Agata Zarebska

29 Aug 2012

Agata Zarebska is a PhD fellow in the Department of Chemical Engineering, Biotechnology and Environmental Technology at the University Of Southern Of Denmark. She has received her Master of Science Degree in Chemical Engineering from Silesian University of Technology in specialization Green Process Technologies. During her graduate studies, she had opportunity to spend a half year visiting the faculty of Engineering at the University of Southern Denmark. Prior to joining SDU, she spent three months as trainee in Renew Energy Company in Svendborg in Denmark working with biogas and nine months as research fellow at the Lulea University in Sweden working with biofuels.  Agata's main research interests lie with sustainable and environmentally friendly technologies and renewable energies. Her thesis focuses on optimization membrane separation process that can produce ammonium fertilizer and reusable water from the liquid part animal wastes. Main challenge to the performance of membrane contactor process is fouling on the membrane surface, which is going to be her topic during NYM14 conference.

Abstract


The application of membrane contactors for ammonia recovery from raw and digested manure

Anaerobic digestion and solid-liquid separation of animal wastes are a viable technology for waste management to reduce transport cost and environmental hazards in areas with increased livestock production (1). However, post processing of manure is necessary due to significant amount of nitrogen and phosphorus, which even though they are essential nutrients also pose potential risk of over fertilizing fields leading to contamination of water streams and air (1).  Liquid-liquid membrane contactors (MC) present a possible technology for ammonia recovery. In general one of the main obstacles though impeding the implementation of membrane contactors is membrane fouling (2). This must also be expected to be the case for the recovery and concentration of ammonia from swine manure. The presence of organic matter and multivalent ions in pig slurry may greatly influence the membrane fouling due to surface adsorption and pore plugging (3). The aim of this work is to add knowledge on how the overall mass transfer coefficient of ammonia (km) is affected by different solid-liquid separation techniques of pig slurry at different temperatures (30ºC, and 50ºC) and feed flow velocity (0.9 m/s and 1.8 m/s). Further a comparison on how digestion of manure influences membrane fouling at 40ºC and a feed velocity of 0.9 m/s is conducted. Ammonia stripping of the liquid fraction of both digested and undigested manure was performed using tubular polypropylene (PP) membranes. Intensity, morphology and composition of fouling layers have been determined using Scanning Electron Microscopy and Fourier Transform Infrared Spectrometry (ATR-FTIR). Based on the experimental results, it can be concluded that mass transfer of ammonia from the liquid fraction is neither influenced by solid-liquid separation nor by anaerobic digestion. For digested manure the overall mass transfer coefficient km was equal to 19±1∙10-3 m/h and for undigested km was found to be 18.9±0.9∙10-3 m/h at 40ºC, and flow velocity of 0.9 m/s. Further, investigations show that increasing the temperature from 30ºC to 50ºC doubled the overall mass transfer coefficient of ammonia, while increasing feed flow velocity had negligible effect on the overall mass transfer coefficient of ammonia. No significant difference was found between undigested manure effluents with different dry matter content but similar particle size distribution, meaning that pre-processing of manure has little influence on the mass transfer coefficient of ammonia as long as the particle size is unchanged. Membrane fouling in case of digested and undigested pig slurry was a combination of organic fouling, biofouling and colloidal fouling. SEM observations revealed presence of bacteria suggesting biofouling, while the obtained ATR-FTIR spectra are characteristic for proteins and carbohydrates deposit.

References

1.            Zeng, L.; Mangan, C.; Li, X. Ammonia recovery from anaerobically digested cattle manure by steam stripping. Water Science and Technology 2006, 54 (8), 137-145.

2.            Gryta, M. Fouling in direct contact membrane distillation process. Journal of Membrane Science 2008, 325 (1), 383-394.

3.            Ko, M. K.; Pellegrino, J. J.; Nassimbene, R.; Marko, P. Characterization of the Adsorption-Fouling Layer Using Globular-Proteins on Ultrafiltration Membranes. Journal of Membrane Science 1993, 76 (2-3), 101-120.