Discussion of the Paper by Mr. L. M. JohnsonAuthor(s): Charles Gilman HydeSource: Sewage Works Journal, Vol. 13, No. 1 (Jan., 1941), pp. 86-88Published by: Water Environment FederationStable URL: http://www.jstor.org/stable/25029150 .

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86 SEWAGE WORKS JOURNAL Jan., 1941

DISCUSSION OF THE PAPER BY MR. L. M. JOHNSON *

By Charles Gilman Hyde

Professor of Sanitary Engineering, University of California, Berkeley, Cat.

This discussion of the subject "Mechanical Devices in Sewage Treat ment" has been prepared as an independent contribution because,

through the fortuity of time and distance, the author's paper has not

been made available to me.

In "Modern Sewage Treatment," the Anniversary Book of this

Federation, Chapter I, Introduction, "A Review of Progress in Sewage Treatment During the Past Fifty Years in the United States," I found occasion to say: "Since 1919, the trend is marked in the United States toward all sorts of mechanical equipment instead of manually operated

devices, with the general result that plants are now far cleaner and more

comfortably operable than in the past and are rapidly approaching the

white uniform and kid glove stage of cleanliness. Moreover, present

day equipment is being constructed with a view to greater ruggedness and longer service.

' '

Pearse, in Chapter II, Functional Outline of Processes of Sewage

Treatment, remarks : ' ' In the forward development of the art of sewage treatment and the greater size of the plants, the use of mechanical de

vices has grown tremendously. In the large works today, mechanical

and electrical engineers work in co-operation with the sanitary engineer on operation and design."

It is indisputably true, with respect to the larger sewage treatment works at least, that the advent of mechanical equipment has induced

profound changes in both design and operation. Today neither can be

the work of a single professional group. Structures are, on the whole, more complicated. Equipment com

prehends devices concerned not alone with the handling of sewage, grit,

screenings, grease and sludge per se, but with electrical and gas power, and with dosing, controlling, indicating and measuring devices of every

description. The electrical power may be produced at the plant by in

ternal combustion engines, sometimes of large capacity. Air compres sors and blowers are employed for grease removal, and in the activated

sludge process. The simpler methods of sludge disposal of the past have given way in many instances to relatively complicated dewatering,

drying and incinerating installations. Fertilizer is being produced and

shipped to far-away destinations. Mechanical filters are being added to improve effluent quality. Plants of the sort in question require com

plicated switch boards and conduit systems to supply the demands for

power, lighting and ventilation. Heating and plumbing are essential to the buildings as well as laboratory facilities. Thus the services of

* Presented at the First Annual Convention of the Sewage Works Federation, Chicago, 111.,

Oct. 3, 1940.

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Vol. 13, No. 1 MECHANICAL EQUIPMENT IN SEWAGE TREATMENT 87

the sanitary, the structural, the mechanical and the electrical engineer,

together with those of the architect and landscape gardener, are de

manded if successful design and construction are to be achieved.

In the operation of these larger works the services of trained electri

cal and mechanical engineers and attendants are required quite as much as are those of the sanitary engineer and chemist. This represents a

very different situation from that which prevailed two decades ago.

However, it must be noted that large plants such as are now fairly nu

merous were not then in existence.

The extent to which mechanical equipment, should be utilized in the

smaller plants is a matter which deserves careful consideration on the

part of designing engineers. While it may be said with some truth that the very existence of such devices may foster better and more intelli

gent operation, the designer must at least face that hazard. It is obvi ous that the proper operation of complicated mechanical equipment and

devices demands intelligent, skillful operation. Unless such is to be

vouchsafed, simpler design is called for.

Due to the natural desire of designing engineers to reduce the phys ical burden of operation, and perhaps to the importunities of those

whose job it is to sell equipment, there has been a tendency to install too much equipment in relatively small plants. This writer has seen

sewage treatment works built to serve a few hundred persons in iso

lated country villages equipped with mechanisms which have never

been made to operate and have lain idle with disastrous results as far

as the quality of the effluents was concerned.

Although this may not be a popular matter to broach at this time, the writer is disposed to air two pet peeves which seem to bother him in

respect to the general subject of equipment. One of these concerns the

trade names with which some of these devices are being dubbed. The

other relates to the character and lack of information in some trade

catalogues, if indeed they are worthy of such a designation. How for example, can any self-respecting, dignified engineer hope to

live down the reputation of having installed in a plant for which he is

responsible an "Aerotapivator," a "Bioflocigester," a "Biochemula

tor," a "Multrotdistrib," or even a "Spirovortjector"! Too many effusions of the manufacturers of equipment?not alone,

by any means, in the sewage works field?seem to be aimed at the school

child rather than at the of-age designer and purchaser. They are like

copies of "Life" or "Look," with many beautiful pictures but a great dearth of the sort of information essential to design and installation. Data of specific performance are too seldom stated and an indication of

costs almost never. Some literature which comes to our hand has com

plicated foldings, opened only at the expense of time and ingenuity, the which becomes as expansive and altogether unwieldy as are our own

daily newspapers in crowded street cars.

Fortunately this castigation does not apply to all such publications. Many are replete with just the information which is sought : capacities,

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88 SEWAGE WORKS JOURNAL Jan., 1941

sizes, speeds, space requirements, specific performance figures, etc. In

some types of enterprises general ranges of prices are stated to the

immense satisfaction of would-be purchasers. As an example of trade literature in another field?that of water

supply?the writer has failed to discover in any manufacturer's publi cation definite information concerning the loss of head, either with downward or upward flow, incident to various rates through various

grades of zeolite. This is perhaps a rather typical illustration of the failure to supply information as essential to design as is the perform ance of the product itself.

Notwithstanding this tirade, the writer feels that as a rule manufac

turers of sewage treatment equipment and accessory devices have been

alert to supply those mechanisms which the designing engineer needs.

These have been steadily improved in respect to performance, durability and appearance. Manufacturers are gradually getting away from the

practice of attempting to make devices developed for use in other fields serve the exacting requirements of this one. In other words new de

vices are being developed for the specific needs of sewage and industrial

wastes treatment. It remains for the engineer to acquaint himself

thoroughly with what the market affords and to select that which is best adapted to his purpose at the least cost for installation and opera tion consistent with effective performance.

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