Communities surrounding an integrated Kraft mill noticed odours from the mill’s effluent treatment plant. A project was therefore commissioned by the mill to proactively manage the odours from both the pulp-processing operations and the effluent treatment plant. This project formed part of a co-ordinated study that was implemented by the mill to limit emissions of the total reduced sulphur (TRS) components from the pulp mill operations. It was found that sulphate-reducing bacteria(SRB) converted the sulphates present in the effluent to hydrogen sulphide (H2S) by dissimilatory respiration. The combined use of a nitrate-releasing biomodifier (Bulab® 9518) and an anthraquinone sulphate-reduction inhibitor (Busperse® 2432) was effective in reducing both SRB activity and H2S levels. The average aqueous H2S levels (40 mg/ℓ) were reduced to between 92% and 99%
