USA > Massachusetts > Middlesex County > Reading > Town of Reading Massachusetts annual report 1905 > Part 8
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148
tions of these two types of water in the filter gallery vary not only with the season of the year, but daily with different rates of pump- ing, the difficulties connected with the treatment of the water become apparent, and the necessity for careful consideration of the problem before its solution can be definitely affirmed, is evident. This is specially true because any plant must be readily adaptable at a moment's notice for the treatment of the water, no matter what its character may be or how it may vary.
EXPERIMENTS
Realizing that unless the experiments be conducted for a long period the conclusions could not be worked out in practice with any degree of certainty, your Honorable Board wisely decided to con- tinue the test until all probable conditions should be thoroughly understood.
Experiments during 1892 by Desmond FitzGerald, C. E., re- sulted in his advice to purify the water by aeration, protracted subsidence and filtration.
In 1895 the State Board of Health, after a series of experi- ments, advised the abandonment of the present supply as soon as arrangements could be made to connect with the Metropolitan System. It also devised the adoption, temporarily, of some system of rapid filtration through sand. Following this advice, the Town installed rapid mechanical filters of the Warren type, and these are in operation today. They make use of chemicals, namely, lime and alum, and remove the iron to a satisfactory degree, although the added chemicals increase the hardness of the water about three- fold.
For the purpose of devising a method which would remove the iron without increasing the hardness of the water, the State Board of Health made extensive experiments during 1903, which resulted in advising the Town to treat the aerated water with metallic iron and to follow the treatment with filtration at a mod erate rate through sand.
The experiments conducted during the past two years h
149
been devoted to the demonstration of this method ; to the trial of improvements tending to decrease its cost and to gaining experi- ence in the operation of the method with the varying character of the water from the filter gallery.
EXPERIMENTS WHERE THE WATER WAS TREATED BY CONTACT WITH IRON CONTAINED IN A REVOLVING DRUM
The State Board of Health recommended that the water be treated by contact with iron in a reservoir. It recommended that the iron be in the form of strips, so that they could be removed from the water and scoured whenever they should become corroded. The experiments with the revolving drum were a modification of this device, with a view to decreasing the expense of treatment. During the experiments the water was passed through a revolving barrel containing particles of iron. The barrel was connected with an aerator, subsiding basins and sand filter, in such a way that the following combinations could be experimented with :
(a) Iron treatment and filtration.
(b) Iron treatment, aeration and filtration.
(c) Iron treatment, subsidence and filtration.
(d) Iron treatment, aeration, subsidence and filtration.
The experimental results are summarized as follows :
TABLE I.
Date
Aerator
Minimum Pe- riod of Sub- sidence
Rate Gals. per A per diam
Av. Parts of Iron per 100,000 in
Notes
Wells
Treated Water
Filtered Water
1904
Aug. 24, 31
Yes
30 hours
6,000,000
.046
.250
.025
Filter clogged badiy
Aug. 31, Oct. 6
No
30 hours
6,000,000
.094
.470
.101
Filter rested
Oct. 31, Dec. 28
Yes
30 hours
6,000,000
176
.810
.074
Filter badly clogged. Iron penetrated sand layer
Filter scraped and new sand added.
1905
Jan. 2, Feb. 18
Yes
30 hours
6,000,000
.155
.59
.044
Idle Jan. 18 to 25
Deb. 27, Apr. 27
Yes
30 hours
6,000,000
.113
.538
.026
Idle April 9 to 14
151
During these experiments the iron gradually penetrated the sand layer and finally appeared in the effluent. The increase in the period of subsidence did not overcome this trouble, neither did resting and aerating the sand layer. The deep scraping of the filter and replacing of fresh sand therein bettered the results for a time only. In view of the expense of operating this process on a large scale, owing to the expensive construction involved and the power required to revolve large drums containing scrap iron, and also in view of the possibility of failure of the plant in practice, because no guaranty could be made that the water by direct contact with the iron would always take up just the suitable and proper amount of iron at all times of the day and year for the proper treatment of the water, it was decided to abandon the experiments with this process and to substitute for the barrel containing pieces of iron, iron plates through which electric current could be passed.
