Sulfur-based autotrophic denitrification of drinking water using a membrane bioreactor

• Autotrophic denitrifying MBR can be used for drinking water treatment.
• Organic supplementation and effluent contamination can be eliminated.
• Autotrophic MBR allows use of powder sulfur particles.
• High denitrification rates and fluxes are possible.
• Process should be further tested for full scale applications.

Sulfur-oxidizing autotrophic denitrification process has drawn significant attention due to its high efficiency, elimination of carbon requirement and the effluent contamination by organic compounds. In the process, nitrate and sulfur are used as electron acceptor, and electron donor, respectively. In the present study, a novel sulfur based autotrophic denitrification process utilizing membrane bioreactor (MBR) was tested for nitrate removal from drinking water. A bench-scale MBR equipped with hydrophilic flat sheet polyethersulfone (PES) membranes (0.45 μm) was used. Sulfur was externally added to the MBR considering the theoretical requirement. Almost complete denitrification efficiency was achieved when the influent nitrate concentrations were 25–50 mg NO3−-N/L at HRT as low as 5 h corresponding to nitrate loading rates up to 0.24 g NO3−-N/(L d). The generated sulfate concentrations were close to the theoretical values. Membrane fouling was not significant at fluxes ⩽20 L/(m2 h).