Building Design and Construction Handbook - Merritt - Ventech!

14.34 SECTION FOURTEEN
Storm water is primarily the water that runs off the roof or the site of the
building. The water usually is directed to roof drains or gutters. These then feed
the water to drainpipes, which convey it to a municipal or private storm-water sewer
system. Special conditions at some building sites, such as large paved areas or steep
slopes, may require the capture of storm water in retention areas or ponds to prevent
the municipal storm sewer systems from being overloaded. From these areas or
ponds, the storm water is generally conveyed to the storm sewers through outfall
structures designed to delay and control the flow of storm water to the municipal
storm sewer systems. Discharge into sanitary sewers is objectionable, because the
large flows interfere with effective wastewater treatment and increase treatment
costs. If kept separate from other types of wastewater, storm water usually can be
safely discharged into a large body of water. Raw domestic wastewater and industrial
wastes, on the other hand, have objectionable characteristics that make some
degree of treatment necessary before they can be discharged. Nevertheless, municipal
combined sewers (sanitary and storm wastes) exist in some areas. Appropriate
local authorities should be consulted to determine which type of system is available
and specific regulations that relate to connection to these systems.
In areas where municipal sanitary sewers are not available, some form of wastewater
treatment is required. Prefabricated treatment plants are available in various
sizes and configurations. Most treatment systems are complex and require many
steps. These include filtration and activated-sludge and aeration methods. The degree
of treatment necessary generally depends on the assimilation potential of the
body of water to receive the effluent, primarily the ability of the body to dilute the
impurities and to supply oxygen for decomposition of organic matter present in the
wastewater.
Industrial waste may present special problems because (1) the flow volume may
be beyond the public sewer capacity, and (2) local regulations may prohibit the
discharge of industrial waste into public sewers. Furthermore, many pollution regulations
prohibit discharge of industrial waste into streams, lakes, rivers, and tidal
waters without suitable prior treatment. Industrial wastes generally require treatments
engineered to remove the specific elements injected by industrial processes
that make the wastes objectionable. Often, these treatments cannot be carried out
in public wastewater treatment plants. Special treatment plants may have to be built
for the purpose. Treatment methods for a variety of industrial wastes are discussed
in W. W. Eckenfelder, Jr., ‘‘Industrial Water Pollution Control,’’ McGraw-Hill Publishing
Company, New York. Specific design procedures for sewers, drains, and
wastewater treatment, with accompanying numerical examples, are given in T. G.
Hicks, ‘‘Standard Handbook of Engineering Calculations,’’ McGraw-Hill Publishing
Company, New York.
14.12 SEWERS
A sewer is a conduit for water carriage of wastes. For the purpose of this section,
any piping for wastewater inside a building will be considered plumbing or process
piping; outside the building, wastewater lines are called sewers.
Sewers carry wastewater. And a system of sewers and appurtenances is sewerage.
Sanitary sewers carry domestic wastes or industrial wastes. Where buildings
are located on large sites, or structures with large roof areas are involved, a storm
sewer is used for fast disposal of rain and is laid out to drain inlets located for best
collection of runoff.