When these plates, arranged in pairs, are immersed in water to be treated and one of each pair of plates is connected with the positive and one with the negative pole of some machine for pro- ducing electric current, the water is decomposed and iron is added to the water in the presence of oxygen, in the form of ferric hydrate-a reddish brown precipitate. The electric current possibly effects a decomposition of combinations of iron and organic matter which are exceedingly difficult to remove from the water by aera- tion and subsidence. The excess of iron added has the effect of neutralizing the organic matter and by its absorptive power it car- ries down with it the iron originally present in the water, which being precipitated with the iron added electrolytically, is either retained in the subsiding tanks or is removed by the filter when the treatment is carried to the proper degree. The effect is similar to that produced by the contact of the water and iron. The advan- tage of the electrolytic device lies in the fact that the iron surface exposed may be very much reduced and that the amount of iron added to the water is always under the direct control of the attend. ant, because, other things being equal, definite amounts of electric current discharge definite amounts of iron into the water as it
152
comes in contact with the plates. This advantage is further increased because of the greater convenience and by the reduced cost of operation.
Experiments, therefore, were made, substituting the electrolytic device for the barrel. The results of these experiments are tabulated as follows :
7
o
EXPERIMENTS WITH THE ELECTROLYTIC IRON DEVICE. TABLE II.
Date
Aerator
Minimum Period of Subsidence Hours
Rate Gals. per A per diam
Av. parts of Iron per 100,000
Notes
Welis
Treated Filtered Water Water
1905
Feb. 27 to Apr. 1
Yes
30
6,000,000
118
1.025
.009
Apr. 2 to Apr. 26
Yes
24
10,000,000
109
0.844
.020
Apr. 27 to May 12
Yes
48
10,000,000
100
1.067
.017
April 9 to 14, idle Stopped by failure of dynamo
June 1"to June 7
Yes
48
10,000,000
. 099
1.212
.016
June 8 to June 21
Yes
48
10,000,000
.106
1.392
052
Filter idle one day
June 22 to Aug. 5
Yes
60
6,000,000
.114
2.91
.112
Fil. went out of service
Sept. 15 to Oct. 14
No
30
6,000,000
141
1.27
.006
10 in. new sand added
Oct. 14 to Oct. 26
No
30
6,000,000
.168
1.50
.000
Oct. 26 to Nov. 11
No
24
10,000,000
.207
1.200
002
Nov. 11 to Nov. 17
No
48
10,000,000
.200
1.100
.000
Nov. 17 to Dec. 13
Yes
48
10,000,000
.190
1.089
.002
11 days idle
Dec. 13 to Dec. 31
No
48
10,000,000
.174
0.241
.000
No electric current
Average Iron in Filtered Town Water, .01.
154
It will be seen from the foregoing that with the exception of the period during June and July, the filters have given excellent results, and for the last five months have almost entirely removed the iron from the water without increasing the hardness thereof. When the inferior results were obtained, the filter was being oper- ated at a rate of 6,000,000 gallons per acre per day, and the water was subjected to about 48 hours subsidence, preceded by aeration. The unfiltered water contained about two parts of dissolved oxygen per million. Strange to say, when aeration was omitted the efficien- cy of the filter was soon restored, and since that time no difficulty has been experienced in treating the water when the theory learned from this experience has been applied.
At this point it will be well to discuss briefly the theory of iron removal, as understood at present.
When ground waters like the Reading water are pumped to the surface, they are clear and when the amount of iron is high, they possess än inky or styptic taste. After standing for some time, however, the water first becomes opalescent, then turbid, and finally the particles producing the turbidity darken in color (or rust), gather in "flocks" and precipitate, leaving the water above the sedi- ment clear, tasteless and almost free from iron. The above clouding and clearing of the water is caused by the changing of the iron from the unoxidized or soluble into the oxidized or insoluble form. The speed of this reaction depends upon the composition of the water, as will be shown beyond. The Reading water very often requires a long time for the complete precipitation of the iron, while the iron-bearing artesian waters of the Jersey coast precipitate within a few hours. Chemically considered, the process may be divided into four parts :
1. The absorption of oxygen from the air by the water.
2. The breaking down of the iron compound originally con- tained in the water into a compound that may be oxidized. This process is called hydrolysis.
