MIL-HDBK-1005/16
restraints, very aggressive environments can exist, especially
just above the water line. In these areas, consideration must be
given to providing more resistant materials of construction or
protecting the substrate with high performance coating systems.
Often there are background levels of hydrogen sulfide
present around a wastewater treatment plant. These low
concentrations of hydrogen sulfide can be very corrosive to
various electrical and control systems because of the large
amount of copper contacts that exist in these systems. Special
consideration should be given to these systems to avoid excessive
corrosion (see pars. 12.2.4 and 12.2.5).
12.2
Materials of Construction. During the design of a
wastewater treatment plant, it is important to accurately define
the conditions of service throughout the process. In addition,
the flow of the wastewater through the plant should be examined
to identify areas where the wastewater will have the potential to
release hydrogen sulfide. A preliminary listing of acceptable
materials of construction should be developed, based on the
information presented in this section and the specific conditions
of the wastewater treatment plant.
12.2.1
Concrete Structures. Concrete structures have
generally given good performance in most wastewater environments.
It is important, however, that American Concrete Institute (ACI)
standards and practices be followed for placement of concrete and
thickness of cover over reinforcing steel. If high sulfate
concentrations are determined to be present, either in the soils
or groundwater, specify the appropriate type of cement. Refer to
Table 21 for the criteria for specifying the type of cement. If
high chlorides are present, it will be necessary to specify a
barrier coating on the exposed concrete surfaces.
Waterproof all underground structures against intrusion
of water or moisture through the walls. Waterproofing is
especially important if the structure will be coated on the
inside surfaces. Hydrostatic pressure through a concrete wall
will cause failure of coatings on the inside surfaces. In areas
of known or suspected exposure to hydrogen sulfide, the use of a
high-performance coating system should be specified. See par.
12.3.1 for details.
12.2.2
Buildings. Customary architectural designs of
buildings may be used for most wastewater treatment plant
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