Perchlorate reduction in a thiosulfate-based denitrifying membrane bioreactor

Abstract

Reductive removals of perchlorate and nitrate, which can be present simultaneously in groundwater, were investigated in a novel thiosulfate-based denitrifying lab-scale membrane bioreactor (MBR) equipped with a polyethersulfone membrane module. Complete denitrification at a hydraulic retention time (HRT) as low as 3 h and a rate of 800 mg NO3--N/(L.d) was accomplished. Simultaneous with nitrate, complete perchlorate reduction was also detected at the feed concentration of 3000 µg/L and at 12 h HRT. Although further rise in perchlorate loading caused its incomplete reduction, the reduction rate reached up to 38 mg/(L.d). Hence, the developed process is promising for simultaneous perchlorate and nitrate reduction from contaminated groundwater. Sustainable filtration performance was observed up to a flux of 12.5 L/(m2.h) (LMH) at which the fouling rate was 85.32 ± 19.65 mbar/d. However, when the flux was raised further to 25 L/(m2.h), the TMP drastically increased to a rate of 393 ± 40 mbar/d.