Mr. TAWNEY. You are here on the invitation of the commission, and
the invitation was extended to you because of your experience in the
matter of sewage treatment in the city of Milwaukee and also because
of the efficiency with which we are advised your plant is being
operated. Give such information to the commission as you are prepared
to give us concerning the method you have in use there, and also as
to its efficiency and operation. We will be very glad to have you
give us any opinion, based on your knowledge and experience, that you
care to.
Mr. HATTON. It may be that I can best describe this process and
the results we are getting from it by giving you the situation in
Milwaukee, which is somewhat, as I take it, comparable with some of
the situations here. We discharge the crude sewage from the city of
Milwaukee into three rivers, from whence it flows into Lake Michigan,
and 3½ miles away from the harbor entrance we take our water supply,
in a depth of 50 feet. At the present time the water supply is being
partially or entirely sterilized by the use of liquid chlorine. There
is at the present time about an average of sixty millions of sewage
per day being discharged into Lake Michigan.
Mr. TAWNEY. Sixty million gallons?
Mr. HATTON. Yes; and during this time the lake for an area of about
25 square miles has become polluted, B. coli being retained in that
entire surface of the lake; and at all times we find the presence
of B. coli at the intake of our water supply, but the treatment of
liquid chlorine has, with one exception, enabled us to sterilize the
water with about twenty-eight hundredths to thirty hundredths part of
liquid chlorine. Last February we got a little larger quantity of B.
coli than usual because of four or five days of southeastern storm,
and in spite of the fact that we put all the liquid chlorine in and
more than the water would absorb, we got a typhoid-fever epidemic in
three or four weeks of about two hundred and some odd cases. Now,
that is the situation in Milwaukee, and for the purposes----
Mr. POWELL. Before you pass on, you say 25 square miles has become
polluted?
Mr. HATTON. Yes.
Mr. POWELL. How far into the lake would the pollution extend?
Mr. HATTON. About 5 miles; 3 miles on either side of the harbor and 5
miles from the shore. The city is located on Milwaukee Bay, which is
a long crescent, about 10 miles from point to point.
Mr. POWELL. How far from the outlet of the sewer to the intake?
Mr. HATTON. Three miles and a half; and in addition to that, there is
a breakwater, which is supposed to partially prevent the water from
flowing from the harbor toward the intake.
Mr. POWELL. You pursued your investigations beyond the 5 or 6 miles?
Mr. HATTON. Yes. Prof. Whipple was employed to do that, and he did it
very thoroughly for many more miles than 25 square miles.
Mr. POWELL. Did he discover traces of it farther than that?
Mr. HATTON. Yes; even farther than that; traces of it 6 miles away to
the north of the intake, but faint traces. It was a question with
us, when the matter of sewage disposal came before us, of not only
treating the sewage so that the water could be properly treated by
filtration or chlorination subsequently, but it was also a question
of getting rid of the sludge from any sewage-disposal treatment which
we might put in, because there was no waste ground in the vicinity of
Milwaukee upon which sludge could be disposed of, and the consensus
of opinion of the citizens of Milwaukee was that the sludge should
not be deposited in the lake, no matter how far out. The feeling was
very strong. I might say, in introducing that matter, that in 1910 a
board of consulting engineers advised that disposition of the sludge,
and that feeling had been growing in the minds of the citizens for
three or four years before I went there, until it had assumed the
attitude that it would not be public policy to discharge the sludge
into the lake, no matter how far out, partially due to the large
amount of shipping which is and was expected to come into the harbors
of Milwaukee, and also from the fact that ships did take their water
supply from that lake before entering the city; so that it was a
matter of taking care of our sludge----
Mr. POWELL. Before you pass to that, how does the current compare
with the current in the other Lakes? There is less current in
Michigan Lake?
Mr. HATTON. Yes. The currents are influenced particularly by the
winds.
Mr. POWELL. There is very little setting of the water out toward the
strait?
