Samples of activated sludge used in this study were obtained
from aerobic tanks of full-scale WWTPs of coke manufacturing
plants in steel companies located in Korea. Relevant parameters
and descriptions of these WWTPs are summarized in Table 1. All
plants—K1, K3, P5—apply a pre-denitrification activated sludge
process composed of anoxic and aerobic tanks, which produce a
single sludge along with the recycling of the nitrified effluent.
The three WWTPs differed mainly in their influent characteristics,
especially their carbon concentrations such as phenol and nitrogen
concentrations in ammonia and thiocyanate (Table 1). Nitrification
activity was directly measured from fresh samples; the remainder
of the fresh samples were immediately stored at 80 C for subsequent
processing.