Skip to main content
Erschienen in: Water Resources Management 15/2016

31.08.2016

Effect of Operational and Design Parameters on Performance of Pilot-Scale Vertical Flow Constructed Wetlands Treating University Campus Wastewater

verfasst von: Vassiliki Papaevangelou, Georgios D. Gikas, Vassilios A. Tsihrintzis

Erschienen in: Water Resources Management | Ausgabe 15/2016

Einloggen

Aktivieren Sie unsere intelligente Suche, um passende Fachinhalte oder Patente zu finden.

search-config
loading …

Abstract

Vertical flow constructed wetlands (VF-CWs) are very popular wastewater treatment systems that can receive and treat heavy loads of wastewater. For the needs of the present study, three VF-CWs operated for almost 3 years treating wastewater from a university campus. The objectives of this study were to evaluate the overall performance of VF-CW systems under different feeding regimes. Another objective was to investigate the influence of vegetation, temperature and seasonal variations in system performance. Finally, the produced results were compared to those of a previous study conducted in the same units and under the same operation conditions but with the use of synthetic wastewater. Results underlined the unit capacity in removal of several pollutants and their satisfying performance as a first treatment stage even though receiving high hydraulic loads. The two planted units demonstrated higher removal capacity and better performance than the unplanted one. The units appear to operate better under warmer conditions. Finally, the previous study, where synthetic wastewater was used, indicated increased removal rates compared to the current, implying that synthetic wastewater cannot fully simulate the nature and complexity of real wastewater.

Sie haben noch keine Lizenz? Dann Informieren Sie sich jetzt über unsere Produkte:

Springer Professional "Technik"

Online-Abonnement

Mit Springer Professional "Technik" erhalten Sie Zugriff auf:

  • über 67.000 Bücher
  • über 390 Zeitschriften

aus folgenden Fachgebieten:

  • Automobil + Motoren
  • Bauwesen + Immobilien
  • Business IT + Informatik
  • Elektrotechnik + Elektronik
  • Energie + Nachhaltigkeit
  • Maschinenbau + Werkstoffe




 

Jetzt Wissensvorsprung sichern!

Springer Professional "Wirtschaft+Technik"

Online-Abonnement

Mit Springer Professional "Wirtschaft+Technik" erhalten Sie Zugriff auf:

  • über 102.000 Bücher
  • über 537 Zeitschriften

aus folgenden Fachgebieten:

  • Automobil + Motoren
  • Bauwesen + Immobilien
  • Business IT + Informatik
  • Elektrotechnik + Elektronik
  • Energie + Nachhaltigkeit
  • Finance + Banking
  • Management + Führung
  • Marketing + Vertrieb
  • Maschinenbau + Werkstoffe
  • Versicherung + Risiko

Jetzt Wissensvorsprung sichern!