Mr. HATTON. Very little. The general idea has been advanced, by those
who have studied the matter, that the water passes south on the west
side of the lake and to the north on the east side of the lake,
requiring approximately 10 years to make the entire circuit.
Mr. POWELL. Is there any continuous flow out of the lake, or does it
flow in, on account of evaporation?
Mr. HATTON. I think there is a flow out of the lake. I think the
record was taken some 12 or 14 years by the United States engineer at
that time, and he printed quite an elaborate report.
Mr. TAWNEY. Through the straits?
Mr. HATTON. Yes; but just what that report contains I am not familiar
enough with it to say.
Mr. POWELL. The flow is always out?
Mr. HATTON. Yes.
Mr. MAGRATH. I have an idea that the water works inward sometimes?
Mr. HATTON. Well, it comes down, as I say, on the west side, passes
round Chicago, and comes up on the east side, and passes out in the
straits; at least, that is my opinion.
Mr. MAGRATH. I may be wrong, but I had an idea that the current moved
inward sometimes, and sometimes outward.
Mr. HATTON. Well, possibly so. This is the general tendency of it,
but I think it does sometimes pass out and in, according to the
direction of the winds.
Mr. POWELL. The Chicago Drainage Canal is not equal, I suppose, to
the inflows from the surrounding country. It does not balance it?
Mr. HATTON. Well, I think not. It is claimed here very recently
that the waters taken from the Chicago Drainage Canal have lowered
the waters in the connecting streams some 5 or 6 inches. How true
that is I am not prepared to say. Now, before deciding upon the
method of sewage disposal for Milwaukee we built rather an elaborate
experimental station, in which we tried to put all those modern
methods of sewage disposal now prevalent in this country and abroad,
and I think we had 23 different processes going on there at one
time--one of the largest experimental stations carried on in this
country for sewage disposal purposes.
Mr. MIGNAULT. When was it established?
Mr. HATTON. In the middle of 1914. We have been operating it just
about two years. We tried out in that experimental station the Imhoff
tank, so-called settling tank, sprinkling filters, colloidal tanks,
electrolytic processes, chemical precipitation, chlorination, and
finally, what we called the activated sludge process, which we have
been trying out now for a year this month.
Mr. MAGRATH. Where did that process originate?
Mr. HATTON. Well, that is a question. Mr. H. W. Clarke, of the
Lawrence experimental station of Massachusetts, claims he discovered
it. Dr. Gilbert J. Fowler, of Manchester, England, now of India,
has assumed the discovery of it and developed it in a laboratory
way perhaps further than anybody else up to the time we took care
of it in Milwaukee. He started his experiments in 1914, or late in
1913, and we started our experiments in 1914, late in 1914. But it
has been developed in Milwaukee to a greater extent than anywhere
else, either in Europe or United States. We started with a laboratory
investigation. From thence we went to tanks, holding or treating
70,000 gallons a day each, and from thence we have gone to tanks
treating 1,600,000 gallons a day, which are now being operated and
have been operated since last January. The process, stated briefly,
consists of, first, coarse screening the sewage, running it through
coarse screens, then into tanks of any depth to suit the conditions
and the situation, say from 10 to 20 feet.
Mr. POWELL. That is the residue after the first screening?
Mr. HATTON. That is the raw sewage after it has been coarse screened.
