Environmental Engineering Reference
In-Depth Information
use of runoff from roofs and other open space areas at household level or small suburb
levels. It is assumed that this water has a very low level of pollution and could be reused
directly for different types of beneficial uses.
A relatively new development in the planning of urban water systems advocates
decentralized wastewater systems, where the segregation of different types of water is
recommended (Dean & Lund 1981). One possible form of combination of storm and gray
water reuse is shown in Figure 2.7.
In decentralized systems, the transport of the different flows is minimized and all
types of flows are treated and reused within a relatively small area. This allows for the
utilization of the vast majority of the products, thus forming a close loop cycle with zero
undesirable emissions. Storm water reuse forms part of the cycle. This practice requires
the provision of storage reservoirs of adequate size. The “harvested” runoff could be
reused again without treatment for irrigation or other beneficial uses, which do not have
high water quality requirements. In other cases, the runoff from larger areas could be
collected, and after treatment, could be reused for different purposes.
Figure 2.7. A schematic representation
of storm water reuse in combination
with gray water reuse.
There are numerous possible configurations of such type of systems at different scales;
but the concept itself is still in the phase of development and research. The example,
shown in Figure 2.7 envisages the combined storage and reuse for irrigation purposes of
gray water and storm water, where gray water is domestic wastewater from household
washing and bathing activities. This scheme does not show the black water released from
toilets, which should be treated and reused in a separate line.
4 MANAGEMENT APPROACHES AND TOOLS
Historically, water resources management has dealt with the provision of water quantities
necessary for the development of the society. Ancient civilizations have started to collect,
store and transport water for different purposes. In ancient Egypt, the water levels of the
