Mr. Hatton. They have not seen it yet.
Mr. Tawney. I thought you said they personally visited it.
Mr. Hatton. They have personally visited it. We put it in operation, but our press broke down. We have only put this portion of it in operation in the last two weeks, and it is only now we have begun to dry it; we did not have a dryer before.
Mr. Mignault. Do you use the rotary dryer?
Mr. Hatton. The rotary direct dryer.
Mr. Magrath. I interrupted you when you were about to say that in 90 days you would demonstrate something, and you stopped.
Mr. Hatton. I told these engineers that in 90 days I would demonstrate the possibilities of disposing of the sludge, but I have already demonstrated it before the end of the 90 days. I think I said that at Syracuse some time ago in an address I delivered.
Mr. Magrath. In an address made, I think, in 1915 you expressed some doubt as to the efficacy of your method in winter months?
Mr. Hatton. Yes; I did; and in order to try out this system in Milwaukee during the winter months was the purpose of building this 1,600,000-gallon plant which we are now operating; that was the primary object of building that plant, which cost us $65,000, and we got it in operation the first week in January and we have operated it since continuously with temperatures as low as 20° below zero, with a clear effluent during the cold winter months coming out of the plant as that effluent which you see there in that bottle. We had no freezing and no trouble with ice. We had, of course, much lower nitrates in our effluent than we had in the summer months; in fact, we had very little nitrates, but we kept up the stability about 104 to 110 hours’ average; some of them went up higher. We go on the basis of 5 days’ stability test instead of 10 days. The American Public Health Association suggest that five days is all we need.
You ask me about the relative cost of the Imhoff tank installation and operating as compared with the activated sludge. Our investigations in Milwaukee show that the cost of the Imhoff tank, without sterilization, is $6.20 per million gallons—that includes all overhead charges—as against $7.81 for the activated sludge. The cost of the Imhoff tank——