Effect of short-term storage temperature on denitrification performance of bioflocs
To explore the effect of storage temperature on the denitrification performance of bioflocs,the bioflocs in Litopenaeus vannamei culture ponds were collected and sealed at room temperature 25 ℃(T25 group),low temperature 4 ℃(T4 group),freezing-20℃(T-20 group)and ultra-low temperature freezing-80℃(T-80 group)for 28 days.The removal rate of nitrate nitrogen by the initial collected bioflocs was 0.71±0.03 mg/(L·h).During the initial 7 days of storage,only the T-80 group exhibited a decrease in the bioflocs'denitrification rate.After 14 days of storage,the denitrification performance of the bioflocs in the T4 group remained stable.On the 28th day,the removal rate of nitrate nitrogen by T4 group was 0.72±0.01 mg/(L·h),which was significantly higher than that of T25 group(0.52±0.02 mg/(L·h)),T-20 group(0.57±0.03 mg/(L·h))and T-80 group(0.52±0.02 mg/(L·h)).Microstructure observation showed that there was no significant change in T4 group and T25 group on the 7th day of biofloc preservation compared with the initial,and the proportion of dead cells increased slowly.On the 28 th day,the bioflocs in the T4 group were slightly deteriorated,and the proportion of dead cells was low.The bioflocs in other groups were severely deteriorated and the proportion of dead cells was high.In summary,4 ℃ is the suitable temperature for short-term preservation of denitrification performance of bioflocs.
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