Then the raw sewage is run into these tanks, which have in the
bottom some method of diffusing air which is discharged into the
bottom of the tank at low pressure, just sufficient pressure to
keep the liquor agitated; while in there this liquor passes through
this tank, taking a certain time in accordance with the standard of
purification required, from two hours to four hours, during which
time it is being agitated and aerated by the air. From these tanks it
passes into a sedimentation tank. All of these tanks are practically
one tank divided by a wall separating the aerating tanks from the
sedimentation tank. After settling in the sedimentation tank from 45
minutes to an hour, or an hour and a half, according to the character
of the effluent you require, it then passes out into the point of
final discharge. The sludge which settles out of the liquor into
the sedimentation tank is then pumped back and discharged into the
raw sewage as it enters, or while passing into the beginning of the
aerating tank. The surplus sludge which settles in the sedimentation
tanks is treated otherwise, which I will describe later. The process
is one of aeration and nitrification practically. The sewage does
absorb a great deal of oxygen from the air which is forced into it
through these diffusing methods. The sludge, however, which we return
and keep intimately mixed with the sewage at all times is perhaps
the chief medium of purification, because that sludge is filled
with microorganisms and nitrifying organisms, which really do the
purification work, and that is the reason that it is called activated
sludge, because it is so filled with the nitrifying organisms, and
the more active the sludge is the more rapid and higher degrees of
purification you secure. It is a natural process entirely, simply
intensified by artificial means. To show you the activity of that
sludge, we got the raw sewage, perhaps a million bacteria per cubic
centimeter, in the first aerating tank, within half an hour; the
sludge contains anywhere from fifteen to twenty million bacteria per
cubic centimeter. In this sludge we give the bacteria the natural
environments for their work. We give them food, lodging, and air,
and that is just exactly what aerobic bacteria need, and the desire
is to have intensified the aerobic bacteria, which we have at all
times when the plant is being properly operated. Now, that is a brief
description of it.
Mr. POWELL. That is the only purpose of aeration?
Mr. HATTON. No; there is another purpose of aeration, and that is
the intimate mixture of the sludge with the liquor. That can be
done mechanically with a little bit of air put in; but to do it
mechanically would increase undoubtedly the cost and the operating
expenses. In order to clarify the liquor it is not only necessary
to nitrify it, but it is necessary, as we call it, to scrub it, and
we remove the colloidal matter by means largely of scrubbing. To
describe that in a layman’s way, not in a chemical way, the colloidal
matter in sewage rests in the interstices between the globules
of water, like water rests in the interstices of the sand at the
seashore. Now, if you disturb that sand on the seashore, the water
runs out and the sand becomes free of it. If you scrub the globules
of water together violently, the colloidal matter is detached from
the water and the water becomes clear. That is as near a layman’s
description as I can give you, and we have tried the experiment out
in our experimental station, to see whether there is any odor in that
sewage, and we have thought that there is to a certain extent, not
altogether. Now, the question as to how to dispose of this sludge
is one of the greatest problems in sewage disposal in the world;
and I think if any of you went over to Toronto, which I had the
pleasure of visiting three weeks ago, you would see the difficulty
that Toronto is up against in getting rid of its sludge, as are all
other cities in the United States, whether it be Detroit or Buffalo,
Cincinnati, Philadelphia, or New York--well, I will not say New York
and Philadelphia, because they are out at the ocean, and they have a
chance to get rid of it, but inland cities will have this difficulty.
Mr. POWELL. They are taking it up in New York.
Mr. HATTON. Yes; they may be able to discharge the sludge in the
sea, but inland cities on the Great Lakes or rivers are going to
be up against the proposition as to how to get rid of the sludge.
Then any method of sewage disposal which will enable the cities to
get rid of the sludge, whether it be at a profit, or whether it be
to break even, or whether it be at a loss, and yet to get rid of it
to the advantage of the agricultural element of this country and
indirectly to ourselves, will be that system of sewage disposal which
will undoubtedly meet the conditions of the large cities. That is
the proposition which is primarily confronting us in Milwaukee, as I
started out to say, and in all of this investigation there has been
no doubt evinced in the last three months by the leading consulting
sanitary engineers in the United States who have visited our plant
that the purification of the sewage has been solved within reasonable
cost, but there has been a great deal of doubt in their minds that
the disposition of the sludge has been solved, and I have told them
that within 90 days----
Mr. MAGRATH. Did you say that there was a feeling that the problem
had not been solved?
