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COOPERATIVE RESEARCH IN PROBLEMS OF WATER
PURIFICATION 1
By Abel Wolman 2
To the practical water works man, "research" frequently con-
notes investigative effort directed into abstract fields to develop
scientific axioms. The publication of such material is haled with
delight by bespectacled and ethereal scientists and with suspicion
and perplexity by those upon whom rests the duty of converting
unpalatable mud into the clear and sparkling elixir of life. To
present a paper, therefore, upon a subject which combines in it the
scientific and the practical, it is necessary to demonstrate that
research of highly specialized and scientific character is necessary in
problems of water purification and that cooperative rather than
individualistic investigative effort should be the desideratum. The
first of these hypotheses should concern more particularly the man
in the works upon whom rests the responsibility of adopting the
scientific methods and of absorbing the new truths which the inves-
tigator discloses. To the experimenter the second problem is of
interest. In it the distinction between isolated and concerted attack
upon the unsolved problems of science is made clear. It is the
present purpose to outline in brief these two phases of cooperative
research in problems of water purification. For purposes of clarity,
however, the second phase will be discussed before the first.
COOPERATIVE VERSUS INDIVIDUALISTIC RESEARCH
Scientific investigation in the field of water purification has pro-
gressed for a number of decades, but it may be stated with safety
that during this entire period the study of problems has been, for
the most part, intermittent, sporadic and disconnected. The devel-
opment of data has been the result of local efforts in the laboratories
1 Read before the Montreal Convention June 24, 1920. Discussion is re-
quested and should be sent to the Editor.
2 Division Engineer, Maryland Department of Health.
572
coSperative research 573
of individual colleges, states, municipalities, or private corporations.
What cooperation has existed has been localized and not national.
Dr. Burton E. Livingston of the Johns Hopkins University describes
this situation in excellent terms when he states: "there appear to be
a large number of good experimenters who do not have well-selected
problems in mind, who work on that which lies close to them rather
than on that which seems to be most fundamental, most far-reach-
ing or most imperatively needed for the growing structure of knowl-
edge." 3
The history of individualistic research effort in water purification,
as in a number of allied fields, has been that of "a kind of guerilla
warfare upon the unknown." 3 While such warfare may result in
temporary victories over isolated problems, in intermittent elimina-
tions of difficulties in one place, it never produces a complete sur-
render of natural opposing forces to the control of man. The solu-
tion of the problem of chlorinating the St. Lawrence River water,
for instance, while of immediate value, is of but little aid in solving
the general problem of chlorination of waters, unless the methods,
conclusions and conditions of the first problem are subjected to the
composite scrutiny and checking of cooperative workers elsewhere.
It is true, no doubt, that under present conditions the individual
scientists find it difficult practically to choose arbitrarily that line
of study which seems to promise more remote but more valuable
results, while the material at hand has the attractiveness of immedi-
ate practical application, if only to the restricted field with which he
is familiar. Every problem will be solved, however, more satis-
factorily and more permanently if the attack is made from many
viewpoints, under different conditions, and by various investiga-
tors. The personal stressing of unimportant aspects, the individual
errors, the apparent but unreal significance of local characteristics,
and the restricted mental conception of a problem, are all likely to
be eliminated or reduced by cooperative research, with the ultimate
production of a sounder and a more accurate series of scientific
observations and conclusions.
It seems hardly necessary to emphasize the abstract desirability
of solving the problems of water purification by a more constructive
system of cooperative effort than now exists. It is of value, how-
ever, to direct the attention of the members to the fact that this
s Livingston, Burton E., Constructive Scientific Research by Cooperation,
Science, March 19, 1920.
574 ABEL WOLMAN
organization may serve as an excellent medium through which to
inaugurate a comprehensive system of cooperation. In this manner,
we may do much to advance scientific knowledge and its practical
application. It has been pointed out that cooperation in research
involves "the union of a number of minds in planning the attack
on a problem, in working out the different parts, and in bringing
the several component results together into a well-considered pres-
entation that might really mark a tangible advance in scientific
knowledge." 3 These various functions the American Water Works
Association can and should perform. It should not be a difficult
matter to supply that "union of minds" to plan the attack on a
series of problems by the proper organization of a research com-
mittee. To subcommittees in turn may be delegated the further
task of "working out the different parts and bringing together the
several component results." It is these functions of coordination
and initiation in cooperative research which the author wishes to
suggest to this body. As far as he is aware, no other organization
is at present so well suited to undertake its development and no
other has yet deemed it desirable to assume this responsibility.
