COMPARATIVE STUDY OF NITROGEN BIOREMOVAL FROM AQUACULTURE WASTEWATER USING BIOFLOCS TECHNIQUE (BFT) VERSUS BIOFILTRATION SYSTEM

Laboratory experiment aimed to comparison between treatment of fish wastewater using biofloc technology (BFT) and biofilter system to re-use water and reduce its change periods. Ammonium concentration increased from 0.51 mg/l at beginning of experiment to 0.54 mg/l and decreased to 0.25 mg/l and is fixed at 0.49 mg/l for biofilter samples. While, these concentrations ware 0.62- 0.87-0.12-0.27 mg/l for biofloc treatment samples. Ammonium reduction ratio of biofilter was 32% versus 17.33% for biofloc technique at beginning of experiment then it still increasing and reached to 42 % for biofilter against 7.45% of biofloc technique. Unexpected decrease in the ammonium reduction ratio for biofilter system by 21.87 and 15.52% versus 62.50 and 53.45% correspondingly for biofloc. These results were referred to biofiltration process adaptation and lack of uniformity of bioflocs throughout whole water tank. Results of measured ammonium concentrations show superiority of the use of biofloc technique over biofilter system. The decline in nitrite reduction ratio for biofilter of 63.16% at the second week of the start of experiment happened and then there was a slight increase in nitrite reduction ratio 63.49% to be settled on the 65% reduction ratio value. This was referred to biofilter clogging and biomass accumulation. Biofloc technique demonstrated an excessive superiority (93.02%) in nitrite reduction ratio at beginning of the experiment over biofilter system (70.54%). Two systems had similar behavior of nitrite reduction ratio throughout the rest of experiment. Finally, use of BFT systems to freshwater tilapia aquaculture benefits both the reduction in ammonium and nitrite concentrations and can be effective in improvement fish production.