Environmental Engineering Reference
In-Depth Information
1.1
Classification of pollution according to pollution pathways
1.1.1 Point sources of pollution
These are sources associated with man-made discharges of pipelines and canals, and are
also known as “end of pipe” sources of pollution. They are identifiable discrete
discharges from municipal and industrial wastewater collection and treatment systems.
They could be broadly subdivided into two categories, based on their composition and
origin:
• Municipal wastewater - The characteristic quality parameters have been well studied,
defined and are relatively easy to measure and control. However, their values vary in
certain limits depending on the geographical and climatic conditions, level of
economic development, mixture of influent sources (industrial/domestic), and size of
community served.
• Industrial wastewater - The quality characteristics are extremely diverse and require
individual assessment for each specific case. We could differentiate between
“manufacturing” wastewater, generated during the production process and “service
water”, generated by canteens, ablution blocks, and other activities, complementary to
the industrial process. The service industrial wastewater usually has the characteristics
of municipal wastewater. Dealing with industrial wastewater as a source of pollution
requires understanding of the production process and, in most cases, segregation of
different types of wastewater flows.
1.1.2
Non-point sources of pollution
They are associated mainly with land drainage and surface runoff, which enters a water
body by dispersed and poorly defined ways. For this reason, the term “diffuse pollution”
is commonly used as well. Atmospheric waste loads are chemicals and particulate matter,
which settle from the atmosphere or are scavenged by precipitation. They could be
classified as possible diffuse sources of pollution if they reach water bodies. Municipal
wastewater applied to land may become a non-point source of pollution in runoff, if not
handled properly. Usually, we differentiate between diffuse pollution from agricultural
sources and diffuse pollution in urban areas. Agricultural sources are associated mainly
with runoff and leachate from agricultural lands and animal operations, and are generated
by the excess application of fertilizers, pesticides, herbicides, as well as, increased
salinity of return flows. Diffuse pollution in urban areas is associated mainly with
polluted urban runoff (drainage), contaminated with materials washed up from streets,
roads, roofs, open spaces, etc.
1.2
Classification according to pollution behavior
• Non-conservative pollutants - these include most organics, some inorganics and many
microorganisms, which are degraded by natural self-purification processes and their
