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Henry R. (Henry Richard) Kenwood.

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Albuminoid ammonia

O absorbed from permanganate (in two

hours at 27° C.) . .
Total solid matters

{a) Volatile

{b) Fixed

{c) Appearance on ignition

Total hardness

{a) Temporary

(&) Permanent
Chlorine
N as nitrates

Notes. — Sample 3. In industrial towns the reaction may be slightl}^ acid,
from the sulphuric acid in the atmosphere; and the water is a little different
in other respects owing to further impurities taken up, such as soot, sulphur
compounds, and increased ammonia. Thus the rain falling in INIanchester
has been found to contain 0-7 part per 100,000 of free ammonia, 0-03 of
albuminoid ammonia, 4-7 parts of sulphuric acid, and 0-5S of hydrochloric



3.


4.


Rain Water
(Country).

Good


Subsoil Water
(Gravel over Chalk)

Good


Faintly
alkaline


Alkaline


0-050


0-002


0-005


0-006


0-005


o-o6i


3-0


29-2


1-5


12-2


1-5

Nil


17-0

Slight

charring


0-5


20-0


o-o


5"5


0-5


14-5


0-25


2-1


0-02


0-2



ii8



L\BOKATORY WORK



acid. Rain collected on the sea coast has been found to contain as much
as 5*4 parts per 100,000 of chlorine (chlorides).

Rain water which is collected in countr}' districts after long periods of
continuous rainfall provides the purest possible nahtral water. Its com-
position varies throughout the year somewhat.

Sample 4. The analysis does not furnish evidence of harmful contamina-
tion; but the ammonias suggest the presence of a little vegetable matter.



Physical characters

Reaction

Free and saline ammonia. .

Albuminoid ammonia

O absorbed from permanganate

hours at 27° C.) . .
Total solid matters

(«) Volatile . .

(6) Fixed

(c) Appearance on ignition



Total hardness

(a) Temporary
{b) Permanent

Chlorine

N as nitrates



(in tw



A Peaty
Surface Water.

Brownish-
yellow
Acid
o-ooi

0'022

0'i6o

I2"0

9-5

2-5
Marked
charring

3.0

o-o

3-0

0-7

O'OI



6.

A N on -peaty

Surface Water on

Millstone Grit.

Nearly

colourless

Neutral

0'002

0*004

0-040
5-5

2-0

3-5
Faint dis-
coloration

2-5

O'O

2-5

0-8
0-05



Note. — In many "peaty waters" the "organic ammonia" and the
" oxygen absorbed " will be found to much exceed the amounts given
above. Neither of the above analyses furnishes evidence of harmful con-
tamination.



Physical characters

Reaction

Free and saline ammonia. .

Albuminoid ammonia

O absorbed from permanganate

hours at 27° C.) . .
Total solid matters

{a) Volatile . .

{b) Fixed

(c) Appearance on ignition



Total hardness

(a) Temporary
(6) Permanent

Chlorine

N as nitrates



in tw



7.

Deep-well Water
(from Chalk).

Excellent

Alkaline

0'Oo6

O'OII

0'oS4

40-0

15-5

24-5
Marked
charring

26*0

15-5

TO-5

4-5
0-6



8.

Deep-well Water

(from New Red

Sandstone).

Good

Alkaline

o-ooi

0'002



0'0I2

30-2
8-6

21'6

Nil

19-5
8-0

"•5

2-2
0.3



THE OPINION ON WATER SAMPLES



119



Notes. — A deep-well water from the chalk may ( ontain total solids up to
200 parts per 100,000, but such an amount is rare.

Sample 7 is a water the analysis of which warrants suspicion of organic
contamination. Slight animal contamination is probable in such a water,
having regard to the figures of the saline and albuminoid ammonia, the
chlorine and the oxidized nitrogen. A careful local inspection might
detect the source of some pollution.

There is no reason to question the purity of Sample 8.



Physical characters
Reaction

Free and saline ammonia. .

Albuminoid ammonia

O absorbed from permanganate

hours at 27° C.) . .
Total solid matters

{a) Volatile . .

{b) Fixed

(c) Appearance on ignition



Total hardness . .
(a) Temporary
{b) Permanent

Chlorine

N as nitrates



9.


10.


River Water.
Good


New River Water

(as supplied in

London).

