윤영만-완-0623-x.hwp

Korean Journal of Environmental Agriculture Korean J Environ Agric. 16;35(2):128-136. Korean Online ISSN: 2233-4173 Published online 16 May 25. http://dx.doi.org/1.5338/kjea.16.35.2.13 Print ISSN: 1225-3537 Research Article Open Access 병열 1차반응속도식을이용한유기성슬러지수열탄화반응온도별메탄생산퍼텐셜평가 오승용, 윤영만 * 한경대학교바이오가스연구센터 Assessment of Methane Potential in Hydro-thermal Carbonization reaction of Organic Sludge Using Parallel First Order Kinetics Seung-Yong Oh and Young-Man Yoon * (Biogas Research Center, Hankyong National University, Anseong 17579, Korea) Received: 2 May 16 / Revised: 12 May 16 / Accepted: 18 May 16 Copyright c 16 The Korean Society of Environmental Agriculture This is an Open-Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. ORCID Seung-Yong Oh http://orcid.org/-1-9116-8279 Young-Man Yoon http://orcid.org/-1-9294-8277 Abstract BACKGROUND: Hydrothermal carbonization reaction is the thermo-chemical energy conversion technology for producing the solid fuel of high carbon density from organic wastes. The hydrothermal carbonization reaction is accompanied by the thermal hydrolysis reaction which converse particulate organic matters to soluble forms (hydro-thermal hydrolysate). Recently, hydrothermal carbonization is adopted as a pre-treatment technology to improve anaerobic digestion efficiency. This research was carried out to assess the effects of hydro-thermal reaction temperature on the methane potential and anaerobic biodegradability in the thermal hydrolysate of organic sludge generating from the wastewater treatment plant of poultry slaughterhouse. METHODS AND RESULTS: Wastewater treatment sludge cake of poultry slaughterhouse was treated in the different hydro-thermal reaction temperature of 17, 1, 19,, and 2. Theoretical and experimental methane potential for each hydro-thermal hydrolysate were *Corresponding author: Young-Man Yoon Phone: +82-31-67-5665; Fax: +82-31-67-5666; E-mail: yyman@hknu.ac.kr measured. Then, the organic substance fractions of hydro-thermal hydrolysate were characterized by the optimization of the parallel first order kinetics model. The increase of hydro-thermal reaction temperature from 17 to 2 caused the enhancement of hydrolysis efficiency. And the methane potential showed the maximum value of.381 Nm 3 kg -1 -VS added in the hydro-thermal reaction temperature of 19. Biodegradable volatile solid(vs B ) content have accounted for 66.41% in 17, 72.7% in 1, 79.78% in 