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( Anna Joicy ),( Hwijin Seo ),( Myoung-eun Lee ),( Jae-woo Chung ),( Yongtae Ahn ) 한국폐기물자원순환학회(구 한국폐기물학회) 2021 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2021 No.-
Pretreatment method improves substrate availability and digestibility for biogas production in MEC reactors. Alkaline-thermal pretreatments at varied proportions were experimented in this study, to compare the performances of pretreated WAS in sludge disintegration, methane generation and microbial community structure in microbial electrolysis cells with non-pretreated WAS. The non-pretreated MEC reactor (control) and pretreated MEC reactors (MEC95 and MEC75) were operated at an applied voltage of 0.6 V, respectively. In MEC95 [mixed alkaline treatment (NaOH/Ca(OH)<sub>2</sub> = 8:2)] and MEC75 [alkaline treatment (NaOH)] the WAS was adjusted to pH 11.5 and allowed to react for 18 hours followed by heat treatment at 95 ℃ (MEC95) and 75 ℃ (MEC75) for 90 min. The SCOD concentration was increased upto 12,800 mg/L in the WAS, and the degree of solubilization reached 70%. At MEC95, the methane yield (277 mL CH<sub>4</sub>/g COD<sub>in</sub>) was higher followed by MEC75 with the methane yeild of 178 mL CH<sub>4</sub>/g COD<sub>in</sub> in comparison with the control reactor of 99 mL CH<sub>4</sub>/g COD<sub>in</sub>. In MEC95 the removal efficiency of SCOD and sludge VS were higher of around 82.1% and 74.4%, respectively. Redox compounds carrying the electrons were obtained from the cyclic voltammogram (CV) and microbial community structure in the bulk solution of the pretreated MEC reactors. Experimental results of MEC95 showed bioelectrochemical method could be combined with thermal-alkaline pretreatment to enhance anaerobic digestion of sludge in comparison with control reactor.
Joicy, Anna,Song, Young-Chae,Lee, Chae-Young Elsevier 2019 Journal of environmental management Vol.233 No.-
<P><B>Abstract</B></P> <P>The bioelectrochemical anaerobic nitrogen removal was demonstrated in an anaerobic batch reactor equipped with a pair of polarized bioelectrodes. The bioelectrochemical reactor was operated in sequential batch mode after inoculating activated sludge and polarizing the electrode to 0.6 V. The medium contains ammonium, nitrite, alkalinity and trace minerals, but no organic carbon source. By the repetitive sequential operation, simultaneous removals of ammonium, nitrite and alkalinity were improved, and the electrochemical activity of the bulk sludge was confirmed from the redox peaks of the cyclic voltammogram. This indicates that ammonia oxidizing exoelectrogens (AOE) and denitritating electrotrophs (DNE) were enriched more in the bulk solution. Biogas production that mainly consisted of nitrogen was observed from the bioelectrochemical reactor, and the minor components in the biogas were methane and carbon dioxide. This demonstrates that AOE use nitrite as an electron acceptor to oxidize ammonia. The requirements of nitrite and alkalinity for the removal of ammonia nitrogen are around 0.72 mg NO<SUB>2</SUB>-N/mg NH<SUB>4</SUB>-N and 1.73 mg as CaCO<SUB>3</SUB>/mg NH<SUB>4</SUB>-N, respectively, and nitrate was not produced as a by-product. The bacterial groups involved in the bioelectrochemical nitrogen removal are electroactive autotrophs and can be enriched from activated sludge by polarized electrode. This bioelectrochemical ammonia oxidation is a novel approach recommended for treatment of nitrogen-rich wastewater.