Excellent


Faintly
alkaline


Faintly
alkaline


O'oog


O'OOI


0-017


0'002


o-ogg


0-014


32-5


31-5


i4'0


9-0


.. i8-5

Marked


22-5

Nil


charring




20-5


22-0


9-0


8-5


II-5

2-4


13-5
1-8


0-4


0-2



Notes. — Sample 9. The composition of river water will alwaj^s, of course,
vary with the following circumstances :

1. The nature of the country through which the river courses, and
which it therefore drains — i.e., whether this be cultivated and manured
or wild, whether there be much or little vegetation, and whether it be
thickly or sparsely populated.

2. The amount of pollution by sewage, waste products of manufactories,
etc., which gain access to the water.

3. The nature of the bed of the river, and of the strata through which
any springs (which feed the river) rise.

4. The rapidity and smoothness of flow — i.e., the more rapid and inter-
rupted this is, the greater the powers of the river in the direction of self-
purification.

No. 9 furnishes evidence of contamination.
No. 10 is a water of great purity.



120



LABORATORY WORK



11.



12.







Jjeep spring w.iter

(from Green'vand

below Chalk).


Spring Water
(from Chalk).


Physical characters




. . Excellent


Excellent


Reaction




Alkaline


Alkaline


Free and saline ammonia. .


0-030


O'OOI


Albuminoid ammonia




O'OOI


0-003


O absorbed from permanganate


(in two




hours at 27° C.)




0'020


O'Oig


Total solid matters




III'2


32-5


(a) Volatile . .




21'0


8-5


{b) Fixed




90'2


24-0


(c) Appearance on


ignition .


..Nil


Nil


Total hardness




.. i8-5


23-0


(a) Temporary'




.. 7-0


i8-o


{b) Permanent




II-5


5-0


Chlorine




12-2


3-0


N as nitrates




..0.4


0'2



Notes. — In Sample 11 the high amounts of saline ammonia, chlorine and
mineral matter so frequently present in pure waters from the lower green-
sand, are shown. Sometimes the nitrates are higher than in this sample.
The absence of recent animal pollution in this case is shown by the very
low figure of albuminoid ammonia.

Sample 12 is a very pure water. The ammonias are quite low.





13.


14.




Well Water from "






Carboniferous


Well Water.




Limestone.




Physical characters


E.xcellent


Excellent


Reaction


Alkaline


Alkaline


Free and saline ammonia. .


0-005


O-OOI


Albuminoid ammonia


0-006


O-OOI


absorbed from permanganate


(in two




hours at 27° C.)


0-066


0-008


Total solid matters


31-9


48-5


{a) Volatile . .


9-8


17-3


(b) Fixed


22-1


31-2


(c) Appearance on ignition .


. . Slight
charring


Nil


Total hardness


24-2


31-5


(a) Temporary


17-9


9-5


{b) Permanent


6-3


22-0


Chlorine


1-9


6-2


N as nitrates


0-3


1-8



Notes. — Sample 13. The ammonia figures indicate slight animal con-
tamination.

Sample 14 furnishes evidence of previous (remote) sewage contamination
in the high figures of N as nitrates and chlorine. The extremely low
albuminoid ammonia figure shows that the organic matter has been almost
completely mineralized. Nitrites were absent, but phosphates were
markedly present.



THE OPINION ON WATER SAMPLES



121



15.


16.


Chalk Water.


Peaty Water.


Excellent


Light brown




tint; clear


Alkaline


Acid


O'OiS


0-005


O-OIO


0-022


0-082


0-122


62-7


15-6


23-2


12-0


39-5


3-6


Marked


Marked


charring


charring


33-5


3-0


22*5


o-o


II-O


3-0


6-8


1-5


0-9


0'2



Physical characters

Reaction

Free and saline ammonia.

Albuminoid ammonia

O absorbed from permanganate (in two

hours at 27° C.)
Total solid matters

{a) Volatile . .

lb) Fixed

(c) Appearance on ignition

Total hardness

(a) Temporary

(6) Permanent
Chlorine
N as nitrates

Notes. — Sample 15 is a chalk water polluted with animal matter, as
evidenced by the high saline ammonia (along with a considerable amount
of organic ammonia) and the high figures of chlorine and oxidized nitrogen.
The hardness is also excessive, but this may readily be reduced to 11 parts
by a water-softening process.

Sample 16 is a peaty water polluted with animal matter, as evidenced
by the fact that the figures of the saline ammonia, the chlorine, and of the
oxidized nitrogen, are excessive for a peaty water. It is a water possessing
a considerable plumbo-solvent action.

17.
Physical characters . . . . . . Brackish

• taste ; blue-

green tint

Reaction Alkaline

Free and saline ammonia. . .. .. o-ooi

Albuminoid ammonia . . . . . . 0-006

O absorbed from permanganate (in two

hours at 27° C.) .



18.

