NH4-N Removal Through Nitrification and Hydrogenotrophic Denitrification in Simple Attached Growth Reactors

Abstract

To provide good quality of drinking water, a biological system to remove ammonium-nitrogen (NH4-N) from groundwater was studied in this research. The NH4-N removal system consists of two attached growth reactors: one for nitrification and the other for hydrogenotrophic denitrification (H. denitrification). The nitrification reactor, fed by the NH4-N contained water, could remove NH4-N without any need of aeration. The nitrification efficiency was increased by reactor length; the highest efficiency of 92 % was achieved at the longest reactor of 100 cm. A high Fe in groundwater affected the reactor performance by decreasing the efficiency, while a low inorganic carbon (IC) had no effects. Despite of good efficiency in terms of NH4-N removal, the nitrification reactor increased the concentration of NO3-N in its effluent. To treat the NO3-N, a H. denitrification reactor was set up after the nitrification reactor. Efficiency of the H. denitrification reactor was enhanced by increasing H2 flow rates. The efficiencies were 3, 27, and 90 % for 30, 50, and 70 mL/min of H2 flow rates, respectively. It was also found that the NO3-N contained water (water from the nitrification reactor) had to supply IC (i.e., NaHCO3 or CO2) for efficient H. denitrification; however, an on-site reactor showed that it can be achieved even without IC addition. The treated water contained low NH4-N and NO3-N of <1.5 and <11.3 mg/L, respectively, which comply with drinking water standards. The good performance of the reactors in terms of high efficiency, no aeration need, and low H2 supply indicated appropriateness of the system for groundwater treatment.