TREATMENT OF INTEGRATED NEWSPRINT MILL WASTE-WATER IN MOVING-BED BIOFILM REACTORS

Wastewaters from three integrated newsprint mills have been treated in a pilot plant Moving Bed Biofilm Reactor (MBBR). In the MBBR the biom ass adheres to small plastic elements which move freely along with the water in the reactor. A reduction of 65-75% for COD and 85-95% for BO D was obtained at HRT of 4-5 hours. By prolonging the HRT the removal efficiencies of COD and BOD increased to about 80% and 96%, respective ly. With a subsequent chemical precipitation a removal efficiency of C OD up to 95% was achieved. The amount of chemicals needed for precipit ation of the biologically treated wastewater was only a quarter to a t hird of that needed for chemical treatment of the untreated wastewater . The results showed the MBBR process to be competitive with conventio nal biological treatment systems and that treatment objectives can be met at short HRTs. (C) 1997 IAWQ.