Synchronous N and P Removal in Carbon-Coated Nanoscale Zerovalent Iron Autotrophic Denitrification─The Synergy of the Carbon Shell and P Removal

Abstract

Fe0 is a promising electron donor for autotrophic denitrification in the simultaneous removal of nitrate and phosphorus in low C/N wastewater. However, P removal may inevitably inhibit bio-denitrification. It has not been well recognized and led to an overdose of iron materials. This study employed carbon-coated zerovalent iron (Fe0@C) to support autotrophic denitrification to mitigate the inhibition effects of P removal and enhance both N and P removal. The critical role of the carbon shell in Fe0@C was to block the direct contact between Fe0 and P and NO3 ––N, to maintain the Fe0 activity. Besides, P inhibited the chemical reduction of NO3 ––N by competing for Fe0 active sites. This indirectly boosted H2 generation and promoted bio-denitrification. P removal displayed negligible effects on microbial species but indirectly enhanced the nitrogen metabolic activities because of promoted H2 in Fe0@C-based autotrophic denitrification. Bio-denitrification, in turn, strengthened Fe–P co-precipitation by promoting the formation of ferric hydroxide as a secondary adsorbent for P removal. This study demonstrated an efficient method for simultaneous N and P removal in autotrophic denitrification and revealed the synergistic interactions among N and P removal processes.

Aerobic Denitrification Promoting by Actinomycetes Coculture: Investigating Performance, Carbon Source Metabolic Characteristic, and Raw Water Restoration

“…All groups were cultured in a shaking biochemical incubator at 120 rpm and 30 °C for 3 days. The cell proliferation tendency of the three groups was measured every 3 h using an ultraviolet spectrophotometer at the 600 nm absorbency value (OD 600 ). , Moreover, the DOC reduction capacity of monoculture and coculture was measured using a TOC-L analyzer every 3 h. , The experiments were conducted in triplicate ( n = 3).…”

“…PYX97 and Streptomyces sp. TSJ96 was examined by exploring their carbon source metabolism activity and cell metabolic characteristics, including adenosine triphosphate (ATP) and electron-transmission system activity (ETSA). , ATP and ETSA concentrations were measured at different time intervals (12, 36, and 72 h), and the method used for analysis was described in a previous study. , Moreover, the carbon source metabolism performance of monocultures and cocultures of strains PYX97 and TSJ96 was explored using Biolog-ECO technology. , After culturing for 57 h, the suspension culture liquid from each of the three cultivations was collected. The OD 600 of these suspension solutions was adjusted to 0.04.…”

Significantly Enhanced Nitrate and Phosphorus Removal by Pyrite/Sawdust Composite-Driven Mixotrophic Denitrification with Boosted Electron Transfer: Comprehensive Evaluation of Water–Gas–Biofilm Phases during a Long-Term Study

“…The iron or sulfur electrons provided by pyrite enter the intracellular electron transfer chain via electron shuttles such as quinones, riboflavins, heme, extracellular flagella, and pili. 2,33,39 Herein, compared with the control group (#4), the functional genes associated with such electron shuttles exhibited higher relative abundances in bioreactors #1 and #2 (Figure 6d). In addition to quinone-like fulvic acid serving as the dominant ETM mentioned in Section 3.3.2, riboflavins, extracellular flagellar, and pili are active ETMs.…”

“…Mixotrophic denitrification has recently gained wide attention for advanced nitrogen removal in wastewater with a low C/N ratio, such as groundwater and the secondary effluent of wastewater treatment plants (SE-WWTP). − Mixotrophic denitrification systems inherit the advantages of autotrophic and heterotrophic denitrification and can achieve high nitrogen loading rates. , On the one hand, autotrophic denitrification avoids issues such as excessive sludge production and biofilter clogging caused by reliance on external carbon sources in heterotrophic denitrification . On the other hand, heterotrophic denitrifiers can shorten the start-up stage and hydraulic retention time (HRT) with limited biomass due to the slow growth rate of autotrophic denitrifiers .…”