Feasibility Test of Autotrophic Denitrification of Industrial Wastewater in Sequencing Batch and Static Granular Bed Reactors

In order to evaluate the efficacy of using reduced sulfur species in lieu of conventional substrates, a sequencing batch reactor (SBR) was used to develop an autotrophic denitrifying culture which in turn was used to seed a static granular bed reactor (SGBR) for continuous flow treatment. Both bioreactors were able to quickly acclimate to the anoxic environment and achieve stable autotrophic denitrification within several weeks of being placed in operation. The seed for the SBR was obtained from operating basins at the Cedar Rapids plant. MiSeq analysis showed the presence of the autotrophic denitrifier Thiobacillus in the seed from the sulfur oxidation basin; however, Shinella and Sulfurovum became the dominant autotrophic denitrifiers in the SBR. Both the SBR and SGBR achieved excellent nitrate removal (i.e., >95%) with stoichiometric amounts of thiosulfate added to the synthetic influent. The results of this feasibility study suggest that anaerobic granules from the UASB at the plant serve as good seed biomass for autotrophic denitrification when augmented by sulfur oxidation basin and sulfide scrubber biomass, and that reduced sulfur species at the plant (or augmented with an external sulfur source) can serve as electron donors for nearly complete denitrification. PRACTITIONER POINTS: Autotrophic denitrification of industrial wastewater was investigated to evaluate reduced sulfur species as electron donor for nitrogen removal. An autotrophic denitrifying culture was cultivated in an SBR, and continuous autotrophic denitrification was accomplished in an SGBR. No increase in head loss was observed in the SGBR, and it was able to operate without the need for backwashing in more than 200 days of operation. Reduced sulfur was demonstrated to be a sufficient electron donor for nearly complete denitrification. MiSeq analysis resolved primary species responsible for autotrophic denitrification in this study.