19, 67.5% in, and 7.31% in 2, respectively. The persistent VS content increased with hydro-thermal reaction temperature, which occupied.18% for 17, 2.96% for 1, 6.32% for 19, 17.52% for, and.55% for 2. CONCLUSION: Biodegradable volatile solid showed the highest amount in the hydro-thermal reaction temperature of 19, and then, the optimum hydro-thermal reaction temperature for organic sludge was assessed as 19 in the aspect of the methane production. The rise of hydro-thermal reaction temperature caused increase of persistent organic matter content. Key words: Anaerobic Digestion, Hydro-thermal Carbonization, Organic Sludge, Organic Substance Fraction, Parallel First Order Kinetics 128

Methane Potential of Organic Sludge Hydrolysate 129 서론 바이오가스의생산은산소가없는극도의환원상태에서혐기미생물의연속적인미생물화학반응에의해일어난다. 유기물의혐기소화는단계적으로가수분해 (Hydrolysis), 산생성 (Acidogenesis), 초산생성 (Acetogenesis), 메탄생성 (Methanogenesis) 반응으로구분할수있으며, 메탄 (CH 4) 과이산화탄소 (CO 2) 가주요한최종산물이다 (Gerardi, 3). 따라서혐기소화에서유기물의분해특성은최종적으로생성되는메탄 (CH 4) 또는이산화탄소 (CO 2) 의발생속도및발생량의분석을통해파악할수있다 (Owen et al., 1979). 혐기소화에서유기물의분해는크게유기기질의종류, 입자의크기, 혐기미생물의활성, 저해물질의농도등에영향을받으며, 이중유기기질의종류와입자의크기는유기물자체의특성에서기인하는유기물분해의영향인자이다 (Chynoweth et al., 1993; Angelidaki et al., 9). 일반적으로유기기질에서의유기물함량과특성은총고형물 (Total solid, TS), 휘발성고형물 (Volatile solid, VS), 화학적산소요구량 (Chemical oxygen demand, COD), 용해성화학적산소요구량 (Soluble chemical oxygen demand, SCOD) 등으로나타낸다. 그러나이러한유기물항목들은바이오가스로전환되는잠재적인유기물의양을정량적으로표현하는방법으로써유기기질의정성적인특성을설명하지는못한다. 일반적으로가축분뇨, 음식물쓰레기, 작물잔사등의유기물에는지방, 단백질외에셀룰로오스 (Cellulose), 헤미셀룰로오스 (Hemicellulose), 리그닌 (Lignin) 등의다양한탄수화물이존재한다. 이중리그닌성분은혐기소화과정에서분해가되지않는것으로보고 (Buffiere et al., 6) 되고있어리그닌을다량으로포함하는기질의경우낮은유기물분해율을나타낸다. 또한유기물의입자크기는유기물로부터생산되는최종메탄생산량에영향을주기보다는바이오가스의생산속도에영향을주는중요한인자이나 (Vavilin and Angelidaki, 5), 입자의크기가최종발생하는바이오가스생산량에영향을미친다는연구결과도보고되고있다 (Pabón Pereira et al., 12). 혐기소화에서유기기질의종류에따른미생물반응특성연구는혐기소화의효율이일차적으로유기기질의유기물조성에의존한다는점에서중요하다. 일반적으로이분해성 (Biodegradable) 유기물함량이많은경우혐기소화의효율은증가되고, 난분해성 (Non-biodegradable) 유기물과분해저항성 (Persistent) 유기물의함량이많은경우혐기소화효율은감소한다 (Buendía et al., 9). 따라서많은연구자들이유기기질의혐기적분해특성을분석하기위하여반응속도 (Kinetics) 연구를진행하였으며, 유기기질의분해특성분석하고자다양한수학적분석모델을제시하고있다 (Owen et al., 1979; Lay et al., 1998; Rao et al., ). 그러나이러한수학적인분석모델은메탄생산퍼텐셜 (Biochemical methane potential, BMP) 시험에서얻은누적메탄생산곡선을해석하고, 전체반응의특성을이해하는데에적용되었다. 수열탄화 (Hydro-thermal carbonization) 기술은가축분뇨, 음식물쓰레기, 폐수슬러지등다양한바이오매스의에너지화를위한열화학적변환기술이다. 수열탄화반응에서바이오매스는고밀도탄화물로전환되어고체연료로이용하고, 이과정에서발생하는열화학적가수분해액 (Hydro-thermal hydrolysate) 은혐기소화를거쳐바이오가스로전환이가능하다. 