Mr. HATTON. They felt that the question of the disposal of the sludge
had not been solved, although we had solved the question of the
disposal of the sewage.
Mr. POWELL. They all recognized that the purification of the sewage
could be accomplished?
Mr. HATTON. They all recognized that the purification of the sewage
could be accomplished in that method at a reasonable cost. But now
we have solved practically the question as to the disposal of the
sludge. It is true we have not reached those definite figures of cost
which are necessary to convince the average municipal officer, but
we are proceeding very rapidly, and we have our own figures which
we feel are perfectly safe. In March for 10 days we dewatered this
sludge by compressing. Now, for two weeks we have dewatered the
sludge, and are drying the sludge, and reducing it into the form of a
fertilizer of low grade, which is marketable anywhere in Chicago, and
marketable along the eastern coast, through the chemical company--I
forget the name of the chemical company there, but it is the largest
fertilizing company in that district. They have offered us a yearly
contract for all the sludge of the character that we have submitted
to them that we could produce, based on the market value of the
ammoniacal nitrogen contained in the sludge, the potash, and the
available phosphoric acid. We have been testing this sludge day by
day for two weeks, and we have averaged from that sludge 5 per cent
of ammoniacal nitrogen--about sixty-seven one-hundredths per cent
is available of phosphoric acid, and nine-tenths of 1 per cent of
potash. Altogether that sludge is worth in the market, based on those
ingredients alone, $15 a ton. There is no doubt about reducing it to
a fertilizer basis. We have the apparatus and are doing it.
Mr. TAWNEY. Have you ever undertaken to extract anything else from
this sludge, such as oils?
Mr. HATTON. We have, through the firm of Susenberger & Sons, of
Chicago--no, it was a branch of Susenberger & Sons, of Chicago, which
carries on the fertilizing end of the Susenberger & Sons’ business.
They extracted the fats from the sludge, and turned the residue into
fertilizer. But we do not have more than 2 or 3 per cent fats in our
sewage, and that percentage of fats is not harmful to fertilizer,
and it does not pay to take it away from the sludge. Unless you
get at least 10 or 12 per cent of fat in your sludge, it does not
pay to remove it, as I am told by those who are in the business of
manufacturing fertilizers.
Mr. TAWNEY. Do you know that there is in operation in England now
a plant where they are extracting from the sludge gasoline and
lubricating oils and pitch?
Mr. HATTON. Well, yes; I have read of it in a casual way.
Mr. TAWNEY. And nitrates, and carbolic acid; is that right, Mr.
Phelps?
Prof. PHELPS. Yes.
Mr. HATTON. I never go away without my box, and I want to show you
some samples which I have here.
Mr. POWELL. You sell this stuff for $20 a ton?
Mr. HATTON. No; $15.
Mr. POWELL. What does it cost to put it in a salable condition after
it is taken out?
Mr. HATTON. Six dollars a ton.
Mr. POWELL. You have a profit of $9 a ton?
Mr. HATTON. Approximately $9 a ton. You understand the ammoniacal
nitrogen varies, of course, and that cost is based upon the
ammoniacal nitrogen, and our average is 5 per cent so far. In
wintertime I imagine it will grow less. In July, August, and
September it will grow more. It is true we have a very strong sewage,
containing, for the last month, for instance, 369 parts of suspended
matter. That is a good deal stronger than the average municipal
sewage. It is industrial sewage, largely. Now, I do not want you to
think these samples I am showing you are picked out samples. These
are samples which a good many gentlemen present will tell you they
have seen in our plant that they have visited day by day. This was
taken yesterday at noon and delivered to me in the afternoon. This
is a bottle of the raw sewage, after passing through the half-inch
screen. I am now showing you a bottle of the sewage taken from the
aerating tanks, containing about 25 per cent of activated sludge, the
nitrifying media which purifies the sewage, and I am now showing you
the effluent passing away from the sedimentation tank 4 hours and
45 minutes after it passed into the influent tank. So far as we can
determine, there is a trace of suspended matter in that sewage. Of
course we could not determine whether it was stable or not, because
that takes time. It was taken out yesterday, but my chief chemist,
who brought the samples to me, told me there was no doubt about the
stability of that liquor.
