four compounds belonging to different categories of DBPs. This investigation was conducted in two water treatment plants in Greece, Menidi and Galatsi, from July 1999 to April 2000. Humic substances were determined by the diethylaminoethyl (DEAE) method with subsequent UV measurement. The techniques used for the determination of DBPs were liquid-liquid extraction, gas chromatography and mass spectrometry. The concentrations of DBPs were generally low. Total trihalomethanes (TTHMs) ranged from 5.1 to 24.6 microg L(-1), and total haloacetic acids (HAAs) concentration ranged from 8.6 to 28.4 microg L(-1), while haloaketones (HKs) and chloral hydrate (CH) occurred below 1 microg L(-1). The content of humic substances was found to influence the formation of DBPs and especially TTHMs, trichloroacetic acid (TCA), dibromoacetic acid (DBA), CH, 1,1-dichloropropanone (1.1-DCP) and 1,1,1-trichloropropanone (1,1,1-TCP). Seasonal variation of TTHMs and HAAs generally followed that of humic substances content with peaks occurring in autumn and spring. The trends of 1,1-DCP, 1,1,1-TCP and CH formation seemed to be in contrast to TTHMs and HAAs. Trends of formation of individual compounds varied in some cases, probably due to influence of parameters other than humic substances content. Statistical analysis of the results showed that the concentrations of TTHMs, CH, 1,1-DCP, 1,1,1-TCP, TCA and DBA are strongly affected from humic substances content (at 0.01 confidence level). The opposite is true for dichloroacetic acid (DCA) concentration. Humic substances also vary to a statistically significant degree during different months, as well as the concentrations of TTHMs, CH, 1,1-DCP, 1,1,1-TCP, TCA and DCA. The variance of DBA was not statistically significant. Regarding the effect of sampling station, humic substances content showed no statistically significant difference between the two raw water sources studied.

Chlorine Compounds↗