Literatur
Zurück zum Zitat Abdalla KZ, Hammam G (2014) Correlation between biochemical oxygen demand and chemical oxygen demand for various wastewater treatment plants in Egypt to obtain the biodegradability indices. Int J Sci: Basic Appl Res (IJSBAR) 13(1):42–48 Abdalla KZ, Hammam G (2014) Correlation between biochemical oxygen demand and chemical oxygen demand for various wastewater treatment plants in Egypt to obtain the biodegradability indices. Int J Sci: Basic Appl Res (IJSBAR) 13(1):42–48
Zurück zum Zitat Abou-Elela SI, Hellal MS (2012) Municipal wastewater treatment using vertical flow constructed wetlands planted with Canna, Phragmites and Cyprus. Ecol Eng 47:209–213CrossRef Abou-Elela SI, Hellal MS (2012) Municipal wastewater treatment using vertical flow constructed wetlands planted with Canna, Phragmites and Cyprus. Ecol Eng 47:209–213CrossRef
Zurück zum Zitat Abou-Elela SI, Golinielli G, Abou-Taleb EM, Hellal MS (2013) Municipal wastewater treatment in horizontal and vertical flows constructed wetlands. Ecol Eng 61(Part A):460–468CrossRef Abou-Elela SI, Golinielli G, Abou-Taleb EM, Hellal MS (2013) Municipal wastewater treatment in horizontal and vertical flows constructed wetlands. Ecol Eng 61(Part A):460–468CrossRef
Zurück zum Zitat Akratos CS, Tsihrintzis VA (2007) Effect of temperature, HRT, vegetation and porous media on removal efficiency of pilot-scale horizontal subsurface flow constructed wetlands. Ecol Eng 29(2):173–191CrossRef Akratos CS, Tsihrintzis VA (2007) Effect of temperature, HRT, vegetation and porous media on removal efficiency of pilot-scale horizontal subsurface flow constructed wetlands. Ecol Eng 29(2):173–191CrossRef
Zurück zum Zitat APHA, AWWA (American Public Health Association, American Water Works Association) (1998) Standard Methods for the Examination of Water and Wastewater, 20th ed., APHA, AWWA (American Public Health Association, American Water Works Association), Washington, DC APHA, AWWA (American Public Health Association, American Water Works Association) (1998) Standard Methods for the Examination of Water and Wastewater, 20th ed., APHA, AWWA (American Public Health Association, American Water Works Association), Washington, DC
Zurück zum Zitat Ávila C, Matamoros V, Reyer-Contreras C, Piña B, Casado M, Mita L, Rivtti C, Barata C, García J, Bayona JM (2014) Attenuation of emerging organic contaminants in a hybrid constructed wetland system under different hydraulic loading rates and their associated toxicological effects in wastewater. Sci Total Environ 470–471:1272–1280CrossRef Ávila C, Matamoros V, Reyer-Contreras C, Piña B, Casado M, Mita L, Rivtti C, Barata C, García J, Bayona JM (2014) Attenuation of emerging organic contaminants in a hybrid constructed wetland system under different hydraulic loading rates and their associated toxicological effects in wastewater. Sci Total Environ 470–471:1272–1280CrossRef
Zurück zum Zitat Brix H, Arias CA (2005) The use of vertical flow constructed wetlands for on-site treatment of domestic wastewater: New Danish guidelines. Ecol Eng 25:491–500CrossRef Brix H, Arias CA (2005) The use of vertical flow constructed wetlands for on-site treatment of domestic wastewater: New Danish guidelines. Ecol Eng 25:491–500CrossRef
Zurück zum Zitat Brix H, Dyhr-Jensen K, Lorenzen B (2002) Root-zone acidity and nitrogen source affects Typha latifolia L. growth and uptake kinetics of ammonium and nitrate. J Exp Bot 53(379):2441–2450CrossRef Brix H, Dyhr-Jensen K, Lorenzen B (2002) Root-zone acidity and nitrogen source affects Typha latifolia L. growth and uptake kinetics of ammonium and nitrate. J Exp Bot 53(379):2441–2450CrossRef
Zurück zum Zitat Caselles-Osorio A, Villafañe P, Caballero V, Manzano Y (2011) Efficiency of mesocosm-scale constructed wetland systems for treatment of sanitary wastewater under tropical conditions. Water Air Soil Pollut 220:161–171CrossRef Caselles-Osorio A, Villafañe P, Caballero V, Manzano Y (2011) Efficiency of mesocosm-scale constructed wetland systems for treatment of sanitary wastewater under tropical conditions. Water Air Soil Pollut 220:161–171CrossRef
