Investigation of effective factors on the ammonia removal efficiency in the wastewater treatment plants using the air stripping process
Subject Areas :
Environment Pullotion (water and wastewater)
Arezoo Zangeneh
1
,
Sima Sabzalipour
2
,
Afshin Takdastan
3
,
Reza Jalilzadeh Yengejeh
4
,
Morteza Abullatif Khafaie
5
1 - PhD Candidate, Department of Environmental Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran.
2 - Assistant Professor, Department of Environmental Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran. *(Corresponding Author)
3 - Professor, Environmental Technologies Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
4 - Associate Professor, Department of Environmental Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran.
5 - Associate Professor, Environmental Technologies Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran.
Received: 2020-12-04
Accepted : 2020-12-26
Published : 2022-10-23
Keywords:
Municipal wastewater,
Ammonia,
Air stripping process,
Abstract :
Background and Objective: Removal of ammonia from wastewater in the treatment plants due to its dangerous and toxic effects on human health and biotic resources is essential. This study was aimed to investigate the effective operational parameters on the efficiency of the air stripping process, determine their priority and degree of effect on ammonia removal and compare the ammonia removal efficiency during the air stripping process in the municipal wastetewater treatment plants using synthetic and real wastewater.
Material and Methodology: In this study, the effect of each operating parameter on the ammonia removal efficiency including initial ammonia concentration, pH and temperature during the air stripping process for synthetic and real wastewater, respectively, based on standard methods (the Nesslerization method, preparation of standard solutions) using a spectrophotometer, pH meter and temperature module were evaluated.
Findings: The results of this study showed that the maximum of ARE for synthetic wastewater with Air to water ratio 80 and an initial ammonia concentration of 59. 6 mg /l, pH 12.05 and temperature 46.3°C was %91. Also, the results of the study on the ARE during the air stripping process showed that the maximum of ARE (%91) for real wastewater (primary sedimentation tank effluent (PST)) with Air to water ratio 80 and an initial ammonia concentration of 61.04 mg/l, pH 12.53 and temperature 45.9 ° C was obtained.
Discussion and Conclusion: Based on the results of univariate regression model, initial ammonia concentration˃ temperature˃ pH have the greatest effect on the ammonia removal efficiency in synthetic wastewater and real wastewater, respectively. In the multivariate regression model, the effect of temperature and pH on the ammonia removal efficiency in synthetic and real wastewater is increasing and decreasing, respectively. Based on the findings of this study, the air stripping process can be successfully used to remove ammonia from wastewater in the municipal treatment plants, especially in the tropics.
References:
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Deng, Q. (2014). Ammonia Removal and Recovery from Wastewater Using Natural Zeolite: An Integrated System for Regeneration by Air Stripping Followed Ion Exchange. (Dissertation), University of Waterloo Ontario, Canada.
Roch, N. (2015). Analysis of Ammonia removal from wastewater market: Feasibility of saltworks introduction new technology. (Dissertation), Simon Fraser University.
EPA. (2013). Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater Office of Water. Washington DC, US-EPA.
Wang, L., Hung, Y., & Shammas, N. (2006). Air Stripping Handbook of Environmental Engineering, Advanced Physicochemical Treatment Processes.Vol. 4, pp. 47–77.
EPA. (2015). Office of Water. Washington DC, US-EPA. http://water.epa.gov/polwaste/npdes/stormwater/upload/msgp2015_part8.pdf.
Jeong, H., Park, J., & Kim, H. (2013). Determination of NH4+ in Environmental Water with Interfering Substances Using the Modified Nessler Method Journal of Chemistry. doi:http://dx.doi.org/10.1155/2013/359217.
Sewage discharge standards by the Environmental Protection Organization of Iran, according to the Regulation on Prevention of Water Pollution.
Capodaglio, A. G., Hlavínek, P., & Raboni, M. (2015). Physico-chemical technologies for nitrogen removal from wastewaters: a review. Revista Ambiente & Agua, 10(3), 481–498.
Gupta, V., Sadegh, H., Yari, M., Shahryari-Ghoshekandi, R., Maazinejad, B., & Chahardori, M. (2015). Removal of ammonium ions from wastewater A short review in development of efficient methods. Global J. Environ. Sci. Manage, 1(2), 149-158. https://doi.org/110.7508/gjesm.2015.7502.7007.
