臺灣博碩士論文加值系統

近年來營養鹽污染的情形日趨嚴重，污水未經處理排入水庫或是河川，造成水中營養鹽含量過高，使得藻類大量繁殖，破壞水域生態與影響供水品質。因此，生物脫氮可將水中的氮化合物轉化成氮氣，為目前廢水去氮常見的程序。這類技術可分成懸浮生長程序與附著生長程序，其中懸浮生長程序為目前國內外污水廠較常見的脫氮技術。附著生長程序的發展較晚，不過具備許多技術上的優勢，例如設備簡單、操作容易、效能穩定以及污泥產量低等。蚵殼表面粗糙，非常適合作為附著生長程序的生物介質，且國內養蚵產業發達，蚵殼的廢棄量相當大，使用蚵殼進行廢水生物處理兼具廢棄物再利用的優勢。本研究以廢棄蚵殼做為生物載體，探討接觸曝氣系統經由同時硝化與脫硝程序進行廢水廢水脫氮的效率，並決定系統的最佳操作參數。試驗依曝氣孔位置的不同分為全槽曝氣與部分曝氣兩種配置。全槽曝氣以槽體溶氧 2.5、3.0、3.5、4.0 mg/L四種條件進行試驗，結果顯示溶氧3.0 mg/L時脫氮效率最佳。根據此一溶氧進行長期穩定試驗的結果顯示，系統脫氮效率為44.7%。部分曝氣試驗在溶氧3.5 mg/L時有最佳脫氮效率，平均去除率為41.2%。碳氮比試驗的結果顯示，當C/N = 12時系統脫氮效率最佳。本研究證實，蚵殼介質間接曝氣系統具有系統穩定、操作簡單的優勢，並可同時去除有機物及氮化合物，達到生活污水的排放標準。

Due intensive discharge of nutrient-containing wastewater, eutrophication has become a common problem of many surface waters. Nitrogen removal from wastewaters is a primary solution for easing eutrophication of these waterbodies. Biological nitrogen removal is commonly adopted for nitrogen removal due to its low cost and environmental friendliness. The various biological nitrogen removing processes can be broadly categorized as suspended growth and attached growth systems. Although suspended growth process such as activated sludge systems has been popular among wastewater treatment facilities, attached grow systems such as biological aerated filters (BAFs) have gained a growing popularity in recent years due to their simplicity, stability, and low sludge production. In this study, a laboratory scale BAF using oyster shell medium was used to test its nitrogen removing efficiency through simultaneous nitrification and denitrification (SND). Results of lab studies show that a long term nitrogen removal efficiency of 44.7 % was achieved when the filter is completely mixed. A slightly lower efficiency of 41.2 % was also attained when the reactor is partially aerated. Best dissolved oxygen levels were 3.0 and 3.5 respectfully for the complete mixed system and the partially mixed system. The results also indicate that a carbon to nitrogen ratio of 12 provided best SND efficiency of the system. It is concluded that, a BAF system using oyster shells as growth medium provides effluents that meet current regulations. The system is also simple and easy to operate and maintain, which is especially suitable for the treatment of municipal wastewater from small communities and businesses.