Zurück zum Zitat Chang J-j, S-q W, Dai Y-r, Liang W, Wu Z-b (2012) Treatment performance of integrated vertical-flow constructed wetland plots for domestic wastewater. Ecol Eng 44:152–159CrossRef Chang J-j, S-q W, Dai Y-r, Liang W, Wu Z-b (2012) Treatment performance of integrated vertical-flow constructed wetland plots for domestic wastewater. Ecol Eng 44:152–159CrossRef
Zurück zum Zitat Cui L, Ouyang Y, Lou Q, Yang F, Chen Y, Zhu W, Luo S (2010) Removal of nutrients from wastewater with Canna indica L. under different vertical-flow constructed wetland conditions. Ecol Eng 36:1083–1088CrossRef Cui L, Ouyang Y, Lou Q, Yang F, Chen Y, Zhu W, Luo S (2010) Removal of nutrients from wastewater with Canna indica L. under different vertical-flow constructed wetland conditions. Ecol Eng 36:1083–1088CrossRef
Zurück zum Zitat Dan TH, Quang LN, Chiem NH, Brix H (2011) Treatment of high-strength wastewater in tropical constructed wetlands planted with Sesbania sesban: horizontal subsurface flow versus vertical downflow. Ecol Eng 37(5):711–720CrossRef Dan TH, Quang LN, Chiem NH, Brix H (2011) Treatment of high-strength wastewater in tropical constructed wetlands planted with Sesbania sesban: horizontal subsurface flow versus vertical downflow. Ecol Eng 37(5):711–720CrossRef
Zurück zum Zitat Gikas GD, Tsihrintzis VA (2010) On-site treatment of domestic wastewater using a small-scale horizontal subsurface flow constructed wetland. Water Sci Technol 62(3):603–614CrossRef Gikas GD, Tsihrintzis VA (2010) On-site treatment of domestic wastewater using a small-scale horizontal subsurface flow constructed wetland. Water Sci Technol 62(3):603–614CrossRef
Zurück zum Zitat Gikas GD, Tsihrintzis VA (2012) A small-size vertical flow constructed wetland for on-site treatment of household wastewater. Ecol Eng 44:337–343CrossRef Gikas GD, Tsihrintzis VA (2012) A small-size vertical flow constructed wetland for on-site treatment of household wastewater. Ecol Eng 44:337–343CrossRef
Zurück zum Zitat Gikas GD, Tsihrintzis VA, Akratos CS (2011) Performance and modeling of a vertical flow constructed wetland-maturation pond system. J Environ Sci Health A 46(7):692–708CrossRef Gikas GD, Tsihrintzis VA, Akratos CS (2011) Performance and modeling of a vertical flow constructed wetland-maturation pond system. J Environ Sci Health A 46(7):692–708CrossRef
Zurück zum Zitat Herouvim E, Akratos CS, Tekerlekopoulou A, Vayenas DV (2011) Treatment of olive mill wastewater in pilot-scale vertical flow constructed wetlands. Ecol Eng 37:931–939CrossRef Herouvim E, Akratos CS, Tekerlekopoulou A, Vayenas DV (2011) Treatment of olive mill wastewater in pilot-scale vertical flow constructed wetlands. Ecol Eng 37:931–939CrossRef
Zurück zum Zitat Hiley P (2003) Performance of wastewater treatment and nutrient removal wetlands. In: Mander ÜU, Jenssen P (eds) Constructed wetlands for wastewater treatment in cold climates (Reedbeds) in cold temperature climates. WIT Press, Southampton, pp 1–18 Hiley P (2003) Performance of wastewater treatment and nutrient removal wetlands. In: Mander ÜU, Jenssen P (eds) Constructed wetlands for wastewater treatment in cold climates (Reedbeds) in cold temperature climates. WIT Press, Southampton, pp 1–18
Zurück zum Zitat Jin X, Wang S, Pang Y, Zhao H, Zhou X (2005) The adsorption of phosphate on different trophic lake sediments. Colloids Surf 254:241–248CrossRef Jin X, Wang S, Pang Y, Zhao H, Zhou X (2005) The adsorption of phosphate on different trophic lake sediments. Colloids Surf 254:241–248CrossRef
Zurück zum Zitat Jing SR, Lin YF (2004) Seasonal effect on ammonia nitrogen removal by constructed wetlands treating polluted river water in southern Taiwan. Environ Pollut (Barking, Essex : 1987) 127:291–301CrossRef Jing SR, Lin YF (2004) Seasonal effect on ammonia nitrogen removal by constructed wetlands treating polluted river water in southern Taiwan. Environ Pollut (Barking, Essex : 1987) 127:291–301CrossRef
