TY - JOUR

T1 - A zero-valent iron and zeolite filter for nitrate recycling from agricultural drainage water

AU - Florea, Adrian F.

AU - Lu, Changyong

AU - Hansen, Hans Chr B.

N1 - Publisher Copyright: © 2021 The Authors

PY - 2022

Y1 - 2022

N2 - Nitrate reduction to ammonium followed by ammonium capture and reuse, represent a new pathway to recycle nitrogen, prevent eutrophication, and to save energy used for industrial ammonium production. The present study investigates the principle of nitrogen recycling to agricultural drainage water using a coupled zero-valent iron (ZVI) and zeolite-based filter column system tested in laboratory and field continuous-flow experiments. A 40-day laboratory test showed 82% nitrate removal, of which 70% was converted to ammonium. In the following pilot scale field test, a total of 59.2 m3 (1700 pore volumes) drainage water with a nitrate concentration of 2–8 mg L−1 NO3−-N was filtrated. An oxidizing unit inserted after the ZVI unit removed iron(II) and optimized ammonium retention in the zeolite unit. Nitrate removal efficiency was 94% for the entire 56-day period with a slight pH increase (pH 8.9). All ammonium produced was retained by the zeolite unit. Formation of green rust carbonate (layered FeII–FeIII-hydroxide) was observed on ZVI particle surfaces, which may increase the redox capacity of the filter system by up to 50% and contribute to its cost-efficiency. Moreover, all phosphate in the influent waters with concentrations between 0.1 and 0.5 mg L−1 was retained due to sorption by iron oxides in the system. Corrosion products formed cause partial filter clogging and should be removed by regular cleaning and backflushing. In conclusion, the ZVI – zeolite coupled filter system serves as a promising and cost-effective technology for nutrient removal and ammonium retention from agricultural drainage water.

AB - Nitrate reduction to ammonium followed by ammonium capture and reuse, represent a new pathway to recycle nitrogen, prevent eutrophication, and to save energy used for industrial ammonium production. The present study investigates the principle of nitrogen recycling to agricultural drainage water using a coupled zero-valent iron (ZVI) and zeolite-based filter column system tested in laboratory and field continuous-flow experiments. A 40-day laboratory test showed 82% nitrate removal, of which 70% was converted to ammonium. In the following pilot scale field test, a total of 59.2 m3 (1700 pore volumes) drainage water with a nitrate concentration of 2–8 mg L−1 NO3−-N was filtrated. An oxidizing unit inserted after the ZVI unit removed iron(II) and optimized ammonium retention in the zeolite unit. Nitrate removal efficiency was 94% for the entire 56-day period with a slight pH increase (pH 8.9). All ammonium produced was retained by the zeolite unit. Formation of green rust carbonate (layered FeII–FeIII-hydroxide) was observed on ZVI particle surfaces, which may increase the redox capacity of the filter system by up to 50% and contribute to its cost-efficiency. Moreover, all phosphate in the influent waters with concentrations between 0.1 and 0.5 mg L−1 was retained due to sorption by iron oxides in the system. Corrosion products formed cause partial filter clogging and should be removed by regular cleaning and backflushing. In conclusion, the ZVI – zeolite coupled filter system serves as a promising and cost-effective technology for nutrient removal and ammonium retention from agricultural drainage water.

KW - Ammonium

KW - Column study

KW - Green rust

KW - Nitrate reduction

KW - Phosphate

KW - Stoichiometry

U2 - 10.1016/j.chemosphere.2021.131993

DO - 10.1016/j.chemosphere.2021.131993

M3 - Journal article

C2 - 34523440

AN - SCOPUS:85114170944

VL - 287

JO - Chemosphere

JF - Chemosphere

SN - 0045-6535

M1 - 131993

ER -