수열탄화기술은다양한바이오매스의효율적인가용화가가능한기술로현재하수슬러지혐기소화분야에서는상용화가진행된기술이다. 그러나수열탄화에의한혐기소화증진사례보고와반대로 Bougrier 등 (8) 과 Ajandous 등 (8) 은다양한고상슬러지의열화학적반응연구에서반응온도에따라수열탄화액중에혐기소화에분해저항성을가지거나혐기소화를저해하는물질이생성된다는보고도있다. 이러한상반되는연구결과에도불구하고수열탄화기술은입자상유기물의고체연료화와가용화를동시에달성하는기술로바이오매스의에너지전환효율을극대화할수있다. 특히수열탄화액의혐기소화측면에서는바이오매스의가용화 (Solubilization) 를통해혐기소화조의유효용적을감소시키고메탄의생산효율을증가시켜혐기소화의경제성을크게향상시킬수있다는장점이있어꾸준한연구가진행되고있다. 그러나지금까지의수열탄화연구는 SCOD의증가효과에따른유기물가용화를중심으로연구되어왔으며, 유기기질의종류와특성에따른혐기소화미생물반응특성연구는미미한상황이다. 따라서본연구에서는유기성슬러지의수열탄화에서반응온도가수열탄화액의혐기소화효율에미치는영향을분석하기위하여유기기질의구성을난분해성 (Non-biodegradable), 분해저항성 (Persistent), 이분해성 (Biodegradable) 의유기물로정의하고, 평행 1차반응속도식 (Parallel first order kinetics) 을이용하여수열탄화반응온도별유기물의분포특성을분석하였다. 재료및방법 시험재료본연구에서사용된시험재료는충청남도진천에위치하는도계가공장의폐수처리시설에서발생하는유기성슬러지를사용하였다. 채취한슬러지의수열탄화반응은외부전기히터 (Heater) 에의해열원을공급하는 2 L용량의밀폐형회분식압력반응기에 1 kg의시료원물을정량투입후 17 2 (17, 1, 19,, 2 ) 온도구간에서실시하였다. 반응기의온도는반응기내부에설치한온도계측기로제어하였으며, 운전시간은승온시간 분, 반응시간 1시간으로하였다. 또한열가수분해반응기는반응기내부온도의균질화를위하여내부에교반기를설치하였으며, 반응기의내부압력은반응온도별로발생하는내부포화수증기압조건으로유지하였다. 열가수분해반응을마친잉여슬러지수열탄화액은정성여과지 (Qualitative filter paper No. 1, Advantec MFS, Inc., Dublin, Califonia, USA) 로여과하여메탄생산퍼텐셜 (Biochemical methane potential, BMP) 시험에공

13 Oh et al. Table 1. Chemical characteristics of input sludge and hydrolysates by the hydrothermal carbonization reaction Parameters Temp a) ( ) ph TS b) VS c) COD d) T-N e) NH 4 + -N f) VFAs g) Alkalinity (mg L -1 as CaCO 3) - -- (%, w/w)-- ---- (mg L -1 ) ---- Sludge cake 7.2.4 18.2 26.8 13,684 2,556 - - 17 6.1 6.1 5.9 8.5 9,748 3,196 188 9,538 Hydro-thermal hydrolysates 1 6. 6.6 6.3 9.3 1,47 2,928 196 9,125 19 6. 6.2 6. 1. 9,787 3,271 4 8,638 6.1 6.9 6.7 9.7 1,881 3,465 191 9,563 2 6.5 7.2 6.9 11.3 11,58 5,268 252 12, a) Hydro-thermal reaction temperature, b) Total solid, c) Volatile solid, d) Chemical oxygen demand, e) Total nitrogen, f) Ammonium nitrogen, g) Volatile fatty acids. Table 2. Chemical composition of inoculum Parameters ph TS a) VS b) COD c) T-N d) NH 4 + -N e) VFAs f) Alkalinity (mg L -1 as CaCO 3) - -- (%, w/w) -- ---- (mg L -1 ) ---- Inoculum 8.8 1.7 1. 4. 4,489 3,435 ND g) 19,175 a) Total solid, b) Volatile solid, c) Chemical oxygen demand, d) Total nitrogen, e) Ammonium nitrogen, f) Volatile fatty acids, g) Not detected. 시하였다. 실험에사용한유기성슬러지와반응온도별수열탄화액의화학적성상은 Table 1과같다. 이론적메탄생산퍼텐셜 (Theoretical methane potential, B th ) 분석이론적메탄생산퍼텐셜은공시시료의원소분석결과를바탕으로 Boyle(1976) 의유기물분해반응식 (Eq. 1) 을이용하여화학양론적으로산출하였다. 완성된유기물분해반응식을바탕으로화학양론식인 Eq. 2을이용하여이론적메탄발생량을산정하였다. (Eq. 1) 는처리구당 3반복으로 serum bottle을이용하였다. 