Xie, Z., Duong, T., Hoang, M., Nguyen, C., & Bolto, B. (2009). Ammonia removal by sweep gas membrane distillation. Water Res, 43, 1693-1699.
Hasan, H. A., Abdullah, S. R. S., Kamarudin, S. K., & Kofli, N. T. (2011). Problems of ammonia and manganese in Malaysian drinking water treatments. World Appl. Sci. J., 12, 1890–1896.
Yuan, M. H., Chen, Y. H., Tsai, J. Y., & Chang, C. Y. (2016). Ammonia removal from ammonia-rich wastewater by air stripping using a rotating packed bed. Process Safety and Environment Protection. doi:http://dx.doi.org/10.1016/j.psep.2016.06.021
El-Gohary, F. A., Khater, M., & Kamel, G. M. (2013). Pretreatment of Landfill Leachate by Ammonia Stripping. Journal of Applied Sciences Research, 9(6), 3905–39
Zhu, L., Dong, D., Hua, X., Xu, Y., Guo, Z., & Liang, D. (2017). Ammonia nitrogen removal and recovery from acetylene purification wastewater by air stripping. Water Science and Technology, 75(11), 2538-2545.
Hasanoglu, A., Romero, J., Perez, B., & Plaza, A. (2010). Ammonia removal from wastewater streams through membrane contactors: Experimental and theoretical analysis of operation parameters and configuration. Chem. Eng. J., 160, 530–537.
Kartohardjono, S., Damaiati, G. M., & Rama, C. T. (2015). Effects of Absorbents on Ammonia Removal from Wastewater Through Hollow Fiber Membrane Contactor. Journal of Environmental Science and Technology 8(5), 225–231. doi:10.3923/jest.225.231.
Kinidi, L., Wei Tan, I., Abdul Wahab, N., Bin Tamrin, K., Hipolito, C., & Salleh, S. F. (2018). Recent Development in Ammonia Stripping Process for Industrial Wastewater Treatment. Hindawi International Journal of Chemical Engineering, 1-14. doi:https://doi.org/10.1155/2018/3181087.
Zhang, F., Li, X., Wang, Z., Jiang, H., Ren, S., & Peng, Y. (2020). Simultaneous Ammonium oxidation denitrifying (SAD) in an innovative three-stage process for energy-efficient mature landfill leachate treatment with external sludge reduction. Water research, 169, 115156.
Campos, J. C., Moura, D., Costa, A. P., Yokoyama, L., Araujo, F. V., Cammarota, M. C., & Cardillo, L. (2013). Evaluation of pH, alkalinity and temperature during air stripping process for ammonia removal from landfill leachate. Journal of Environmental Science and Health, Part A, 48(9), 1105-1113. http://dx.doi.org/1110.1080/10934529.10932013.10774658
Viotti, P., & Gavasci, R. (2015). Scaling of ammonia stripping towers in the treatment of groundwater polluted by municipal solid waste landfill leachate: study of the causes of scaling and its effects on stripping performance. Revista Ambiente & Agua, 10(2), 240-252. doi:10.4136/ambi-agua.1567
Smaoui, Y., Bouzid, J., & Sayadi, S. (2020). Combination of air stripping and biological processes for landfill leachate treatment.
Dos Santos, H. A. P., de Castilhos Júnior, A. B., Nadaleti, W. C., & Lourenço, V. A. (2020). Ammonia recovery from air stripping process applied to landfill leachate treatment. Environmental Science and Pollution Research, 1-13.
Jurczyk, Ł., Koc-Jurczyk, J., & Masłoń, A. (2020). Simultaneous Stripping of Ammonia from Leachate: Experimental Insights and Key Microbial Players. Water, 12(9), 2494.
Folino, A., Calabrò, P. S., & Zema, D. A. (2020). Effects of Ammonia Stripping and Other Physico-Chemical Pretreatments on Anaerobic Digestion of Swine Wastewater. Energies, 13(13), 3413.
Georgiou, D., Liliopoulos, V., & Aivasidis, A. (2020). Upgrading of biogas by utilizing aqueous ammonia and the alkaline effluent from air-stripping of anaerobically digested animal manure. Application on the design of a semi-industrial plant unit. Journal of Water Process Engineering, 36, 101318.
