DOUBLE FILTRATION OF WATER AS PRACTISED IN EUROPE
Subject Treated by George W. Fuller at Joint Meeting of New York Section A. W. W. A. and Sanitary Section A. S. C. E.
THE subject of water purification in European cities, and especially the practice of double filtration in some of the cities which take their supplies from highly polluted streams, was interestingly treated by George W. Fuller, C. E., president of the American Water Works Association, at a luncheon meeting of the New York Section on January 17. The meeting was held in the ball room of the Hotel Pennsylvania, at 12:30 P. M., and was a departure from the usual procedure of the Section in that it combined with the Sanitary Section of the American Society of Civil Engineers. The consequence was that the room was crowded, and it became necessary to install several extra tables to accommodate the guests.
After the luncheon had been served the meeting was opened by D. W. French, superintendent of the Hacksensack, N. J., Water Company, who presided in place of President Chas. R. Bettes, chief engineer. Queens County Water Works, who was unable to be present. Mr. French welcomed the members of the Sanitary section of the American Association of Civil Engineers, and said that he believed that the meeting of the two sections conjointly would result in great benefit to both. Mr. French then called upon Kenneth Allen, president of the Sanitary Section, who, in a short address said that at first it was thought the formation of the Sanitary Section might interfere with the American Water Works Association, but it had proved otherwise, and that the two bodies, it was found, would work together, each in their own province, and in harmony. He hoped that there would be many joint meetings between the two sections.
George W. Fuller on Double Filtration in Europe
George W. Fuller followed Mr. Allen and gave an interesting talk on “The Practice of Double Filtration of Water in Europe.” Mr. Fuller opened his address by referring to the advantage to be gained by the meeting together of the two sections and added a word of welcome to the members of the Sanitary Section. He then launched into his subject, which he said was based upon his experiences in visiting the various cities of Europe whose water systems he described in his address.
Water treatment plants providing for double filtration he said furnished quite a ready means of showing some of the prevailing views in different countries on this subject. To deal with the economics of the situation it would be necessary to consider various local details far beyond the scope of any short talk like this. However, he thought it might be of interest to call attention briefly to some of the developments which have taken place in this field during .the past dozen years or so.
Mr. Fuller then proceeded to describe the double filtration system in use in several cities on the Continent and in England, as follows:
The Method at Zurich
Zurich, Switzerland, derives its water supply from Lake Zurich, a long, narrow lake, somewhat resembling the Hudson River above West Point. For years it had a slow sand filter plant operated at a rate at certain seasons of the year approximating 5 m.g.d., which is about double the so-called standard rate abroad. This filter plant has been entirely abandoned since the construction in 1912-14 of a complete new plant situated several miles up the lake. Intercepting sewers have been built from a point above two miles still further up the lake and protected the new intake from pollution, which was considered objectionable at the old intake. This lake water is very clear and the purpose of filtration is essentially that for the removal of relatively large forms of vegetable and animal life designated as plankton. The intake is about a thousand feet offshore, where the water is nearly 200 feet deep. Steel pipe is supported by piles so as to draw water at approximately mean depth, thus avoiding both surface and bottom growths.
The water first passes through prefilters at about a 50million gallon rate without any coagulant. The filters resemble very much mechanical filters in this country as to sand, gravel and perforated strainer system for the introduction of water and of air for cleaning the beds, which are roughly about 20 x 80 feet in size. These filters are cleaned by applying air and water together for about 10 minutes and then water alone to rinse the bed. The frequency of washing ranges from once to twice per day to once to twice per week, depending upon growths which appear in the lake water.
The clear effluent from the prefilters is applied to slow sand filters operated at a nominal rate of about three m. g. d. There is so little material in the water for clogging the sand beds that sometimes 400 days or more elapse between cleanings. The purpose of these final filters is a safeguard hygienically. The quality of the water is considered to he very’ high with efficiency of final filters measurably below normal for some little time after they have been cleaned. I saw no signs of the use of any chemicals whatever.
