Environmental Engineering Reference
In-Depth Information
Figure 2.3. Schematic representation of
storage volume determination, based
on triangular hydrographs.
their purpose. A schematic representation of the principles of storage volume
determination is shown in Figure 2.3.
Recently, storage facilities are designed as multipurpose basins, where in addition to
storage, a substantial pollution reduction is achieved. These structures are retention type
basins, named sometimes “dual-purpose” basins, where the wet pool is designed as a
pond or wetland. During peak runoff events they retain the peak flow and release it to the
stream at a delayed rate, while the lower part of the basin is always wet and perform the
function of a treatment facility, as shown in Figure 2.4. Many different configurations
could be developed, given the topographic and soil conditions.
Dual-purpose basins could be used as recharge facilities for ground water infiltration,
as well. The application of storage facilities is most effective in cases where the
topographic conditions allow for natural depressions, which could be easily transformed
to storage basins.
3.3.2
Stabilization ponds
Stabilization ponds are widely used for wastewater treatment. The function and design
principles are the same with respect to storm water treatment. However, it should be
remembered that storm water usually has a lower organic content, compared to
wastewater, and this consideration would influence the configuration and size of the pond
system. They resemble closely the natural processes of stabilization of organic materials
in natural water bodies, but are engineered in terms that adequate inlet and outlet
facilities, retention time and depth are designed in advance, in order to allow for the
provision of a proper process environment. Stabilization ponds are usually excavated
basins, but if the topography allows, natural depressions could be used. There are three
major types of ponds applied in practice-anaerobic, facultative and maturation ponds.
With respect to the treatment of polluted runoff, which has relatively low pollutants