반응기의용적 (Total volume) 은 ml, 유효용적 (Working volume) 은 ml, 상층부여유공간 (Head space) 은 ml로하였다. 여기서투입기질 (Substrate, S) 은기질의 VS 함량과접종액의 VS 함량의비율 (S/I ratio) 이.5가되도록조절하였으며, 상층부여유공간은 N 2 가스를충진하여공기가없는상태에서완전밀폐시켜중온 (38 ) 에서일일 1회손으로반응기를흔들어교반하면서 9일간배양하였다. 또한접종액에서발생하는메탄가스를보정하기위하여접종액만을투입한 3반복의혐기반응기를시료와동일한조건에서바탕시험으로운영하였다. 시험에사용한접종액의성상은 Table 2와같다. (Eq. 2) 최종메탄생산퍼텐셜 (Biochemical methane potential, B u) 시험메탄생산퍼텐셜시험에사용한접종액 (Inoculum, I) 은경기도일죽에위치하는 5 m 3 day -1 규모한경대학교바이오가스상용화연구시설에서혐기소화액을채취하여사용하였다. 채취한혐기소화액은 2 mm 체를통과시킨후, 38 항온배양기에서배양하여소화액중의이분해성의유기물과잔여가스를충분히제거하여접종액으로사용하였다. 회분식반응기 이때, V dry gas 는표준상태 (, 1기압 ) 에서의건조가스의부피, T는반응기의운전온도, V wet gas at T 는반응기운전온도 (38 ) 에서의습윤가스의부피, P는가스의부피측정당시의대기압, PT는 T 에서의포화수증기압 (mmhg) 이며, 본연구에서는 P를 7 mmhg로간주하고 P T 는 38 서의포화수증기압으로계산하였다. 회분식혐기반응기의바이오가스발생량은반응기운전 1까지는일일 1회측정하였으며, 1일이후 2-5일간격으로측정하였다. 바이오가스발생량의측정은 2% 황산에

Methane Potential of Organic Sludge Hydrolysate 131 resazurin.1% 를함유하는수주차식가스량측정기를사용하였으며 (Beuvink et al., 1992; Williams et al., 1996), 발생바이오가스는 Eq. 2와같이온도와수분을보정하여표준상태 (, 1기압 ) 에서의건조가스부피로환산하여누적메탄생산곡선을구하였다. 메탄생산퍼텐셜산출을위한누적메탄생산곡선은 (Eq. 3) 을이용하여 SigmaPlot(SigmaPlot Version 1., Systat Software Inc., San Jose, Califonia, USA) 으로해석하였다 (Lay et al., 1998). : 난분해성 (Non-biodegradable) VS 의함량 (g) (Eq. 6) 이때, 는최종메탄생산퍼텐셜 (Nm 3 -CH 4 kg -1 -VS added), 는이론적메탄생산퍼텐셜 (Nm 3 -CH 4 kg -1 -VS added) 이다. (Eq. 7) exp exp (Eq. 3) 이때, M 은누적메탄생산량 (ml), t 는혐기배양기간 (days), P는최종메탄생산량 (ml), e는 exp(1), R m 은최대메탄생산속도 (ml day -1 ), λ는지체성장시간 (lag growth phase time, days) 이다. 유기기질의유기물분포특성분석모델본연구에서는유기성슬러지수열탄화액의반응온도별유기물의분포특성을분석하기위하여병렬 1차반응속도식 (Parallel first order kinetics) (Eq. 4) 을적용하였다 (Rao et al., ; Luna-delRisco et al., 11; Shin, 13). Eq. 4에서의상수 k 1, k 2, f e 는 SigmaPlot(SigmaPlot Version 1., Systat Software Inc., San Jose, Califonia, USA) 을이용하여메탄생산퍼텐셜시험에서얻은누적메탄생산곡선에 Eq. 4를최적화하여구하였다. max (Eq. 4) 여기서 B t 는시간 t에서의메탄생산량 (ml), B u 는최종메탄생산량 (Ultimate methane production, ml), f e 는병열 1차반응분배계수 (g g -1 ), k 1 과 k 2 는병열 1차반응속도상수 (Kinetic constant) 이다. 또한, 본연구에서는혐기소화과정에서분해되는기질 (Substrate) 중의유기물 ( ) 을 (Eq. 5) 와같이혐기소화과정에서메탄으로전환되는생분해성 (Biodegradable) 유기물 ( ) 과메탄으로전환되지않는난분해성 (Nonbiodegradable) 유기물 ( ) 로정의 (Eq. 6) 하였으며, 또생분해성유기물 ( ) 은 Eq. 7과같이혐기소화과정에서초기에쉽게분해되는이분해성 (Easily biodegradable) 유기물 ( ) 과분해저항성이있어혐기소화후기에천천히분해되는분해저항성 (Persistent) 유기물 ( ) 로구분하여정의하였다. (Eq. 5) 이때, 는총휘발성고형물 (VS; volatile solid) 의함량 (g), 는분해성 (Biodegradable) VS의함량 (g) 이다. 이때, 는이분해성 (Easily biodegradable) VS 의함량 (g), 는분해저항성 (Persistent) VS의함량 (g), 는이분 해성 (Easily biodegradable) 유기물계수 (, g/g) 이다. 