Abstract
Denitrification is the conversion process of nitrate to gaseous nitrogen forms carried out by bacteria commonly referred to as denitrifiers. Microbial Electrolysis Cell (MEC) is a type of bioelectrochemical system (BES) that is connected to external power source to aid the reactions. This research investigates the effect of applied voltage value on denitrification by nitrate removal efficiency of two model denitrifying species from the genus Pseudomonas in single-chambered MEC. Pseudomonas aeruginosa and Pseudomonas nitroreducens exhibited native removal efficiency at 70.62% and 68.20%, respectively. These values respectively reached up to 89.67% and 88.58% at 1.20 V, the upper limit of this study. Pseudomonas aeruginosa displayed better performance in MEC based off its produced current stability (mA) across the 0.35-1.20 V range. The effect of applied voltage on nitrate removal efficiency and setup performance was more prominent on known exoelectrogenic species of Pseudomonas such as Pseudomonas aeruginosa compared to Pseudomonas nitroreducens. Operating applied voltages of 0.35 V and 0.70 V was recommended for the application of the system based on technical and economical considerations. Further studies are needed to determine the response of the bacteria on wider range of applied voltages in MEC as well as elucidating these effects on autotrophic systems.
Highlights
Global water pollution problems have prompted the need to optimize current water treatment technologies
Pseudomonas aeruginosa was positive for cytochrome dependent nitrite reductase, while Pseudomonas nitroreducens was positive for the copper dependent (CuNIR) nitrite reductase (Table 1)
The findings of this study presented a positive correlation between applied voltage and nitrate removal efficiency in Microbial Electrolysis Cell (MEC) as seen in Table
Summary
Global water pollution problems have prompted the need to optimize current water treatment technologies. Nitrate-nitrogen (NO3-N) concentration is considered as one the main parameters for water pollution. US EPA have set the limit for NO3-N in water at 10 mg/L, yet wastewaters that are released directly to the environment may contain up to 30 mg/L NO3-N, three times above the limit [1]. To address this problem, methodologies such as ion exchange, reverse osmosis, and electrodialysis were developed. Some main advantages of denitrification over physicochemical methods were by having lower energy requirement as well as the generation of safer by-products in lesser quantity
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