Zurück zum Zitat Kadlec RH, Wallace SD (2009) Treatment wetlands. CRC Press, Boca Raton Kadlec RH, Wallace SD (2009) Treatment wetlands. CRC Press, Boca Raton
Zurück zum Zitat Keffala C, Ghrabi A (2005) Nitrogen and bacterial removal in constructed wetlands treating domestic waste water. Desalination 185:383–389CrossRef Keffala C, Ghrabi A (2005) Nitrogen and bacterial removal in constructed wetlands treating domestic waste water. Desalination 185:383–389CrossRef
Zurück zum Zitat Kim B, Gautier M, Prost-Boucle S, Molle P, Michel P, Gourdon R (2014) Performance evaluation of partially saturated vertical-flow constructed wetland with trickling filter and chemical precipitation for domestic and winery wastewaters treatment. Ecol Eng 71:41–47CrossRef Kim B, Gautier M, Prost-Boucle S, Molle P, Michel P, Gourdon R (2014) Performance evaluation of partially saturated vertical-flow constructed wetland with trickling filter and chemical precipitation for domestic and winery wastewaters treatment. Ecol Eng 71:41–47CrossRef
Zurück zum Zitat Kotti IP, Gikas GD, Tsihrintzis VA (2010) Effect of operational and design parameters on removal efficiency of pilot-scale FWS constructed wetlands and comparison with HSF systems. Ecol Eng 36(7):862–875CrossRef Kotti IP, Gikas GD, Tsihrintzis VA (2010) Effect of operational and design parameters on removal efficiency of pilot-scale FWS constructed wetlands and comparison with HSF systems. Ecol Eng 36(7):862–875CrossRef
Zurück zum Zitat Kuschk P, Wießner A, Kappelmeyer U, Weißbrodt E, Kästner M, Stottmeister U (2003) Annual cycle of nitrogen removal by a pilot-scale subsurface horizontal flow in a constructed wetland under moderate climate. Water Res 37:4236–4242CrossRef Kuschk P, Wießner A, Kappelmeyer U, Weißbrodt E, Kästner M, Stottmeister U (2003) Annual cycle of nitrogen removal by a pilot-scale subsurface horizontal flow in a constructed wetland under moderate climate. Water Res 37:4236–4242CrossRef
Zurück zum Zitat Li C, Wu S, Dong R (2015) Dynamics of organic matter, nitrogen and phosphorus removal and their interactions in a tidal operated constructed wetland. J Environ Manage 151:310–316CrossRef Li C, Wu S, Dong R (2015) Dynamics of organic matter, nitrogen and phosphorus removal and their interactions in a tidal operated constructed wetland. J Environ Manage 151:310–316CrossRef
Zurück zum Zitat Molle P, Liénard A, Grasmick A, Iwema A (2006) Effect of reeds and feeding operations on hydraulic behaviour of vertical flow constructed wetlands under hydraulic overloads. Water Res 40:606–612CrossRef Molle P, Liénard A, Grasmick A, Iwema A (2006) Effect of reeds and feeding operations on hydraulic behaviour of vertical flow constructed wetlands under hydraulic overloads. Water Res 40:606–612CrossRef
Zurück zum Zitat Molle P, Prost-Boucle S, Lienard A (2008) Potential for total nitrogen removal by combining vertical flow and horizontal flow constructed wetlands: a full-scale experiment study. Ecol Eng 34:23–29CrossRef Molle P, Prost-Boucle S, Lienard A (2008) Potential for total nitrogen removal by combining vertical flow and horizontal flow constructed wetlands: a full-scale experiment study. Ecol Eng 34:23–29CrossRef
Zurück zum Zitat Morari F, Giardini L (2009) Municipal wastewater treatment with vertical flow constructed wetlands for irrigation reuse. Ecol Eng 35(5):643–653CrossRef Morari F, Giardini L (2009) Municipal wastewater treatment with vertical flow constructed wetlands for irrigation reuse. Ecol Eng 35(5):643–653CrossRef
Zurück zum Zitat Paing J, Guilbert A, Gagnon V, Chazarenc F (2015) Effect of climate, wastewater composition, loading rates, system age and design on performances of French vertical flow constructed wetlands: a survey based on 169 full scale systems. Ecol Eng 80:46–52CrossRef Paing J, Guilbert A, Gagnon V, Chazarenc F (2015) Effect of climate, wastewater composition, loading rates, system age and design on performances of French vertical flow constructed wetlands: a survey based on 169 full scale systems. Ecol Eng 80:46–52CrossRef