3. The oxidation of the iron into the colloidal or gelatinous form of iron hydrate which though oxidized is, like starch, so
155
peculiar in structure that it remains in a state bordering upon solu- tion (in this state it would not be retained by a filter ) until
4. The iron hydrate gathers together into "flocks" or aggre- gates, and precipitates as the hydrated iron oxide or, as it is generally called, iron-rust.
The chemistry of this process is rather complicated and the action is retarded by the presence of many interfering substances, particularly carbonic acid and the organic acids which form a part of vegetable matters. Aeration serves to remove carbonic acid, and at Reading the experience shows that the organic acids may be removed either as at present, by neutralizing with lime, or as tried during these experiments, by adding metallic iron to the water either by contact or with the aid of an electric current. The com- pound resulting from the action of these organic acids and metallic iron seems to be oxidizable, and furthermore, this added iron com- bines with and removes the organic matter which interferes with the oxidation and precipitation of the iron originally contained in the water.
It has been the opinion in Europe and in this country that aeration could never be overdone, but the experiments at Reading show that when the water is of a certain character, the small amount of oxygen dissolved in the gallery waters effects a better removal of the iron than a large amount of oxygen added by artificial aeration, as was shown when the inferior results of last July were obtained. It is believed at the present time that when the water is aerated in an excessive degree it causes the rapid precipitation of the iron added electrolytically before it has time to combine and absorb the iron originally present in the water.
This phenomenon was demonstrated by bottle experiments which were first made on October 24th, and which have been con- tinued daily until the present writing. These experiments were conducted in gallon bottles, which were filled with water and were allowed to stand twenty-four and forty-eight hours, after which the iron remaining in the water above the sediment was determined. Experiments were made with the water before and after treatment
156
with iron, which was added electrolytically. These experiments proved conclusively that for days at a time the iron in the aerated water, after treatment with iron (electrolytically) subsides much more rapidly than the unaerated water, while on the other hand, the unaerated gallery water precipitates its iron much more rapidly than after it is aerated. This goes to prove that the added iron and the original iron precipitate at different speeds, and it is the object of any plant designed to treat the Reading water to cause these precipitations to take place at about the same rate and time, in order that the larger amount of added iron when precipitating may induce the removal of the iron originally present in the gallery water.
AMOUNT OF IRON NECESSARY TO ADD TO THE WATER TO EFFECT SATISFACTORY PURIFICATION
During December, 1905, it has been necessary to add very little iron to the water to effect its satisfactory purification. In fact, during part of this month no electric current has been used, yet the iron removal has been complete. On the other hand, the water may at times require as much as 0.8 parts per 100,000, although recent experience indicates that much smaller amounts of iron will be necessary in the future on an average than were thought neces- sary at the beginning of the tests.
The greater the amount of iron added, the shorter the period which the filter can be operated without scraping its surface. Therefore it is an advantage to add as little iron to the water as will effect purification.
LENGTH OF PERIODS BETWEEN SCRAPINGS
The length of periods between scrapings has varied greatly. During some of the experiments it has been of only about ten hours duration ; again the period has been over 160 hours. It should be borne in mind in this connection that the experimental filter has only 1 ft. depth of water above the surface of the sand, and that in practice filters are built with a water depth of 4 ft.
157
During the first part of the year considerable trouble was experienced with the clogging of the filters with air. This difficulty has been overcome by suitable devices for filling the filter from below, and at present the filters are running for about 5 hours a day for about three weeks at a time.
More data is desired along these lines before it can be definitely stated how long the periods between scrapings would be in practice, and for this reason among others the extension of the experiments is recommended. This is especially desirable in view of the fact that during certain times of the year plain subsidence and filtration will effect satisfactory removal of the iron from the water.
PERIOD OF SUBSIDENCE
Any purification plant which would be constructed would probably have to be built so that the devices for treating the water with iron would be operated during the daytime under the care of an attendant, while the filters would naturally operate day and night. This would require a sufficiently large subsiding basin to allow the filters to operate continuously. This basin would have to have a capacity of at least 24 hours flow. The present evidence goes to show that this period would suffice for the satisfactory treatment of the water.
