Combination of Activated Carbon with Biological Wastewater Treatment at Full-Scale - Activated Carbon for Water and Wastewater Treatment - page 138

refractory organics are oxidized and converted into more readily biodegradable
organics that are amenable to removal in BAC filtration. In this treatment scheme,
preliminary ozonation did not lead to a decrease in the sum parameters COD and
DOC, but reduced 36% of UV 254 . This indicated that large aromatic compounds
were degraded by ozonation, but total mineralization was not achieved. The
succeeding BAC and GAC units removed 29% and 13% of COD, respectively.
These two units decreased COD to about 10mg L 1 in total.

5.2.1.3
Reclamation of Domestic and Industrial Wastewaters for Nonpotable Uses
In a recent study aiming at reuse of treated wastewater, BAC filtration could sig-
nificantly reduce organic carbon and total nitrogen from a secondary effluent. Con-
tinuous-flow laboratory-scale BAC columns were operated for 320 days for the
treatment of the secondary effluent of Pasakoy Advanced Wastewater Treatment
Plant in Istanbul, Turkey. BAC filters removed about 65-81% of DOC with fresh
activated carbon during the initial stage of operation. After breakthrough was
reached, DOC removal efficiencies dropped to about 38-46%. This removal took place
primarily by biodegradation. Nitrification and denitrification were also achieved
within the BAC column, resulting in total nitrogen removal of about 52-54%.
For reclamation purposes, the recommendation was made to place BAC filters ahead
of disinfection units at full-scale domestic wastewater treatment plants [21].
A pilot study was performed in Beishiqiao wastewater purification center of
Xi'an municipality in China to obtain high-quality water from domestic waste-
water in order to meet the water reuse standards for various purposes [22]. In order
to achive this aim, secondary domestic effluent was ozonated and then treated
by BAC. Ozonation removed only 12% of the initial TOC, which was about
10-15 mg L 1 . On the other hand, ozonation oxidized nonbiodegradable sub-
stances and raised the ratio of biodegradable DOC (BDOC) to total DOC from
0.28 to 0.6. This increase then led to an additional 35% removal in succeeding
BAC filtration. While the COD in secondary effluent was at about 20mg L 1 , it was
reduced to about 5mg L 1 after BAC filtration.
The South Caboolture Water Reclamation Plant in Queensland in Australia was
designed to reduce river pollution and to provide water at a rate of 10 000 m 3 d 1 to
industry and community consumers for nonpotable uses. In fact, the plant was
also capable of providing water that met drinking water standards [23]. The
physicochemical/biological treatment scheme incorporated biological denitrifica-
tion, preozonation, coagulation/flocculation, dissolved air flotation/sand filtration,
ozonation, and BAC treatment. Preozonation converted refractory organic

Municipal
wastewater

Potable
use

Maturation
pond

Physicochemical
sedimentation

Sand
filtration

GAC Disinfection

Ozonation BAC

Figure 5.6 New Goreangab reclamation plant in Windhoek, Namibia. (redrawn after [20])