摘要................................................................................................................................i
第一章 前言..................................................................................................................1
1.1 研究起源.............................................................................................................1
1.2 研究內容與目的.................................................................................................1
第二章 文前回顧..........................................................................................................4
2.1 廢水脫氮程序.....................................................................................................4
2.1.1 兩階段生物脫氮......................................................................................4
2.1.2 硝化作用..................................................................................................4
2.1.3 脫硝作用..................................................................................................5
2.2 廢水脫氮技術.....................................................................................................6
2.2.1 傳統脫氮..................................................................................................6
2.2.2 曝氣生物濾池..........................................................................................6
2.2.3 厭氧氨氧化..............................................................................................7
2.2.4 短程硝化脫硝..........................................................................................8
2.2.5 混合系統..................................................................................................9
2.2.6 同時硝化脫硝........................................................................................10
2.2.6.1 SND操作條件.............................................................................12
2.2.7 硝化與脫硝反應的平衡........................................................................16
2.3 生物載體的使用...............................................................................................16
2.3.1 接觸曝氣系統效率................................................................................20
2.4 蚵殼接觸濾材...................................................................................................20
第三章 研究材料與方法............................................................................................22
3.1反應器構造........................................................................................................22
3.2 試驗條件 – 全槽曝氣.....................................................................................24
3.3 試驗條件 – 部分曝氣. ...................................................................................25
3.4 水質採樣與分析...............................................................................................25
3.5 水質監測...........................................................................................................26
第四章 結果與討論....................................................................................................27
4.1 全槽曝氣...........................................................................................................28
4.1.1 最佳溶氧試驗........................................................................................28
4.1.2 系統長期操作效率................................................................................31
4.2好/缺氧區分隔之影響.......................................................................................28
4.3 廢水碳氮比之影響...........................................................................................37
4.4 系統脫氮效率綜合評估...................................................................................41
4.5 水力停留時間對系統效率之影響...................................................................42
4.6 反應器負荷.......................................................................................................44
4.6.1 系統污染負荷........................................................................................44
4.6.2 微生物負荷............................................................................................45
4.7不同槽體的系統效率差異的顯著性................................................................48
4.8 不同碳氮比對系統效率影響之顯著性...........................................................48
第五章 結論................................................................................................................49
第六章 建議................................................................................................................49
第七章 參考文獻........................................................................................................50

Arrigo, K. R. (2005). Marine microorganisms and global nutrient cycles. Nature, 437(7057), 349-355.
Aoi, Y. , T. Miyoshi, T. Okamoto, S. Tsuneda, A. Hirata, A. Kitayama, T. Nagamune (2000). Microbial Ecology of Nitrifying Bacteria in Wastewater Treatment Process Examined by Fluorescence In Situ Hybridization. Journal of Bioscience and Bioengineering, 90(3), 234-240.
Azimi, S. , M. Malakootian, K. Yaghmaeian, M. Ahmadian, S. Rahimi (2014). Studying the efficiency of a biological aerated filter (BAF) with oyster media on improving the quality of effluent produced by treatment plants. Fresenius Environmental Bulletin, 23(10), 2041-2406.
Amir, Z. , S. Fatihah, M. Denecke, S.M. Zain (2010). Simultaneous Carbon and Nitrogen Removal in Wastewater Treatment Using a Partially Packed Biological Aerated Filter (BAF) without Backwashing Process. Journal of Environmental Science and Engineering, 4(7), 15-23.
Breisha, G. Z. (2010). Bio-removal of nitrogen from wastewaters—A review. Nature and Science, 8(12), 210-228.
Bakti, N. A. K. , R. I. Dick (1992). A model for a nitrifying suspended-growth reactor incorporating intraparticle diffusional limitation. Water Research, 26(12), 1681-1690.
Bertanza, G. (1997). Simultaneous nitrification denitrification process in extended aeration plants: pilot and real scale experiences. Water Science and Technology, 35(6), 53-61.
Chen, K., S. Lee, S. Chin, J. Houng (1998). Simultaneous carbon-nitrogen removal in wastewater using phosphorylated PVA-immobilized microorganisms. Enzyme and Microbial Technology, 12(5), 311-320.
Chiu, Y. , L. Lee, C. Chang, A. C. Chaoc (2007). Control of carbon and ammonium ratio for simultaneous nitrification and denitrification in a sequencing batch bioreactor. International Biodeterioration & Biodegradation, 59(1), 1-7.
Characklis, W. G. (1981). Bioengineering report: Fouling biofilm development: A process analysis. Biotechnology and Bioengineering, 23(9) 1923-1960.
Clifford, E. , P. Forde, S. McNamara, M. Rodgers, E.O’Reilly (2013). Performance of Air Suction Flow Biofilm Reactor in Treating Municipal-Strength Wastewater. Journal of Environmental Engineering, 193(6), 1943-7870.
Choi, C. , J. Lee, K. Lee, M. Kim (2008). The effects on operation conditions of sludge retention time and carbon/nitrogen ratio in an intermittently aerated membrane bioreactor (IAMBR). Bioresour Technol, 99(13), 5397-5401.
Cho, J. , K. Song, S. H. Lee, K. Ahn (2005). Sequencing anoxic/anaerobic membrane bioreactor (SAM) pilot plant for advanced wastewater treatment. Desalination, 178(1), 219-225.
Chu, L. , J. Wang (2011). Comparison of polyurethane foam and biodegradable polymer as carriers in moving bed biofilm reactor for treating wastewater with a low C/N ratio. Chemosphere, 83(1), 63-38.
