Page 725 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

680 Fundamentals of Water Treatment Unit Processes: Physical, Chemical, and Biological

BOX 22.1 CARBON DIOXIDE
engineering program took form in 1891. The academics
AS A GREENHOUSE GAS
engaged included Professor William Thomson Sedg-
The carbon dioxide from a biological reaction does not wick (a biologist), Professor William Ripley Nichols,
add fossil carbon, e.g., as in oil or coal, to the atmosphere. Ellen Swallow Richards (1842–1911), the first female
Rather, biological treatment merely makes the carbon graduate of MIT, and Professor Thomas Messinger
dioxide available for photosynthesis as a part of the carbon Drown. Allen Hazen (1869–1929) was at the Station
cycle. It speeds up what would otherwise be a part of the from 1890 to 1892 where he developed the effective
natural process of microbial degradation in the ambient size and uniformity coefficient characterizations of filter
environment. While this explanation may not put the sand. George Warren Fuller (1868–1934) was at the Sta-
matter to rest, photosynthesis will occur at some point in tion 1890–1895, after graduation from MIT. In 1895 he
the carbon cycle and convert the carbon dioxide again to went on to Louisville, Kentucky where he conducted his
organic matter, a sequestered form, as cells. Human activ- famous workonrapid filtrationforthe purposeof filtering
ity may increase the rate of processes, such that they may water from the Ohio River. Except for Mr. Mills, the
occur in hours, days, or years; in natural cycles the pro- aforementioned persons were either biologists or chem-
cesses may occur in years or decades, or perhaps centur- ists. In 1904, Allen Hazen formed the consulting engin-
ies. Reduction of the photosynthesis capacity of the land eering firm of Hazen and Whipple and was recognized
reduces the rate of sequestering and if a carbon-cycle as one of the foremost of sanitary engineers (http:==
model were available the effect on accumulation in the www.libraries.mit.edu=archives=exhibits=hazen). In
atmosphere could be assessed. 1911, Malcolm Pirnie (1889–1967) joined the firm and
Two other gases, methane, CH 4 , and nitrous oxide, in 1929 the firm became the present Malcolm Pirnie.
N 2 O, are also emitted from wastewater treatment plants At the time the Lawrence Experiment Station was
and are considered potent greenhouse gases. The captured organized, microbiology had just emerged as a scientific
methane from anaerobic digesters may be combusted to discipline and analytical chemistry was not a mature field.
CO 2 and water and yield energy and thus not add to the Mills was aware of the work of two European scientists
greenhouse effect to the same extent. Anaerobic reaction who had concluded that the oxidation of organic matter in
also occurs in sludge stored at the bottom of primary filtration through sand was most probably due to the
clarifiers, however, and methane=carbon dioxide gas bub- action of microscopic organisms. Mills was determined
bles may be seen breaking the water surface and escaping to ferret out how to apply such knowledge to sewage
the system. The same phenomenon may be observed in treatment on a practical scale. He started with 10 tanks,
natural waters where the benthic debris may have a sig- each with under-drains and filled with gravel or sand and
nificant organic fraction. Nitrous oxide has a 300-fold with different kinds of materials on the top surface, includ-
stronger effect than CO 2 as a greenhouse gas and emerged ing garden soil, dust, sand, peat, etc. In 1890, aware of the
as a concern of wastewater treatment probably after 1995. role of water in transmitting the typhoid bacillus, he
Kampschreur et al. (2009) gave 1990 global emissions initiated studies of drinking water filtration. In 1893, the
from wastewater treatment as 0.22 TgN=year (220,000 Station started studies on the biological treatment of
metric tons=year), which is about 0.03 fraction of the industrial wastes, including such familiar examples as
total from the anthropogenic sources. They determined dairy, carpet mill, wool, textile, paper mill, etc., and acid
that N 2 O occurs as a reaction product of both nitrification neutralization. In 1993, the station was renamed, the Sen-
and denitrification and have recommended operational ator William X. Wall Experiment Station (www.mass.
procedures to minimize N 2 O production. gov=dep=about= organization=wespost.htm, February 13,
2007). The station remains a viable organization for
research in environmental science and engineering.

BOX 22.2 LAWRENCE EXPERIMENT
STATION
22.1.4 DEFINITIONS
In 1886 a new law reconstituted the Massachusetts State
Board of Health to find practical methods for sewage Biological treatment involves a body of knowledge with
disposal. Hiram Francis Mills (1836–1921), an eminent many definitions; some are given in the glossary rather than
Boston consulting hydraulic engineer, was appointed to in the text. Some terms in the glossary are explained in
the Board. From this, the Lawrence Experiment Station considerable detail in order to complement the text but in
took form in 1887, with Hiram Mills as the administrator, some cases they would be difficult to place.
a position he held until 1915 when the Board was abol-
ished and the Massachusetts State Department of Public 22.1.4.1 Reaction Classifications
Health was created. Mr. Mills developed a relationship Reaction classifications are reviewed here, however, so that
with MIT which was symbiotic in that the MIT sanitary they may be seen in one place. The definitions were taken
from several sources, including Benefield and Randall (1980,