COMPLAINTS
The complaints that have been made against chlorinated water since the
practice was commenced have been very diversified in character and can
be numbered by the legion and although some have been justifiable, the
great majority has been unsubstantiated and must be ascribed to
auto-suggestion.
Almost every one who has had charge of chlorination plants has noted the
latter phenomenon, for in some instances complaints have been made
following the publication of the information that chlorination was to be
commenced but antecedent to its actual operation, and in others when for
some reason or another, the chlorination plant has been temporarily
stopped. Similar observations have been made in laboratory experiments
when independent observers have been requested to detect the chlorinated
waters from an equal number of treated and untreated waters. Such
observers are wrong in the majority of the waters which they designate
as treated ones if the dosage is not in excess of that required for
satisfactory purification.
One amusing example of auto-suggestion was experienced by the author
some years ago. During a ceremonial visit to the waterworks, the Mayor
and several civic representatives happened to visit a hypochlorite plant
that was built on a pier over the river and which had no ostensible
connection with the city mains. One of the party expressed a desire for
a drink of good river water without any hypochlorite in it and was
served with water from the plant supply by an assistant engineer of the
waterworks department. The water was consumed by all with great relish
and as it was being finished, the writer entered the plant and was
invited to join them in the enjoyment of this "dopeless" water; on
asking where it had been obtained he was astonished to hear that it was
from a tap which was supplied with the ordinary chlorinated water of the
city.
On many occasions, complaints are justifiable and should be carefully
investigated instead of, as is often the case, being attributed to
auto-suggestion. The time and energy that are often devoted to
endeavouring to persuade water consumers that their complaints are
without foundation, can better be utilised in so improving the
chlorination process as to eliminate tastes and odours. All complaints
should be carefully investigated and a record kept for future reference,
for the cause, although not manifest at the time, may be discovered
later. The records then provide valuable corroborative evidence.
The nature of the complaints against chlorinated water is very
diversified and includes imparting foreign tastes and odours, causing
colic, killing fish and birds, the extraction of abnormal amounts of
tannin from tea, the destruction of plants and flowers, the corrosion of
water pipes, and that horses and other animals refuse to drink it.
_Tastes and Odours._ When an excess of hypochlorite or liquid chlorine
is added to a water it imparts a sharp pungent odour and acid taste,
characteristic of chlorine, that render it offensive to the nose and
palate. In some instances the presence of chlorine compounds is not
obtrusive when the temperature of the water is low but becomes so when
the temperature is raised. It is especially observable when the faucets
of hot water services are first opened and the chlorine is carried off
as a vapour by the other gases liberated by the reduction in pressure.
For this reason the complaints regarding hot water are relatively more
numerous and sometimes constitute the whole of the complaints. In cold
water containing appreciable quantities of mineral salts the
hypochlorites and hypochlorous acid might not be entirely dissociated;
they may become more hydrolysed with an increase in temperature and
finally broken down under the influence of the carbonic acid liberated
from the bicarbonates by heat.
Chlorine also forms chlorinated organic compounds by action on the
organic matter present in water and some of the objectionable tastes and
odours of chlorinated waters have been attributed to this agency. Some
observers have stated that chloramines were amongst the chloro-organo
compounds produced but the author's experience with the Ottawa supply
has demonstrated that simple chloramine (NH_{2}Cl) can be successfully
employed for water treatment without causing complaints. It was
suggested on page 28 that some of the higher chloro-amines might be the
cause of some complaints but at present there is no definite information
regarding the formation of these compounds in water and all such
hypotheses are little more than conjectures. Letton[1] has reported that
at Trenton, in 1911, when the water of the Delaware River was first
treated, the dosage was as high as 1.2 p.p.m. of available chlorine and
although chemical tests showed the absence of free chlorine, the water
had an extremely disagreeable taste which was especially noticeable in
the hot water. The conclusion was reached that "the taste and odour were
not those of chlorine, but were due to some complex chemical change
brought about by the action of the chlorine on the organic matter
present in the water."
The waters that require the most accurate adjustment of chlorine dosage,
if complaints are to be avoided, are those containing very small amounts
of organic matter. The margin between the dosage required for the
attainment of a satisfactory degree of bacteriological purity and that
which may cause complaints is usually very small, often less than 25
per cent, with the waters of the Great Lakes and many filter effluents.
On the other hand, coloured waters containing large amounts of organic
matter can be treated with an excess of chlorine without causing tastes
and odours. The author found that the addition of 1.5 p.p.m. of
available chlorine to the Ottawa River water did not cause complaints
although only 0.8 to 0.9 p.p.m. were usually required for satisfactory
purification. Harrington of Montreal has had a similar experience with
this water.
The presence of traces of foreign substances in water sometimes produces
chlorinated derivatives having repugnant tastes and odours. Creosote and
tar oils have caused an odour somewhat resembling that of iodoform and
industrial wastes have also produced complaints.