Chowdhury, N. , G. Nakhla, J. Zhu (2008). Load maximization of a liquid–solid circulating fluidized bed bioreactor for nitrogen removal from synthetic municipal wastewater. Chemosphere, 71(5), 807-815.
Desbos, G. , F. Rogalla, J. Sibony, M. M. Bourbigot (1990). Biofiltration as a compact technique for small wastewater treatment plants. Water Science and
Technology, 22(3), 145-152.
Ding, D. , C. Feng, Y. Jin (2010). Effect of C/N Ratio on Nitrogen Removal in a Novel Sequencing Batch Biofilm Reactor. 2010 4th International Conference on Bioinformatics and Biomedical Engineering, ISSN: 2151-7614.
Espinosa, L. M. , T. Stephenson (1999). A Review of Biological Aerated Filters (BAFs) for Wastewater Treatment. Environmental Engineering Science, 16(3), 201-216.
Ebeling, J. M. , M. B. Timmons, J.J. Bisogni (2006). Engineering analysis of the stoichiometry of photoautotrophic, autotrophic, and heterotrophic removal of ammonia–nitrogen in aquaculture systems. Aquaculture, 257(4), 346-358.
Ford, D. L (1980). Comprehensive analysis of nitrification of chemical processing wastewaters. Water Pollution Control Federation, 52(11), 2726-2746.
Feng, S. , S. Xie, X. Zhang, Z. Yang, W. Ding, X. Liao, Y. Liu, C. Chen (2012). Ammonium removal pathways and microbial community in GAC-sand dual media filter in drinking water treatment. Journal of Environmental Sciences, 24(9), 1587–1593.
Filippis, P. D. , L. D. Palma, M. Scarsella, N. Verdone (2013). Biological Denitrification of High-Nitrate Wastewaters: a Comparison Between Three Electron Donors. T Chemical Engineering Transactions. 32, 319 - 324.
Fuerst, J. A. , E. Sagulenko (2011). Beyond the bacterium: planctomycetes challenge our concepts of microbial structure and function. Nature Reviews Microbiolgy, 9(6), 403-413.
Feng, Q. , J. Cao, L. Chen , C. Y. Guo , J. Tan, H. Xu (2011). Simultaneous nitrification and denitrification at variable C/N ratio in aerobic granular sequencing batch reactors. Journal of Food Agriculture and Environment, 9(2), 1135-1140.
Feng, Q. , Y. Wang, T. Wang, H. Zheng, L. Chu, C. Zhang, H. Chen, X. Kong, X. Xing (2012). Effects of packing rates of cubic-shaped polyurethane foam carriers on the microbial community and the removal of organics and nitrogen in moving bed biofilm reactors. Bioresource Technology, 117, 201-207.
Gupta, S. K. , M. Kshirsagar (2000). Quantitative estimation of thiosphaera pantotropha from aerobic mixed culture. Water Research, 34(15), 3765 - 3768.
Graaf, A. A. , P. d. Bruijn, L. A. Robertson, M. Jetten, J. G. Kuenen (1996). Autotrophic growth of anaerobic ammonium-oxidizing micro-organisms in a fluidized bed reactor. Microbiology, 142(8), 2187-2196.
Guo, J. , L. Zhang, W. Chen, F. Ma, H. Liu, Y. Tian (2013). The regulation and control strategies of a sequencing batch reactor for simultaneous nitrification and denitrification at different temperatures. Bioresource Technology, 133, 59-67.
Ghusain, I. A. , A. Member (1995). Use of pH as Control Parameter for Aerobic/Anoxic Sludge Digestion. Journal of Environmental Engineering, 121(3), 225-235.
Gong, L. , L. Jun, Q. Yang, S. Wang, B. Ma, Y. Peng (2012). Biomass characteristics and simultaneous nitrification–denitrification under long sludge retention time in an integrated reactor treating rural domestic sewage. Bioresource Technology, 119, 277–284.
Gill, L. , C. Doran, D. Misstear, B. Sheahan (2009). The use of recycled glass as a filter media for on-site wastewater treatment. Desalination and Water Treatment, 4(1), 198-205.
