Environmental Engineering Reference
In-Depth Information
(b)
1200
(a)
1000
800
600
Upstream samples (KR1)
Control samples
Upstream samples (KR2)
Control samples
400
Downstream samples (KR5)
Control samples
Downstream samples (KR6)
Control samples
200
0
1000
(d)
(c)
Downstream samples (KR5)
Control samples
Downstream samples (KR6)
Control samples
800
600
400
Upstream samples (KR1)
Control samples
Upstream samples (KR2)
Control samples
200
0
0
1
2
3
4
5
0
1
2
3
4
5
Incubation time (h)
Fig. 11
The decay of peroxides by the occurrence of bacterial incidences in upstream and pol-
luted river waters with an addition of standard 1,000 nM of H
2
O
2
(
a
) and 1,000 nM of peracetic
acid (
b
) under dark incubation in NK system BIOTRON at controlled temperature (21 °C). Con-
trolled or sterilized samples (addition of 2 % solution of HgCl
2
) conducted under the same condi-
tion and same incubation period.
Data source
Mostofa et al. (Manuscript in preparation)
rivers (74 %) where the bacteria are more numerous (of order 10
6
cells mL
−
1
)
(Fig.
11
a). Similarly, the decay of peracetic acid (ROOH) was 40 % and 85 %,
respectively (Fig.
11
b). The initial degradation rate is roughly double for ROOH
(peracetic acid) than for H
2
O
2
, thus the concentrations of ROOH found in rivers
are generally lower than those of H
2
O
2
. It is suggested that ROOH compounds are
chemically unstable and more reactive than H
2
O
2
in natural waters (Mostofa and
Sakugawa
2009
). Therefore, enzymatic or microbial degradation of peroxides is a
rapid process that may control the steady-state concentrations of both H
2
O
2
and
ROOH compounds in natural waters (Fujiwara et al.
1993
; Cooper and Zepp
1990
;
Zepp et al.
1987
; Serban and Nissenbaum
1986
; Tanaka et al.
1985
).
It has been shown that the algal-catalyzed decomposition of H
2
O
2
under dark
conditions is second-order overall, first-order with respect to H
2
O
2
and first-
order with respect to the algal biomass (Petasne and Zika
1997
; Zepp et al.
1987
;
Cooper and Lean
1992
). The median second-order rate constant for nine algae is
approximately 4
×
10
−
3
m
3
(mg Chl
a
)
−
1
h
−
1
. Natural levels of the blue-green
Cyanobacterium
sp.
can greatly increase the decay rates of H
2
O
2
, which follow a
second-order rate constant of 3.5
×
10
−
10
L cell
−
1
h
−
1
(Petasne and Zika
1997
).
Similar kinetics has been observed for
Vibrio alginolyticus
, in which case the