시험분석바이오가스의가스성분분석은 TCD(Thermal conductivity detector) 가장착된 Gas chromatography(clarus 6, PerkinElmer, Waktham, Massachusetts, USA) 를이용하였다. 컬럼은 HayesepQ packed column(3 mm 3 m, ~ mesh size) 을이용하였으며, 고순도아르곤 (Ar) 가스를이동상으로사용하여 flow 3 ml min-1의운전상태에서주입부 (Injector) 온도 15, 컬럼부 (Column oven) 9, 검출부 (Detector) 15 에서분석하였다 (Sorensen et al., 1991). 시료의원소분석은원소분석기 (EA118, Thermo Finnigan LLC, San Jose, Califonia, USA) 를사용하였으며, 총고형물 (Total solid, TS), 휘발성고형물 (Volatile solid, VS), 총화학적산소요구량 (Total chemical oxygen demand, TCOD), 총질소 (Total nitrogen, TN), 암모니아태질소 (NH + 4 -N), 알칼리도 (Alkalinity), 휘발성지방산 (Volatile fatty acid, VFA) 등은표준분석법 (APHA, 1998) 에따라 3 반복으로수행하였다. 통계분석유기성슬러지의수열탄화액의누적메탄생산곡선은각각 과 Parallel First Order Kinetics를이용하여최적화하였으며, 두수학적모델에의한최적화도는평균제곱근편차 (Root mean square deviation, RMSD) (Eq. 8) 를분석하여비교하였다. 이론적메탄생산퍼텐셜 (Eq. 8) 결과및고찰 유기성슬러지수열탄화액의원소분석결과와이로부터 Boyle(1976) 의유기물분해반응식 (Eq. 1) 을이용하여화학양론적으로산출한이론적메탄생산퍼텐셜 (B th) 은 Table 3과

132 Oh et al. Table 3. Elemental composition and theoretical methane potential of hydrothermal hydrolysate Parameters Temp 1) ( ) Elemental composition C H O N S ---------- (%, w/w) ---------- B th 2) (Nm 3 kg -1 -VS added) 17 45.4 7.4 26.6 12.5.2.499 Hydro-thermal hydrolysates 1 45.2 7.4 25.6 12.8.1.55 19 45.5 8. 26.2 13. ND.514 45.5 7.5 22.3 13.2 ND.537 2 44.9 6.8 25.4 12.7 ND.493 1) Hydro-thermal reaction temperature, 2) Theoretical methane potential. Hydro-thermal reactor temperature 17 o C Hydro-thermal reactor temperature 1 o C Hydro-thermal reactor temperature 19 o C Hydro-thermal reactor temperature o C Hydro-thermal reactor temperature 2 o C Fig. 1. The optimization curves of cumulative methane production curve by and parallel first order kinetic model. 같다. 유기성슬러지의수열탄화액의탄소함량은 44.9 45.5%, 수소함량은 6.8 8.%, 산소함량은 22.3 26.6%, 질소함량은 12.7 13.2% 의범위를보였으며, 황함량은수열탄화온도 17 와 1 에서각각.2,.1% 를나타내었다. 수열탄화액의이론적메탄생산퍼텐셜은수열탄화반응온도가 17 에서 까지상승함에따라.499에서.537 Nm 3 kg -1 -VS added 로증가하였으며, 수열탄화온도 2 에서는.493 Nm 3 kg -1 -VS added 으로감소하였다. 최종메탄생산퍼텐셜 Fig. 1은유기성슬러지의메탄생산퍼텐설시험을통해얻은수열탄화액의누적메탄생산곡선과 Modified Gompertz model, Parallel first order kinetics model을이용하여최적화한곡선을비교하였다. 또한 Table 4와 Table 5는각각 유기성슬러지수열탄화액의누적메탄생산곡선을각각 과 Parallel first order kinetics model을이용하여최적화한최종메탄생산퍼텐셜 (B u) 과모델인자들을나타내었다. 유기성슬러지수열탄화액의메탄생산퍼텐셜시험을통해얻은누적메탄생산곡선에 을최적화하여얻은최종메탄생산퍼텐셜은수열탄화반응온도 17 에서 19 까지.35에서.377 Nm 3 kg -1 -VS added 로증가하였으며, 이후수열탄화반응온도 와 2 에서각각.315,.29 Nm 3 kg -1 -VS added 으로감소하였다. 또한최대메탄생산속도 (R m) 는수열탄화반응온도 17 에서 14.487 ml day -1 로가장높았으며, 이후수열탄화온도가증 가함에따라점차감소하여수열탄화반응온도 2 에서는 9.478 ml day -1 를나타내었다. Parallel first order kinetics

