Corncob PRB for on-site nitrate removal in groundwater
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ORIGINAL PAPER
Corncob PRB for on-site nitrate removal in groundwater Yong Liu 1 & Yajing Liu 2,3 & Lei Ma 2 & Ying Gong 2 & Jiazhong Qian 2,3 Received: 27 May 2020 / Accepted: 6 October 2020 # Saudi Society for Geosciences 2020
Abstract In order to obtain a new technology of on-site nitrate removal, a permeable reactive barrier (PRB) column was prepared by coupling the denitrifying bacteria with the use of agricultural waste. Nitrate removal in groundwater at low temperature (16 °C) and different hydraulic conditions was investigated in laboratory. Corncob was considered to be the most effective carbon source after the optimization experiments of nitrate removal. The PRB column was prepared by a 15-cm-high of corncob sandwiched between two layers of activated zeolite, where corncob was pre-mixed with denitrifying bacteria. The denitrification was studied at 16 °C and hydraulic retention time (HRT) ranged from 2.5 to 20.0 h, as well as the initial nitrate-N concentration in the range of 20–80 mg/L in groundwater. The values of NO3−-N, NO2−-N, NH4+-N, and chemical oxygen demand (COD) and the optical density at a wavelength of 600 nm (OD600) were measured as detection indexes. The results showed that the content of NO3−-N and COD continued to decrease, but the NO2−-N and NH4+-N increased first and then decreased quickly in the effluent. The removal efficiency of NO3−-N obtained 99.8%, 97.8%, 94.3%, and 85.9% at different initial nitrate-N of 20, 40, 60, and 80 mg/L and HTR of 24 h, respectively. The removal efficiency of NO3−-N and COD was 83.2% and 95.7% at HRT of 20 h and initial nitrate-N of 70 mg/L. Therefore, the corncob PRB column combined comprehensively utilization of agricultural residues with remediation of nitrate, which was effective for nitrate removal in groundwater at site temperature and HRT. Keywords Nitrate remediation . Carbon source . Denitrification . Permeable reactive barrier (PRB) . On-site
Introduction Groundwater is one of the most important water resources in the world (Luo et al. 2018), which is often used for drinking water and agricultural irrigation and other aspects (Solangi et al. 2019). However, the water quality is commonly threatened by various pollutants, and nitrate has become one of the most worrying and widely polluted pollutants in groundwater. Responsible Editor: Broder J. Merkel * Yong Liu [email protected] * Jiazhong Qian [email protected] 1
School of Food and Biological Engineering, Hefei University of Technology, Hefei 230009, China
2
School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China
3
Key Laboratory of Nanominerals and Pollution Control of Anhui Higher Education Institutes, Hefei University of Technology, Hefei 230009, People’s Republic of China
Nowadays, nitrate pollution has become a serious environmental issue (Houria et al. 2020) in many countries due to the excessive use of fertilizers (Mollamohammada et al. 2020), animal manure, industrial sewage discharge (Hou et al. 2019), and high-pressure at
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