The intention is to indicate the desirability of this Society fostering
actively the principle of cooperative research. The specific mode
of action of such a research committee and the possibilities of its
cooperation with other organizations, such as the National Research
Council, are simply matters of detail.
Granting the abstract desirability of developing such cooperation,
what are some of the problems which today remain to be solved?
Although considerable advance in the practical methods of water
purification has taken place in the United States, may we state
definitely that the fundamental laws of coagulation, filtration and
chlorination are accurately known? If so, are these laws applied
in every-day operation? Some of us, perhaps, are not so sanguine
about our complete understanding of the processes involved in the
above mechanisms of purification. An opportunity to engage in a
cooperative attack upon such problems will be welcomed. In order
to make clear some of these unsolved difficulties, the second portion
of this paper is devoted to a brief survey of a few of the possible
fruitful sources of investigative work. These possibilities doubtless
are already known to most of the members, but summarizing them
in this connection may make more apparent the necessity for the
plan which this discussion has set forth.
COOPERATIVE RESEARCH 575
SOME UNSOLVED PROBLEMS IN WATER PURIFICATION
a. Coagulation and sedimentation. The factors determining effec-
tive coagulation and sedimentation of waters differ in degree with
different waters, but their characteristics in general are the same,
regardless of the nature of the water. The effects of time, tempera-
ture, agitation, and hydrogen-ion concentration upon coagulation
have been studied only superficially. The material for such study
has been accumulated in a number of different fields in allied sciences,
but has not yet been adapted to water purification problems. It is
stated often, for example, that the formation of satisfactory floe
is retarded by low temperature and by inadequate agitation, yet
how many plants observe and record the nature of the floe pro-
duced each day, so as to provide the material for correlated study of
its variations with other characteristics of the water during an
entire year? Isolated observations of inadequate floe formation
which are roughly and often fallaciously connected with tempera-
tures aid little in pointing out fundamental principles. An ade-
quate measure or series of measures of the characteristics of floe
offers an excellent research problem, the solution of which would
aid considerably in the studies of water works control.
The measurement of floe formation in its various aspects, how-
ever, should be preceded by a study of the raw waters with a view
to determining a more accurate and satisfactory method of appor-
tioning coagulant to raw water to obtain satisfactory coagulation.
The usual method of turbidity reading, with adjustments for rising,
falling, constant, fine, medium, and coarse turbidities, leaves much
to be desired, particularly when frequently the actual procedure
results in abandoning all methods other than adding chemical until
the coagulation becomes satisfactory. These methods are neces-
sarily wasteful, since for each water there exists a critical concen-
tration of coagulation which is most effective and economical. Can
we not devise a satisfactory index to the "coagulant demand" of a
water by a simple test? When it is borne in mind that the floccu-
lation of waters is dependent upon the nature and amount of fine
particles present, it would appear that the search for such a measure
should be in the field of colloid chemistry. It is suggested that
perhaps the use of a nephelometer, an instrument measuring the
cloudiness of a water, may be developed to study the character of a
water after a very brief period of settling when the coarse material
576 ABEL WOLMAN
of low "coagulant demand" has been removed. It would be inter-
esting to learn what such "post-settling" turbidity readings would
disclose as to proper chemical dosage. An experimental quantita-
tive study of the "coagulant demand" of the various sizes of par-
ticles in the same water should prove interesting and valuable.
Another phase of the coagulation problem which has taken on an
importance in recent years is the effect of the varying hydrogen-ion
concentration upon flocculation. There appears to be an optimum
range of P H within which the coagulation proceeds most satis-
factorily. Water works operators and investigators should begin
to accumulate complete data regarding the P H values of different
waters in the country under all conditions. In Maryland the State
Department of Health has been making, for several months, deter-
minations of hydrogen-ion concentration on all waters and has
instituted these tests as a daily procedure in several large filtration
plants. It is too early to predict the results of these studies, but, at
any rate, material should be collected to determine the importance
of this characteristic.
