Iron Robustly Stimulates Simultaneous Nitrification and Denitrification Under Aerobic Conditions

Abstract

Simultaneous nitrification and denitrification (SND) is a promising single-reactor biological nitrogen-removal method. Activated sludge with and without iron scrap supplementation (Sludge-Fe and Sludge-C, respectively) was acclimated under aerobic condition. The total nitrogen (TN) content of Sludge-Fe substantially decreased from 25.0 ± 1.0 to 11.2 ± 0.4 mg/L, but Sludge-C did not show the TN-removal capacity. Further investigations excluded a chemical reduction of NO-N by iron and a decrease of NH-N by microbial assimilation, and the contribution of SND was verified. Moreover, the amount of aerobic denitrifiers, such as bacteria belonging to the genera Thauera, Thermomonas, Rhodobacter, and Hyphomicrobium, was considerably enhanced, as observed through Miseq Illumina sequencing method. The activities of the key enzymes ammonia monooxygenase (AMO) and nitrite oxidoreductase (NXR), which are associated with nitrification, and periplasmic nitrate reductase (NAP) and nitrite reductase (NIR), which are related to denitrification, in Sludge-Fe were 1.23-, 1.53-, 3.60-, and 1.55-fold higher than those in Sludge-C, respectively. In Sludge-Fe, the quantity of the functional gene NapA encoding enzyme NAP, which is essential for aerobic denitrification, was significantly promoted. The findings indicate that SND is the primary mechanism underlying the removal of TN and that iron scrap can robustly stimulate SND under aerobic environment.

Aerobic Denitrification Microbial Community and Function in Zero-Discharge Recirculating Aquaculture System Using a Single Biofloc-Based Suspended Growth Reactor: Influence of the Carbon-to-Nitrogen Ratio

“…The predominant phyla in the fish tank in the CN20 system included Proteobacteria (31.1%), Bacteroidetes (23.1%), Firmicutes (13.16%), and Planctomycetes (12.2%), whereas those in the SGR were Proteobacteria (68.0%) and Bacteroidetes (11.8%). The Proteobacteria in R20 was 2.0, 1.8, and 2.2 times higher than in T15, R15, and T20, respectively, which implied the high aerobic denitrification potential in the SGR of the CN20 system because aerobic denitrifying bacteria mainly belonged to this phylum ( Chen et al, 2018 ).…”

“…Dechloromonas exhibited an excellent aerobic denitrification ability in tidal flow constructed wetland and was the dominant denitrifying and phosphorus-removing bacteria in the single-sludge sequencing batch reactor ( Xu et al, 2018 ; Tan et al, 2020 ). Rhodobacter demonstrated enhancement in the single reactor for nitrogen removal under aerobic conditions ( Chen et al, 2018 ). Flavobacterium (phylum Bacteroidetes ) served as a complete aerobic denitrifier in the granular reactor ( Pishgar et al, 2019 ).…”

“…For nitrate reduction, the NAR encoded by narG is seriously inhibited by oxygen, whereas the NAP encoded by napA can be expressed under aerobic and anaerobic conditions ( Sparacino-Watkins et al, 2014 ; Pan et al, 2020 ). The expression of the napA gene was often applied as an evidence of aerobic denitrification ( Chen et al, 2018 ). The enzymes that catalyze the reduction of NO 2 – to NO are encoded by nirK and nirS genes.…”

Role of heterotrophic aerobic denitrifying bacteria in nitrate removal from wastewater

“…Konohana et al () proposed that Bacillus licheniformis eliminated NO 3 − and NH 4 + under aerobic conditions and its growth increased with 1·5 mmol l −1 FeSO 4 in the medium. Chen et al () used iron as a supplement for biological nitrogen removal. A comparative study was made using sludge‐Fe and sludge‐C.…”

Degradation of Organic Constituents in a Biphasic Anaerobic Digester for Treating Pharmaceutical Wastewater

“…The COD level of pharmaceutical wastewater was found very high, the difference between diverse manufacturing activities can be still huge, where the COD of influent wastewater was found to be 4,410 to 40,000 mg/l [6], [21]. The various methods was applied to treat pharmaceutical wastewater which include process such as Coagulation, Sedimentation, Adsorption, Advanced Oxidation Processes (AOPs) and Biological treatment [8], [13], [27], [30]. In recent years the discharge and treatment of pharmaceutical wastewater creates health issue with release of antibiotic drugs in the natural environments, due to their microbial activity there was only limited efficiency achieved through common biological treatment [4], [10].…”