Excellent



Alkaline
0-004
0-005



Total solid matters

(a) Volatile

(&) Fixed

(c) Appearance on ignition .



Total hardness

{a) Temporary
(6) Permanent

Chlorine

N as nitrates



0-050
249-2
32-8
216-4
Slight dis-
coloration
Very high



109-5
0-9



0-042

34'0

ii-o

23-0
Faint dis-
coloration

23-5
13-0
10-5

1-9

0.3



Notes. — Sample 17 is a deep-well water in the chalk contaminated by
sea water. This is evidenced by the fact that the chlorine is enormously
high and magnesium chloride is abundant. The well was near the coast



122 LABORATORY WORK

and, prior to the contamination, the chlorine was 4 parts per 100,000 and
the total hardness 24. The water is quite unfit for domestic uses on account
. of its excessive hanlness, the brackish taste, the deposit it will give rise to
in boilers and kettles, and the fact that it will impair the palatability of
tea, coffee, etc.; and it is altogether unsuitable for washing and cooking
purposes.

Sample 18 is a polluted water. The above figures would barely warrant
such an opinion, but a previous analysis of the water from the same source
gave the saline and organic ammonias as 0-002 and 0-003 respectively,
and the chlorine and oxidized nitrogen as i-S and 0-20 respectively. Some
pollution has therefore recently gained access to the water, and the sample
is included to illustrate the value of periodical analyses of a water-supply
in detecting intermittent pollution.

An examination of the bed of a waterway or pond may serve
to furnish corroborative evidence of the sewage contamination of
the water. Of such contamination there is httle or no reliable
indication by chemical anatyses, nor does a low-power micro-
scopic examination and a bacteriological examination supply
valuable evidence; and unless the pollution is gross, it is not
possible to conclude that a mud is contaminated with human
excrement, either from chemical or bacteriological data.

If any parts of the bed are covered with gravel or large stones
which are not clean, and especially if the greyish flocculent
growths characteristic of certain sewage fungi are found to be
attached to them or to any other part of the bed, and if the mud
is of a dark colour and emits gas bubbles and offensive odour
on being disturbed, then there are good reasons for suspecting
gross sewage contamination. It is common in these circum-
stances to find some opalescent floating bubbles, which have but
little tendency to burst, on parts of the surface of the overlying
\\ater.

Although the organic matter in pond and river mud will be
found on an ordinary microscopical examination to be largely
in the form of unrecognizable debris, with only a relatively small
(but variable) quantity of the vegetable structure of plant life
distinguishable, a textile fibre or animal hair, etc., \\'ould indicate
dangerous contamination {vide p. 155).

Water markedly contaminated with sewage or sewage effluent
is unlit to be used by cows for drinking purposes; for, apart from
the risk to the health of the animal, there is a danger of specific
organisms of intestinal origin getting upon the teats and udders
of the cows, and thereby into the milk in the process of milking.

Gerber and Sheldon botli agree that dirty drinking-water



THE OPINION ON WATER SAMPLES 123

may give rise to impure and tainted milk. We know that
improper food, such as fermented potatoes or cabbages, affect
the taste and keeping quahties of cow's milk; and there is no
reason why what applies to food should not apply to drink.
It is, moreover, only reasonable to suppose that the drinking of
polluted water is injurious to the cow as well as to the milk; and
that the purer the food and water given to cows tlie better both
for the animal and for the milk she furnishes.

The presence of a small amount of domestic sewage in a stream
of fair volume and flow is apparently not injurious to fish.
Oysters, mussels, and cockles are tolerant of considerable sewage
pollution, although there is evidence that oysters become scarcer
and smaller in the presence of gross pollution; but in the case
of these shellfish, their capacity to retain specific disease-pro-
ducing bacteria when bathed in polluted water makes the con-
sumption of them, when collected from such waters, a grave
danger, the reality of which has been abundantly demonstrated
in this and other countries.

Fresh-water fish generally are more affected by pollution from
chemical wastes than by sewage; but they vary considerably in
their susceptibihty to sewage contamination. In experimenting
upon the effect of the sewage contamination of a stream upon
fish life, allowance must be made for this fact. Trout appear to
be very susceptible, and they require to be kept in running
water. Gold-fish, gudgeon, and roach (of which the latter two
are very sensitive to various forms of pollution in water, while
the former is relatively resistant) are suitable fish to experi-
ment with. These may be kept in the contaminated water,
while at the same time control fishes are kept in pure water;
and by observation of their active movements, their food con-
sumption, the healthy appearance of their eyes, fins, tails, etc.,
the weight of the survivors at the end of the experiment, and
the rate of mortality, it is not difficult to learn from the com-
parative data collected whether the polluted water has proved
inimical or not.