Iron Removal New Berlin Development
Early’ in 1919 Berlin annexed a dozen or more suburbs and is now a city said to range from 4 to 4’/i millions in population. Quite a number of the former suburban water plants have been given up in the interests of economy. The iron removal plants treating ground water in the vicinity of Lake Tegel and Lake Muggel have not been recently changed other than the aerating arrangements at the Tegel plant consisting of wooden scrubbers being replaced by brick or stone, as found to be most economical. The only new development which I found at Berlin was the ground water plant with iron removal arrangements at “Wuhlheide.” This plant went into service in July 1914. It is said to be the most economical plant to operate, although it is very liberal in the amount of head required for aeration from spray’ jets located above the prefilters or scrubbers with relatively coarse material and operated at a rate about 170 m. g. d. The final filters are of the rapid ty’pe locally’ known as “Bollmann” filters. They are placed in steel tanks and operated at a rate of about 200 m. g. d. At intervals the sand passes through an injector located in the conical bottom of the tanks.
Chlorination in Place of Coagulation in Hamburg District
The city of Altoona continues to derive its supply from the river Elbe below Hamburg but the river water before it reaches the slow sand filters is now passed through mechanical filters of the Jewell ty’pe.
At Hamburg the former engineer at the filter plant, Mr. Schroeder, is now the director of the city water works plant. With the exception of two new pumps there has been practically’ no change in the construction of the works during the last dozen years. Filters receiving river water now operate without the aid of any coagulant applied to the water as it passes through relatively large settling basins. The earlier custom of applying coagulant practically every day in the year was abandoned on account of cost. In place of coagulant the water is now chlorinated.
About four-fifths of the city supply is taken from the river and one-fifth from deep wells, the water of which is aerated and passed through prefilters and final filters of the rapid sand type. The prefilter or scrubber contains about 9 feet of coarse coke and the water is aerated after leaving the coke bed on its way to the thin sand beds operated at a rate said to be normally’ about 125 m. g. d.
Slow Sand Filters in Schiedan
This city takes its supply from the river Maws just below Rotterdam. The water passes through a preliminary settling basin and then it is twice filtered through filters of the slow sand type. I could see no signs of any recent changes in this plant.
Rapid and Slow Sand Used in London
Rapid sand filters have been installed as preliminary filters by the Metropolitan Water Board. They are used without any coagulant and the purpose seems to be to increase the output of the slow sand filters and perhaps to guard very particularly against a falling off in the capacity of the latter at times of unusual plankton growths. Without getting into the economics of the situation, it seems to be the view that the output of the preliminary and final filters taken as a whole, may be increased sufficiently to justify the investment in the prefilters.
Mechanical filters have been under investigation for some years by the board under the direction of Sir Alexander Houston, honorary member of the American Water Works Association. In 1921 the board authorized the construction of mechanical filters of a capacity of 9.0 m. g. d. (U. S.) at Barn-Elms. These filters are in concrete tanks and have a general resemblance to the mechanical filters seen in this country. They treat water from the river Thames after it has passed through a reservoir holding about three weeks’ supply and before the water goes to the slow sand filters of what was formerly the West Middlesex Water Company.
These filter units were installed by the Paterson Engineering Company and have units about 12 to 20 feet in size with galvanized iron laterals to which are attached strainer cups looking downward. Above the graded gravel is about 3 1/2 feet of sand. They have worked with three different grades of sand samples, which I found to be as follows:
The freeboard is about 18 inches and the filters are cleaned by applying air for about two minutes first and then water for 8 to 10 minutes. The rate is about 160 U. S. gallons per acre daily. The effluent looks quite clear, although it is said that the removal of bacteria is not much more than 50 per cent. The final sand filters in England are uncovered and algae growths are very noticeable in the w’ater above the sand in some instances. The rate of these filters is only about 2 m. g. d. daily, but of course it is one fifth larger than stated in U. S. gallons.
These final filters apparently will operate several hundred days without cleaning. Although algae growths seem to be the clogging element, a f tor to be reckoned with is the amount of organic matte* in the effluent of the pre-filters sufficient to keep the final filters in a well-ripened condition. I judge that it is thought quite likely that some reservoir water may have to be applied directly to the final filters for purposes of ripening.
Preliminary filters of the mechanical type used without a coagulant on water that is stored in reservoirs for about three weeks or so, are sufficiently well thought of so that last summer the Metropolitan Water Board of London authorized the installation of two additional preliminary filter plants above Hampton, and quite generally similar to those at Barn-Elms. The filters now building at Walton and Kcmpton Park have daily capacities in U. S. gallons of 21.6 and 38.4 m.g.d. respectively.
