Achieving Stable Nitritation for Mainstream Deammonification by Combining Free Nitrous Acid-Based Sludge Treatment and Oxygen Limitation

• Published in: Scientific reports 2016-05, Vol.6 (1), p.25547-25547, Article 25547
• Main Authors: Wang, Dongbo, Wang, Qilin, Laloo, Andrew, Xu, Yifeng, Bond, Philip L., Yuan, Zhiguo
• Format: Article
• Language: English
• Subjects: 704/158; 704/172; Abundance; Dissolved oxygen; Domestic wastewater; Energy conservation; Fluorescence in situ hybridization; Humanities and Social Sciences; multidisciplinary; Nitrites; Nitrogen removal; Nitrous acid; Reactors; Science; Sludge; Sludge treatment
• ISSN: 2045-2322; 2045-2322
• DOI: 10.1038/srep25547

Stable nitritation is a critical bottleneck for achieving autotrophic nitrogen removal using the energy-saving mainstream deammonification process. Herein we report a new strategy to wash out both the Nitrospira sp. and Nitrobacter sp. from the treatment of domestic-strength wastewater. The strategy combines sludge treatment using free nitrous acid (FNA) with dissolved oxygen (DO) control in the nitritation reactor. Initially, the nitrifying reactor achieved full conversion of NH 4 + to NO 3 − . Then, nitrite accumulation at ~60% was achieved in the reactor when 1/4 of the sludge was treated daily with FNA at 1.82 mg N/L in a side-stream unit for 24 h. Fluorescence in-situ hybridization (FISH) revealed FNA treatment substantially reduced the abundance of nitrite oxidizing bacteria (NOB) (from 23.0 ± 4.3 to 5.3 ± 1.9%), especially that of Nitrospira sp. (from 15.7 ± 3.9 to 0.4 ± 0.1%). Nitrite accumulation increased to ~80% when the DO concentration in the mainstream reactor was reduced from 2.5–3.0 to 0.3–0.8 mg/L. FISH revealed the DO limitation further reduced the abundance of NOB (to 2.1 ± 1.0%), especially that of Nitrobacter sp. (from 4.9 ± 1.2 to 1.8 ± 0.8%). The strategy developed removes a major barrier for deammonification in low-strength domestic wastewater.