Purify effect of drawer-type biofilter

In contrast to submerged fixed bed biofilter, purifying effect of a drawer filter used in recirculating aquaculture system and effect of oxygen content on removal rates of TAN, NO2-N, COD, heterotrophic bacteria and vibrio were studied. The results showed that removal rates of TAN, NO2-N, COD, heterotrophic bacteria and vibrio of unit volume drawer filter were significantly higher than those of submerged fixed bed biofilter, which was 2.68, 7.37, 3.33, 24.87, 46.67 times higher than that of submerged fixed bed biofilter, respectively. The removal rates of TAN, NO2-N, COD, heterotrophic bacteria of unit volume filter material in high oxygen content condition were significantly higher than those in low oxygen content condition, but the removal rates of vibrio was lower than those in the low oxygen content condition; meanwhile the contents of TAN, NO2-N, COD, vibrio bacteria in high oxygen content condition were lower than that in low oxygen content condition. The fish grew well and the concentrations of TAN, NO2-N, COD were lower in the highest breed density. The survive rate of fish exceeded 98%. So, the drawer biofilter is a kind of biofilter with easy wash, small volume, high purifying efficiency. High oxygen content can increase fish growth rate and biofilter purifying rate, and can bate vibrio growth.