AERATION
Aeration would probably not be necessary at Reading during a greater part of the year. Certain waters have been experimented with, however, which seem to be purified more rapidly with aeration than without.
ELECTROLYTIC IRON DEVICE
The addition of iron at certain times of the year, especially at the time when the amount of organic matter is high, is absolutely necessary for the satisfactory purification of the water by this method, but for the greater part of the year it is probable that little or no electricity would have to be used with the iron plates.
158
This method of adding iron to the water, applied for the first time in this connection, has worked with entire satisfaction, the amount of iron being at all times under the direct control of the attendant.
RATE OF FILTRATION
When the water is properly treated it seems to make no difference whether the filters are operated at a rate of 3,000,000, 6,000,000, or 10,000,000 gallons per acre per 24 hours. In other words, the treatment of the water is all important; the rate of filtration relatively unimportant. It is not believed, however, on account of the comparatively short periods between scrapings, that rates much higher than 10,000,000 gallons per acre per 24 hours could be used to an advantage.
SUMMARY
The results of the experiments to date may be summarized as follows :
1. The filter gallery water at Reading is one exceedingly difficult to treat on account of its rapidly changing character, and especially on account of those constituents which interfere with the rapid oxidation and precipitation of the iron contained in the water.
2. With the exception of certain details, the general process for the removal of the iron from the supply without increasing the hardness has been demonstrated to be entirely feasible.
During part of the year aeration, subsidence and filtration would suffice ; during part, subsidence and filtration alone would effect removal of the iron. Again, the addition of iron electrolyti- cally, with or without aeration as the circumstances demand, would be necessary in addition to subsidence for the satisfactory prepara- tion of the water for filtration during the remainder of the year. The continuance of the experiments for a few months more is desired in order that more experience may be gathered with a water like that which occurred during June and July of 1905, and that more data may be obtained regarding the lengths of periods between scrapings under different conditions of operation.
·
159
The further continuance of these experiments is not very costly, as they are carried on under the immediate charge of your very competent pumping station engineer, who has spare time for this work, and again, this small annual expense is justified by the saving which might be effected if soft water could be substituted for hard, and if the present cost of filtering water could be reduced. For the last five years this latter has been as follows :
COST OF FILTRATION-READING WATER WORKS 1901 to 1905
Per Annum
Wages
$800 00
Interest on investment, $21,000 x 4 per cent.
840 00
Sinking fund and repairs
678 00
Coal
248 00
Sulphate of alumina
281 00
Lime
154 00
$3,001 00
The cost of filtered water then is about $54 per million gallons. It may be said for comparison that the cost of filtering water at other small plants rarely exceeds $25 per million gallons. The possible saving, therefore, makes the expenditure of a certain small annual amount for experiments a judicious step, and the writer recommends their continuance.
The experiments have been conducted under the direct charge of Mr. Frank F. Strout, to whose care and devotion to the work the success of the experiments is chiefly due. The writer also wishes to thank your Superintendent and the members of your Honorable Board for material aid in the preparation of this report.
Respectfully presented,
ROBERT SPURR WESTON.
Feb. 6, 1906.
,
TOWN OF READING
ELEVENTH ANNUAL REPORT
OF THE
Electric
Light Commissioners
OF
TOV
9
LED
INC
FOR THE YEAR ENDING DECEMBER 31
1905
OFFICERS OF THE ELECTRIC LIGHT AND POWER DEPARTMENT
Commissioners
WM. S. KINSLEY, Chairman
.
Term expires 1906
WALTER F. COOK, Secretary
66
1907
FRANK W. WILLIS .
99
6: 1908
Manager M. L. SWIFT
OFFICE :
Room 9, Masonic Block
REPORT OF MUNICIPAL LIGHT BOARD
FOR THE YEAR ENDING DECEMBER 31, 1905
FINANCIAL STATEMENT -
.
CONSTRUCTION
RECEIPTS
Appropriation for 1905, taken from receipts of Plant $3,000 00
EXPENDITURES
ELECTRIC PLANT
Boston & Maine R. R.
$1 04
The Bristol Co.
54 00
Rossiter, McGovern & Co.