The substitution of chlorine gas (liquid chlorine) for bleach solutions
has apparently eliminated tastes and odours in some cases but this may
be due to a more perfect control over the dosage rather than to any
property of the bleach _per se_.
In some instances the sludge from bleach plants has caused complaints by
producing an excessive concentration of chlorine during the period of
its discharge. This occurred in Ottawa on several occasions before it
was discovered and corrected. When the sludge in the storage tanks
reached the discharge valve it was customary to wash out the tank and
discharge the sludge into the river. The operators opened the wash out
valves to the full extent and the sludge and liquor were discharged into
the river about 70 feet away from the inlet to the sedimentation basin
and on the downstream side of it. A portion of the hypochlorite was
almost invariably carried into the basin and increased the dosage. This
condition was remedied by carrying the sludge drain farther down stream
and insisting upon the sludge being discharged at a slower rate.
Kienle[2] has reported similar occurrences at Chicago. The hypochlorite
was applied at the intake cribs situated a considerable distance off
shore. The direction of the wind often necessitated holding the sludge
for a considerable length of time but occasionally it was found
impossible to await favourable conditions with the result that the wind
and wave action carried a portion of the sludge back into the crib and
down into the shaft and tunnel.
The temperature of the water at the time of treatment is another factor
bearing on the production of tastes and odours. When the temperature is
low, water absorbs relatively less chlorine (_vide_ Diagram No. II, page
38) in the same period of time with the consequence that, if the dosage
is kept constant, more chlorine is present in the free condition. At
Milwaukee (Kienle)[2] with a dosage of 0.24 p.p.m. of available chlorine
(as bleach) no complaints were received during the spring, summer, and
autumn seasons but when the temperature reached 40 deg. F., they were
compelled to reduce the chlorine to 0.12 p.p.m. in order to prevent
objectionable tastes and odours in the tap waters.
Abnormal conditions such as freshets, and storms, sometimes cause
complaints regarding tastes and odours. Adams[3] found that the
complaints in Toronto usually accompanied a change in the direction of
the wind, a sustained east wind being the one most productive of
trouble. The exact cause for this could not be ascertained but it was
usually found that there was an accompanying increase in the number of
microscopical organisms (plankton) present in the raw water.
Freshets usually increase the bacterial contamination and necessitate an
increased dosage which may cause complaints.
Complaints as to tastes and odours can be best avoided by ensuring
regularity of dosage, perfect admixture, and storage of the treated
water for a reasonable period. These factors are discussed in detail
elsewhere.
_Colic._ Although claims have been made that the consumption of
chlorinated water has produced "colic" no corroborative evidence has
been adduced and the symptoms have probably been due to some other
cause. Dilute solutions of chlorine have been used as intestinal
antiseptics in the treatment of typhoid fever without producing
irritation of the mucous lining and the usual dose for this treatment is
one grain of chlorine. Before taking a _medicinal_ dose of chlorine 140
gallons of water containing 0.1 p.p.m. would have to be consumed, a
quantity greater than is ordinarily drunk in a year.
Chlorine and hypochlorites are destructive and irritant to skin and it
is possible that hot chlorinated water has, in some instances, a similar
effect.
It is inconceivable that the addition of minute traces of bleach or
chlorine to water should cause it to extract abnormal amounts of tannin
from tea but it is possible that free chlorine, when present, acts upon
the tea extractives and produces compounds having obnoxious tastes and
odours. Tannin to the ordinary tea drinker represents the disagreeable
portion of the tea and an obnoxious taste in tea brewed with chlorinated
water would consequently be ascribed to the extraction of abnormal
quantities of tannin.
Almost all waterworks departments using chlorination have received
complaints to the effect that the water had killed fish and small birds.
There is usually no evidence that the loss was due to chlorinated water
but it is generally impossible to convince the owners that the process
of water treatment was not the cause. Many continuous physiological
tests have been made of the effect of chlorinated water on small fish
and have shown that the concentration used in water treatment is without
effect. The author kept a tank of minnows in one of the pumping stations
for months without loss although the tank was continuously supplied with
water that had been treated but a few seconds previously. The bleach
solution was discharged into the suction of the pumps and the water for
the fish test was taken from the discharge header.
It has been found on many occasions that fish are extremely susceptible
to chlorine and hypochlorites. This knowledge has been sometimes used
for such nefarious purposes as fish poaching, a few pounds of bleach in
a small stream being a simple and most effective method of killing all
the fish which are then carried down stream into a convenient net.
Chlorinated sewage effluents have also been known to destroy the fish
life of the stream into which they were discharged.
The opinion of fish culturists as to the action of chlorinated waters
upon fish eggs in hatcheries is almost unanimously to the effect that it
is a destructive one. Fish eggs are extremely sensitive to chlorine and
hypochlorous acid and very few will survive in a water containing 0.1
p.p.m. of free chlorine. The Department of Fisheries of the Dominion of
Canada has informed the author that free chlorine in the water had a
marked adverse effect on the hatching of the eggs of Atlantic salmon,
Great Lake trout, pickerel, and whitefish, but no effect was noticed
when free chlorine was absent. The Department has, however, decided to
remove all the hatcheries to localities where water that does not
require chlorination can be obtained.