Mr. MIGNAULT. Have you analyzed it to determine whether there
subsists a certain amount of B. coli?
Mr. HATTON. No; this was taken yesterday; but we do get some B. coli;
we do not get complete sterilization. We attempt to get 95 per cent
reduction of bacteria in our effluent. We have not had occasion yet,
except when our plant was broken down, or the lake was so high that
it backed into our plant, to reduce our standard. We could always get
95 per cent, and we more often got 98 or 99 per cent. I do not know
whether I should show you this box I have here very closely, because
it does not smell very well.
Mr. TAWNEY. You do not deodorize your sludge?
Mr. HATTON. No. I am showing you now a sample of the pressed sludge.
Mr. TAWNEY. The reason I ask that is that I saw a sample of pressed
sludge recently, treated by the process I mention in operation in
England, where there was absolutely no odor to it at all.
Mr. HATTON. There is no odor in this sludge until it has been out in
the air 24 hours. Then it begins to get very odorous. That is the
pressed sludge ready for the dryer. When that came out there was
no odor except an earthy odor. I am showing you now a sample of the
dried sludge ready for the fertilizer.
Mr. TAWNEY. That is in ground form?
Mr. HATTON. No; that is not ground. That is just as it comes out
of the dryer. Some of it would have to be ground no doubt; we are
expecting to grind it.
Mr. MIGNAULT. The dried sludge has no smell?
Mr. HATTON. The dried sludge has no smell. There it is; it has been
on my desk for a good long while. We obtain about half a ton of this
dried sludge per 1,000,000 gallons of sewage treatment. It means that
we would get about $7.50 per 1,000,000 gallons out of our sludge, and
spend from $3 to $4 getting it out of the sewage, making a profit of
from $3 to $4.
Mr. POWELL. The process of sedimentation in that bottle has just
taken three minutes and a half.
Mr. HATTON. That is where we were deceived in designing our
sedimentation tanks. As a matter of fact, there is a lot of finely
suspended matter, and it is that finely suspended matter which takes
the time to settle. But I want to draw your attention to the absence
of colloidal matter, and I want to say also that, outside of broad
land irrigation, or slow sand filtration, I think I am justified in
saying there is not any other method of sewage disposal process which
will so effectually take the colloidal matter out of sewage, and
make the sewage at least satisfactory, ethically, to all the cities
and municipalities. I am quite sure if you can discharge an effluent
of that kind in any of the rivers and waters between Canada and the
United States that no citizen of Canada or no citizen of America
can possibly object. He goes largely by what he sees, not by the
ingredients which some chemist tells him are in the water.
Mr. TAWNEY. Have you any of the by-products you extract from the
sludge?
Mr. HATTON. We do not attempt to extract any by-products. We propose
to sell the sludge as a fertilizer in the shape I have shown to
you in this box. I might say that there is no other process of
sewage disposal at present in common use in America favorable to
this locality comparable with this process, except Imhoff tank and
sprinkling filters, followed by final sedimentation.
Mr. TAWNEY. What is this process called?
Mr. HATTON. Activated sludge. We tried out the Imhoff tank process
with chlorination in this same sewage, and found the cost a little
bit less than the cost of this process, without finally disposing of
the sludge. We also tried out Imhoff tank, followed by sprinkling
filters, and found the cost much more than this process. We also
found, in our climate of Milwaukee, that, instead of averaging two
and a half million gallons, or getting two and a half million gallons
per acre per day through sprinkling filters in wintertime, there were
three months that we could not get more than a million and a half.