Rapid and Slow Sand Filters in Other British Cities
In Great Britain there are several dozen filter plants of the rapid sand or mechanical type of which the more recent ones are quite generally similar to those found in this country. In most instances these filters serve for the preliminary treatment of slow sand filters in order to lessen the load on the latter. There are some cases where coagulants are used chiefly however, for removing deep vegetable stain from moorland waters. The cost of coagulants during the war and since has been so high that water works men in Europe have given considerable attention to means of lessening or eliminating this item of cost.
Edinburgh has both mechanical filters and slow sand filters. Its mountain supplies are less colored than they were in earlier years and an unusual effort is made to mix the water from several sources so as to secure a product which is of moderate hardness and in this mixing program the color of the unfiltered water is kept within the range which slow sand filters may reasonably treat. In consequence of this program and the desire to avoid the cost of coagulants, filter extensions at Edinburgh are being built of the slow sand type.
Double Filtration Versus Coagulation
Speaking generally of double filtration in Europe, pre-filters for iron removal have unquestionably come to stay, and the rapid sand filter serves well for the purpose of final treatment in this process of removal of iron and manganese from ground waters. Plankton or growths of organisms large enough to clog slow* sand filters have brought the mechanical filter to the front as a helpful arrangement in guarding against the clogging of final filters notwithstanding that the available operating records are scarcely extensive enough to generalize on the best way of handling double filters for this purpose.
To the American water works engineer who is so accustomed to the use of coagulants and rapid sand filters, it is rather difficult to appreciate at first why the water works men in Europe lean so strongly to double filtration in instances where American practice would provide for plant extensions only a single filter of the rapid sand and mechanical type. The best general answer is that the Europeans, largely as a result of tradition, have to progress more slowly and are forced by public opinion to give great weight to precautionary arrangements which will protect the public health even if it involves substantial expense at a period when water works men abroad are put hard to it to secure funds with which to make betterments and extensions.
Discussion of Mr. Fuller’s Address
At the conclusion of Mr. Fuller’s address, Mr. French called for discussion and Mr. Moegnen was the first speaker. He advocated the use of coagulating tanks and the sedimentation of water in preference to double filtration, remarking what was the use of going to the expense of double filters when one could use coagulating basins.
I he second speaker was Allen Hazen, consulting engineer, New York City, who referred to the fact that double filtration is practised in this country in at least two instances, those of Albany and Poughkeepsie, N. Y. The rapid sand filters of Albany are now under construction and those of Poughkeepsie have been in service for some time. Both purify the highly polluted waters of the upper Hudson, into which the waste from Troy and other cities is emptied. He thought that this was a notable achievement.
