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.