Approximately 64% of SCOD in the synthetic wastewater and 61% of SCOD in the sewage were reduced by or sorbed into the activated sludge in 30-min contact. While the SCOD of the diluted livestock wastewater was reduced by about 43% at the same contact time. Based on the result, the specific mass of organic matter uptaken was 55 mg SCOD/g MLSS in 30 min. In the same manner, 20.1 and 14.3 mg SCOD/g MLSS were calculated as the values in the sewage and livestock wastewater, respectively.
During the contact reaction, the dissolved ammonium was ranged between 26 and 29 mg $NH_4^+-N$/L, while the extractable ammonium between 28 and 32 mg $NH_4^+-N$/L. Thus, the detachable ammonium was about 2.82 mg $NH_4^+-N$/l, that was 9.4% of the influent ammonium of 30 mg $NH_4^+-N$/l. The specific mass of ammonium adsorbed was 0.94 mg $NH_4^+-N$/g MLSS. An interesting observation was the amount of ammonium adsorbed was far less than that of organic matters uptaken in the same period. It indicated that the organic-rich sludge flow and the ammonia-rich supernatant stream were effectively separated through biological uptake reaction.
Due to the low growth rate of nitrifying bacteria, immobilization of nitrifiers was tried in order to improve nitrification efficiency and to prevent washing-out of nitrifiers. The proposed separate-sludge system showed very stable nitrification efficiency. In this system, it is possible to control the streams individually in the nitrifying and denitrifying step. Moreover, the separation of an ammonium-rich stream from an organic-laden stream through the biological uptake reaction gave nitrifiers a favorable condition in growth as well as competition. It leads to the optimal control of the separate nitrification step in the proposed activated sludge system.
In sequestered denitrification, it was found that 8.72 mg SCOD was consumed for denitrifying 1 mg nitrate. Thus, it means that the required organic matter for denitrification can be saved up to 63% in the proposed system. In 130 days of operation of denitrifying SBR, about 80% of nitrate in the nitrified effluent from the fixed-film reactor was denitrified by sludge uptaken sewage. The denitrification rate and organic requirement of the sequestered denitrification using organic uptaken sludge were similar to those of sewage. However, other utilization of sludge, primary sludge or ENR, was found to have a low rate.
The ion exchange capacity for phosphate on LDH-Cl was measured as 2.35-2.83 meq of P/g. The isotherm of phosphate uptake by LDH-Cl followed a typical Langmuir-type adsorption. The ratio of [LDH($HPO_4$)] to $[LDH]_0$ is expressed in terms of equilibrium phosphate and chloride concentrations given by following equation. In the proposed biological treatment system, 73% of organically bound phosphorus (T-P) was converted to ortho-phosphate at the end of biological nitrogen process, while in the following chemical elimination step, biologically converted ortho-phosphate was completely removed by LDH.
本 硏究는 有機物 濃度가 낮은 國內 下水特性을 바탕으로 實用的이며, 安定的인 窒素·燐 除去工程을 提示하고자 生物學的 窒素 除去와 化學的 燐 交換을 提案·結合하였다. 生物學的 窒素 除去工程에서는 流入水에 포함된 有機物質을 脫窒過程의 炭素原으로 最大한 活用하기 위해 生物學的 接觸工程을 導入하였으며, 窒酸化 微生物의 固定化 方法과 分離型 슬러지 시스템 (separate-sludge system)의 適用을 통해 生物學的 窒素 除去의 律速段階로 作用하는 窒酸化過程의 效率 및 反應速度의 向上을 圖謀하였다. 아울러 生物學的 處理工程으로 窒素와 燐을 同時에 安定的으로 處理하기 어렵다는 前提下에 化學的 燐 交換을 結合하였으며, 특히 環境分野에 새롭게 시도되는 層狀二重水酸化物을 合性·適用함으로써 旣存 化學處理劑의 問題點을 克服하고자 하였다.
大部分의 有機物質이 生物學的 工程의 好氣性 段階에서 消耗되는 것을 防止하기 위해 生物學的 接觸工程을 導入한 結果 實下水 및 合成下水의 61-64%에 該當하는 容存性 有機物 成分이 活性슬러지 微生物에 吸着되었으며, 吸着된 有機物을 後續 脫窒過程의 電子供與體로 活用하였다. 이를 뒷받침하기 위해 微生物에 의한 有機物吸着式을 提案, 比吸着量을 算定하여 合性下水의 경우 55 mg 溶存性 有機物/g 微生物을 얻었다. 結果的으로 後續 脫窒過程에서 約 63%의 潛在的인 效率 向上 可能性을 確認하였다.
窒酸化와 脫窒 段階에 關與하는 微生物을 分離함으로써 窒酸化 微生物에 友好的인 環境條件을 造成, 窒酸化率을 높였으며, 아울러 alginate와 SrCl2 溶液을 利用한 固定化 方法을 適用하여 암모니아 濃度 50 mg/L에서도 滯留時間 4 時間 내에 95% 以上의 窒酸化率을 나타내었다.
脫窒過程에서는 連續回分式反應槽를 이용하여 單一反應槽에서 反應-沈澱-流出을 모두 遂行하였고, 특히 100% 排出 方式으로 운영하여 處理容量 擴大의 可能性을 確認하였다. 微生物에 吸着된 有機物質이 脫窒過程에서 炭素原으로 活用되는 量을 定量하여 8.72 mg 溶存性有機物/mg 窒酸鹽의 推定値를 얻었다. 이와 함께 脫窒炭素原別 脫窒反應速度를 比較해 볼 때 슬러지 自體의 酸化를 통해 이루어지는 內生脫窒과는 달리 吸着된 有機物을 利用하는 機作을 따른다고 思料된다.
環境分野에는 先驅的으로 燐 除去를 위해 層狀二重水酸化物을 合成·適用함으로써 旣存 化學的 凝集劑의 短點인 過多한 슬러지 發生과 後續處理에 따른 費用上昇, 凝集劑의 一回性 消耗 등의 問題點을 改善할 수 있을 것으로 期待된다. 元素分析, 分光學的分析, 熱分析 등을 통해 合成한 構造物의 層狀構造 特性을 確認하였고, 等溫吸着式을 이용한 層狀二重水酸化物의 燐 吸着當量을 實驗한 結果 2.35-2.83 meq 燐/g 層狀二重水酸化物로 旣存 이온交換性 物質에 比해 優秀한 交換能力을 나타내었다. 또한 生物學的 窒素除去 過程을 통해 實下水에 存在하는 總-燐의 70% 以上이 溶存性 燐酸鹽 形態로 轉換되어 層狀二重水酸化物에 의한 모두 除去됨으로써 生物學的 窒素 除去工程과 化學的 燐 交換工程이 效率的으로 結合되었음을 確認하였다.