Others who spoke on the subject were Sol Pincus, Sanitary Engineer, New York City, and Theodore Horton, Chief Sanitary Engineer, Department of State Engineer.
(Continued on page 174)
New York Section Meeting
(Continued front page 164)
At the conclusion of Mr. Horton’s talk, Chairman French announced that as there was another meeting to take place at once after the adjournment, that further discussion would have to he dispensed with, and the meeting then adjourned. Those who attended the meeting were as follows:
Henry T. Shelly, Phila., Pa.; B. P. Stewart, Detroit, Mich.; Geo. T. Hammond, Brooklyn, N. Y.; Frank C. Kimball, Summit, N. J.; W. Donaldson, N. Y. City; A. E. Clark, Newburgh. N. Y.; Chas. F. Mebus, Phila., Pa.; Wm. A. McCaffrey, Oswego. N. Y.; Francis S. Fried, Phila., Pa.; W. Rudolfs, New Brunswick. N. J.; Louis L. Tribus, N. Y. City; Geo. L. Bean, Phila., Pa.; Wm. H. Lyon, White Plains, N. Y.; Fred I.uthy, Orange, N. J.; John S. Warde. N. Y. City; J. W. Wade, Oswego, N. Y.; E. G. Kastenhuber, Jr., Easton, Md.; C. E. Keefer, Baltimore, Md.; Robt. B. Morse. Hyattsville, Md.; J. A. Downes, Bound Brook, N. J.; H. W. Jacobs, N. Y. City; J. R. Van Gorder, Syracuse, N. Y.; John C. Churchill, Oswego, N. Y.; Geo. W. Fuller, N. Y. City; D. W. French, Wechawken, N. J.; John H. Feigel, Buffalo, N. Y.; Arthur P. Ackerman, Hackensack, N. J.; John A. Albertson, Hackensack, N. J.; Geo. C. Andrews, Buffalo, N. Y.; Kenneth Allen, N. Y. City; T. M. James, N. Y. City; Wm. W. Brush, N. Y. City; J. M. Diven, Troy, N. Y.; J. F. Sanborn, N. Y. City; F. C. Jordan, Indianapolis, Ind.; Abel Wolman, Baltimore, Md.; Edward Bartow, Iowa City, la.; Geo. W. Batchelder, Worcester, Mass.; H. E. Wolbert, Mt. YTernon, N. Y.; F. A. Snyder, N. Y. City; Wm. C. Sherwood, N. Y. City; O. C. Hanks, N. Y. City; Robt. A. Allton, Akron, Ohio; Wm. J. Keogh, N. Y. City; Richard V. Donnelly, Newark, N. J.; Gilbert H. Pratt, Newark, N. J.; Sol Pincus, N. Y. City; F. W. Green, Little Falls, N. J.; Franklin Henshaw, Searsdale, N. Y.; Howard T. Critchlow, Trenton, N. J.; S. J. Scarriaferro, Clifton, N. J.; Chas. L. Walker, Cornell University, N. Y.; Hubert P. Matte, Harrison, N. J.
E. K. Wilson, N. Y. City; C. F. Hostrup, N. Y. City; Chas. F. Meyerherm, N. Y. City; John M. Goodell, Montclair, N. J.; H. L. Dunn, New London, Conn.; Allan T. Ricketts, N. Y. City; Nicholas S. Hill, Jr., N. Y. City; J. N. Chester, Pittsburgh, Pa.; Geo. H. Fenkell, Detroit, Mich.; H. F. Huy, Buffalo, N. Y.; J. M. Hartering, Detroit, Mich.; John F. Reagan, Jr., Utica, N. Y.; Roswell M. Roper, E. Orange, N. J.; C. A. Holmquist, Albany, N. Y.; A. L. Sherman, Newark, N. J.j Joseph T. Cunningham, Brooklyn, N. Y.; Merritt H. Smith, N. Y. City;. E. S. Chase, Boston, Mass.; H. F. Neehan, N. Y. City; Howard P. Barnes, Croton, N. Y.; J. Frederick Jackson, New Haven, Conn.; John F. Skinner, Rochester, N. Y.; Allan M. E. Johnstone, N. Y.; F. C. Hopkins, N. Y. City; O. J. Burke, N. Y. City; C. H. Corbin, N. Y. City; John T. Metcalf, Brooklyn, N. Y.; A. E. Hanson, N. Y. City; Robt. A. Streater, Boston, Mass.; M. N. Baker, N. Y. City; Geo. Bowers, Lowell, Mass.; John C. Chase, Derry. N. H.; Chas. W. Lowitt, N. Y. City; P. A. Maignen. Phila.. Pa.; Elton D. Walker, State College, Pa.; J. E. Root, Akron, Ohio; Thos. F. Bowe, N. Y. City; Edw. M. Craig, Jr., Wanaque, N. J.; C. G. Wigley, N. Y. City; F. C. Wintermute, Wilkes-Barre, Pa.; W. H. Halsey, Southampton, L. I.; Howard E. Moses, Harrisburg, Pa.; C. A. Emerson, Jr., Phila., Pa.; E. W. Jacobs, N. Y. City; Fred B. Nelson. N. Y. City; Milton J. Roark, Baltimore. Md.