Ulu, F., & Kobya, M. (2020). Ammonia removal from wastewater by air stripping and recovery struvite and calcium sulphate precipitations from anesthetic gases manufacturing wastewater. Journal of Water Process Engineering, 38, 101641.
Guo, J., Abbas, A., Chen, Y., Liu, Z., Fang, F., & Chen, P. (2010). Treatment of landfill leachate using a combined stripping, Fenton, SBR, and coagulation process. Journal of hazardous materials, 178, 699–705.
Bui H.H, Nguyen L.H, Nguyen X.T. (2020) Removal of ammonia from anaerobic co-digestion effluent of organic fraction of food waste and domestic wastewater using air stripping process. Vietnam Journal of Science, Technology and Engineering. 24;62(2):19-23.
Melgaço LA, Meers E, Mota CR. (2020) Ammonia recovery from food waste digestate using solar heat-assisted stripping-absorption. Waste Management. 15; 113:244-50.
Hanira NM, Hasfalina CM, Rashid M, Luqman CA, Abdullah AM, editors. Effect of dilution and operating parameters on ammonia removal from scheduled waste landfill leachate in a lab-scale ammonia stripping reactor. IOP Conference Series: Materials Science and Engineering; 2016.
Sengupta, S., Nawaz, T., & Beaudry, J. (2015). Nitrogen and phosphorus recovery from wastewater. Current Pollution Reports, 1.(3), 155-166. https://doi.org/110.1007/s40726-40015-40013-40721.
Alam, R., & Hossain, M. (2009). Effect of packing materials and other parameters on the air stripping process for the removal of ammonia from the wastewater of natural gas fertilizer factory. Journal of Water Resources and Protection, 3, 210-215.
Blauvelt, A. (2009). Removal of Ammonia from Landfill Leachate Worchester. (Dissertation), Worcester MA, United States
Association, A. P. H. (2017). Standard methods for the examination of water and wastewater: American Public Health Association. 23rd Edition.
Jafari, M. J., Omidi, L., Rezazadeh Azari, M., Massoudi Nejad, M. R., & Namdari, M. (2014). Raschig Rings Versus PVC as a Packed Tower Media in Scrubbing Ammonia from Air. Iranica Journal of Energy & Environment, 5(3), 270–276. doi: 10.5829/idosi.ijee.2014.05.03.06.
Taşdemir, A., Cengiz, İ., Yildiz, E., & Bayhan, Y. K. (2020). Investigation of ammonia stripping with a hydrodynamic cavitation reactor. Ultrasonics sonochemistry, 60, 104741.
Jenkins, D., McCallum, D., Ruzbacky, R., Saunders, S., & Brent, A. (2007). Air stripping of ammonia and methanol in a bubble‐cap column. Environmental progress, 26(4), 365-374.
Cotman, M., & Gotvajn, A. (2010). Comparison of different physico-chemical methods for the removal of toxicants from landfill leachate. Journal of hazardous materials, 178, 298 –305.
Hossini, H., Rezaee, A., Ayati, B., & Mahvi, A. H. (2016). Off-gas treatment of ammonia using a diffused air stripper: A kinetic study. Health Scope, 5(1).
Li, W., Shi, X., Zhang, S., & Qi, G. (2020). Modelling of ammonia recovery from wastewater by air stripping in rotating packed beds. Science of The Total Environment, 702, 134971.
Tao, W., & Ukwuani, A. T. (2015). Coupling thermal stripping and acid absorption for ammonia recovery from dairy manure: Ammonia volatilization kinetics and effects of temperature, pH and dissolved solids content. Chemical Engineering Journal, 280, 188-196.
Quan X, Wang F, Zhao Q, Zhao T, & J., X. (2009). Air stripping of ammonia in a water-sparged aerocyclone reactor. J Hazard Mater., 170(2), 983–988.
Bonmati, A., & Flotats, X. (2003). Air Stripping of Ammonia from Pig Slurry: Characterisation and Feasibility as a Pre- or Post-treatment to Mesophilic Anaerobis Digestion. Waste Management, 23(1), 261-272.