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Electroactive autotrophs are enriched from activated sludge by polarized electrode. </LI> <LI> The autotrophs remove NH<SUB>4</SUB>-N and NO<SUB>2</SUB>-N bioelectrochemically in anaerobic condition. </LI> <LI> Nitrite required for the ammonium removal is 0.72 mg NO<SUB>2</SUB>-N/mg NH<SUB>4</SUB>-N. </LI> <LI> Alkalinity required for the ammonium removal is 1.73 mg as CaCO<SUB>3</SUB>/mg NH<SUB>4</SUB>-N. </LI> <LI> Bioelectrochemical N removal process does not produce nitrate as a by-product. </LI> </UL> </P>
Song, Young-Chae,Joicy, Anna,Jang, Seong-Ho Elsevier 2019 International journal of hydrogen energy Vol.44 No.4
<P><B>Abstract</B></P> <P>A bioelectrochemical anaerobic ammonium oxidation via direct interspecies electron transfer in bulk solution was first found in an anaerobic reactor equipped with a pair of bioelectrode polarized at 0.6 V. The removal of ammonium along with a decrease in nitrite and alkalinity was observed when ammonium and nitrite are available as electron donor and acceptor, respectively, in a bioelectrochemical reactor. The requirements of nitrite nitrogen and alkalinity for the removal of ammonium nitrogen are around 0.58 mg NO<SUB>2</SUB> N/mg NH<SUB>4</SUB> N and 2.0 mg as CaCO<SUB>3</SUB>/mg NH<SUB>4</SUB> N, respectively. The bioelectrochemical ammonium oxidation does not produce nitrate as a by-product as well. The microbial groups involved in bioelectrochemical ammonium oxidation are electroactive autotrophs and can be enriched from anaerobic digestion sludge from sewage treatment plant by the polarized electrode. This bioelectrochemical ammonium oxidation is a novel approach recommended for treatment of nitrogen-rich wastewater.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ammonium and nitrite are bioelectrochemically removed by DIET in bulk solution. </LI> <LI> The requirement of nitrite for the removal of ammonium is 0.58 mg NO<SUB>2</SUB> N/mg NH<SUB>4</SUB> N. </LI> <LI> The requirement of alkalinity for the removal of ammonium is 2.0 mg as CaCO<SUB>3</SUB>/mg NH<SUB>4</SUB> N. </LI> <LI> Bioelectrochemical nitrogen removal (BENR) does not produce nitrate as a by-product. </LI> <LI> The bacterial groups in BENR are electroactive autotrophs enriched by polarized electrode. </LI> </UL> </P>
하수슬러지 전처리를 통한 미생물전기분해전지의 메탄 생산 특성
서휘진 ( Hwijin Seo ),( Anna Joicy ),이명은 ( Myoung-eun Lee ),장해남 ( Haenam Jang ),안용태 ( Yongtae Ahn ) 한국폐기물자원순환학회(구 한국폐기물학회) 2021 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2021 No.-
혐기성 소화(anaerobic digestion; AD)는 유기물과 독성 화합물, 병원균, 슬러지 부피를 효과적으로 줄일 수 있으며, 바이오가스의 형태로 에너지를 회수할 수 있으나 유기산 축적으로 인한 pH 불균형, 안정화 및 소화 시간이 오래 소요되어 기질 종류에 따른 큰 소화 효율 변동 등의 문제들이 보고되고 되었다. 이러한 단점들을 해결하기 위해 생물전기화학 중 하나인 미생물전기분해전지(microbial electrolysis cell; MEC)가 개발되어 외부 전원 공급을 통해 유기물을 산화하고 환원전극 표면에서 빠르게 메탄을 생산할 수 있도록 하고 있다. 빠른 메탄생성을 위해서는 AD와 MEC의 공통적 율속단계인 가수분해를 단축하기 위한 공정이 필요하며, 이를 위해 슬러지 전처리가 연구되고 있다. 그러나 활성 슬러지(waste activated sludge; WAS)의 다양한 전처리를 통한 소화효율 향상 등에 관한 논문들이 많이 발표되었지만 1차 하수슬러지 전처리 관련 연구들은 아직 상태이다. 본 연구에서는 0.6V가 인가된 1.7L MEC를 이용하여 하수슬러지(MEC), 초음파 전처리(MEC US), 알칼리 및 초음파 전처리(MEC ALK-US) 조건에서 실험을 수행하였으며, 바이오가스 발생량과 유기물 제거 등에 대한 분석을 진행하였다. COD 제거 효율에 있어 MEC US가 65.9%로 가장 높은 처리효율을 나타냈으며, MEC ALK-US는 60.2%로 MEC에 비해 1.8% 증가하였다. 메탄 생산량에 있어 서는 MEC US의 경우 4,754mL로 MEC(4,376mL)에 비해 1.8%, MEC ALK-US는 5,660mL로 29.3% 증가하였다. 따라서 유기물 제거에 있어 서는 단일 전처리인 초음파 전처리가 유리하나 메탄 생산량에 관해서 알칼리 초음파 전처리가 타당한 것으로 판단된다.