Page 733 - Fundamentals of Water Treatment Unit Processes : Physical, Chemical, and Biological

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

formula for anaerobic cells was given as C 5 H 9 O 3 N (Sherrard,
TABLE 22.5 1977, p. 1971).
BOD and COD for Sampling of Industrial Wastewaters Another formula by Orhon and Artan (1994, p. 81), based
on the composition of total and organic solids from two
BOD COD
Wastewater (mg=L) (mg=L) municipal wastewater treatment plants, was C 66 H 124 O 26 N 13 P,
with MW ¼ 1545 g=mol. The formula differs little from the
Pharmaceutical 3290 5780 Eckenfelder et al. (2009,
Porges et al. (1956, p. 42) formula for an N ¼ 1 basis.
p. 27)
Cellulose 1250 3455 nd
Tannery 1160 4360 nd Example 22.1 Ash Content of Cells
Paper mill 380 686 nd
Domestic 135 Eckenfelder and Weston Given
(1956, p. 30) The atomic weight for bacterial cells was given by Porges
Tomato 450 nd et al. (1956, p. 42) as MW(C 5 H 7 O 2 N) ¼ 113 g=mol.
Packing house 1020 nd
When ash is included they gave MW(C 5 H 7 NO 2 þ ash) ¼
Pharmaceutical 1684 3198 nd 124 g=mol.
Pharmaceutical 2532 3980 nd
Required
Refinery 79 262 nd
Determine the ash content of cells in (g ash=100 g cells
with ash).
22.3.1.2 Industrial Wastewaters Solution
Assume the cell wall, protoplasm, etc. has an overall
Industries that generate wastewaters number in the thousands. A
MW ¼ 124 g=mol. In other words, for 1 mol of proteins
sampling is shown in Table 22.5, which shows also the variation
(i.e., cells) their mass is 124 g, and the mass of ash is 11 g.
found in BOD and COD of the raw wastewaters. The treatment
Thus, for 100 g cell mass (which includes ash), the mass of
of industrial wastewaters is often specialized due to high ash is (11 g ash=124 g cells with ash) (100 g cells with
concentrations, toxic substances, or limited nutrients. ash) ¼ 8.87 g ash.

22.3.2 COMPOSITION OF CELLS 22.3.3 BIOLOGICAL REACTIONS
Microbial cells (heterotrophic and autotrophic) are composed As noted, biological reactions are complex and involve bio-
of elements, C, H, O, N, P, S, and trace metals. Empirical chemical cycles, energy transfers, and reaction stoichiometry.
formulae can depict the element ratios in simple terms, but A reaction is depicted first on a conceptual basis, building to
actually, the molecular composition and structure is complex. stoichiometric equations. The idea is to highlight the aspects
of a reaction that are important for engineering purposes.
22.3.2.1 Empirical Formulae for Cells Section 22.3 deals with the biochemistry, to add understand-
Porges et al. (1956, p. 42) gave an N ¼ 1 based formula as ing to the reactions.
C 5 H 7 O 2 N(MW ¼ 113), which has been adopted most exten-
sively and remains current (e.g., Grady et al., 1999; Orhan and 22.3.3.1 Substrate to Cells
Artan, 1994; Rittman and McCarty, 2002) and has been used for A chemoorganotrophic, i.e., heterotrophic, biological reac-
all categories of cells. With the inclusion of inert matter, they tion, may be depicted,
obtained the molecular weight, MW(C 5 H 7 O 2 N þ inerts) ¼ 124.
Stumm (1964, pp. 216–230), gave a P ¼ 1 based formula substrate þ E(bacteria) þ reactants
as, C 106 H 180 O 45 N 16 P. From the formula, the mole ratios ! new-cells(bacteria) þ E(bacteria) þ products (22:6)
are C:N:P ¼ 106:16:1, which is useful in estimating nutrient
additions, such as for an industrial waste. Also, the formula where
gives a basis for estimating the uptake of N and P, such as substrate is any substance that may serve as an ‘‘electron-
from a municipal wastewater. For reference, Stumm (1964, donor’’ for a biochemical reaction, e.g., degradable
p. 219) gave a balanced equation for the oxidation of the cell organic matter, ammonia, CO 2 (kg=m )
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matter as E(bacteria) is an enzyme contained in microbial cells that
serves to degrade the organic matter
C 106 H 180 O 45 N 16 P þ 154O 2
reactant is any chemical substance that serves as a reactant
3 (22:5)
¼ 106CO 2 þ 90H 2 O þ 16NO 3 þ PO 4 along with the other substances listed on the left side,
e.g., oxygen (mg=L)
For anaerobic organisms, McCarty (1970, p. 236) gave a P ¼ 1 new-cells(bacteria) are the microbial cells that have been
3
based formula as C 60 H 87 O 23 N 12 P (see also Sherrard, 1977, synthesized as a result of the reaction (kg cells=m )
p. 1971), for which the molecular ratios were approximately products are any chemical substances that result due to the
the same as given by Porges et al. (1956). An N ¼ 1 based reaction, e.g., carbon dioxide, water (mg=L)