We also found that up to the present date we have not been able to
dry sludge in the open air coming from the Imhoff tank from the first
of last November up to the present day, and in making our estimates,
we do not believe we could get three months in the whole year in
this climate--I am speaking of Milwaukee--when we could dry sludge
effectually from the Imhoff tank or any other sedimentation process.
We have too much rain in June to dry sludge, and the only way we
could possibly dry Imhoff tank sludge was by covering with glass,
heating the place, as suggested by a gentleman in Cleveland, Ohio.
Mr. MIGNAULT. How long does the drying process last?
Mr. HATTON. Well, that is all according to the weather. If the
weather is very nice and warm, and we have the sun, and not too damp,
it will dry out in about two weeks; it will dry into a spadable
condition in five to six days in good dry weather, but if there is
a little bit of rain comes along overnight, or if it is alongside a
lake, and there is considerable moisture or damp, it may take two or
three days longer.
Mr. POWELL. How do you dry the sludge?
Mr. HATTON. In a drier, an industrial drier, just the same as they
use in the packing houses in Chicago and many of the breweries and
many other places throughout the United States in industrial works.
Mr. MIGNAULT. Does it require much space?
Mr. HATTON. No; the amount of land which we have laid out to treat
a hundred million gallons a day, which is the quantity we will have
to treat, is 20 acres; that is, including our pumping stations,
our ministration houses, sludge-disposal houses, and everything
concerned. In fact, to be distinct, this system can treat from ten to
twelve million gallons of sewage per acre per day.
Mr. TAWNEY. What does it cost?
Mr. HATTON. The cost of the treatment?
Mr. TAWNEY. The installation?
Mr. HATTON. About the same as the Imhoff tank. I say that because
we worked out the Imhoff tank layout, and also our activated sludge
layout, upon the same ground, and it broke even as to cost.
Mr. MIGNAULT. When you say you make a profit on the sludge, in the
disposal of it, what cost do you consider?
Mr. HATTON. I did not catch that.
Mr. MIGNAULT. When you say you make a profit out of the disposal of
the sludge, what cost do you consider? The cost of the drying----
Mr. HATTON. The cost of the drying, the cost of the dewatering,
the cost of the freight and the overhead charges of the machinery
necessary to dewater and to dry, and the attendance cost--all those
have to be taken into consideration.
Mr. POWELL. You take the raw sewage that comes from the tank?
Mr. HATTON. We take the raw sewage as it comes from the sedimentation
tank containing 97 per cent of water and deal with that.
Mr. POWELL. That all enters into cost?
Mr. HATTON. Yes.
Prof. PHELPS. That is $6?
Mr. HATTON. Yes.
Prof. PHELPS. Would you tell us the cost of the aeration in preparing
the sludge?
Mr. POWELL. That would be taken into account as against some other
system.
Mr. HATTON. I think I have that. I will read to you from a copy of
the Second Annual Report of the Sewage Commission of the City of
Milwaukee of 1915:
The cost of the activated sludge, continuous flow, with a
removal of 95.5 per cent bacteria--
I say that because the cost of the operation and the plant depends
entirely upon the character of effluents you want to secure. A lower
grade of effluents lowers the first cost and operating cost, so this
is based on a removal of 95.5 per cent, which is our standard----
The disposal of sludge in cost per million gallons, $3.
The interest and depreciation on the cost of the plant,
based at 7½ per cent, $2.81. Cost of operation, exclusive
of sludge, $2, making a total cost of $7.81 per million
gallons treated.
From this $7.81 must be taken the value of the recoverable sludge,
which, as I stated to you, so far in our investigations has been $3
per million gallons, or making a total net cost of $4.81 per million
gallons, which includes overhead charges.
Mr. TAWNEY. What was the cost of your Milwaukee plant?
Mr. HATTON. Well, we have a 1,600,000-gallon plant now. The aggregate
cost of our total plant is estimated to be about two and a half
million dollars--will be that much.