Methane Potential of Organic Sludge Hydrolysate 133 Table 4. Ultimate methane potential and parameters estimated by the optimization of in the hydro-thermal hydrolysate of organic sludge Parameters Temp a) B u b) parameters P c) R m d) λ e) RMSD f) ( ) (Nm 3 kg -1 -VS added) (ml) (ml day -1 ) (day) (ml) 17.35 98.7 14.487.13 1.31 Hydro-thermal hydrolysates 1.338 18.7 14.6.6 13.37 19.377 121.6 14.177.3 16.43.315 11.1 11.434 16.49 2.29 94.1 9.478 21.67 a) Hydro-thermal reaction temperature, b) Ultimate methane potential, c) Maximum methane production, d) maximum methane production rate, e) lag growth phase time, f) Root mean square deviation. Table 5. Ultimate methane potential and kinetics model parameters estimated by the optimization of Parallel first-order kinetics model in the hydro-thermal hydrolysate of organic sludge Parameters Temp a) ( ) B u b) (Nm 3 kg -1 -VS added) c) d) f e k 1 k 2 RMSD e) - - - (ml) 17.38.997.222.428 12.59 Hydro-yhermal hydrolysate 1.341.961.. 12.87 19.381.921.177.177 13.62.335.739.197.4 7.7 2.322.78.217.14 8.21 a) Hydro-thermal reaction temperature, b) Ultimate methane potential, c) Distribution coefficient of the Parallel first order kinetics, d) Kinetic constant, e) Root mean square deviation. model을최적화하여얻은유기성슬러지수열탄화액의최종메탄생산퍼텐셜은 로부터얻은최종메탄생산퍼텐셜과비교하여수열탄화반응온도에따라약 1 1% 증가하는것으로나타났으며, 최종메탄생산퍼텐셜은 17 에서 19 까지.38에서.381 Nm 3 kg -1 -VS added 로증가하였으며, 수열탄화반응온도 와 2 에서각각.335,.322 Nm 3 kg -1 -VS added 으로감소하여 을적용하여얻은유기성슬러지수열탄화액의최종메탄생산퍼텐셜과유사한경향을나타내었다. 또한이분해성유기물계수 (f e) 은수열탄화반응온도 17 에서.997을나타내어총생분해성유기물 (VS B) 의 99.7% 가이분해성유기물로분포하는것으로나타났으며, 수열탄화온도의증가와함께 1 에서 96.1%, 19 에서 92.1%, 에서 73.9%, 그리고 2 에서 7.8% 로이분해성유기물의분포가감소하였다. 이러한열화학적반응에서반응온도의증가와함께이분해성유기물의분포가감소하는것은고온, 고압의열화학적반응조건에서마이야르 (Maillard) 반응에의해질소화합물과탄수화물이반응하여멜라노이딘 (Melanoidine) 이라는분해저항성을지니는물질을생성하기때문이라는보고 (Martins et al., ; Bougrier et al., 8) 가있다. 이러한보고는수열탄화반응온도의증가가이분해성유기물의분포를감소시키고있는본연구의결과와유사한특성을나타낸다. 또한 Kim과 Jeon(15) 은이러한분해저항성물질의생성은절대적인고온 고압조건에서만생성되는것은아니며, 열가수분해반응기의운전에있어서빠른승온시간또는승온속도, 반응기내불균일한교반효율로인하여분해저항성물질이생성되는정도에차이가있다는보고가있어향후유기성슬러지의수열탄화액의혐기소화효율향상을위해서는수열탄화반응조건에대한최적화연구가필요할것으로생각된다. 본연구에서적용한 Modified Gompertz mode과 Parallel first order kinetics model의최적화도를비교하면, 두개분석모델의최적화과정에서얻은평균제곱근편차 (RMSD) 는수열탄화반응온도 17 를제외하고 Parallel First Order Kinetics model 의적용이통계적으로높은최적화도를나타내어 보다는 Parallel first order kinetics model이수열탄화액의최종메탄생산퍼텐셜을예측하는데더욱유리한것으로판단된다.

