『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.
Keywords: Attached growth reactor; Nitrification; Hydrogenotrophic
denitrification; Groundwater; NH4-N removal』
1. Introduction
2 Materials and methods
2.1. Reactors set-up and operation
2.1.1. Attached growth reactor for nitrification
2.1.2. Attached growth reactor for hydrogenotrophic denitrification
2.2. Synthetic water preparation
2.2.1. NH4-N water for nitrification reactor
2.2.2. NO3-N water for denitrification
reactor
2.3. Analytical methods
3. Results and discussion
3.1. Performance of laboratory nitrification reactor
3.1.1. For various reactor lengths
3.1.2. For various Fe and IC concentrations
3.2. Start-up of on-site nitrification reactor
3.3. Performance of laboratory H. denitrification reactor
3.3.1. For various H2 flow rates
3.3.2. For various IC concentrations
3.4. Start-up of on-site H. denitrification reactor
4. Conclusions
Acknowledgments
References