Bacteriological Evidence.

Like the chemical, the value of this evidence has certain
limitations. As ordinarily performed, even the bacterial counts
furnish evidence only of the discrete masses of organisms. There
is no necessary relationship between these and the numbers of



124 LABOKATOKY WORK

separate organisms originally present, because with efflux of
time the organisms, like other suspended particles, tend to
agglutinate. Again, at the present day it is often impossible to
reco\ier or recognize the specific germ, even shortly after this has
been experimentally added to water; and the organisms which
denote sewage contamination are the same whether they are
derived from the lower animals or from human beings. Yet,
despite these facts, the results of a bacteriological examination
of water samples, interpreted in the light of topographical cir-
cumstances, is generally of great value.

The Colleciion and Transmission of Samples. — Great care is
required in the collection of the samples; even apparently trivial
errors or omissions may entirely vitiate the result. Very precise
and seemingly trifling directions must be given, unless the sample
is collected by an expert.

For the ordinary examination 2-ounce (57 c.c.) glass-stoppered
bottles are sufficient. When larger amounts are required, a
Winchester quart bottle may be used. The bottles should be
sterilized, with their stoppers loosely inserted, at 160° C. for one
hour, and allowed to cool slowly.

If the specimen cannot be examined at once, and delay is
unavoidable, the sample should be packed in ice, and then trans-
mitted to the laboratorj^ Special apparatus have been designed
for this purpose.

That figured on p. 125 is a convenient form. Two-ounce
glass-stoppered bottles are used. Each of these, after thorough
washing, and drying in the hot-air apparatus, has its stopper
inserted, and is then placed in a tin into which it just shps.
The bottom of the tin has a layer of cotton-wool and then a
piece of asbestos cardboard.

Several thicknesses of asbestos cardboard are also fitted in
the cover of the tin, so that when in place the bottle is firmly in
contact with the asbestos above and below. The tins with their
contained bottles are then sterilized in the hot-air apparatus-
Labels are placed on the outside of the tins, and they are ready
for use. The ice-boxes are made to just receive one, two, or
four such tins. The tins are not opened after sterilization until
immediately before the sample is taken.

To take samples from various depths, a number of different
forms of apparatus have been devised. The ordinary collecting-
bottle may, however, be also used for this purpose. It is tied



BACTERIOLOGICAL EVIDENCE



125



into a leaden cage, and lowered to the required depth by catgut
or string attached to the cage. The loosened stopper is then
removed by a jerk upon a second string previously tied to the
stopper, and the sample collected.

In collecting samples from a reservoir, lake, or river, plunge
below the surface before removing the stopper, thus avoiding
scum and surface contaminations. If from a tap, allow the
water to first run to waste for five to ten minutes. If from
wells with a pump, pump away a considerable quantity of water





FIG. l6. COLLECTING-
BOTTLE AND TIN.

A, Asbestos cardboard in lid;
B, asbestos cardboard below
bottle D ; C, cotton-wool
layer.



FIG. 17. ICE-BOX.

A and B, felt lining; C, metal ice re-
ceptacle, with depression D, to hold
two collecting-tins (with contained
bottles) .



before collecting the sample; while if a complete investigation
is required, a second sample should be obtained after several
hours' pumping.

Owing to the extreme difficulty of detecting the actual
specific organisms of disease, such as the organisms of typhoid
fever and cholera, it is necessary to resort to other methods of
investigation.

Hygienists are unanimous in recognizing that sewage and the
excreta of human beings, diseased or healthy, must be looked
upon as potential vehicles for disease production. The presence



126 LABORATORY WORK

of the excreta of animals must also be looked upon as prejudicial,
since it may contain harmful bacteria and other parasites.

A number of organisms have been advocated as fulfilling the
requirements necessary for indicators of sewage contamination.
Of these, B. coli and allied organisms, B. ententidis sporogenes,
and certain streptococci, are the only ones which have been
extensively advocated and merit detailed consideration.

For these organisms it is not only necessary to ascertain their
presence or absence, but, in addition, their numbers.

Significance and Interpretation of Results. — The detection of the
cholera spirillum or the typhoid bacillus in a water, in whatever
amount, is sufficient to condemn the water. The other results
obtained in the bacteriological examination of water-supplies are,
however, only data from which an opinion upon the purity or
contamination of the water can be deduced with more or less
confidence according to the data available.

Such deductions require much special experience, and for a
detailed consideration of the matter the reader is referred to
Dr. Savage's book on the subject,* limits of space only allowing
here a bald summar}' and review.