Zurück zum Zitat Prochaska CA, Zouboulis AI (2009) Treatment performance variation at different depths within vertical subsurface-flow experimental wetlands fed with simulated domestic sewage. Desalination 237:367–377CrossRef Prochaska CA, Zouboulis AI (2009) Treatment performance variation at different depths within vertical subsurface-flow experimental wetlands fed with simulated domestic sewage. Desalination 237:367–377CrossRef
Zurück zum Zitat Prochaska CA, Zouboulis AI, Eskridge KM (2007) Performance of pilot-scale vertical-flow constructed wetlands, as affected by season, substrate, hydraulic load and frequency of application of simulated urban sewage. Ecol Eng 31:57–66CrossRef Prochaska CA, Zouboulis AI, Eskridge KM (2007) Performance of pilot-scale vertical-flow constructed wetlands, as affected by season, substrate, hydraulic load and frequency of application of simulated urban sewage. Ecol Eng 31:57–66CrossRef
Zurück zum Zitat Rustige H, Tomac I, Honer G (2003) Investigations on phosphorus retention in subsurface flow constructed wetlands. Water Sci Technol 48(5):67–74 Rustige H, Tomac I, Honer G (2003) Investigations on phosphorus retention in subsurface flow constructed wetlands. Water Sci Technol 48(5):67–74
Zurück zum Zitat Silveira DD, Belli Filho P, Philippi LS, Kim B, Molle P (2015) Influence of partial saturation on total nitrogen removal in a single-stage French constructed wetland treating raw domestic wastewater. Ecol Eng 77:257–264CrossRef Silveira DD, Belli Filho P, Philippi LS, Kim B, Molle P (2015) Influence of partial saturation on total nitrogen removal in a single-stage French constructed wetland treating raw domestic wastewater. Ecol Eng 77:257–264CrossRef
Zurück zum Zitat Stefanakis AI, Tsihrintzis VA (2009) Performance of pilot-scale vertical flow constructed wetlands treating simulated municipal wastewater: effect of various design parameters. Desalination 248:753–770CrossRef Stefanakis AI, Tsihrintzis VA (2009) Performance of pilot-scale vertical flow constructed wetlands treating simulated municipal wastewater: effect of various design parameters. Desalination 248:753–770CrossRef
Zurück zum Zitat Stefanakis AI, Tsihrintzis VA (2012a) Effects of loading, resting period, temperature, porous media, vegetation and aeration on performance of pilot-scale vertical flow constructed wetlands. Chem Eng 181–182:416–430CrossRef Stefanakis AI, Tsihrintzis VA (2012a) Effects of loading, resting period, temperature, porous media, vegetation and aeration on performance of pilot-scale vertical flow constructed wetlands. Chem Eng 181–182:416–430CrossRef
Zurück zum Zitat Stefanakis AI, Tsihrintzis VA (2012b) Use of zeolite and bauxite as filter media treating the effluent of vertical flow constructed wetlands. Microporous Mesoporous Mater 155:106–116CrossRef Stefanakis AI, Tsihrintzis VA (2012b) Use of zeolite and bauxite as filter media treating the effluent of vertical flow constructed wetlands. Microporous Mesoporous Mater 155:106–116CrossRef
Zurück zum Zitat Steinmann CR, Weinhart S, Melzer A (2003) A combined system of lagoon and constructed wetland for an effective wastewater treatment. Water Res 37:2035–2042CrossRef Steinmann CR, Weinhart S, Melzer A (2003) A combined system of lagoon and constructed wetland for an effective wastewater treatment. Water Res 37:2035–2042CrossRef
Zurück zum Zitat Tchobanoglous G, Burton FL, Stensel HD (2003) Wastewater engineering: treatment and Reuse, Metcalf & Eddy, 4th edn. McGraw-Hill, Boston Tchobanoglous G, Burton FL, Stensel HD (2003) Wastewater engineering: treatment and Reuse, Metcalf & Eddy, 4th edn. McGraw-Hill, Boston
Zurück zum Zitat Tsihrintzis VA, Gikas GD (2010) Constructed wetlands for wastewater and activated sludge treatment in north Greece: a review. Water Sci Technol 61(10):2653–2672CrossRef Tsihrintzis VA, Gikas GD (2010) Constructed wetlands for wastewater and activated sludge treatment in north Greece: a review. Water Sci Technol 61(10):2653–2672CrossRef
