Environmental Engineering Reference
In-Depth Information
origin fulfill the definitions of FC, therefore results with respect to FC should be
interpreted with caution.
Viruses are obligate parasitic particles consisting of a strand of genetic material with a
protein coat. They do not have the ability to synthesize new compounds; instead they
invade the living (host) cell where the viral genetic material redirects cell activities to the
production of new viral particles at the expense of the host cell. When an infected cell
dies, large numbers of viruses are released to infect other cells. Viruses that are excreted
by human beings may become a major hazard to public health. The FC test indicates the
possible presence of pathogen bacteria and viruses.
Algae are single-celled plants and can cause nuisance in surface waters because they
reproduce rapidly under conditions of nutrient supply, warm temperature and sunlight,
leading to the formation of large floating colonies in streams, lakes, and reservoirs, called
algae blooms.
Other microorganisms would include plants and animals of importance, ranging in
size from microscopic rotifers and worms to macroscopic crustaceans. Knowledge of
these organisms is helpful in evaluating the condition of streams and lakes. Methods to
control surface water quality by the use of biological indicator organisms (the procedure
is known as “biomonitoring”) are described briefly in Chapter 12.
3 DIFFUSE POLLUTION - GENERATION AND SOURCES
Diffuse pollution is generated during the process of rainfall and the corresponding runoff
to natural water bodies and as such is difficult to be clearly evaluated and defined. In
order to do it, we need a considerable database regarding the natural water quality status
of the corresponding body, which needs to be analyzed, and trends of deterioration
regarding specific parameters or benchmarks established. In this context the evaluation
and detection of diffuse pollution is directly connected to the continuous and regular
control, monitoring and assessment of the water quality status of natural water bodies. In
addition, the level of diffuse pollution is directly related to the quantity and quality of
runoff, which depends on the rainfall pattern, the land topography and land cover. Thus,
in many cases of diffuse pollution, the major causes are associated with changed land use
practices, caused by deforestation and large-scale construction.
Basically, we could divide the sources of diffuse pollution into two broad categories,
depending on their location - in urban areas, and in rural (non-urban areas). However, in
many cases we could find mixed patterns.
Most of the chemical composition of surface runoff is due to erosion from soil
surfaces and the wash-off of particles from impervious surfaces. Organic matter, metals,
different cations and anions may be transported and delivered to natural water bodies in
particulate or dissolved form. Diffuse pollution of ground water occurs mainly in
dissolved form. Based on the transportation pattern, diffuse pollution constituents in
surface runoff could be found in:
• Solid phase - these are chemicals, which are strongly associated with particulate matter.
These includ eorganic nitrogen, particulate phosphorus and heavy metals. The
assignment of metals to this category is arbitrary, since dissolved forms are often
present under acidic conditions. Therefore, it is assumed here that the primary sources