The number of organisms developing upon gelatine plates is
largely an index of the amount of organic matter in the water,
although there is no constant or exact relationship between the
two. Still, the addition of organic matter almost invariably
means an addition both of foreign bacteria and of material
which enables the water, for a time at least, to become a better
nutrient medium, and so causes an increased proliferation of
bacteria.

A low gelatine count is, therefore, a satisfactory feature; but,
on the other hand, a high gelatine count cannot in itself be con-
sidered a sufficient reason for condemning a water. For surface
waters the contamination is frequently with harmless organic
matter, and of comparative unimportance.

Good deep-well and spring waters frequently contain less than
50 bacteria per c.c. developing on gelatine plates, while in surface
waters, even when free from pollution, up to 500 or more per c.c.
are not infrequently met with.

The blood-heat count (agar plates at 37° C.) is an index of the
addition of bacteria other than those natural to pure water, but

* " The Bacteriological Examination of Water-Supplies " (H. K. Lewis,
London, 1906).



BACTERIOLOGICAL EVIDENCE I27

they need not be harmful. The addition of harmless soil bacteria
will cause a great increase in the number of the ^Y' ^^- organisms.
The number present in deep-water sources, when pure, is very
low, frequently less than i per c.c, and 10 or more per c.c. is
not satisfactory. In the case of surface waters and rivers, soil
washings are common, and a more generous margin (50 to 100
per c.c.) is necessary. On the whole, a marked increase in the
number of bacteria growing at 37° C. is of greater significance
than a proportionate increase of the gelatine count.

Of much greater importance is the interpretation of the B. coli
estimation. The views of different workers show considerable
variance. This bacillus is abundant in human and animal
excreta and in sewage, and it serves as a meas^ure of excretal
pollution.

Deep-well and spring water should not be liable to any poUu-
tion by material containing B. coli. Water from these sources,
even if originally polluted, must have passed through a con-
siderable depth of soil, and thus have become purified from all
bacterial evidence of contamination. If such sources are properly
protected at their outlets, there is no reason why they should
contain any B. coli. It is, therefore, justifiable to maintain an
attitude of great suspicion towards any water from such sources
which contains B. coli in 100 c.c. or less.

In the case of surface supplies and shallow wells the position
is different. For example, considering upland surface waters,
the opportunity for contamination by B. coli contained in animal
{e.g., sheep) excreta may be considerable. The B. coli from
sheep excreta are indistinguishable from those from sewage or
human feeces, yet no one would contend that they are of equal
significance, or that it is equally important to prevent their
presence.

As a matter of experience, on the other hand, it will generahy
be found that B. coli rigidly defined is not found in shallow wehs,
or in the majority of surface supplies, in 10 c.c. or less, unless
that water is being polluted with excrementitious matters in
undesirable amount.

While, therefore, admitting that dogmatic standards are
especially untrustworthy for these classes of waters, a working
standpoint that the finding of excretal B. coli in 10 c.c. or less points
to undesirable pohution is both justifiable and in accordance
with actual experience. If no B. coli are present in 50 c.c. the



128 LABORATORY WORK

water ma}- be safely passed as satisfactory. For rivers used as
sources of drinking-water, without artificial purification, similar
standards are applicable.

Sometimes the organisms isolated are not typical B. coli, but
differing in the absence of one or more of the characteristic
properties of this organism. In the opinion of most bacteriolo-
gists of experience the nearer these lactose-fermenting coli-like
bacilli approach typical B. coli in their characters, the more
nearly are our numerical standards for that organism applicable
to them, while if the}' lack essential characters a proportion-
ately greater number must be present to justify an adverse
opinion.

Determinations of the number of streptococci have been made
much less frequently than in the case of B. coli. As a pro-
visional guide, and without attaching an equal significance to
the findings, a standard similar to that for B. coli may be em-
ployed — i.e., their presence in lOO c.c. or less of deep-well or
spring water, or in lo c.c. or less of surface and shallow-well
waters, would justify an adverse opinion as to the purity of the
water in question.

On its negative side the streptococcus test is not of great
value, and the absence of streptococci, even in a considerable
bulk of water, cannot be taken as showing purity or freedom
from danger.

Opinion is not united as to the value of B. enterilidis sporo-
genes as an indicator of pollution. It is fairly abundant in
sewage and excreta, but it is a spore-bearing organism with
prolonged powers of resistance, and therefore, even if it be



Online LibraryHenry R. (Henry Richard) KenwoodPublic health laboratory work → online text (page 11 of 36)