Zurück zum Zitat Vymazal J (2002) The use of sub-surface constructed wetlands for wastewater treatment in the Czech Republic: 10 years experience. Ecol Eng 18:633–646CrossRef Vymazal J (2002) The use of sub-surface constructed wetlands for wastewater treatment in the Czech Republic: 10 years experience. Ecol Eng 18:633–646CrossRef
Zurück zum Zitat Vymazal J (2007) Removal of nutrients in various types of constructed wetlands. Sci Total Environ 380:48–65CrossRef Vymazal J (2007) Removal of nutrients in various types of constructed wetlands. Sci Total Environ 380:48–65CrossRef
Zurück zum Zitat Wang R, Baldy V, Perissol C, Korboulewsky N (2012) Influence of plants on microbial activity in a vertical-downflow wetland system treating waste activated sludge with high organic matter concentrations. J Environ Manage 95:158–164CrossRef Wang R, Baldy V, Perissol C, Korboulewsky N (2012) Influence of plants on microbial activity in a vertical-downflow wetland system treating waste activated sludge with high organic matter concentrations. J Environ Manage 95:158–164CrossRef
Zurück zum Zitat Wiessner A, Kappelmeyer U, Kuschk P, Kastner M (2005) Influence of the redox condition dynamics on the removal efficiency of a laboratory-scale constructed wetland. Water Res 39:248–256CrossRef Wiessner A, Kappelmeyer U, Kuschk P, Kastner M (2005) Influence of the redox condition dynamics on the removal efficiency of a laboratory-scale constructed wetland. Water Res 39:248–256CrossRef
Zurück zum Zitat Wu H, Fan J, Zhang J, Ngo HH, Guo W, Hu Z, Liang S (2015a) Decentralized domestic wastewater treatment using intermittently aerated vertical flow constructed wetlands: impact of influent strengths. Bioresource Technol 176:163–168CrossRef Wu H, Fan J, Zhang J, Ngo HH, Guo W, Hu Z, Liang S (2015a) Decentralized domestic wastewater treatment using intermittently aerated vertical flow constructed wetlands: impact of influent strengths. Bioresource Technol 176:163–168CrossRef
Zurück zum Zitat Wu H, Zhang J, Ngo HH, Guo W, Hu Z, Liang S, Fan J, Liu H (2015b) A review on the sustainability of constructed wetlands for wastewater treatment: design and operation. Bioresource Technol 175:594–601CrossRef Wu H, Zhang J, Ngo HH, Guo W, Hu Z, Liang S, Fan J, Liu H (2015b) A review on the sustainability of constructed wetlands for wastewater treatment: design and operation. Bioresource Technol 175:594–601CrossRef
Zurück zum Zitat Zhang D-Q, Jinadasa KBSN, Gersberg RM, Liu Y, Tan SK, Ng WJ (2015) Application of constructed wetlands for wastewater treatment in tropical and subtropical regions (2000–2013). J Environ Sci 30:30–46CrossRef Zhang D-Q, Jinadasa KBSN, Gersberg RM, Liu Y, Tan SK, Ng WJ (2015) Application of constructed wetlands for wastewater treatment in tropical and subtropical regions (2000–2013). J Environ Sci 30:30–46CrossRef
Zurück zum Zitat Zhao YQ, Sun G, Lafferty C, Allen SJ (2004) Optimizing the performance of a lab-scale tidal flow reed bed system treating agricultural wastewater. Water Sci Technol 50(8):65–72 Zhao YQ, Sun G, Lafferty C, Allen SJ (2004) Optimizing the performance of a lab-scale tidal flow reed bed system treating agricultural wastewater. Water Sci Technol 50(8):65–72
Zurück zum Zitat Zurita F, De Anda J, Belmont MA (2009) Treatment of domestic wastewater and production of commercial flowers in vertical and horizontal subsurface-flow constructed wetlands. Ecol Eng 35(5):861–869CrossRef Zurita F, De Anda J, Belmont MA (2009) Treatment of domestic wastewater and production of commercial flowers in vertical and horizontal subsurface-flow constructed wetlands. Ecol Eng 35(5):861–869CrossRef
Metadaten
Titel
Effect of Operational and Design Parameters on Performance of Pilot-Scale Vertical Flow Constructed Wetlands Treating University Campus Wastewater
verfasst von
Vassiliki Papaevangelou
Georgios D. Gikas
Vassilios A. Tsihrintzis
Publikationsdatum
31.08.2016
Verlag
Springer Netherlands
Erschienen in
Water Resources Management / Ausgabe 15/2016
Print ISSN: 0920-4741
Elektronische ISSN: 1573-1650
DOI
https://doi.org/10.1007/s11269-016-1484-6

Weitere Artikel der Ausgabe 15/2016

Water Resources Management 15/2016 Zur Ausgabe