Holman, J.B. , D.G. Wareham (2005). COD, ammonia and dissolved oxygen time profiles in the simultaneous nitrification/denitrification process. Biochemical Engineering Journal, 22(2), 125-133.
He, S. , G. Xue, B. Wang (2009). Factors affecting simultaneous nitrification and de-nitrification (SND) and its kinetics model in membrane bioreactor. Journal of Hazardous Materials, 168(2), 704-710.
Hiratsuka, J. , J. H. Kim, H. Tanaka, H. Sasaki, R. Sudo (2000). Influence of streamside surface area on aquatic biota and biofilm activity. Journal of Water and Environment Technology, 1(1), 105-110.
Ha, J.H. , S.K. Ong (2007). Nitrification and denitrification in partially aerated
biological aerated filter (BAF) with dual size sand media. Water Science & Technology, 55(2), 9-17.
Jetten, M. , M. Wagner, J. Fuerst, M. Loosdrecht, G. Kuenen, M. Strous (2001). Microbiology and application of the anaerobic ammonium oxidation (‘anammox’) process. Current Opinion in Biotechnology.12(3), 283 - 288.
Jácome, A. , J. Molina, R. Novoa, J. Suárez, S. Ferreiro (2014). Simultaneous carbon and nitrogen removal from municipal wastewater in full-scale unaerated/aerated submerged filters. Water Science Technol, 69(1), 217-221.
Junga, Y. , H. Koha , W. Shinb, N. Sung (2006). A novel approach to an advanced tertiary wastewater treatment: Combination of a membrane bioreactor and an oyster-zeolite column. Desalination, 190(1), 243-255.
Knowles, R. (1982). Denitrification. Microbiol Rev, 46(1), 43-70.
Loosdrecht, M. , X. Hao, M. Jetten, W. Abma (2004). Use of Anammox in urban wastewater treatment. Water Science and Technology:Water Supply, 4(1), 87–94.
Li, Y.Z. , Y.L. He, D.G. Ohandja, J. Ji, J.F. Li, T. Zhou (2007). Simultaneous nitrification–denitrification achieved by an innovative internal-loop airlift MBR: Comparative study. Bioresource Technology, 99(13), 5867-5872.
Liu, Y. , S. F. Yang, J. H. Tay (2003). Elemental compositions and characteristics of aerobic granules cultivated at different substrate N/C ratios. Applied Microbiology and Biotechnology, 61(5), 556-561.
Liu, F. , C. C. Zhao, D. F. Zhaoa, G. H. Liu (2008). Tertiary treatment of textile wastewater with combined media biological aerated filter (CMBAF) at different hydraulic loadings and dissolved oxygen concentrations. Journal of Hazardous Materials, 160(1), 161-167.
Luo, H. , G. Huang, X. Fu, X. Liu, D. Zheng, J. Peng, K. Zhang, B. Huang, L. Fan, F. Chen, X. Sun (2013). Waste oyster shell as a kind of active filler to treat the combined wastewater at an estuary. Journal of Environmental Sciences, 25(10), 2047-2055.
Liu, Y. , T. Yang, D. Yuan, X. Wu (2010). Study of municipal wastewater treatment with oyster shell as biological aerated. Desalination, 254(1), 149-153.
Li, H. , Z. Yu, Y. Min, K. Yoichi (2013). Effects of hydraulic retention time on nitrification activities and population dynamics of a conventional activated sludge system. Frontiers of Environmental Science & Engineering, 7(1), 43-48.
Lee, Y. H. , S. Islam, S. J. HONG, K. M. CHO, R. Math, J. Y. Heo, H. Kim, H. D. Yun (2010). Composted oyster shell as lime fertilizer is more effective than fresh oyster shell. Bioscience biotechnology and Biochemistry, 74(8), 1517-1521.
Masic, A. (2013). Investigation of a biofilm reactor model with suspended biomass. Doctoral Theses in Mathematical Sciences, ISSN 1404-0034.
Münch, V. (1996). Simultaneous nitrification and denitrification in bench-scale sequencing batch reactors. Water Research, 30(2), 277-284.
Meng, Q. , F. Yang, L. Liu, F. Meng (2007). Effects of COD/N ratio and DO concentration on simultaneous nitrification and denitrification in an airlift internal circulation membrane bioreactor. Journal of Environmental Sciences, 20(8), 933-939.