Norddahl B, Christensen KV, Horn V, Larsson M, & A, d. J. (2006). membrane contactor for ammonia stripping, pilot scale experience
Liehr, S., Classen, J., Humenik, F., Baird, C., & Rice, M. (2006). Ammonia Recovery from Swine Belt Separated Liquid. Paper presented at the 2006 ASAE Annual Meeting.
Ding, Z., Liu, L., Li, Z., Ma, R., & Yang, Z. (2006). Experimental study of ammonia removal from water by membrane distillation (MD): The comparison of three configurations. Journal of membrane Science, 286(1-2), 93-103. doi:https://doi.org/10.1016/j.memsci.2006.09.015
Mohammed-Nour, A., Al-Sewailem, M., & El-Naggar, A. H. (2019). The Influence of Alkalization and Temperature on Ammonia Recovery from Cow Manure and the Chemical Properties of the Effluents. Sustainability, 11(8), 2441.
Guˇstin, S., & Marinˇsek-Logar, R. (2011). Effect of pH, temperature and air flow rate on the continuous ammonia stripping of the anaerobi digestion effluent. Proc. Saf. Environ. Protect, 89(1), 61–66.
_||_
1.Urbini, G., Gavasci, R., & Viotti, P. (2015). Oxygen control and improved denitrification efficiency by means of a post-anoxic reactor. Sustainability, 7(2), 1201-1212.
Deng, Q. (2014). Ammonia Removal and Recovery from Wastewater Using Natural Zeolite: An Integrated System for Regeneration by Air Stripping Followed Ion Exchange. (Dissertation), University of Waterloo Ontario, Canada.
Roch, N. (2015). Analysis of Ammonia removal from wastewater market: Feasibility of saltworks introduction new technology. (Dissertation), Simon Fraser University.
EPA. (2013). Aquatic Life Ambient Water Quality Criteria for Ammonia - Freshwater Office of Water. Washington DC, US-EPA.
Wang, L., Hung, Y., & Shammas, N. (2006). Air Stripping Handbook of Environmental Engineering, Advanced Physicochemical Treatment Processes.Vol. 4, pp. 47–77.
EPA. (2015). Office of Water. Washington DC, US-EPA. http://water.epa.gov/polwaste/npdes/stormwater/upload/msgp2015_part8.pdf.
Jeong, H., Park, J., & Kim, H. (2013). Determination of NH4+ in Environmental Water with Interfering Substances Using the Modified Nessler Method Journal of Chemistry. doi:http://dx.doi.org/10.1155/2013/359217.
Sewage discharge standards by the Environmental Protection Organization of Iran, according to the Regulation on Prevention of Water Pollution.
Capodaglio, A. G., Hlavínek, P., & Raboni, M. (2015). Physico-chemical technologies for nitrogen removal from wastewaters: a review. Revista Ambiente & Agua, 10(3), 481–498.
Gupta, V., Sadegh, H., Yari, M., Shahryari-Ghoshekandi, R., Maazinejad, B., & Chahardori, M. (2015). Removal of ammonium ions from wastewater A short review in development of efficient methods. Global J. Environ. Sci. Manage, 1(2), 149-158. https://doi.org/110.7508/gjesm.2015.7502.7007.
Xie, Z., Duong, T., Hoang, M., Nguyen, C., & Bolto, B. (2009). Ammonia removal by sweep gas membrane distillation. Water Res, 43, 1693-1699.
Hasan, H. A., Abdullah, S. R. S., Kamarudin, S. K., & Kofli, N. T. (2011). Problems of ammonia and manganese in Malaysian drinking water treatments. World Appl. Sci. J., 12, 1890–1896.
Yuan, M. H., Chen, Y. H., Tsai, J. Y., & Chang, C. Y. (2016). Ammonia removal from ammonia-rich wastewater by air stripping using a rotating packed bed. Process Safety and Environment Protection. doi:http://dx.doi.org/10.1016/j.psep.2016.06.021
El-Gohary, F. A., Khater, M., & Kamel, G. M. (2013). Pretreatment of Landfill Leachate by Ammonia Stripping. Journal of Applied Sciences Research, 9(6), 3905–39
Zhu, L., Dong, D., Hua, X., Xu, Y., Guo, Z., & Liang, D. (2017). Ammonia nitrogen removal and recovery from acetylene purification wastewater by air stripping. Water Science and Technology, 75(11), 2538-2545.
