Synergistic Partial-Denitrification, Anammox, and in-situ Fermentation (SPDAF) Process for Advanced Nitrogen Removal from Domestic and Nitrate-Containing Wastewater

Abstract

This study presents a new method for energy-efficient wastewater treatment that synergizes the partial-denitrification, anammox, and in-situ fermentation (SPDAF) processes in an up-flow reactor. Nitrate-containing wastewater and actual domestic sewage were fed into this SPDAF system, which was operated for 180 days without the addition of external carbon sources and aeration. The total inorganic nitrogen (TIN) removal efficiency reached 93.1% with a low C/N ratio of 1.6, a NO3 ––N/NH4 +–N ratio of 1.13 and a TIN concentration of 92.5 mg N/L. The contribution of anammox to nitrogen removal accounted for 95.6%. Batch tests demonstrated that the partial-denitrification process was able to use organics from either the influent or those produced by fermentation, thus providing nitrite for anammox. Significantly, fermentation played a key role in using the slowly biodegradable organics and provided adequate electron donor for partial-denitrification. Metagenomic sequencing analysis showed that the genera related to partial-denitrification, anammox, and fermentation bacteria were coexisted in this SPDAF system. The key functional genes of anammox bacteria (Hzs, 3986 hits; Hdh, 2804 hits) were highly detected in this study. The abundances of cytoplasmic nitrate reductase (58 706 hits) and periplasmic nitrate reductase (70 540 hits) were much higher than copper nitrite reductase (16 436 hits) and cytochrome cd1 nitrite reductase (14 264 hits), potentially contributing to the occurrence of partial-denitrification. Moreover, different abundances of genes involved in fermentation metabolism suggested that fermentation likely generated easily biodegradable organics for partial-denitrification.

Anammox and partial denitrification coupling: a review

“…C/N is the key to start an anammox and partial denitrication coupling reactor, and it is also an important control parameter to maintain stable reactor operation and efficient nitrogen removal. 19,30,125 The presence of organic matter is generally believed to have adverse effects on the anammox process because the heterotrophic denitrifying bacteria grow at a much higher rate and with a higher cellular synthesis growth yield compared to autotrophic anammox bacteria. 106 Anammox bacteria are autotrophic bacteria, and the participation of organic carbon will inhibit bacterial growth.…”

“…It is worth noting that in the long-term and short-term effects of pH on denitrication, a high pH value is benecial to achieve partial denitrication of nitrite accumulation. [147][148][149] The SPDAF (synergizes the partial denitrication, anammox and in situ fermentation) collaborative process established by Ji et al 30 has the disadvantages of slow degradation of organic matter and low utilization rate. The sludge in the fermentation tank was inoculated into the UASB reactor to promote denitrication.…”

New Insight into Partial Denitrification (PD)-based Anammox Process and Potential Engineering Application: A Review

“…As we all known, the key reason for efficient nitrogen removal via PDA process was the coexistence of diverse microbial flora, owing to PD biomass known as classical heterotrophic bacteria along with intense proliferation growth might lead to autotrophic anammox bacteria possibly inhibited. Notably, maintaining dominant anammox nitrogen removal pathway was essential, since researchers have reported that anammox contributed more than 95% nitrogen removal in PDA [11]. On the other hand, PD occurred ahead of anammox was a prerequisite due to NO 2 --N-electron acceptor supply must be warranted for anammox microbes [1].…”

“…Du et al conducted two sludge nitrification and PDA reactor to treat real municipal sewage and artificial nitrate wastewater with sodium acetate solution as external organics, achieving as low as 5 mg/L TN effluent despite frequent temperature fluctuations (16.3~25.7°C) [10]. In addition, Ji et al successfully coupled in-situ fermentation with PDA in a single reactor for advanced nitrogen removal from domestic and nitrate-containing wastewater, and the slowly biodegradable organics could be hydrolyzed and acidized to volatile fatty acids (VFAs) via fermentation, thus in-situ carbon source generated for further NO 3 --N reduction without external addition [11]. This provided new insight into practical application of PDA in a cost-effective and environmental-friendly way.…”

“…Increasing interest focused on combining PD with anammox for treating NH 4 + -N and NO 3 --N contained wastewater, and numerous lab-scale actual wastewater treatment by PDA has been reported, i.e., domestic and nitrate contained wastewater (simulated industrial nitrate wastewater) [10][11][12], tertiary/secondary municipal sewage [13][14][15][16], high strength anammox-based wastewater [9,[17][18][19][20]. Nevertheless, there has been limited literature to show us comprehensive knowledge of PDA potential application, which might accelerate the popularization of PDA process.…”