Kraft pulp mill effluent treated by activated sludge and aerated lagoon genotoxicity assess

Organic compounds present in the bleached kraft pulp mill (BKPM) effluents may be reduced by biological treatment like: activated sludge (AS) or aerated lagoon (AL). However, after biological treatment, BKPM effluent still contains specific compounds. Some of them have been related with chronic effects (DNA damage, reproductive and physiological) observed on fishes exposed to BKPM effluents. The DNA damages or genotoxicity caused by BKPM effluent has been also studied using bacterial test. Bacillus subtilis mutant deficient in repair functions has been isolated. The comparison between the mutant bacteria and the wild-type serves to assess DNAdamaging agents. The aim of this work is to evaluate genotoxicity of kraft pulp mill effluent using Bacillus subtilis “rec” assay, before and after treatment by activated sludge (AS) and aerated lagoon (AL). Effluent sample from a local BKPM, which process Pinus radiata was used. It was characterized regarding to Chemical Oxygen Demand (COD), Biological Oxygen Demand (BOD5), phenolic compounds (UV215), color (VIS 440), pH, lignins, resin acid contents. AL and AS reactors (0.9 L) were operated for more than 200 days. The organic load rate (OLR) increases from 0.2 to 0.6 g COD/L·d on three steps. Reactor’s performance were verified by measuring COD, BOD5, color (VIS440), total phenolic compounds (UV215) and lignin derived (UV272 and UV280). The genotoxicity was assessed by using Bacillus subtilis PB1791 (rec-) and Bacillus subtilis PB 1652 (rec+), through a quantitative methods of the efficiency of plating (A). The “rec” assay using Bacillus subtilis was verified on influents and effluents. The COD and BOD5 removal were around 65 % and 97 % in the AS and around 60% and 98 % in the AL. Color and total phenolic compounds are only partially removed. AS and AL reactors remove genotoxicity as well as specific chemical compounds removal during biological treatment.