Moosavi, G.H. , K. Naddafi, A.R. Mesdaghinia, R. Nabizadeh (2005). Simultaneous Organics and Nutrients Removal from Municipal Wastewater in an Up-flow Anaerobic/Aerobic Fixed Bed Reactor. Journal of Applied Sciences, 5(3), 503-507.
Odell, L. H. , G. J. Kirmeyer, A. j. Wilczak, J. G. Jacangelo, J. P. Marcinko, R. L.Wolfe (1996). Controlling nitrification in chloraminated systems. American Water Works Association, 88(7), 86-98.
Orhon, D. (2014). Evolution of the activated sludge process: the first 50 years. Journal of Chemical Technology and Biotechnology, 90(4), 1-30.
Obaja, D. , S. Mace, J. Costa, C. Sans, J. M. Alvarez (2002). Nitrification, denitrification and biological phosphorus removal in piggery wastewater using a sequencing batch reactor. Bioresource Technology, 87(1), 103-111.
Pramanik, B. K. , S. Fatihah, Z. Shahrom, E. Ahmed (2012). Biological aerated filters (BAFs) for carbon and nitrogen removal: a review. Journal of Engineering Science and Technology, 7(4), 428 - 446.
Peng, Y. , G. Zhu (2006). Biological nitrogen removal with nitrification and denitrification via nitrite pathway. Applied Microbiology and Biotechnology, 73(1), 15-26.
Puznava, N. , M. Payraudeau and D. Thornberg (2001). Simultaneous nitrification and denitrification in biofilters with real time aeration control. Water Science and Technology, 43(1), 269–276.
Pochana, K. , J. Keller (1999). Study of factors affecting simultaneous nitrification and denitrification (SND). Water Science and Technology, 39(6), 61–68.
Park, H. D. (2004). Evaluating the effect of dissolved oxygen on ammonia-oxidizing bacterial communities in activated sludge. Water Research, 38(14-15), 3275-3286.
Peng, Z. , Z. Qi (2007). Simultaneous nitrification and denitrification in activated sludge system under low oxygen concentration. Frontiers Environmental Science Engineering, 1(1), 49-52.
Pedros, P.B. , J. Y. Wang , W. K. Dobie , H. Metghalchi (2005). Experimental and numerical results of a single submerged attached growth bioreactor (SAGB) for simultaneous oxidation of organics and nitrogen removal. Water science and technology, 52(7), 97-105.
Pochana, K. , J. Keller, J. Lant (1999). Model development for simultaneous nitrification and denitrification. Water Science and Technology, 39 (1), 235–243.
Ruiz, G. , D. Jeison, R. Chamy (2003). Nitrification with high nitrite accumulation for the treatment of wastewater with high ammonia concentration. Water Research, 37(6), 1371-1377.
Robertso, L. A. , J. G. Kuenen (1984). Aerobic denitrification: a controversy revived. Archives of Microbiology, 139(4), 351-354.
Rittmann, B. E. , W. E. Langeland (1985). Simultaneous denitrification with nitrification in single-channel oxidation ditches. Water Pollution Control Federation, 57(4), 300-308.
Rong, Q. , Y. Kun, Y. Z. xian (2007). Treatment of coke plant wastewater by SND fixed biofilm hybrid system. Journal of Environmental Sciences, 19(2), 153-159.
Srivastava, N.K. , C.B. Majumder (2008). Novel biofiltration methods for the treatment of heavy metals from industrial wastewater. Journal of Hazardous Materials, 151(1), 1-8.
Strous, M. , J. J. Heijnen, J. G. Kuenen(1998). The sequencing batch reactor as a powerful tool for the study of slowly growing anaerobic ammonium-oxidizing microorganisms. Appl Microbiol Biotechnol, 50(5), 589-596.
Strous, M. , J. G. Kuenen, M. S. M. Jetten(1999). Key Physiology of Anaerobic Ammonium Oxidation. Applied and environmental microbiology, 65(7), 3248-3250.
Sun, S. , C. Nacher, B. Merkey, Q. Zhou, S. Xia, D. Yang, J. Sun, B. Smets (2010). Effective Biological Nitrogen Removal Treatment Processes for Domestic Wastewaters with Low C/N Ratios: A Review. Environmental Engineering Science, 27(2), 111-126.
