Page 377 - Fair, Geyer, and Okun's Water and wastewater engineering : water supply and wastewater removal

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10.1 Sources of Wastewaters 337
and hydrogen sulfide destroy cement, concrete, and metals; hot wastes crack tile and
masonry conduits; poisonous chemicals disrupt biological treatment, kill useful aquatic
life, and endanger water supplies; fertilizing elements add to the eutrophication of lakes;
anthrax and other living organisms are infective to man; flammable or explosive liquors
imperil the structures through which they flow; and toxic gases or vapors are hazardous to
workmen and operators of wastewater works. Industrial wastewaters are usually pretreated
before their discharge into public sewers
Groundwater may enter gravity sewers through pipe joints. In combined systems
and stormwater drains, runoff from rainfall and melting ice and snow adds the washings
from streets, roofs, gardens, parks, and yards. Entering dirt, dust, sand, gravel, and other
gritty substances are heavy and inert and form the bed load. Leaves and organic debris
are light and degradable and float on or near the water surface. Waters from street flush-
ing, firefighting, and water-main scouring, as well as wastewaters from fountains,
wading and swimming pools, and drainage waters from excavations and construction
sites swell the tide.
Domestic wastewaters flow through house or building drains directly to the public
sewer (Fig. 10.4). Runoff from roofs and paved areas may be directed first to the street gut-
ter or immediately to the storm sewer. In combined systems, water from roof and yard
areas may be led into the house drain. Other storm runoff travels over the ground until it
reaches a street gutter along which it flows until it enters a stormwater inlet or catch basin
and is piped to a manhole and to the drainage system. In separate systems, connections to
the wrong sewer are commonly in violation of sewer regulations. The dry-weather flows of
combined sewers are primarily domestic and industrial wastewaters; the wet-weather
flows are predominantly storm runoff. The first flush of stormwater may scour away de-
posited and stranded solids and increase the discharge of putrescent organic matter through
stormwater overflows.

Caulked pipe sleeve
Fresh-air inlet

Foundation
Street Sidewalk
wall
Vent

Caulked pipe sleeve Clean-out Basement floor

Common or
public sewer
House drain;
cast iron;
House sewer or service slopes 8 in.
1
connection; vitrified tile; House or or more per ft
1
slopes about 4 in. per ft; running trap
not less than 4 in. in diameter,
preferably 6 in. or more
Figure 10.4 Connecting Building Drainage System to Sewer (Trap may be
installed or omitted). Conversion factors: 1 in 25.4 mm; 1 ft 0.3048 m