Primary sludge fermentate as carbon source for mainstream partial denitrification–anammox (PdNA)

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This research examined the feasibility of raw fermentate for mainstream partial denitrification-anammox (PdNA) in a pre-anoxic integrated fixed-film activated sludge (IFAS) process. Fermentate quality sampled from a full-scale facility was highly dynamic, with 360-940 mg VFA-COD/L and VFA/soluble COD ratios ranging from 24% to 48%. This study showed that PdNA selection could be achieved even when using low quality fermentate. Nitrate residual was identified as the main factor driving the PdN efficiency, while management of nitrate conversion rates was required to maximize overall PdNA rates. AnAOB limitation was never observed in the IFAS system. Overall, this study showed PdN efficiencies up to 38% and PdNA rates up to 1.2 ± 0.7 g TIN/m 2 /d with further potential for improvements. As a result of both PdNA and full denitrification, this concept showed the potential to save 48-89% methanol and decrease the carbon footprint of water resource recovery facilities (WRRF) by 9-15%. Practitioner points• Application of PdNA with variable quality fermentate is feasible when the nitrate residual concentration is increased to enhance PdN selection.• To maximize nitrogen removed through PdNA, nitrate conversion rates need enhancement through optimization of upstream aeration and PdN control setpoints.• The IFAS PdNA process was never anammox limited; success depended on the degree of PdN achieved to make nitrite available.• Application of PdNA with fermentate can yield 48-89% savings in methanol or other carbon compared with conventional nitrification and denitrification.• Integrating PdNA upstream from polishing aeration and anoxic zones guarantees that stringent limits can be met (<5 mg N/L).

Section: Resultssupporting

confidence: 82%

Section: Resultscontrasting

confidence: 63%

\begin{matrix} lefttrue \\ AnAOB - based nitrite removal (\frac{g {NO}_{2}^{-} - N}{d}) \\ = \begin{array}{l} (({italicNH}_{4}^{+} ‐ N_{cell 5} - {italicNH}_{4}^{+} ‐ N_{cell 8}) \times (Q_{italicin} + Q_{italicRAS}) \\ + {italicNH}_{4}^{+} ‐ N_{italicfermentate} \times (Q_{fermentate})) \times 1.32 \end{array} \end{matrix}

where

{NH}_{4}^{+} - N_{italiccell 5}

and

{NH}_{4}^{+} - N_{italiccell 8}

were the measured ammonium concentrations (mg N/L) at cells 5 and 8;

Q_{in}

was the influent flow rate (m 3 /d);

Q_{RAS}

was the return activated sludge (RAS) flow rate (m 3 /d);

Q_{fermentate}

was the fermentate flow rate (m 3 /d) into PdN zone;

{NH}_{4}^{+} ‐ N_{fermentate}

was the ammonium concentration added with fermentate (mg N/L).…”

Section: Methodsmentioning

confidence: 99%

\begin{matrix} lefttrue \\ PdNA contribution to TIN removal \\ = \begin{array}{l} \frac{(Q_{in} goodbreak+ Q_{RAS}) \times normalTIN_N_{cell 5} - (Q_{in} goodbreak+ Q_{RAS} goodbreak+ Q_{fermentate}) \times normalTIN_N_{cell 8} + Q_{fermentate} \times normalTIN_N_{fermentate}}{Q_{in} \times normalTIN_N_{in}} \\ goodbreak\times 100 % \end{array} \end{matrix}

where

italicTIN_N_{in}

was the influent TIN concentration (mg/L);

italicTIN_N_{italiccell 5}

was the measured TIN concentration (mg/L) at cell 5 (see Figure 1);

italicTIN_N_{italiccell 8}

was the measured TIN concentration (mg/L) at cell 8;

Q_{in}

was the influent flow rate (m 3 /d);

Q_{RAS}

was the return activated sludge (RAS) flow rate, (m 3 /d);

Q_{fermentate}

was the fermentate flow rate (m 3 /d) into PdN zone; and

italicTIN_N_{fermentate}

was TIN concentration added with fermentate (mg N/L).…”

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Partial denitrification–anammox (PdNA) application in mainstream IFAS configuration using raw fermentate as carbon source

Ladipo‐Obasa

Forney

Riffat

et al. 2022

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Media selection for anammox‐based polishing filters: Balancing anammox enrichment and retention with filtration function

Fofana

Peng

Huynh

et al. 2022

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Retrofitting conventional denitrification filters into partial denitrification‐anammox (PdNA)‐ or anammox (AnAOB)‐based filters will reduce the needs for external carbon addition. The success of AnAOB‐based filters depends on anammox growth and retention within such filters. Studies have overlooked the importance of media selection and its impact on AnAOB capacity, head loss progression dynamics, and shear conditions applied onto the AnAOB biofilm. The objective of this study was to evaluate viable media types (10 types) that can enhance AnAOB rates for efficient nitrogen removal in filters. Given the higher backwash requirement and lower AnAOB capacity of the conventionally used sand, expanded clay (3–5 mm) was recommended for AnAOB‐based filters in this study. Owing to its surface characteristics, expanded clay had higher AnAOB activity (304‐ vs. 104‐g NH4+‐N/m2/day) and higher AnAOB retention (43% more) than sand. Increasing the iron content of expanded clay to 37% resulted in an increase in zeta potential, which led to 56% more anammox capacity compared to expanded clay with 7% iron content. This work provides insight into the importance of media types in the growth and retention of AnAOB in filters, and this knowledge could be used as basis in the development of PdNA filters. Practitioner Points Expanded clay showed the lowest head loss buildup and most likely will result in longer runtime for full‐scale PdNA applications The highest AnAOB rates were achieved in expanded clay types and sand compared with smaller media typically used in biofiltration Expanded clay resulted in better AnAOB retention under shear, whereas sand could not withstand shear and required more frequent backwashing Expanded clay iron coating enhanced AnAOB enrichment and retention, most likely due to increased surface roughness and/or positive charge

Full‐scale transition from denitrification to partial denitrification–anammox (PdNA) in deep‐bed filters: Operational strategies for and benefits of PdNA implementation

Fofana

Parsons

Long

et al. 2022

Self Cite

This study shows for the first time more than 2 years of operation of a mainstream anammox application at full-scale under temperate climate. This implementation of partial denitrification-anammox (PdNA) in deep bed filters at the HRSD York River treatment plant was demonstrated to achieve the benefits of shortcut nitrogen removal without nitrite oxidizing bacteria (NOB) out-selection. The transition from denitrification to PdNA filters required bleeding ammonium to the filters using an optimized ammonium versus NOx (AvN) control in the upstream aeration tanks and maintaining a nitrate residual in the filter effluent through feedforward/feedback control. The latter actions led to savings of 85% in methanol, 100% in alkalinity, and 35% in capacity enhancement. Up to 6 mg NH 4 + -N/L with an average of 2.2 ± 0.98 mg NH 4 + -N/L was removed through the anammox pathway, which accounted for about 15% of the overall plant nitrogen removal. Anammox enrichment was confirmed by activity testing and molecular analysis. The large excess of AnAOB capacity present in the filters (5-10 times more than normal operation) resulted in stable and reliable operation through winter conditions and showed potential for further intensification. Practitioner Points• For the first time, long-term mainstream anammox was established fullscale through PdNA implementation in deep-bed filters. • PdNA implementation required upstream aeration control optimization to provide a blend of ammonium and nitrate to the filters.• Efficient anammox enrichment and retention resulted in reliable PdNA performance under different seasonal and influent conditions.All authors are members of the Water Environment Federation (WEF).