하수슬러지 가수분해를 통해 생성되는 아미노산의 혐기성분해

Abstract

본 연구에서는 하수슬러지 가수분해를 통해 생성되는 아미노산의 혐기성 분해과정을 알아보기 위해 개별조건과 혼합조건에서 아미노산의 혐기성분해를 평가하였다. 아미노산의 개별평가 시, 두 종류 아미노산 간의 공동대사 반응인 stickland reaction은 제한시켰고, 혼합조건에서만 stickland reaction조건을 충족시켜 주었다. 혐기성분해가 진행되는 동안 COD, T-N, NH4+-N, VFAs (Volatile fatty acids), Biogas, CH4 등의 변화를 분석했다. 본 연구에서는 아미노산의 탈아미노화에 의해 생성되는 암모니아성질소를 통해 아미노산 탈아미노화율을 판단하였고, 이를 위해서 개별 조건에서 각 아미노산의 질소농도를 1,000 mg/L로 고정하여 연구를 진행하였고, 혼합조건에서는 아미노산의 질소농도를 1,800 mg/L로 고정하고 암모니아성질소 농도를 0, 1, 2, 3, 4, 5 g/L로 설정하여 연구를 진행하였다. 그 결과 알라닌, 리신, 아르기닌, 글리신, 히스티딘, 시스테인, 메티오닌, 류신의 항목 중 시스테인, 류신, 메티오닌은 탈아미노화가 61.55%, 54.59%, 46.61% 밖에 이루어지지 않았다. 특히 시스테인과 메티오닌의 경우, 탈아미노화에 기인된 유기물질의 혐기성분해가 전혀 이루어지지 않았다. 이 3종류 아미노산이 폐수에 높게 함유되어 stickland reaction이 완벽하게 충족되지 않는 조건이라면, 이 아미노산들은 혐기성소화 공정의 처리효율 저하의 원인이 될 수 있다고 판단된다. 혼합조건에서는 stickland reaction조건이 충족되었기 때문에, 개별조건에서 탈아미노화가 완벽하지 않았던 시스테인, 메티오닌, 류신 또한 탈아미노화가 100% 진행되었다. 하지만 초기암모니아성 질소가 높을수록 탈아미노화율이 감소하였고, 특히, 다른 아미노산들은 암모니아성질소 농도에 저해를 받더라도 중간산물인 δ-aminovalerate, α-aminobutyrate, γ-aminobutyrate로 존재하는 반면에, β-Alanine만은 암모니아성질소 농도에 직접적으로 영향을 받아서 분해가 이루어지지 않았다. 단백질 및 아미노산을 고농도로 함유한 폐수의 혐기성소화에서 생성되는 암모니아성질소의 영향은 탈아미노화율 감소, 유기질소화합물의 축적, VFAs의 축적으로 판단된다. 하수슬러지 폐수와 같이 단백질 함량이 높은 폐수에서 그로 인하여 생성된 고농도 암모니아성질소는 그것을 생산하는 단백질 자체의 분해에도 저해를 주기 때문에, 원활한 혐기성소화를 위해서는 암모니아성질소에 대한 미생물 종들의 순응과 함께 폐수의 단백질 및 아미노산 함량을 고려하는 것이 중요할 것이라 판단된다.|In this study, the anaerobic degradation of amino acids was evaluated in order to understand the anaerobic digestion process of amino acids that are generated through the hydrolysis of sewage sludge. In order to evaluate amino acids, the Stickland reaction, which is an intermediate reaction between two kinds of amino acids, was restricted. Changes in the chemical oxygen demand (COD), T-N, NH4+-N, biogas, and CH4 were analyzed for the anaerobic digestion process. The degradation rate of the amino acids was determined based on the ammonia form of nitrogen, which is generated by the deamination of amino acids. Therefore, this study was carried out by adjusting the nitrogen concentration of each amino acid by 1,000 mg/L. As a result, the removal rates and deamination of cysteine, leucine, and methionine were just 61.55, 54.59, and 46.61%, respectively, in the samples which included alanine, lysine, arginine, glycine, histidine, cysteine, methionine, and leucine. In particularly, cysteine and methionine, which showed removal rates of 61.55 and 46.61%, respectively, did not achieve any anaerobic degradation of organic matter. If wastewater contains high levels of cysteine, leucine, and methionine and, therefore, does not meet the requirements of a Stickland reaction, these amino acids may reduce the efficiency of the anaerobic digestion. The deamination of cysteine, methionine and leucine was approached 100 % which was not complete at individual condition because the stickland reaction was sufficient at mixed condition. However the deamination rate decreased at a higher initial NH4+-N concentration. β-Alanine was not decomposed due the direct influence of ammonia even though other amino acid possessed the by productions of δ-aminvalerate, α-aminobutyrate and γ-aniobutyrate. It was estimated that the influence of the NH4+-N from anaerobic digestion wastewater containing high concentration protein and amino acid wad because of the decrease of deamination rate, the accumulation of organic nitrogen compounds and VFAs. The acclimation of microbial species for NH4+-N and the content of protein and amino acid in wastewater should be considered for a successful anaerobic digestion.; In this study, the anaerobic degradation of amino acids was evaluated in order to understand the anaerobic digestion process of amino acids that are generated through the hydrolysis of sewage sludge. In order to evaluate amino acids, the Stickland reaction, which is an intermediate reaction between two kinds of amino acids, was restricted. Changes in the chemical oxygen demand (COD), T-N, NH4+-N, biogas, and CH4 were analyzed for the anaerobic digestion process. The degradation rate of the amino acids was determined based on the ammonia form of nitrogen, which is generated by the deamination of amino acids. Therefore, this study was carried out by adjusting the nitrogen concentration of each amino acid by 1,000 mg/L. As a result, the removal rates and deamination of cysteine, leucine, and methionine were just 61.55, 54.59, and 46.61%, respectively, in the samples which included alanine, lysine, arginine, glycine, histidine, cysteine, methionine, and leucine. In particularly, cysteine and methionine, which showed removal rates of 61.55 and 46.61%, respectively, did not achieve any anaerobic degradation of organic matter. If wastewater contains high levels of cysteine, leucine, and methionine and, therefore, does not meet the requirements of a Stickland reaction, these amino acids may reduce the efficiency of the anaerobic digestion. The deamination of cysteine, methionine and leucine was approached 100 % which was not complete at individual condition because the stickland reaction was sufficient at mixed condition. However the deamination rate decreased at a higher initial NH4+-N concentration. β-Alanine was not decomposed due the direct influence of ammonia even though other amino acid possessed the by productions of δ-aminvalerate, α-aminobutyrate and γ-aniobutyrate. It was estimated that the influence of the NH4+-N from anaerobic digestion wastewater containing high concentration protein and amino acid wad because of the decrease of deamination rate, the accumulation of organic nitrogen compounds and VFAs. The acclimation of microbial species for NH4+-N and the content of protein and amino acid in wastewater should be considered for a successful anaerobic digestion.