Volume 2 - 2000

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.

Field experiments have been conducted to investigate flow and dispersion through obstacle arrays.
Model obstacles which represent real structures at a nominal scale between 1/10 and 1/20 were used.
The main purpose of the experiments was to examine flow and dispersion of contaminants in the vicinity
of individual obstacles embedded in an array of cubes. Two array configurations were used, namely
the in-line and staggered array configurations. The field experiments were supported by flow visualisation
trials performed in the wind tunnel. In the light of the results of these wind tunnel trials, the field
experiments were carried out using an array spacing S/H = 1.5 (where S is the space between two consecutive
array elements). Dispersion around an isolated model building has already been investigated
in the field (Mavroidis and Griffiths, 1996). Thus comparison is allowed between dispersion around an
isolated obstacle and around the same obstacle embedded in an array of cubes.

Fire agencies worldwide apply millions of gallons of fire suppression chemicals on a broad array of
ecosystems. These chemicals are considered to have minimal effects on the health of people who might
be exposed to them. Only incidents of skin and eye irritation have been reported as a result of prolonged
fire retardant and firefighting foam contact. Fire suppression chemicals have minor toxicological
or ecological effects and, as a result, do not generally harm terrestrial ecosystems. Major impacts,
suppression chemicals have on the environment, may be through the adverse effects on water quality,
and subsequently to aquatic ecosystems. Retardants may encourage eutrophication and, in some cases,
contribute to fish kill when applied on watersheds, or if accidentally applied directly to water bodies.
Foams are generally more toxic than retardants to aquatic biota, but they are applied in much smaller
quantities. Application of retardants increases the total amount of smoke and airborne particulate produced,
but air quality implications are minimal since additional smoke emission by the retardant is
insignificant compared to the major output by the wildfire. Recommendations are offered for mitigation
of potential human health and environmental impacts from the use of fire suppression chemicals,
nevertheless, risks must be assessed on a site-by-site basis.

During the production of cephradine (a main constituent of anti-osmotic drug) a large quantity of concentrated
effluent was produced. The main polluting compounds in this effluent are osmotic drug,
acetic acid and ammonia. The main objectives of the study were to assess the toxicity in terms of specific
methanogenic activity on anaerobic degradation of cephradine with Volatile Fatty Acid (VFA) as
co-substrate in batch systems using adapted and non-adapted cultures and to study the effect of
bioaugmentation with adapted and non-adapted cultures on anaerobic treatment of anti-osmotic drug
based pharmaceutical effluent in continuous mode using a fluidised bed reactor. The toxicity assessment
was measured in terms of specific methanogenic activity (ml CH4 g-1 VSS d-1), which was found
to decrease with increase in cephradine concentration and attained a maximum at 100 mg l-1. The COD
reduction (%) in continuous mode reached maximum of 88.5 at a Hydraulic Retention Time (HRT) of
12 h using bioaugmentation through periodic addition of 14 to 20 g l-1 of biomass (acclimated cells)
every 2 days from an off-line enricher-reactor.