Hasanoglu, A., Romero, J., Perez, B., & Plaza, A. (2010). Ammonia removal from wastewater streams through membrane contactors: Experimental and theoretical analysis of operation parameters and configuration. Chem. Eng. J., 160, 530–537.
Kartohardjono, S., Damaiati, G. M., & Rama, C. T. (2015). Effects of Absorbents on Ammonia Removal from Wastewater Through Hollow Fiber Membrane Contactor. Journal of Environmental Science and Technology 8(5), 225–231. doi:10.3923/jest.225.231.
Kinidi, L., Wei Tan, I., Abdul Wahab, N., Bin Tamrin, K., Hipolito, C., & Salleh, S. F. (2018). Recent Development in Ammonia Stripping Process for Industrial Wastewater Treatment. Hindawi International Journal of Chemical Engineering, 1-14. doi:https://doi.org/10.1155/2018/3181087.
Zhang, F., Li, X., Wang, Z., Jiang, H., Ren, S., & Peng, Y. (2020). Simultaneous Ammonium oxidation denitrifying (SAD) in an innovative three-stage process for energy-efficient mature landfill leachate treatment with external sludge reduction. Water research, 169, 115156.
Campos, J. C., Moura, D., Costa, A. P., Yokoyama, L., Araujo, F. V., Cammarota, M. C., & Cardillo, L. (2013). Evaluation of pH, alkalinity and temperature during air stripping process for ammonia removal from landfill leachate. Journal of Environmental Science and Health, Part A, 48(9), 1105-1113. http://dx.doi.org/1110.1080/10934529.10932013.10774658
Viotti, P., & Gavasci, R. (2015). Scaling of ammonia stripping towers in the treatment of groundwater polluted by municipal solid waste landfill leachate: study of the causes of scaling and its effects on stripping performance. Revista Ambiente & Agua, 10(2), 240-252. doi:10.4136/ambi-agua.1567
Smaoui, Y., Bouzid, J., & Sayadi, S. (2020). Combination of air stripping and biological processes for landfill leachate treatment.
Dos Santos, H. A. P., de Castilhos Júnior, A. B., Nadaleti, W. C., & Lourenço, V. A. (2020). Ammonia recovery from air stripping process applied to landfill leachate treatment. Environmental Science and Pollution Research, 1-13.
Jurczyk, Ł., Koc-Jurczyk, J., & Masłoń, A. (2020). Simultaneous Stripping of Ammonia from Leachate: Experimental Insights and Key Microbial Players. Water, 12(9), 2494.
Folino, A., Calabrò, P. S., & Zema, D. A. (2020). Effects of Ammonia Stripping and Other Physico-Chemical Pretreatments on Anaerobic Digestion of Swine Wastewater. Energies, 13(13), 3413.
Georgiou, D., Liliopoulos, V., & Aivasidis, A. (2020). Upgrading of biogas by utilizing aqueous ammonia and the alkaline effluent from air-stripping of anaerobically digested animal manure. Application on the design of a semi-industrial plant unit. Journal of Water Process Engineering, 36, 101318.
Ulu, F., & Kobya, M. (2020). Ammonia removal from wastewater by air stripping and recovery struvite and calcium sulphate precipitations from anesthetic gases manufacturing wastewater. Journal of Water Process Engineering, 38, 101641.
Guo, J., Abbas, A., Chen, Y., Liu, Z., Fang, F., & Chen, P. (2010). Treatment of landfill leachate using a combined stripping, Fenton, SBR, and coagulation process. Journal of hazardous materials, 178, 699–705.
Bui H.H, Nguyen L.H, Nguyen X.T. (2020) Removal of ammonia from anaerobic co-digestion effluent of organic fraction of food waste and domestic wastewater using air stripping process. Vietnam Journal of Science, Technology and Engineering. 24;62(2):19-23.
Melgaço LA, Meers E, Mota CR. (2020) Ammonia recovery from food waste digestate using solar heat-assisted stripping-absorption. Waste Management. 15; 113:244-50.
