Environmental Engineering Reference
In-Depth Information
concentrations change with time due to decomposition and different types of
transformation processes.
• Conservative pollutants - these are the ones, which are not affected by natural processes
and their concentrations do not change with time. Typical examples are inorganic
substances that can only have their concentrations reduced by dilution.
1.3
Classification of pollution according to pollution characteristics
• The addition of biodegradable organic material - it will result in the depletion or
complete removal of dissolved oxygen in the water body, with corresponding adverse
effects on its environmental status. It has been widely recognized that this type of
pollution is of the greatest importance. Most of the efforts in water pollution control
and abatement have been implemented to control or reduce the biodegradable organic
matter discharged to surface or ground waters.
• Toxicity and mutagenic pollutants - it is due to the presence of synthetic organic
compounds, salts of heavy metals, acids and alkalis, radioactive and other materials,
which have toxic or mutagenic effect on living organisms. There are a variety of toxic
substances resulting from industrial and agricultural operations, municipal practices
and even normal domestic activities, which inhibit the normal aquatic activities of a
water body and most importantly, pose serious threats to public health if the receiving
body is used as a drinking water source or as a recreational site.
• Enhanced eutrophication - this is a natural phenomenon of lake aging, which could be
classified as pollution when the natural process has been largely accelerated by the
activities of men. It is dependent on the increases of potentially soluble inorganic
nutrient materials, both in the sediment and in the lake water itself. Eutrophication
could be considered as a truly natural process, only in cases when the inflow of
nutrients to a lake is consistently higher than the outflow, within the unaltered
conditions of the catchment area. Enhanced eutrophication becomes apparent
principally by the development of large blooms of algae as the increased potential
productivity of the lake responds to sunlight, with the production of heavy algal
blooms and the appearance of algal mats on lake surfaces together with the dense
growth of certain macrophytes.
• Salinization - this is the process of increasing the naturally dissolved solids
concentrations of water resources due to certain activities. This type of pollution is
often found in arid regions. Portions of the water for irrigation are lost through
seepage and evaporation. Part of it is consumed by plant evapo-transpiration, and the
excess passes through the soil to be collected by tile drainage and returned to the river.
If tile drainage system is not available, it will percolate to the nearest aquifer. As the
salt concentration of river and drained water is the same, but the volume of drained
water is considerably diminished, the salt concentrations of the receiving water body
would rise with time. More severe salinity problems can be met in cases when
transient leaching of soil salts occur, and when treated wastewater is used for
irrigation purposes.
• The addition of inert, insoluble mineral material - this type of pollution is mainly due to
the erosivity of runoff, and is generally considered a minor source of surface water
pollution. It is associated with excess sediment deposition, increased turbidity and