The study of sedimentation problems in the light of recent devel-
opments in physical chemistry may require some modifications in
our older concepts. The effect of electrolytes, of competing and
protective colloids, of surface tension and osmotic pressure are of
more than purely scientific interest. Recent work has demon-
strated, for instance, that the Brownian movement is observed with
practically every type of clay suspended in water, varying from the
rapid motion of the finest particles to the more sluggish one of the
larger particles or aggregates or when hampered by the presence of
electrolytes. 4 An extended journey into the field of physical chem-
istry promises an excellent return to the water supply investigator.
b. Filtration. The internal forces within a sand filter bed are of
greater magnitude than is generally realized. Experience in Mary-
land with a number of peculiar phenomena in filter beds has dis-
closed a startling variety of forces released in filter beds, which
appear to be intimately connected with the character of sand and of
applied water. The appearance of internal contraction in a sand
bed of such strength that the surface area of the bed may be reduced
by more than 5 per cent of its original area is of importance in call-
ing attention to the unsolved problems concealed within the bed.
4 Alexander, Jerome, quoted in "Ceramic Processes Associated with Col-
loid Phenomena," by A. V. Bleininger, Journal of Industrial and Engineering
Chemistry, Vol. 12, No. 5, May, 1920.
COOPERATIVE RESEARCH 577
If we consider the whole principle of filtration as founded upon
"a sort of instability, both chemical and biological (and physical
— A. W.), in the behavior of matter in solution or in suspension,
when spread out in thin films over surfaces, or flowing in fine fila-
ments through interstitial capillaries of constantly varying cross-
section," 6 we obtain some idea of the intricacy of the problems.
That these problems are of more than academic interest has been
clearly demonstrated in the difficulties encountered in the shrinkage
of sand beds, in their selective action upon bacteria, in the adsorp-
tion of materials in water softening plants, in the sudden discharge
of slugs of chlorine taste where chlorine is applied before filtration,
and in many other phenomena. The researches of Dunbar 5 and
Baldwin-Wiseman 5 on the variations of surface tension within a
sand bed and their conclusion that the elimination of a dissolved
salt by filtration is inversely proportional to the degree of concen-
tration of the solution mark only the beginnings of the studies on
internal forces. The work of the Maryland State Department of
Health on the varying adsorptive capacities of different sands and
Hannan's observations 6 on the effect of surface electrical charges of
sands and of bacteria indicate the promising possibilities of more
research in filtration.
c. Chlorination. Sanitarians have established definitely that water
may be made safe for potable purposes by chlorination. The water
works official, however, must go a step further. He must make the
water potable in addition to safe. If the water is unpalatable and
objectionable because of tastes and odors, then the problem of
chlorination may not be considered as solved. It is only a few years
since the conception of the mechanism of chlorine treatment has
undergone some modification from the simple hypothesis of direct
oxidation. But in this comparatively short period, a series of
questions has arisen which is still imperfectly answered.
In this field again we must have recourse to highly technical
investigations to aid us in clarifying our concepts of chlorination
processes and in controlling their operation. Even today it is
difficult to answer definitely whether the action of chlorine is phys-
ical, physico-chemical, or chemical, whether its action is selective
for different types of bacteria and, if so, what the causes for such
6 Baldwin-Wiseman, W. R., Statistical and Experimental Data on Filtra-
tion, Proc. Inst. C. E., Vol. CLXXXI, 1909-10.
• Personal communication.
578 ABEL WOLMAN
selection are. The action of other disinfectants is elective and their
toxicity is dependent upon their position in definite ionic series and
upon the characteristics of the different bacteria, such as their
response to Gram stain. The surface character of different classes
of bacteria shows a marked influence upon their behavior under
different conditions.
Where we attempt to treat raw waters of complex organic and
inorganic content, our present methods of control are entirely
empirical and not infrequently unsuccessful. The causes of tastes
with low doses and the absence of tastes, at times, with excessive
doses of chlorine are still in the category of the unknown. It is not
a solution of the difficulty to state that tastes and odors may be
prevented by proper regulation of applied chemical, for the terms
"proper regulation" are indeed broad in interpretation. Proper
chlorination control, on the contrary, would seem to be possible Qf
attainment only after a complete understanding of the details of
the complex disinfection processes has been reached. May we not
call upon this Association to take the lead in the initiation of these
studies?