27aC05
水中気泡内放電によるジクロロメタンの分解と微生物処理方式との併用
Decomposition of Dichloromethane by Combined Process of Biodegradation andDischarge inside Bubble in Water
高橋克幸，晴山渉，高木浩一，颯田尚哉
TAKAHASHI Katsuyuki, HAREYAMA Wataru, TAKAI Koichi, SATTA Naoya

3. Experimental Results
Figure 1 shows DCM removal efficiency andDCM decomposition efficiency as a function ofdischarge treatment time. The initial DCM
concentration is 73.8 mg/L. The DCM removal
efficiency increases without discharges because ofvolatility of bubbling gas. The DCM removal
efficiency and decomposition efficiency withdischarges at treatment time of 25 min are 96% and80%, respectively, which indicates that approximately
83% of removed DCM is decomposed into hydrogenchloride [2] by discharges.
Figure 2 shows the DCM removal efficiency as afunction of biodegradation time after the dischargetreatment. The initial concentration of DCM is 500mg/L. The discharge treatment time is 12.5 min. The
DCM removal efficiency is 84% at the end ofdischarge treatment. Without discharge treatment, the1008080606040402020001020Discharge treatment time [min]0DCM decomposition efficiency [%]2. Experimental setup and procedure
The discharge treatment system used in this study
was described in the previous paper [1]. Ar gas is
injected into the reactor at gas flow rate of 30 mL/min.
The peak value of the output voltage is 16 kV. The
pulse repetition rate is fixed at 100 pulses per second.
DCM is dissolved into 15 mL of purified water atconcentration of 73.8 or 443 mg/L. DCM removal
efficiency and decomposition efficiency are obtainedby the concentrations of total organic carbon andchloride ion in the solution, respectively [2].
Aerobic DCM-degrading microorganisms collectedfrom the groundwater at illegal waste dump site [3],and are employed for biodegradation after thedischarge treatment with mineral salt medium. Afterthe discharge treatment, 0.06 g of activated carbon
made from poultry manure is added to the solution todecrease hydrogen peroxide produced by thedischarge, and the pH is adjusted to 6 by adding NaCl.

DCM removal rate with discharges
DCM removal rate without discharges
DCM decomposition rate with dischargesDCM decomposition rate without discharges

100Fig. 1. DCM removal efficiency and decomposition
efficiency as a function of discharge treatment timewith or without discharges.
With 12.5 min discharge treatment
Without discharge treatment

DCM removal efficiency [%]1. Introduction
Dichloromethane (DCM) is one of hazardous
chlorinated volatile organic compounds and isdifficult to decompose owing to its chemical stability.
In this study, the decomposition of DCM by combined
process of biodegradation and discharge inside bubble
in water is investigated.

DCM removal efficiency [%]岩手大学
Iwate University

10080

The end of thedischarge treatment

6040NaOH addtion pH 3.0 → 6.0

2000100200
Biodegradation time [h]Fig. 2. DCM decomposition efficiency as functionof biodegradation time with or without dischargetreatment.
pH value decreases from 6.5 to 3.0 in approximately
150 h due to the decomposition of DCM. NaOH isadded at 150 h to adjust the pH value because thedecrease of pH prevents bacteria from decomposing
DCM. With discharge treatment, the DCM is removed
completely at 85 hour without pH adjustment duringthe process. This result shows the treatment time issignificantly reduced by the combined process.
References
1) S. Kawano, et al., J. Phys.: Conf. Ser, 441,(2013) 012007
2) Yonezawa, et al., J. Inst. Electrostat. Jpn, 35,(2011) 31-37
3) Q. Yimiti, et al. Resour. Process., 58, (2011)
47–51