Page 428 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

Rapid Filtration 383

Iam firmly convinced, therefore, of the soundness of the Washington, District of Columbia with 22, or New Orleans
conclusion that it is best to build mechanical filters for the with 14. [The current similarity might be in terms of cases
purification of the Croton water supply. of giardiasis or cryptospiridousis.] The dissenting member,
Mr. Frazee stated,
The plans and estimates with data were submitted to a five
member board of experts appointed by the Commissioner (of I am of the opinion that it would be as satisfactorily efficient at
the Department of Water Supply, Gas, and Electricity) that this time, and far more economical, to strike at the sources of
included Allen Hazen and George A. Johnson. They stated trouble, some of which were recognized as existing ten years
that the ‘‘the mechanical filters shown by the plans are in ago, but toward the abatement of which nothing has been done.
general accordance with modern practice.’’ The plans for the
mechanical filter plant were completed June 25, 1912. The The advancement of sanitary and medical science in recent
plans included a mixing chamber, five settling basins with six years in the development of this treatment (hypochlorite appli-
hours detention time, a sixth basin to settle wash water, a cation) and the innocculation against typhoid, tend strongly to
discount the conjectural possibility of future outbreaks pend-
coagulant addition at ‘‘Gate House 8’’ through a rubber pipe
ing delay and particularly so if the pollution sources known to
grid, from two 5 in. coagulant supply pipes, 80 filters divided
exist in part and to be indicated are abated.
into four series of 20 each, with 10 on each side of the operating
gallery. The net area of the filter beds was 2.7 acres, giving a
Mr. Frazee’s dissent continued noting that the problems of
filtration velocity of 1.89 gpm (calculated for a design flow of
water quality were mainly esthetic and that the water at times
320 mgd). Sand size specified was 0.60 d 10 0.70. After
exceeded standards set by experts. He further called for what
filtration the water was to be treated with ‘‘hypochlorite of
was later called a ‘‘protected’’ watershed. He calculated the
lime.’’ A three story building for a laboratory was to be con-
financial savings of delay at $31,000,000 (Fuller, 1914,
nected to the south end of the four filter galleries. The filtered
p. 171); Fuller took issue with the premises on Mr. Frazee’s
water reservoir had a net area of 53.55 acres with capacity of
calculations were based. On May 22, 1913, a Mr. Mitchell,
356 mg. The plans provided for alum storage and lime or soda
who became mayor, cast the vote that killed the project. His
storage, alum solution tanks, lime suspension tanks, and hypo-
rationale was that hypochlorite would make the water safe and
chlorite solution tanks. The cost estimate was $5,916,700, with
that aeration would remove 50%–75% of the tastes and odors
nine bids received ranging from a low 13% less to 14% higher.
and color and turbidity.
The Board of Estimate responded, after their review and sug-
Fuller argued for filtration with both rationale and passion
gestions for minor changes with the remark,
(Fuller, 1914, p. 136):
In general, specifications are in our judgment admirable in
. . . And it is noteworthy that such filtration is considered
form and arrangement and exceptionally free from ambiguity,
necessary, not because any tests indicate a danger of infection,
and we can see no reason why they should not be approved by
but because a surface supply is always liable to pollution from
the Committee.
unexpected sources.
At the time the plans were prepared opposition appeared which
and (Fuller, 1914, p. 174),
criticized the site selected, and the method of filtration and the
matter was referred to an advisory commission of
The various phases of this matter have been clearly before the
five engineers (four were consulting engineers with one,
city officials for many years. It has never been represented as
Mr. John H. Frazee being Assistant Engineer, Department of absolutely imperative. Neither is it imperative for the city to
Finance. The majority report addressed all issues including the clean its streets daily, to maintain good smooth pavements, or
quality of the Croton water, the site at Jerome Park, the design, to build a $15,000,000 office building. But it is certainly
the costs, the overall economics (related to users not having to desirable that a city of the rank of ours should have a pride
filter their own water, which was common especially for in doing these things; and it should have a pride in drinking a
hotels), and concluded the that the system should be built. water for which it need not apologize as reasonably safe, at
Their summary statement (Fuller, 1914, p. 170), sheds some most times, and fairly decent looking at most times.
light on the general feeling about the water filtration, that is,
Real safety we are not getting. Limited by the need of adding
only enough hypochlorite not to spoil the taste, and with an
It is of the opinion of this commission that the filtration of the
Croton water supply is not imperative, but that it is highly organic content in the water varying from day to day, it is not
advisable to filter the water at this time both with a view to physically possible to vary the hypochlorite dose so as to
oxidize both the organic matter and the bacterial content and
improving the physical quality and as a safeguard against
leave no objectionable excess. And conditions may arise at
potential danger, and we so recommend with the exception
any time when the hypochlorite treatment will not be effective
of one member dissenting.
in preventing the transmission of disease.
At the time, the ‘‘danger’’ was measured in terms of number
of typhoid deaths per 100,000 persons, which was 10 in the After the decision not to proceed, Fuller stated (Fuller, 1914,
year 1912, and was lower than say Detroit with 18 or p. 174),