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Adsorption and removal of commercial dyes were studied in aqueous suspensions of fly ash mixtures
with a sandy clay loam soil of low organic matter content. The commercial dyes, acid orange 7, acid yellow
23, disperse blue 79, basic yellow 28 and direct yellow 28 represent the widely used nitroazo structures.
Batch and column experiments were carried out at equilibrium conditions for concentrations of
dyes between 5 and 60 mg l-1. The logarithmic form of Freundlich equation gave a high linearity and
the k constants are increasing with the increase of fly ash content in adsorbent mixtures and the affinity
between the adsorbent surface and adsorbed solute. The mean removed amounts of dyes by adsorption
batch experiments in soil mixture with 20% fly ash content were up to 53.0% for acid yellow 7,
44.9% for acid yellow 23, 99.2% for direct yellow 28, 96.8% for basic yellow 28 and 88.5% for disperse
blue 79. The removal of dyes from column experiments decrease with the increase of the solution concentration
form 10 to 50 mg l-1 at 20 °C, showing the process to be highly dependent on the concentration
of the solution. The mean removed amounts of dyes by adsorption on columns of soil mixture
with 20% fly ash content and for initial concentration of dye solutions 50 mg l-1 were up to 33.8% for
acid yellow 7, 59.4% for acid yellow 23, 84.2% for direct yellow 28, 98.2% for basic yellow 28 and 60.3%
for disperse blue 79.

Modeling of Anaerobic Digestion - A Review

Lyberatos G. and Skiadas I.V., Pages:63-76

DOI:

https://doi.org/10.30955/gnj.000112

Paper Topic:

General

Issue:

Issue 2

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Abstract

Anaerobic digesters often exhibit significant stability problems, that may be avoided only through appropriate
control strategies. Such strategies require, in general, the development of appropriate mathematical
models, which adequately portray the key processes that take place. This paper reviews the current
state of the art in anaerobic digestion modelling, and identifies the key areas that require further research
endeavors.

Conceptual site modelling for evaluating contaminant mobility and pump-and-treat remediation

Nikolaidis N.P. and Shen H., Pages:67-76

DOI:

https://doi.org/10.30955/gnj.000114

Paper Topic:

General

Issue:

Issue 1

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Abstract

The development of a conceptual site model (CSM) is an invaluable tool used for assessing and planning
remedial actions at a contaminated site. The CSM incorporates site-specific, hydrogeologic and
geochemical information to identify contaminants of concern, sources of pollution, environmental
pathways and retardation mechanisms, and points of exposure. The model is dynamic and continually
revised as new information is obtained during the course of investigation. A ground water contamination
case study is examined to illustrate the development and application of a CSM. The site is a metal
plating facility that has contaminated the ground water with chromium. The CSM was incorporated
into a 3-D fate and transport model. The Heavy Metal model, HM-3D, was used to simulate the fate
and transport of chromium at the site and evaluate pump-and-treat remediation scenarios.

Relation between air pollution episodes and discomfort index in the greater Athens area, Greece

Paliatsos Ath. and Nastos P., Pages:91-97

DOI:

https://doi.org/10.30955/gnj.000119

Paper Topic:

General

Issue:

Issue 2

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Abstract

An attempt is made for a first general study of the relation between high/very high concentrations of
nitrogen dioxide and ozone with the discomfort index (DI) values. The nitrogen dioxide data of
«Patision» station and ozone data of «Liosia» and «Marousi» station have been analysed. The relation
between air pollution episodes and the corresponding values of DI during the period 1993-1995 have
been examined for the Greater Athens Area (GAA). For the warm period of the year, the frequency of
the DI values for different levels of air pollution in the GAA is also examined.

Application and Verification of a three-dimensional Hydrodynamic Model to Hamilton Harbour, Canada

Tsanis I.K. and Jian Wu, Pages:77-89

DOI:

https://doi.org/10.30955/gnj.000132

Paper Topic:

General

Issue:

Issue 1

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Abstract

A multi-layered three-dimensional hydrodynamic model has been developed to provide flow fields and
water level changes in Hamilton Harbour. The field data collected in Hamilton Harbour during 1990
& 1991 field seasons was used for model verification. The simulated currents were compared with current
meter data. Results from the trajectory model are in good agreement with the drogue experimental
data. A quantitative criterion to evaluate the trajectory comparison was established with the help of
the trajectory model using the random-walk approach. By using the water level changes in the
Burlington Ship Canal, the model predictions were validated with the measurements at three water
level stations in the Harbour. These comparisons demonstrate that the models can simulate the major
features of the water current and level changes in Hamilton Harbour.

Winter Southern wind flow and air pollution episodes over Athens, Greece

Kassomenos P.A., Lykoudis S. and Kallos G., Pages:99-110

DOI:

https://doi.org/10.30955/gnj.000126

Paper Topic:

General

Issue:

Issue 2

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Abstract

The greater area comprising the Attica peninsula and the Saronic Gulf is greatly influenced by various
local circulation types. During winter months, moderately high air pollutants concentrations are
observed when the prevailing condition is either stagnant or a weak southern flow. The case studied in
this paper regards an episode that occurred in mid-December. This episode is characterized by very
weak pressure gradient over Greece, and very little change in wind speed and direction with height,
without the precedence of exceptionally strong warm advection in the lower troposphere during the
days before the episode. This episode was not characterized by very high air pollution values, a rather
common feature during December, that even though it presents one of the highest episode frequencies,
the observed values are not high enough to require the enforcement of restrictive measures.

Simulating of the admixture spreading in a steady 2D lengthy stream of the viscous fluid

Babayan A.V. and Nadolin K.A., Pages:91-97

DOI:

https://doi.org/10.30955/gnj.000155

Paper Topic:

General

Issue:

Issue 1

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Abstract

The problem of the passive contaminant spreading in a steady viscous fluid stream is discussed while the
admixture's dissipation and diffusion are taken into account. The channel is assumed to be a horizontal
plane, curvilinear and quite lengthy, so that the ratio of the stream width to its length can be regarded as
a small parameter. A mathematical model of the process derived by the small parameter technique from
the 2D steady Navier-Stokes equations for incompressible viscous fluid and non-steady convection-diffusion
equation of a substance in the moving medium is introduced. A finite element method is applied for
numerical study of the proposed model and results of computer experiments are presented.

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Removal of dyes from aqueous solutions by adsortion on mixtures of fly ash in batch and column techniques

Modeling of Anaerobic Digestion - A Review

Conceptual site modelling for evaluating contaminant mobility and pump-and-treat remediation

Relation between air pollution episodes and discomfort index in the greater Athens area, Greece

Application and Verification of a three-dimensional Hydrodynamic Model to Hamilton Harbour, Canada

Winter Southern wind flow and air pollution episodes over Athens, Greece

Simulating of the admixture spreading in a steady 2D lengthy stream of the viscous fluid

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