271 80
Westinghouse Electric & Mfg. Co.
426 28
Pettingell-Andrews Co.
7 35
Sundries
7 50
$767 97
LINES -
Pay Rolls
$394 94
Pettingell-Andrews Co.
553 45
Boston Lumber Co.
189 00
Buffalo Specialty Mfg. Co.
73 48
Boston & Maine R. R.
1 36
$1,212 23
165
ARC LAMPS AND GLOBES
Boston & Maine R. R.
$31 37
Western Electric Co.
377 58
F. O. Dewey Co.
66 50
Adams-Bagnall Co.
1,026 00
Pettingell-Andrews Co.
7 75
$1,509 20
METERS
Westinghouse Electric & Mfg. Co.
$628 16
Boston & Maine R. R. .
1 69
$629 85
CONVERTERS
American Express Co.
$3 85
Boston & Maine R. R.
14 20
Westinghouse Electric & Mfg. Co.
65 52
$83 57
$4,202 82
SUMMARY
Total charges to Construction account . $4,202 82
Amount borrowed from Maintenance ac-
count, 1904
1,208 15
$5,410 97
Total credit to Construction account
3,000 00
Amount borrowed from Maintenance ac-
$2,410 97 count, 1905
166
RECAPITULATION
COST OF MUNICIPAL LIGHT AND POWER PLANT DEC. 31, 1905
Total cost to Dec. 31, 1904 . .
$85,134 75
TOTAL CHARGES FOR YEAR ENDING DECEMBER 31, 1905
Electric plant
$767 97
Lines
1,212 23
Arc lamps and globes
1,509 20
Meters
629 85
Converters
83 57
$4,202 82
$89,337 57
Construction stock on hand Dec. 31, 1905 . 980 43
Total cost to Dec. 31, 1905
$88,357 14
MAINTENANCE
Cash on hand Dec. 31, 1904 $933 18
Amount loaned Construction Account 1904 1,208 15
Appropriation for Arc Light Rentals . 7,590 00
$9,731 33
Cash from Commercial Incandescent Lights $4,852 53 Cash from Domestic Incandescent Lights . 6,611 92
Cash from Town Incandescent Lights 282 93
Cash from Meter Rents 416 20
Cash from Wiring, Labor and Fixtures 547 42
Cash from Incandescent Lamps 271 60
Cash from Coal .
49 05
Amount carried forward $13,031 65
-
167
Amount brought forward Cash from Miscellaneous Articles 1 98
$13,031 65
Cash from Oil and Waste
9 10
Cash from Interest on Deposits
24 33
$13,067 06
Less amount appropriated for Construction
3,000 00
$10,067 06
$19,798 39
EXPENDITURES
FUEL
Pay Rolls .
$15 50 ·
Boston & Maine R. R.
488 15
E. C. Hanscom .
69 45
S. P. Burton & Co.
2,741 13
$3,314 23
OIL AND WASTE
Eagle Oil and Supply Co.
$178 03
Boston & Maine R. R.
1 13
A. W. Harris Oil Co.
6 45
A. S. Cook & Co.
1 00
$186 61
WATER
Reading Water Works
$20 52
STATION WAGES
Pay Rolls
.
.
$2,921 99
168
REPAIRS OF REAL ESTATE
Wm. Hall & Co.
$ 61
Pay Rolls .
74 76
Wendell Bancroft & Co.
141 86
Francis Bros.
7 50
A. J. Wilkinson & Co.
2 08
Walter F. Cook
87 35
E. C. Hanscom
448 60
O. P. Symonds & Sons
5 50
Geo. A. Shackford
2 00
Geo. H. Atkinson Co.
8 00
Sundries
1 15
REPAIRS OF STEAM PLANT
T. C. Fife .
32 24
W. Bancroft & Co.
9 50
R. P. Burgess
5 00
Eagle Oil & Supply Co.
51 99
Cummings Express Co.
2 64
Sundries
5 05
Hayden & Co.
19 60
American Express Co.
1 20
H. R. Worthington
55
The Fairbanks Co.
6 50
Woburn Machine Co.
6 08
The Lumsden & Van Stone Co.
206 74
Robb-Mumford Boiler Co. .