Hanira NM, Hasfalina CM, Rashid M, Luqman CA, Abdullah AM, editors. Effect of dilution and operating parameters on ammonia removal from scheduled waste landfill leachate in a lab-scale ammonia stripping reactor. IOP Conference Series: Materials Science and Engineering; 2016.
Sengupta, S., Nawaz, T., & Beaudry, J. (2015). Nitrogen and phosphorus recovery from wastewater. Current Pollution Reports, 1.(3), 155-166. https://doi.org/110.1007/s40726-40015-40013-40721.
Alam, R., & Hossain, M. (2009). Effect of packing materials and other parameters on the air stripping process for the removal of ammonia from the wastewater of natural gas fertilizer factory. Journal of Water Resources and Protection, 3, 210-215.
Blauvelt, A. (2009). Removal of Ammonia from Landfill Leachate Worchester. (Dissertation), Worcester MA, United States
Association, A. P. H. (2017). Standard methods for the examination of water and wastewater: American Public Health Association. 23rd Edition.
Jafari, M. J., Omidi, L., Rezazadeh Azari, M., Massoudi Nejad, M. R., & Namdari, M. (2014). Raschig Rings Versus PVC as a Packed Tower Media in Scrubbing Ammonia from Air. Iranica Journal of Energy & Environment, 5(3), 270–276. doi: 10.5829/idosi.ijee.2014.05.03.06.
Taşdemir, A., Cengiz, İ., Yildiz, E., & Bayhan, Y. K. (2020). Investigation of ammonia stripping with a hydrodynamic cavitation reactor. Ultrasonics sonochemistry, 60, 104741.
Jenkins, D., McCallum, D., Ruzbacky, R., Saunders, S., & Brent, A. (2007). Air stripping of ammonia and methanol in a bubble‐cap column. Environmental progress, 26(4), 365-374.
Cotman, M., & Gotvajn, A. (2010). Comparison of different physico-chemical methods for the removal of toxicants from landfill leachate. Journal of hazardous materials, 178, 298 –305.
Hossini, H., Rezaee, A., Ayati, B., & Mahvi, A. H. (2016). Off-gas treatment of ammonia using a diffused air stripper: A kinetic study. Health Scope, 5(1).
Li, W., Shi, X., Zhang, S., & Qi, G. (2020). Modelling of ammonia recovery from wastewater by air stripping in rotating packed beds. Science of The Total Environment, 702, 134971.
Tao, W., & Ukwuani, A. T. (2015). Coupling thermal stripping and acid absorption for ammonia recovery from dairy manure: Ammonia volatilization kinetics and effects of temperature, pH and dissolved solids content. Chemical Engineering Journal, 280, 188-196.
Quan X, Wang F, Zhao Q, Zhao T, & J., X. (2009). Air stripping of ammonia in a water-sparged aerocyclone reactor. J Hazard Mater., 170(2), 983–988.
Bonmati, A., & Flotats, X. (2003). Air Stripping of Ammonia from Pig Slurry: Characterisation and Feasibility as a Pre- or Post-treatment to Mesophilic Anaerobis Digestion. Waste Management, 23(1), 261-272.
Norddahl B, Christensen KV, Horn V, Larsson M, & A, d. J. (2006). membrane contactor for ammonia stripping, pilot scale experience
Liehr, S., Classen, J., Humenik, F., Baird, C., & Rice, M. (2006). Ammonia Recovery from Swine Belt Separated Liquid. Paper presented at the 2006 ASAE Annual Meeting.
Ding, Z., Liu, L., Li, Z., Ma, R., & Yang, Z. (2006). Experimental study of ammonia removal from water by membrane distillation (MD): The comparison of three configurations. Journal of membrane Science, 286(1-2), 93-103. doi:https://doi.org/10.1016/j.memsci.2006.09.015
Mohammed-Nour, A., Al-Sewailem, M., & El-Naggar, A. H. (2019). The Influence of Alkalization and Temperature on Ammonia Recovery from Cow Manure and the Chemical Properties of the Effluents. Sustainability, 11(8), 2441.
Guˇstin, S., & Marinˇsek-Logar, R. (2011). Effect of pH, temperature and air flow rate on the continuous ammonia stripping of the anaerobi digestion effluent. Proc. Saf. Environ. Protect, 89(1), 61–66.
