Mainstream-sidestream wastewater switching promotes anammox nitrogen removal rate in organic-rich, low-temperature streams

• Published in: Environmental technology Vol. 42; no. 19; pp. 3073 - 3082
• Main Authors: Zekker, Ivar, Raudkivi, Markus, Artemchuk, Oleg, Rikmann, Ergo, Priks, Hans, Jaagura, Madis, Tenno, Taavo
• Format: Journal Article
• Language: English
• Published: England Taylor & Francis 24-08-2021; Taylor & Francis Ltd
• Subjects: Ammonia-oxidizing bacteria; Bacteria; biofilm; Biofilms; Biogas; Biomass; Bioreactors; Chemical oxygen demand; denitrification; hydrazine; Low temperature; Municipal wastewater; Nitrogen removal; oxidation-reduction potential; Reactors; Specific anammox activity; Switching; Wastewater; hydrazine; Specific anammox activity; denitrification; oxidation–reduction potential; biofilm
• ISSN: 0959-3330; 1479-487X
• DOI: 10.1080/09593330.2020.1721566

The main issues with mainstream anammox application are loss of bacterial activity by low temperatures and by a high organic content of wastewater. We demonstrate a novel switching method between sidestream and mainstream wastewater. The wastewater flow was switched between sidestream (reject water at >22°C) and mainstream (municipal wastewater at 16.5°C), so that the anammox biomass activity and biomass growth could benefit from sidestream conditions. Real sidestream wastewater (biogas plant effluent) (≈1000 mg NH
+
4
-N L
−1
) and synthetic mainstream (municipal wastewater-like source) (≈100 mg NH
+
4
-N) wastewater were used for 20 L biofilm reactor feeding. The highest total nitrogen removal rate (TNRR) of 527 g N m
−3
 d
−1
(average TNRR 180 (±140) g N m
−3
 d
−1
) was achieved with sidestream wastewater at a low chemical oxygen demand (COD)/TN ratio of 1.1/1. For reactor feeding with mainstream, the highest TNRR achieved was 61 g N m
−3
 d
−1
. Average TNRR for mainstream of 20 (±15) g N m
−3
 d
−1
was low due to a higher COD/N ratio of 3.2/1. The highest TNRR in a batch test was achieved at the COD concentration of 480 mg L
−1
, reflecting a TNRR of ≈5 mg N g
−1
TSS h
−1
. With a high COD concentration of 2600 mg L
−1
(TOC/TN = 8/1), TNRR decreased similarly in both feeds to 1.6 mg N g
−1
TSS h
−1
. The anammox microorganism's genus Candidatus Brocadia enrichment in deammonification biofilm reactor was higher in the mainstream operation (7.6% of all bacteria) than in sidestream operation period (<0.7% of all bacteria).