Research Of Ammonia Nitrogen Removal From Fish Breeding Water By Membrane Oxygenators (Artificial Lung)

Membrane Oxygenator is usually used to add O₂ and remove CO₂ from blood during heart surgery operation. The present paper deals with a new application of membrane oxygenator-to remove ammonia nitrogen from fish breeding water, which is also a new method for molecular ammonia removal from the water.Firstly, the efficiency of ammonia removal was studied experimentally. Three stripping methods-O2 stripping, vacuum extracting, acid absorbing-Were used for comparison. Effects of a few factors, such as pH, initial ammonia concentration, feed flow rate, temperature and different stripping conditions, on the ammonia nitrogen removal were investigated. The results showed that for a single stripping method, ammonia removal rate was usually enhanced by higher pH, initial ammonia concentration, temperature or proper flow rate; for the three stripping methods, acid stripping was the most effective, which is suggested to treat ammonia polluted fish breeding water in emergency, and as vacuum extracting was less effective but more expensive, it can be used only in laboratory, and although O2 sweeping isn't aseffective as the other two, it is somewhat superior in that ammonia removal can be coupled with Oa enrichment in the same oxygenator.Secondly, ammonia mass transfer was studied theoretically. At first, a theoretical model for ammonia mass transfer coefficients was made and examined by experimental data. This model is helpful in optimizing structure of membrane oxygentor and operating conditions. Then a semi-empirical model for ammonia mass transfer rate was built, which helped with predicting membrane size or circulating time in dealing with a fish breeding water.