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 96

Table 4.3 PAC addition to activated sludge for the treatment of a
refinery wastewater (adapted from [12]).

Influent (mg L -1 ) Effluent (mg L -1 ) Parameter

COD 300 140

BOD 5 90 1.6

Phenolics 1.6 0.02

Oil and Grease 54 5

o

In a refinery in the United States, addition of PAC to an activated sludge system
was tested at laboratory-scale with the purpose of reusing the wastewater in the
cooling tower [12]. The low BOD 5 /COD ratio in the wastewater was a factor
favoring the use of activated carbon. The PACT system met the requirements of
reuse in the cooling tower (Table 4.3).
Another study examined the BAC treatment of a wastewater contaminated with
petroleum products [13]. Special emphasis was put on polycyclic aromatic
hydrocarbons (PAHs). The study showed that bacteria-covered coconut shell-based
activated carbon removed 99.5-99.6% of total petroleum hydrocarbons and PAHs.
The BAC reactors performed much better than activated sludge. Because of the
higher adsorption capacity of activated carbon, the BAC process was also superior
compared to other attached-growth processes involving sorbents such as zeolite
and anthracite.
Petrochemical industrial wastewater containing acrylonitrile butadiene styrene
(ABS) was treated by a moving bed BAC reactor following ozone treatment [14].
Depending on the organic loading rate, COD removal efficiencies ranged between
70% and 95%. The service life of the BAC bed was four to five times longer than
the GAC bed.
In the treatment of an oilfield wastewater in a two-stage Granular Activated
Carbon-Fluidized-Bed Reactor (GAC-FBR) system (aerobic and anaerobic), removal
efficiencies were 99% for BTEX (Benzene, Toluene, Ethylbenzene, Xylene), 74%
for COD, 94% for total volatile hydrocarbons (TVH) and 94% for oil at initial COD,
BTEX, TVH, and oil concentrations of 588, 17.7, 64, and 72mg L 1 , respectively
[15]. Another two-stage GAC-FBR system, anoxic and aerobic in series, also exhib-
ited >98% removal for BTEX, >99% removal for COD, and 81% removal for oil and
grease in the case of a gas well-produced wastewater at initial BTEX, oil, and TOC of
15.9, 53, and 211mg L 1 , respectively [15]. In the treatment of an oily wastewater
emerging from the reprocessing of used emulsions or suspensions, PAC addition
to an activated sludge reactor increased the TOC removal from 70% to 96% [16].

4.1.4
Textile Wastewaters

Textile wastewaters are generally strongly colored with a high organic content.
They are difficult to treat by conventional biological treatment processes because