Encyclopedia of Environmental Science and Engineering, Volume I and II

ENVIRONMENTAL HEALTH 347

toluene) but does oxidize some inorganic compounds which

are not measured, that is, affected by the BOD analysis.

When storm water and domestic sewage enter a sewer

it is called a combined sewer. If domestic sewage and storm

water are collected separately, in a sanitary sewer and in

a storm sewer, then the result is a separate sewer system.

A sewage works or sewage system is a combination of

sewers and appurtenances for the collection, pumping and

transportation of sewage, sometimes, also called sewerage,

plus facilities for treatment and disposal of sewage, known

as the sewage treatment plant.

The privy, or one of its modifi cations, is the common

device used when excreta is disposed of without the

aid of water. When excreta is disposed of with water, a

water-carriage sewage disposal system is used; generally

all other domestic liquid wastes are included.

Stream Pollution and Recovery

Although the 5-day BOD is the best single measure of

wastewater or polluted water organic loading, aquatic organ-

isms when measured with the biochemical oxygen demand,

the chemical oxygen demand where indicated, the dissolved

oxygen, and the sanitary survey taken all together are the

best indicators of water pollution. Other chemical and bacte-

rial analyses provide additional information.

In a freshly polluted water, during the fi rst stage (5 to

20 days at 20°C), mostly carbonaceous matter is oxidized.

This is demonstrated by an immediate increase in the stream

BOD and oxygen utilization in the area of pollution dis-

charge, followed by the second or nitrifi cation stage where

a lesser but uniform rate of oxygen utilization takes place

for an extended period of time. This is accompanied by a

related characteristic change in the stream biota. The amount

of dissolved oxygen in a receiving water is the single most

important factor determining the waste assimilation capacity

of a body of water.

Stream pollution (organic) is apparent along its length by

a zone of degradation just below the source, a zone of active

decomposition and, if additional pollution is not added, a

zone of recovery. In the zone of degradation the oxygen in the

water is decreased, suspended solids may be increased and

the stream bottom accumulates sludge. The fi sh life changes

from game and food species to coarse. Worms, snails, and

other biota associated with pollution increase. In the zone of

active decomposition, the dissolved oxygen is further reduced

and may approach zero. The water becomes turbid and gives

off foul odors. Fish disappear, anaerobes predominate in the

Spring in rock

Spring in sand

4 " reinforced concrete

1/4" rods 6" o.c. both ways or

4 " x 4 " mesh, No. 6 wires

4 " reinforced concrete

1/4" rods 6" o.c. both ways or

4 " x 4 " mesh, No. 6 wires

1 " overflow or larger

24 " manhole, optional

12 "

6 "

21 2 "

Animal fence

Surface water

diversion ditch

around spring

25 ' to 30'

Clay or hardpan

Water bearing stratum

(sand and gravel)

Dry wall; loose stones

Shutoff valve

Strainer Pipe poured in place

Delivery pipe, below frost to

storage tank, pump, building etc.

Rock

Fill all surface

cracks in rock

with cement grout

Concrete gutter

around spring

Water source

fissure or fault

Gutter

Earth

Clay soil backfill

wet and tamped

Wall keyed

in rock

Backfill

Drain

Union

Overflow set at

normal water level

Floor drain pan and 2"

drain pipe poured in place

FIGURE 5 Properly constructed springs. Reprinted, with permission, from Environmental

Sanitation, Joseph A. Salvato, Jr., John Wiley & Sons, Inc., copyright, 1958.

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