Evaluation of aerobic and anaerobic treatment of Kraft pulp mill effluent for organochlorines removal

The purposes of the experiments described in this paper were to evaluate the performance of an upflow anaerobic sludge blanket (UASB) activated sludge reactor, both bench scale reactors, in the treatment of wastewaters containing organochlorines compounds, which simulate a kraft plant wastewater. Both reactors received a wastewater prepared with diluted black liquor and a mixture of organochlorines: 2 Chlorophenol (2 CP); 2,4 Dichlorophenol (2,4 DCP); 2,6 Dichlorophenol (2,6 DCP); 2,4,6 Trichlorophenol (2,4,6 TCP); and Tetrachlorocatechol (TeCC). The activated sludge reactor also received 4, 5, 6 Trichloroguaiacol (4, 5, 6 TCG). The chemical oxygen demand (COD) and organochlorine concentrations in the effluent indicated that the two systems displayed a similar performance in terms of COD removal, with average efficiencies of 79% for the UASB reactor and of 77% for the activated sludge reactor. The average individual values for organochlorine removal efficiency, the first figure representing the UASB reactor removal, were: 99.9% and 91% for the 2 CP; 97% and 80% for the 2,4 DCP; 94% and 80% for the 2,6 DCP; 99% and 75% for the 2,4,6 TCP; and 93% and 90% for the TeCC. Both systems showed to be capable of treating pulp plant wastewaters containing chlorophenols, with a certain advantage for the anaerobic system from the standpoint of removal efficiencies.