Weston Gavett, Plainfield, N. J.; Homer N. Calver, N. Y. City; Chas. Gilman, N. Y. C.; Chas. Haydocic, Phila, Pa.; Rich. H. Gould, N. Y. C.; Sam. A. Greeley, Chicago, 111.; W. S. L. Cleverdon, Bronx, N. Y.; I. S. Walker, Phila., l’a.; F. G. Cunningham, Memphis Tenn.; Geo. N. Schoonmaker, Toledo, O.; F. H. Luce, Woodhaven, N. Y.; Rich. Anketicr, N. Y. City; Earle Talbot, Wechawken, N. J.; Chas. F. Brietzke, Boonton, N. J.; J. A. Foulks, Newark, N. J.; Wm. Gavin Taylor, Newark, N. J.; E. B. Nesselievre, Dorr Co., N. Y.; R. B. H. Begg, Blacksburg, Va.; J. B. Ferguson, Hagerstown, Md.; H. N. Lendall, New Brunswick, N. J.; Arthur M. Crane, Nutley, N. J.; R. J. Quinn, N. Y. City; F. W. Haley Boston, Mass.; John A. Kienle, N. Y. City; R. W. Lawton, Los Angeles, Cal.^ James E. Williamson, N. Y.; Asher Atkinson, New Brunswick, N. J.; E. D. Case, N. Y. City; Alfred Millikin, Albany, N. Y.; J. M. Diven, Jr., N. Y. City; E. K. Sorenson, Nutley, N. J.; F. P. Larmon, Omaha, Nebr.; Henry Ryon, Albany, N. Y.; F. E. Beck, Utica, N. Y.; C. G. Bogcrt, N. Y. City; Robt. H. Lockwood, N. Y. City; Chas. C. Hopkins, Rochester, N. Y.; H. Burdet Cleveland, N. Y. City; Allen Hazen, N. Y. City; W. E. Spear, N. Y. City; J. S. Langthorn, N. Y. City; M. L. Enger, Urbana, 111.; F. A. Barbour, Boston, Mass.; J. E. O Leary, N. Y. City; Anson Marston, Ames, la.; J. C. Harding, Jr., N. Y. City; Reeves J. Newsom, Lynn, Mass.; C. H. Becker, Phila., Pa.; I. M. Glace, Harrisburg, Pa. . _ _
A. Prescott Folwell, N. Y.; G. C. Whipple, Cambridge, Mass.; C. B. Hayward, N. Y. City; M. F. Tiernan, Newark, N. J.; Karl M. Mann, N. Y. City; Merril H. Stinlward, Syracuse, N. Y.; Glenn D. Holmes, Syracuse, N Y.; Louis Mitchell, Syracuse, N. Y.; A. N. Talbot, Urbana, 111.; Harry A. Holmes, Waterford, N. Y.; Geo. H. Murray, N. Y. City; Frank A. Marston, Boston, Mass.; R. L. Sackett, State College, Pa.; Theo. Horton, Albany, N. Y.; John H. Gregory, Baltimore, Md.; 1 heo. R. Kendall, N. Y. City; V. E. Arnold, N. Y. City; H. P. Stearns, Far Rockay, N. V.; N. Durland. Far Rockaway, N .Y.; A. C. Grandy, N. V. City; N. M. Loney, New York City; Wm. L. Herron, N. Y. City; C. V. A~eH, N. V. City; W. C. Mallalicu, Jersey City. N. J.; J. K. Girsey. Shrewsbury. Pa.; E. A. Fisher, Rochester, N. V.; X. H. Goodnough, Boston, Mass.; James L. Tighe, Holyoke, Mass.; Morris Knowles, Pittsburgh, Pa.; J. Waldo Smith, N. Y. City; L. A. Kempf, Newark, N.J.; T. Chalkley Hatton. Milwaukee. Wis.; Frank E. Ilale, Brooklyn* N. Y.; F. T. Kemble, New Rochelle, N. Y.; W. H. Van Winkle, N. Y. City; R. W. Conrow, N. Y. City; James Bedell, Ossining, N. Y.; Thorndike Saville, Chapel Hill, N. C.; E. E. Miller, Palisades N. J.; G. N. Spaulding, Hackensack, N. J.; W. S. Cetti, Brooklyn, N. Caleb M. Saville, Hartford, Conn.; Harold C. Stevens, N. Y. City; Seth M. Van Loan, Phila., Pa.; Chas. A. Finley, Pittsburgh, Pa.; F. A. Tillman Johnson City, N. Y.; Robt. B. Hoadley, Binghamton, N. Y.; Edwin G. Reynolds, New Rochelle, N. Y.
Purchase of Pumper for Yankton, S. D., Recommended— Fire Commissioner W. F. Jencks has recommended to the city commission the purchase of an American-LaFrance pumper for the use of the fire department.