Effect of Activated Carbon on Biological Treatment of Specific Pollutants and Wastewaters: Laboratory- and Pilot-Scale Studies - Activated Carbon for Water and Wastewater Treatment - page 107

Table 4.6 Comparison of PACT and activated sludge in removal of priority pollutants
(adapted from [5]).

gL -1 ) Pollutant Influent ( l Removal in AS (%) Removal in PACT (%)

Benzene 81 98.5 99.6

Chlorobenzene 3660 99.1 99.8

Methylene Chloride 138 98.5 W 99.7

1,2-DCE 18 90.6 W 99

2,4-Dinitrotoluene 1000 31 90

2,6-Dinitrotoluene 1100 14 95

Nitrobenzene 330 94.5 99.9

2,4-Dichlorophenol 19 0 93

2,4-Dinitrophenol 140 39 W 99

4-Nitrophenol 1100 25 97

advantage of PACT was most pronounced for compounds such as dinitrotoluene,
dinitrophenol, nitrophenol, and dichlorophenol. Another PACT system also
showed enhanced elimination of such compounds. The effluent concentrations of
1,2-dichlorobenzene, nitrobenzene, and 2,4-dinitrotoluene were 0.4, 1.7, and
70mg L 1 , respectively. On the other hand, the concentrations of the same com-
pounds in the effluent of an activated sludge were 1.7, 18, and 950mg L 1 ,
respectively [45].
PACT was also effective in the removal of lindane at influent concentrations up
to 100 m gL 1 with efficiencies above 96% at a PAC dosage of 30mg L 1 [67].
Lindane is a compound having a high octanol-water partition coefficient. Other
priority pollutants with physicochemical properties similar to lindane are expected
to exhibit comparable behavior in a PACT system.
The anaerobic GAC-FBR configuration was shown to be effective in the removal
of hazardous chemicals, namely phenol (500-1000mg L 1 ), pentachlorophenol
(PCP) (100-400mg L 1 ), tetrachloroethylene (PCE) (2.7-16mg L 1 ), and chlor-
oacetaldehyde (CAA) (90mg L 1 ). Stable and high removal was achieved for these
compounds. Even under startup and shock load conditions, the first three com-
pounds and CAA were removed to the extent of 99.9% and 98%, respectively [68].

4.2.6
Dyes

Specific textile azo dyes such as Orange II and Reactive Black 5 were reduced
anaerobically in upflow fixed-bed BAC reactors [69]. Physical properties of acti-
vated carbon had a significant impact on the decolorization rate of azo dyes
whereas chemical surface characteristics had a moderate effect. The researchers
suggested that specific sites of activated carbon play a role in the catalytic reduction
of azo dyes in the absence of surface oxygen groups [69]. The importance of
surface oxgen groups in integrated treatment is discussed in Chapter 7. In another