The effect of chlorinated water upon seeds, plants, and flowers has been
investigated by the Dominion Department of Agriculture and Dr. Gussow
(Dominion Botanist) and Dr. Shutt (Agricultural Chemist) who were in
charge of the work, have reported that water treated with hypochlorite
caused no apparent injury to carnations and hybrid roses. Six varieties
of wheat seed, after soaking in freshly prepared hypochlorite solutions
(0.05 to 10 parts per million of available chlorine) were all sown on
the same day. Germination was found to be uniform throughout and no
effect of the chlorine was observed either as regards the rate of
germination or the development of the young plants. Experiments on
barley and oats produced similar results. Radishes, turnips, cucumbers,
and beans also showed no retardation in development after treatment with
chlorinated water.
These experiments were conducted with solutions of bleach in distilled
water, but identical results were obtained in a later series when the
treated city supply (Ottawa) was used.
The results proved conclusively that statements alleging damage to
plants, flowers, and seeds by the hypochlorite treatment of water are
unfounded and do not merit the slightest consideration.
_Corrosion of Pipes._ Chlorinated water, it has been alleged on many
occasions, causes rapid corrosion of galvanised iron water services and
especially of the water tubes of boilers, water heaters, etc. When
bleach is used for water treatment, a slight increase in the hardness is
produced but as this is mostly due to calcium chloride, there is no
corresponding increase in the salts that form a protective coating. The
presence of traces of calcium chloride and chloro-organic compounds
might tend to increase the corrosive properties of a water but this
increase is probably so small as to be negligible.
If pipe corrosion is considered by the carbonic acid hypothesis, the use
of bleach should tend to reduce it because bleach contains an excess of
base that combines with a portion of the free carbonic acid. The results
of routine tests for free carbonic acid made on the raw and treated
waters at Ottawa are as follows:
-------+----------------------+-------------------------
| CARBONIC ACID. |
| PARTS PER MILLION |
Year. +----------+-----------+ Nature of Treatment.
|Raw Water.|Chlorinated|
| | Water. |
-------+----------+-----------+-------------------------
1915 | 1.44 | 1.41 | Bleach
1916 | 0.92 | 0.85 | Bleach
1917 | 0.84 | 0.81 | Bleach first four months
| | | Chloramine during last
| | | eight months
-------+----------+-----------+-------------------------
These figures shown that the hypochlorite treatment produced a small but
definite decrease in the carbonic acid content and should, _caeteris
paribus_, tend to reduce and not increase corrosion.
If the corrosion of pipes is considered according to the electrolytic
theory, a slight increase, due to an increased electrical conductivity,
might be anticipated. The effect of the addition of hypochlorite upon
the electrical conductivity of distilled water and the Ottawa River
water is shown in Diagram VI.
[Illustration: DIAGRAM VI
Effect of Calcium Hypochlorite on Electrical Conductivity]
With the concentrations of hypochlorite ordinarily used in water
treatment it is inconceivable that the slight increase in the electrical
conductivity has any practical significance at low temperatures. The
conductivity increases rapidly, however, with increase of temperature
and any increment due to chlorination might produce a slight appreciable
effect at temperatures approaching the boiling-point of water.
Liquid chlorine does not increase the conductivity to the same extent as
an equivalent quantity of hypochlorite but it increases the carbonic
acid content in proportion to the dosage used.
The author investigated the action of hypochlorite on galvanised pipes
in 1914 and was unable to detect any definite corrosion with normal
concentrations of chlorine. The experiments were made with 2-inch pipes
and an examination of the first consignment received showed that,
although the galvanising on the outside was perfect, the inner coat was
very inferior: in some parts there was an excess of zinc that broke away
on scraping whilst in others the iron pipe was bare.
A committee of the Pittsburg Board of Trade, appointed to investigate
complaints as to pipe corrosion, reported in 1917 that they were largely
due to inferior qualities of pipes and not to the method of water
purification employed (slow sand filtration and chlorination).
The effect of chlorination on the _plumbo-solvency_ of water was
investigated in 1904 by Houston who found that chlorine, as chloros, in
amounts between one and ten parts per million, did not appreciably
increase the plumbo-solvent action of either unfiltered or filtered
water. Similar results were obtained by the author with the Toronto
supply: raw lake water, filtered water, and water treated with 0.25 and
0.50 p.p.m. of chlorine, all dissolved the same quantity of lead in
twenty-four hours. The amount in each case was too small to be of any
significance.
BIBLIOGRAPHY
[1] Letton. J. Amer. Waterworks Assoc., 1915, 2, 688.
[2] Kienle. J. Amer. Waterworks Assoc., 1915, 2, 690.
[3] Adams. J. Amer. Pub. Health Assoc., 1916, 6, 867.