134 Oh et al. Table 6. Organic fractions estimated by the optimization of in the hydro-thermal hydrolysate of organic sludge Parameters Temp a) ( ) b) VS B c) d) VS e VS p Sum VS NB e) ---------------------------------------- (%, w/w) ---------------------------------------- 17 66.23.18 66.41 33.59 Hydro-yhermal hydrolysate 1 69.84 2.86 72.7 27.3 19 73.46 6.32 79.78.22 49.53 17.52 67.5 32.95 2 49.76.55 7.31 29.69 a) Hydro-thermal reaction temperature, b) Biodegradable volatile solid, c) Easily biodegradable volatile solid, d) Persistent volatile solid, e) Non-biodegradable volatile solid. Organic fraction (mg L -1 ) 17 1 19 2 Hydro-thermal reactor temperature ( o C) VSe VSp VSNB Fig. 2. The volatile solid fractions of hydro-thermal hydrolysate, which estimated by the optimization of parallel first-order kinetics model (VS e means a easily biodegradable volatile, VS p means a persistent volatile solid, VS NB means a non-biodegradable volatile solid). 병열 1차반응속도식에의한유기물구성추정 Table 6은 Parallel first order kinetics model을이용하여추산한 17 2 의수열탄화반응온도에서생산된수열탄화액의유기물분포를나타내고있다. 생분해성유기물 (VS B) 의분포는수열탄화반응온도 17 에서 66.41%, 1 에서 72.7%, 19 에서 79.78% 를나타내면서증가하는경향을보였으며, 이후 에서는 67.5% 로크게감소하였다가 2 에서는 7.31% 를나타내었다. 또한난분해성유기물 (VS NB) 의분포는생분해성유기물 (VS B) 의분포와반대의경향을나타내었다. 이분해성유기물 (VS e) 의분포는수열탄화반응온도 17 에서 66.23% 를나타내었으며, 이후수열탄화온도의증가와함께지속적으로감소하여수열탄화반응온도 2 에서 49.76% 까지감소하였다. 또한분해저항성유기물 (VS p) 의분포는 17.18% 에서 2.55% 로증가하면서이분해성유기물 (VS e) 의분포와반대의경향을나타내었다. Fig. 2는유기성슬러지의수열탄화액의유기물 (VS) 함량을기준으로하여각각의반응온도에서생산된수열탄화액중이분해성유기물 (VS e), 분해저항성유기물 (VS p), 난분해성유기물 (VS NB) 의함량을나타내었다. 수열탄화액의유기물 (VS) 함량은 Table 1에나타낸바와같이수열탄화반응온도 17 에서 6.1%, 1 에서 6.3%, 19 에서 6., 에서 6.7, 그리고 2 에서 6.9% 를나타내었으며, 이때이분해성유기물 (VS e) 함량은수열탄화반응온도 17 에서 19 까지는증가하였으며, 이후 와 2 에서는급격한이분해성유기물 (VS e) 함량의감소를나타내었다. 이와함께분해저항성유기물 (VS p) 함량은수열탄화반응온도의증가와함께지속적으로증가하는것으로나타났다. Parallel first order kinetics model은기본적으로서로다른반응속도를가지는두가지종류의유기물에대하여각각의 1차반응식을조합하여해석하는반응속도식이다. 따라서이분해성유기물계수 (f e) 는혐기조건에서반응속도를달리하는두종류의기질특성을분배하는계수이다. Rao et al. () 는 Parallel first order kinetics model을이용한하수슬러지의유기물구성특성연구에서회분식혐기반응기에서운전초기빠른반응속도를지니는유기물과상대적으로후반에느린반응속도를지니는유기물로구분하고하수슬러지의누적메탄생산곡선을해석한바있다. 본연구는회분식혐기반응기에서메탄으로전환되지않는유기물을난분해성유기물 (VS NB) 로정의하였고, 상대적으로빠른반응속도를나타내는유기물을이분해성유기물 (VS e), 상대적으로느린반응속도를보이는유기물을분해저항성유기물 (VS p) 로정의하여 Parallel first order kinetics model을전개하였다. 본연구에서나타난바와같이 Parallel first order kinetics model을이용하여유기물의분해반응속도의차이로유기물의특성을분별하는것은유기성폐자원의혐기소화연구에서유기물의혐기소화특성을이해하는데매우유리한측면이있다. 그러나 Parallel first order kinetics model을이

Methane Potential of Organic Sludge Hydrolysate 135 용한이분해성유기물 (VS e) 과분해저항성유기물 (VS p) 의분획은단순히혐기적분해반응속도의차이만을의미하며, 분해속도의차이를나타내는유기물의구조적, 성분적특성을밝히는데는한계가있다. 따라서유기물들의혐기적분해반응속도의차이를규명하기위해서는향후반응속도를달리하는유기물의구조특성의연구가요구된다. 결론 본연구는유기성슬러지의수열탄화전처리가수열탄화액의혐기소화와혐기적유기물분해특성에미치는영향을분석하고자 17 2 의열화학적반응온도에서생산된유기성슬러지수열탄화액에대하여메탄생산퍼텐셜을측정하고평행 1 차반응속도식 (Parallel first order kinetics) 을이용하여유기물의분포특성을분석하였다. 수열탄화액의이론적메탄생산퍼텐셜은 에서.537 Nm 3 kg -1 -VS added 로가장높게나타났으며, 실험적메탄생산퍼텐셜은 19 에서.381 Nm 3 kg -1 -VS added 로가장높게나타났다. 평행 1 차반응속도을이용하여추정한수열탄화액의생분해성유기물 (VS B) 의분포는수열탄화반응온도 17 에서 66.41%, 18 에서 72.7%, 19 에서 79.78%, 에서 67.5%, 2 에서 7.31% 를나타내었으며, 이중이분해성유기물 (VS e) 의분포는수열탄화반응온도 17 에서 66.23%, 18 에서 69.84%, 19 에서 73.46%, 에서 49.53%, 2 에서 49.76% 을나타내었다. 