Seifia, M. , M. H. Fazaelipoor (2012). Modeling simultaneous nitrification and denitrification (SND) in a fluidized bed biofilm reactor. Applied Mathematical Modelling, 36(11), 5603-5613.
Strauss, E. A. , G. A. Lamberti (2000). Regulation of nitrification in aquatic sediments by organic carbon. Limnology and Oceanography, 45(8), 1854-1859.
Trapani, D. , G. Mannina, M. Torregrossa, G. Viviani(2008). Hybrid moving bed biofilm reactors: a pilot plant experiment. Water Science and Technology, 57(10), 1539-1545.
Third, K. A. , B. Gibbs, M. Newland, R. C. Ruwisch (2005). Long-term aeration management for improved N-removal via SNDin a sequencing batch reactor. Water Research, 39(15), 3523-3530.
Wijeyekoona, S. , T. Minob, H. Satohb, T. Matsuo (2004). Effects of substrate loading rate on biofilm structure. Water Research, 38(10), 2479-2488.
Wang, J. , LB. Wu (2004). Wastewater treatment in a Hybrid Biological Reactor (HBR): Nitrification characteristics. Biomedical and Environmental Sciences, 17(3), 373-379.
Wang, J. , H. Shi, Y. Qian (2000). Wastewater treatment in a hybrid biological reactor (HBR): effect of organic loading rates. Process Biochemistry, 36(4), 297-303.
Wang, J. , Y. Peng, S. Wang, Y. Gao (2008). Nitrogen Removal by Simultaneous Nitrification and Denitrification via Nitrite in a Sequence Hybrid Biological Reactor. Chinese Journal of Chemical Engineering, 16(5), 778-784.
Xia, S. , J. Li, R. Wang, J. Li, Z. Zhang (2010). Tracking composition and dynamics of nitrification and denitrification microbial community in a biofilm reactor by PCR-DGGE and combining FISH with flow cytometry. Biochemical Engineering Journal, 49(3), 370-378.
Xiong, X. , Z. Ye (2006). Study of nitrification behavior in aerated biofilters using
Oyster shell carrier. Aquatic Ecosystem Health & Management, 9(1), 15-19.
Xing, X. , B. Jun, M. Yanagida, Y. Tanji, H. Unno (2000). Effect of C/N values on microbial simultaneous removal of carbonaceous and nitrogenous substances in wastewater by single continuous-flow fluidized-bed bioreactor containing porous carrier particles. Biochemical engineering journal, 5(1), 29-37.
Yang, S. , F. Yang(2011). Nitrogen removal via short-cut simultaneous nitrification and denitrification in an intermittently aerated moving bed membrane bioreactor. Journal of Hazardous Materials, 195(15), 318-323.
Yoo, H. , K. H. Ahn, H. J. Lee, K. H. Lee, Y. J. Kwak, K. G. Song (1999). Nitrogen removal from synthetic wastewater by simultaneous nitrification and denitrification (SND) via nitrite in an intermittently-aerated reactor. Water Research, 33(1), 145-154.
Yoon, G. , B. T. Kim, B. O. Kim, S. H. Han (2003). Chemical–mechanical characteristics of crushed oyster-shell. Waste Management, 23(9), 825-834.
Zajzon, G. (2012).Simultaneous nitrification and denitrification process in the municipal wastewater treatment. Conference of Junior Researchers in Civil Engineering, 282-288.
Zhu, S. , S. Chen (2002). The impact of temperature on nitrification rate in fixed film biofilters. Aquacultural Engineering, 26(4), 221-237.
Zhang, L. , C. Wei, K. Zhang, C. Zhang, Q. Fang, S. Li (2009). Effects of temperature on simultaneous nitrification and denitrification via nitrite in a sequencing batch biofilm reactor. Bioprocess and Biosystems Engineering, 32(2), 175-182.
曾四恭、曹明浙(2003)。同槽硝化脫硝反應去除廢水氨氮之研究。國立台灣大學環境工程學研究所碩士論文。
張景盛、呂仲倫、吳育昇、陳秀男(2012)。煅燒牡蠣殼粉在水產養殖上的應用。國立臺灣大學漁業科學研究所
中野拓治、糸井徳彰、北尾高嶺(2002)。研究無氧濾床與接觸曝氣濾池對農業排放水的脫氮性能。農業土木學會，2002(222)，37-46。