Autotrophic denitrification with sulphide in a sequencing batch reactor

In this study a sequencing batch reactor was used to simultaneously remove both sulphide and nitrate via an autotrophic denitrification process. The sulphide loading rates were gradually increased from 200 mg S2− L−1 d−1–450 mg S2− L−1d−1while the nitrogen loading rates were kept at 450 mg NO3−–N L−1d−1. The obtained results demonstrated that it was possible to carry out autotrophic denitrification in a Sequencing Batch Reactor with removal efficiencies of sulphide and nitrogen of 100% and 67%, respectively. The efficiency of the process was influenced by the pH value in the reactor. The operation at pH values higher than 9.0 decreased the efficiency of sulphide oxidation into sulphate to 11.3%. The main bacteria populations present in the sludge belonged to Thiobacillus genus.

► The simultaneous removal of sulphide and nitrate by autotrophic denitrification was implemented.
► Removal was efficient on sulphide and nitrogen rendering an effluent safe to the environment.
► Thiobacillus sp. was identified as the responsible microorganism for the sulphide oxidation.
► The SBR used was suitable for carrying out the autotrophic denitrification.
► The study provides insight on the applicability of the SBR for complex wastewaters treatment.