Core-shell bioactive capsule for aquaculture wastewater denitrification

The lack of denitrifying bacteria and organic carbon sources, and the inhibition of dissolved oxygen (DO) result in nitrate accumulation in aquaculture wastewater. In order to solve this problem, an encapsulation method was introduced to prepare a novel bioactive capsule, which can provide organic carbon source, denitrifying bacteria, and anoxic microenvironment for aquaculture wastewater denitrification. And can reduce the recovery time of the enclosed denitrifying bacteria. The morphology of the capsule, its nitrate removal rate, and nitrogen conversion pathway in synthetic aquaculture wastewater were investigated. The capsule had a porous surface and the pore diameter ranged from 150.0 nm to 300.0 nm. The enclosed denitrifying bacteria had a reduced recovery time and excellent denitrification performance. The nitrate removal rate reached 86.2 % on the first day and was maintained at 99.7 %. Nitrogen conversion pathways in the capsule include denitrification, assimilatory/dissimilatory nitrate reduction, and nitrogen fixation. The denitrifying capsule has short recovery time and good denitrification performance, which would help to achieve denitrification in aquaculture wastewater or other low C/N wastewater.