1 50
Boston & Maine R. R.
6 29
REPAIRS OF ELECTRIC PLANT
Pay Rolls
75 25
Bowker, Torrey & Co.
12 00
American Express Co.
14 92
Amount carried forward $102 17
»
$779 41
$354 88
169
Amount brought forward
$102 17
Byers & Smith
6 00
Geo. H. Atkinson Co.
55
Walter F. Cook
13 15
Cummings Express Co.
7 05
Francis Bros.
11 30
Geo. A. Shackford
5 00
Westinghouse Electric & Mfg. Co.
199 36
Crown Woven Wire Brush Co.
18 00
The Fairbanks Co.
6 50
J. T. Freeman & Co. .
9 90
General Electric Co.
16 08
E. W. Nash Co.
4 10
Sam'l Pierce Organ Pipe Co.
90
Pettingell-Andrews Co.
2 70
Condit Electric Mfg. Co.
6 50
Boston & Maine R. R.
1 53
Sundries
3 70
$414 49
STATION TOOLS AND APPLIANCES
Eagle Oil and Supply Co.
$57 03
Fred Wallace
14 21
Francis Bros.
35 85
Pettingell-Andrews Co.
3 48
Sundries
1 50
W. A. Dennison
15 35
Samuel Brown
8 50
American Express Co.
1 35
Western Electric Co.
2 25
Revere Rubber Co.
9 38
E. C. Metcalf
8 65
A. S. Cook & Co.
1 20
Hayden & Co.
20 00
Boston & Maine R. R.
35
$179 10
170
WAGES, CARE OF LIGHTS
Pay Rolls
.
.
REPAIRS OF LINES AND LAMPS
Pay Rolls .
$792 01
Pettingell-Andrews Co.
353 37
Boston & Maine R. R.
43 44
American Express Co.
12 10
Francis Bros.
4 03
Electric Gas Lighting Co.
43 00
Sundries
8 40
Buffalo Specialty Mfg. Co.
39 57
Adams-Bagnall Co.
67 00
Union Hardware & Supply Co.
7 50
$1,370 42
CARBONS
National Carbon Co. .
$107 57
Boston & Maine R. R.
4 37
Pettingell-Andrews Co.
16 99
$128 93
INCANDESCENT LAMPS
Western Electric Co.
$332 75
G. I. Are Light Co.
18 47
Boston & Maine R. R.
50
Stuart-Ilowland Co.
13 03
F. O. Dewey Co.
20 00
Pettingell-Andrews Co.
1 34
$386 09
GENERAL SALARIES
Pay Rolls . . .
$634 00
Board expenses
1 70
GENERAL OFFICE EXPENSES
New Eng. Tel. & Tel. Co.
$99 20
Turner Mfg. Co. 26
Amount carried forward $99 46
$400 51
P
.
1
171
Amount brought forward
$99 46
H. Prentiss, P. M.
96 30
A. S. Cook & Co.
3 49
Hobbs & Warren Co.
26 85
Sundries
37 64
Adams, Cushing & Foster
23 00
J. L. Fairbanks & Co.
5 50
The Bristol Co.
3 75
Reading Chronicle office
42 05
$338 04
RENTS
Masonic Temple Corporation .
.
$110 04
INSURANCE
Prentiss & Viall
. .
$699 09
INCIDENTALS
Dr. S. H. Parks, professional services $4 50
A. P. Brooks, prints of plans
3 00
E. F. Parker, Treasurer
5 53
Lewis Murr
1 96
$14 99
INTEREST
Interest on Bonds
. $1,600 00
Interest on Notes
140 00
.
$1,740 00
STABLE
F. P. Abbott
$240 00
Sundries
9 60
P. J. Seaman
34 55
Geo. A. Shackford
7 50
F. W. Danforth
10 00
C. D. Wells
29 00
W. C. Taylor
14 15
O. O. Ordway
4 20
$349 00
172
WIRING, LABOR AND FIXTURES
Pay Rolls .
$29 28
Stuart-Howland Co.
1 80
Pettingell-Andrews Co.
63 26
Boston & Maine R. R.
70
American Express Co.
14 69
Cummings' Express Co.
4 50
Western Electric Co.
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