Environmental Engineering Reference
In-Depth Information
requires a thorough investigation and understanding of the fate of pollutants in the water
environment and their impact on water use. Also, it requires the application of site-
specific effluent standards to be defined and administered; therefore it is not as
straightforward as the UES approach to apply in practice. Also, it requires a higher
standard and more complex skills from the regulatory organizations and consequently its
application is a more costly procedure.
5.2.3
The Waste Assimilative Capacity Concept
One example of the combination of both approaches, which is applied in the USA
(Novotny 2003), is the Waste Assimilative Capacity Concept (WACC). This concept
combines both the UES and RWQO approaches and its main advantage is that it
incorporates specific procedure for evaluation, assessment and control of diffuse
pollution, together with the consideration of point sources pollution and the
environmental health, not only of receiving water bodies, but also of all environmental
elements. The main goal of this concept is the determination of the waste assimilative
capacity (WAC) of the environment (water, air and soil). WAC represents the amount of
pollution load, which could be absorbed and assimilated, without altering its integrity.
The term “loading capacity” (LC) is introduced, which represents the sum of the load
from background pollution (BL) and WAC. The procedures used during the application
of the WACC could be summarized as follows:
• Establish background load (BL) - this procedure requires information regarding
background quality and flow rates;
• Establish receiving body criteria, based on beneficial use - as per RWQO approach;
• Establish loading capacity (LC) - this procedure requires the estimation of the total
assimilative capacity of the water body, which usually is based on the application of
specific models, with respect to specified parameters, e.g hydrological models for
water quantities estimation, qualitative models representing the DO assimilation, or
toxicity evaluation of given toxic compounds;
• Estimate admissible load - WAC=LC-BL.
• Establish the actual pollution load for each specific case, from point and diffuse
pollution sources;
• If WAC > pollution load - RWQO approach to be applied
• If WAC < pollution load - ES approach to be applied
It should be noticed that this concept is very sound in its logic and provides a possibility
for more accurate evaluation of the available resources and the potential for their
sustainable exploitation. Also, a very important consideration is the fact that decisions
with respect to the use of available water resources could be done, based on scientific
information. However, this approach requires very extensive data sets with respect to
quantitative and qualitative characteristics not only for surface water, but for ground
water, soils and air, which is a costly and time consuming exercise. The practical
application of the concept requires the development of sound models, reflecting with
enough accuracy, the assimilative processes in the environment. Correspondingly, the
application of such models requires an advanced level of the technical support in terms of
hardware and human resources. All this makes its practical implementation difficult even
