Enhancing nitrogen removal of aerobic granular sludge with optimization of dissolved oxygen spatial distribution

Poly(vinyl alcohol)/modified porous starch gel beads for microbial preservation and reactivation: preparation, characterization and its wastewater treatment performance

“…7(b), the effluent nitrite nitrogen concentrations of all reactors significantly accumulated in the 14th, 14th, 20th, and 15th cycles, and the maximum nitrite nitrogen concentrations were 15.33 mg L −1 , 17.19 mg L −1 , 15.84 mg L −1 , and 16.07 mg L −1 , respectively. This may be because PVA–MPS gel beads has a distinct spatial stratification structure that is similar to aerobic granular sludge (AGS), 37 which is constrained by the diffusion of dissolved oxygen in the beads and the creation of a low dissolved oxygen environment inside them, and the competitive growth of nitrite-oxidizing bacteria (NOB) is inhibited to a certain extent due to the stronger oxygen utilization ability of ammonia-oxidizing bacteria (AOB) than NOB. 38 The accumulation of effluent nitrate nitrogen concentration lagged behind that of effluent nitrite nitrogen concentration, reaching maximum values of 20.21 mg L −1 , 25.76 mg L −1 , 5.92 mg L −1 , and 27.03 mg L −1 in cycles 44, 46, 44, and 40, respectively.…”