Environmental Engineering Reference
In-Depth Information
approach requires a corresponding regulatory basis, orientated towards the water quality
of the receiving body. The so-called “clean” water, or in other words, the acceptable
standard of water quality, varies depending on the use of the water. The water quality
objectives or guidelines, with respect to a natural water body, could be defined as: “the
desirable level of water quality to be attained and maintained in receiving waters”. They
should be formulated, considering the different beneficial uses of the water body, such as
municipal and industrial water supply, agriculture, recreation, aesthetics and the
propagation of wildlife. The purpose of all pollution control and abatement measures
should be aiming at the attainment of these objectives, together with the protection of the
water body assimilative capacity, shell and fin fish, wildlife, and the preservation and/or
restoration of the aesthetic and recreational value of natural waters.
The regulation of diffuse pollution in the USA is based on the established non-point
source management programs under section 319 of the Clean Water Act (USEPA 1995).
This approach helps the states to address non point sources, and runoff pollution by
identifying water affected by such pollution and adopting and implementing management
programs to control it. Such programs recommend where and how to use the best
management practices (BMPs) in order to prevent runoff from becoming polluted. In the
case of identified pollution levels, the programs recommend specific measures to reduce
the amount of pollution that reaches the surface waters. Some of the BMPs include:
• Proper planning to store and dispose materials;
• Erosion prevention by planting fast growing annual and perennial grasses, to shield and
bind the soil;
• Specific requirements for urban planning and development, encouraging the
introduction of pervious pavements and environmental buffer zones;
• Installation of detention ponds and sand filters and the use of temporary check ditches
to divert runoffaway from the storm drains.
In addition, a receiving water quality approach has been recommended, which links the
specified receiving water quality objectives to the recommended beneficial water use and
accounts for the assimilative capacity of the receiving water body. A permissible
pollution load (Total Maximum Daily Load or TMDL), which includes point and non-
point pollution sources is evaluated and allocated to the water bodies, which are
controlled and protected. The consideration of the loads from all point source permits in
the catchment of this specific water body, together with all non-point pollution sources,
should not exceed the TMDL. It must be emphasized, that such an approach requires
legal intervention at national level. Although storm water and environmental
management programs are created and executed at local level, national regulatory
instruments would be the driving force and would place the framework for such
activities. However, as previously mentioned in Chapter 2, the practical implementation
of this or similar approach is costly and requires an extensive data base, together with
high technical background for its implementation. Its applicability for developing
countries could be a point of discussion and most probably a long term and phased
implementation strategy should be adopted.
In South Africa, a similar trend has been followed, and the regulatory instrument
applied is the National Environmental Management Act (NEMA) (DWAF 1996). It
recognizes in one of its principles on water resources that the quantity, quality and
