Simultaneous nitrate and perchlorate reduction in an elemental sulfur-based denitrifying membrane bioreactor

• Published in: International biodeterioration & biodegradation 2019-10, Vol.144, p.104741, Article 104741
• Main Authors: Ucar, Deniz, Sahinkaya, Erkan, Yilmaz, Tulay, Cakmak, Yakup
• Format: Article
• Language: English
• Subjects: Alkalinity; Bioreactors; Calcium carbonate; Denitrification; Elemental sulfur; Groundwater; Hypothyroidism; Load distribution; Membrane bioreactor; Membrane processes; Membranes; Nitrate reduction; Nitrates; Perchlorate; Perchlorate reduction; Perchloric acid; Polyethersulfones; Pore size; Porosity; Reduction; Sodium bicarbonate; Sulfate; Sulfur; Ultrafiltration
• ISSN: 0964-8305; 1879-0208
• DOI: 10.1016/j.ibiod.2019.104741

Perchlorate is a man-made and naturally occurring anion that causes hypothyroidism and is often present in groundwater together with nitrate. In this study, a novel elemental sulfur-based denitrifying membrane bioreactor was tested for simultaneous nitrate and perchlorate reduction. A bench scale 4 L bioreactor equipped with polyethersulfone (PES) ultrafiltration membranes (0.04 μm of pore size) was used. Influent nitrate was varied between 25 and 100 mg NO3−-N/L. Complete denitrification of 100 mg NO3−-N/L was achieved at HRT as low as 6 h corresponding to 400 mg NO3−-N/(L.d) denitrification rate. Complete reduction of perchlorate was also achieved when the influent concentration was 3000 μg/L and HRT of 12 h. Further increase in perchlorate load resulted in elevated effluent perchlorate concentration and maximum perchlorate reduction rate was 15.1 mg/(L.d). Sulfate was produced as a result of sulfur based denitrification. Influent was supplemented with NaHCO3 (1000 mg CaCO3/L) to meet the alkalinity requirement of the process. Membrane fouling was not significant at 12.5 L/(m2.h) membrane flux. •Simultaneous nitrate and perchlorate reduction was achieved in 4 L membrane bioreactor.•Maximum denitrification rate was 400 mg NO3−-N/(L.d) at HRT 6 h.•Complete reduction of perchlorate was achieved when the influent concentration was 3000 μg/L at HRT 12 h.•Membrane fouling was not significant at 12.5 L/(m2.h) membrane flux.