Part 15

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.

Mr. TAWNEY. And that will take care of----

Mr. HATTON. A hundred million gallons.

Mr. POWELL. What is your population?

Mr. HATTON. The present population, 450,000; we are building a plant to provide for a population of 800,000.

Mr. MIGNAULT. What is the per capita cost?

Mr. HATTON. I have not worked it out.

Mr. POWELL. Does the cost decrease relatively in larger plants?

Mr. HATTON. Quite so; yes, sir.

Mr. POWELL. It is not adding simply a unit?

Mr. HATTON. No. Of course, the cost of this plant largely depends upon the cost of the air. The larger the air plant the less the cost of air. We figure our cost of air based upon a cost of electricity of seventy-seven one-hundredths per cent per kilowatt hour, which is the rate fixed by the Wisconsin Railway Commission for that sort of power; so that that rate is actually fixed.

Mr. POWELL. Is that power quite an item in the cost?

Mr. HATTON. Quite an item; the biggest item in the cost; the cost of power for compressing the air--that and the overhead charges, such as the interest on the money invested.

Mr. MIGNAULT. Are you aware whether power is more expensive in Milwaukee than in Detroit?

Mr. HATTON. I am not; I do not know what the cost of power is in Detroit.

Mr. POWELL. About what is the cost of horsepower? What is the cost to you people?

Mr. HATTON. I say it costs us seventy-seven one-hundredths of a cent per kilowatt hour, and horsepower is about three-quarters of a kilowatt in round numbers--six-tenths of a cent, I should say.

Mr. MIGNAULT. Is there any nuisance resulting from the drying process?

Mr. HATTON. No. The gases must be washed, and then after passing through the washer are taken into the plant itself--into the liquor, and the liquor is a deodorizer; so there is no odor arises from the cooking of the sludge, as we call it.

Mr. MIGNAULT. That is the drying of the sludge?

Mr. HATTON. Well, that is what we call cooking.

Mr. POWELL. This is not the same principle of the two tanks where the material is taken into one tank and has a certain bacterial operation, and then passes into another tank, and then finally into beds?