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Aeration is one of the most common stages in the liquid waste clarification process. Most aeration
tanks are equipped with aeration devices that inject oxygen to enhance the biodegradation of the liquid
waste. In this work an aeration process is simulated, where the air is injected from the bottom of a
cylindrical tank. Two numerical models are developed and two different geometries are considered.
Their results are verified against published data. Both models solve the momentum, continuity and k-
å equations for the relevant phases. The first model considers liquid and gas phases as homogeneous
fluid. The calculated velocity refers to the mixture of the phases. The second model assumes liquid and
gas as two distinct phases. Velocity and volume fraction profiles portray the induced motion of the liquid
and the extent of the aeration process. Regarding the two different geometries, the first assumes a
flat free liquid surface, while the second a liquid surface free to swell according to the gas injection rate.
It is shown that the second geometry gives more accurate results.

The changes in greenhouse gases and aerosols emissions are expected to lead to regional and global
changes in temperature, precipitation, and other climate variables. The degree to which human conditions
and the natural environment are vulnerable to the potential effects of climate change is a key concern
for governments and the environmental science community. Regional differences in climate
change and its impacts have recently been identified as current gaps in the present scientific knowledge.
Air quality regional impacts of global climate change, namely the effects on photochemical production,
are not a common subject of scientific studies. The main objective of this paper is to provide a basis of
scientific information for policy makers and public use by the assessment of the vulnerability of
Portuguese air quality to climate change. A General Circulation Model was applied in order to provide
initial and driving meteorological boundary conditions, assuming a present climate situation and a scenario
of double carbon dioxide concentration in the atmosphere, for higher resolution mesometeorological
and photochemical models. Results emphasise a possible significant impact of the climate
change scenario on the photochemical pollution, namely at noon.

The structure and function of communities and biological systems favorable and unfavorable to salt
production in the ponds of solar saltworks are described. Favorable systems maintain a diverse biota
and power the organisms at levels that enable a saltworks to economically and continuously produce
high quality salt at design capacity. Unfavorable systems-the result of disturbances and high concentrations
of nutrients in the water-are dominated by a few species that release massive quantities of
organic substances, decrease pond surface areas and volumes, and decrease salt quality and quantity.
Management practices to obtain and maintain favorable systems under a variety of conditions are
reviewed.

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.