Post-denitrification using alginate beads containing organic carbon and activated sludge microorganisms

Performance and microbial community of a novel PVA/iron-carbon (Fe–C) immobilized bioreactor for nitrate removal from groundwater

An efficient immobilized denitrification bioreactor functioning under anaerobic conditions was developed by combining bacterial immobilization technology with iron-carbon (Fe–C) particles. The effects of key factors on nitrate (NO3 −–N) removal efficiency were invested, such as the carbon-nitrogen ratio (C/N), pH and hydraulic retention time (HRT). Experimental results show that 100.00% NO3 −–N removal efficiency and a low level of nitrite (NO2 −–N) accumulation less than 0.05 mg L−1 were obtained under the condition of a C/N ratio of 3, pH 7.0 and HRT of 6 h. Meteorological chromatographic analysis showed that the final product of denitrification was mainly nitrogen (N2). The main component of precipitation formed in the bioreactor was characterized as Fe3O4 by X-ray diffraction. High-throughput sequencing analysis indicated that the dominant bacterial class in the Fe–C bioreactor was Gammaproteobacteria, while the dominant genera were Zoogloea and Azospira, the relative abundances of which were as high as 23.25 and 15.43%, respectively.

Porous solid carbon source-supported denitrification in simulated mariculture wastewater

A porous solid carbon source was prepared by semen litchi (SL), poly(vinyl alcohol) (PVA) and sodium alginate (SA) in aqueous. The effect of SL content on the structures and denitrification performance of the porous solid carbon source in simulated mariculture wastewater was investigated. The SL/PVA/SA beads showed a network structure with a wide range of macropores. Compared with blank beads, the SL/PVA/SA beads showed an increased rough surface and whole distribution on the surface with the increase of SL. In addition, SL/PVA/SA beads have more uniform pore size, but the porosity of SL/PVA/SA beads was decreased with the increase of SL. The porosity of the beads was 83.24%, 74.24%, 71.48% and 71.29% for blank beads and SL/PVA/SA beads contained 30%, 40% and 50% SL, when it was used as a solid carbon source for denitrification. Owing to their good porosity and biocompatibility, SL/PVA/SA beads had shorter acclimation time. Nitrate removal rate could reach up to 100% after two days of adaptation. After the exhaustion of carbon sources, nitrate removal rate less than 50% occurred at the 9th, 10th and 11th day for SL/PVA/SA beads that contained 30%, 40% and 50% SL, respectively. The beads that contained 50% SL exhibited longer lifetime during the denitrification reaction and denitrification rate could reach 243.5 ± 7.08 mg N (L d)^-1. It could be used as an economical and effective carbon source for denitrification in mariculture wastewater.