Enhancement of rice bran as carbon and microbial sources on the nitrate removal from groundwater

Abstract

The use of rice bran as carbon and microbial sources has the potential to enhance the groundwater denitrification performance. This research investigated the effects of rice bran dosage, filling modes and biofilm carriers’ types on the nitrate-contaminated groundwater remediation through batch and a series of column studies. NO3− removal rate increased as the rice bran increase in batch studies; however, the highest total nitrogen removal efficiency of 96.2% was achieved at 7 d with 1.50 g rice bran. Microorganism analysis indicated that bio-degradation (Massilia, Sphingomonas, Chryseobacterium and Sorangium) and bio-denitrification (Pseudomonas, Flavobacterium, Delftia and Comamonadace-ae) microorganisms were coexisted in rice bran denitrification system. Moreover, rice bran-gauze segmented (RGS) column had the lowest and most stable average effluent NO3− with low accumulations of NO2− and NH4+. The highest NO3− removal rate of 262.20 g·(m3·d)−1 was obtained when hydraulic retention time (HRT) was12 h. The results indicate that rice bran was an effective carbon and microbial sources for denitrification in NO3−-contaminated groundwater.