Nitrogen concentrations of effluent before and after treatment plant i
n two mills have been measured during five days time in a bleached kra
ft pulp mill and in a newsprint mill. In effluents before treatment th
e concentration of inorganic nitrogen was low but in the effluent of k
raft pulping process, the main part is inorganic nitrogen. In effluent
after treatment the concentration of inorganic nitrogen is low. After
activated sludge treatment plant the concentration of dissolved organ
ic nitrogen is about 0.6 mg/l and nitrogen in suspended solids determi
nes fluctuation of nitrogen content in treated effluent. There is no n
eed for biological nitrogen removal processes if the addition of nitro
gen in the treatment is correct. (C) 1997 IAWQ.