The ammonia removal cycle
for a submerged biofilter used in a recirculating eel culture system
Kuo-Feng Tseng, Kuo-Lin Wu-2004
Aquacultural Engineering, 31(1-2): 17-30
Abstract:
Ammonia removal by a submerged biofilter varied in a
cyclic manner with the growth and detachment of biofilm on the medium.
Maintaining an active biofilm in a biofilter is required and is usually
achieved by backwashing. In order to predict the time to be washed a
laboratory scale system was designed and constructed to investigate the
effects of operating parameters—temperature, ammonia and suspended solids
concentrations—on the performance of biofilters. The results indicated
that the ammonia removal rate per unit surface area of medium (specific
ammonia removal rate, SNR) increased initially at the start of the
operation, until it reached a maximum value. It maintained this maximum
removal rate over a period, and then decreased sharply thereafter. The
experimental results were used to develop a series of equations describing
the relationship between ammonia removals and operating conditions (initial
ammonia removal rate, temperature, concentrations of ammonia and suspended
solids in influent). These equations were used to predict the biofilter
performance in a commercial recirculating eel culture system. The observed
values were within the 90% confidence interval of the model. Thus, the model
allows a filter designer to select a backwash frequency that will maintain a
stable water quality in recirculating aquaculture systems.
(Department of Aquaculture, National Taiwan Ocean
University, Keelung 202, Taiwan, e-mail: kftseng@mail.ntou.edu.tw)