특히분해저항성유기물 (VS p) 은수열탄화반응온도의증가와함께증가하여 17 에서.18%, 1 에서 2.86%, 19 에서 6.32%, 에서 17.52%, 2 에서.55% 로나타나수열탄화반응온도가상승할수록분해저항성을지니는유기물의분포가증가하였다. 따라서수열탄화온도의상승에따라메탄생산효율은 19 에서가장우수하였으며, 19 이상으로수열탄화반응온도를상승시키는것은분해저항성유기물의생성을증가시키는것으로나타났다. Acknowledgment This work was supported by Korea Institute of Planning and Evaluation for Technology in Food, Agriculture, Forestry and Fisheries (IPET) through Agri-Bio industry Technology Development Program, funded by Ministry of Agriculture, Food and Rural Affairs(MAFRA)(Project No. 31-4-2-HD). References Ajandouz, E. H., Desseaux, V., Tazi, S., & Puigserver, A. (8). Effects of temperature and ph on the kinetics of caramelisation, protein cross-linking and Maillard reactions in aqueous model systems. Food Chemistry, 17(3), 1244-1252. Angelidaki, I., Alves, M., Bolzonella, D., Borzacconi, L., Campos, J. L., Guwy, A. J., Kalyuzhnyi, S., Jenicek, P., & van Lier, J. B. (9). Defining the biomethane potential (BMP) of solid organic wastes and energy crops: a proposed protocol for batch assays. Water Science & Technology, 59(5), 927-934. American Public Health Association. (1998). Standard methods for the examination of water and wastewater, th ed. Continental Edition, USA. Beuvink, J. M. W., Spoelstra, S. F., & Hogendorp, R. J. (1992). An automated method for measuring timecourse of gas production of feedstuffs incubated with buffered rumen fluid. Netherlands Journal of Agricultural Science, (4), 1-7. Bougrier, C., Delgenès, J. P., & Carrère, H. (8). Effects of thermal treatments on five different waste activated sludge samples solubilisation, physical properties and anaerobic digestion. Chemical Engineering Journal, 139(2), 236-244. Buendía, I. M., Fernández, F. J., Villaseñor, J., & Rodríguez, L. (9). Feasibility of anaerobic co-digestion as a treatment option of meat industry wastes. Bioresource Technology, (6), 193-199. Buffiere, P., Loisel, D., Bernet, N., & Delgenes, J. P. (6). Towards new indicators for the prediction of solid waste anaerobic digestion properties. Water Science and Technology, 53(8), 233-241. Chynoweth, D. P., Turick, C. E., Owens, J. M., Jerger, D. E., & Peck, M. W. (1993). Biochemical methane potential of biomass and waste feedstocks. Biomass and bioenergy, 5(1), 95-111. Gerardi, M.H. (3). The microbiology of anaerobic digesters. John Wiley & Sons, Inc., Hoboken, New Jersey, USA. Kim, H., & Jeon, Y. W. (15). Effects of hydro-thermal reaction temperature on anaerobic biodegradability of piggery manure hydrolysate. Korean Journal of Soil Science and Fertilizer, 48(6), 2-9. Lay, J. J., Li, Y. Y., & Noike, T. (1998). Mathematical model for methane production from landfill bioreactor. Journal of Environmental Engineering, 124(8), 73-736. Luna-delRisco, M., Normak, A., & Orupold, K. (11). Biochemical methane potential of different organic wastes and energy crops from Estonia. Agronomy Research, 9(1-2), 331-342. Martins, S. I. F. S., Jongen, W. M. F., & Van Boekel, M. A. J. S. (). A review of Maillard reaction in food and implications to kinetic modelling. Trends in Food Science & Technology, 11(9-1), 364-373.

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