Stable nitritation of mature landfill leachate via in-situ selective inhibition by free nitrous acid

• Published in: Bioresource technology 2021-11, Vol.340, p.125647-125647, Article 125647
• Main Authors: Ren, Shang, Wang, Zhong, Jiang, Hao, Qiu, Jingang, Li, Xiyao, Zhang, Qiong, Peng, Yongzhen
• Format: Article
• Language: English
• Subjects: Free ammonia (FA); Free nitrous acid (FNA); In-situ selective inhibition; Landfill leachate; Nitritation
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2021.125647

[Display omitted] •Undiluted raw mature landfill leachate was used during the long-term operation.•Compared to FA, FNA selective inhibition property was more substantial.•AOB were more sensitive to the FA environment but recovered faster than NOB.•In-situ sludge treated with FNA (0.175 mg N/L, 6 h) achieved stable nitritation.•Over long-term SBR operation, the nitrite accumulation rate reached 90 ~ 100%. In-situ free nitrous acid (FNA) and free ammonia (FA) treatments are more feasible than side-stream methods to achieve nitritation. To assess the optimum conditions and long-term performance of in-situ inhibition by FNA, batch tests and a sequencing batch reactor (SBR) treating mature landfill leachate were conducted and established. As a result, the selective inhibition characteristic by FNA was more conspicuous than FA, and FNA (0.175 mg N/L, 6 h) treatment are more biocidal to nitrite oxidizing bacteria (NOB). Moreover, ammonia oxidizing bacteria (AOB) were more sensitive to the FA environment but its activity recovered preferentially compared to NOB. The SBR achieved a sustained nitrite accumulation rate above 90% for 200 days, with a significant decrease of NOB activity and microbial abundance according to qPCR and 16S rRNA gene sequencing results. In-situ selective inhibition by FNA (0.175 mg N/L, 6 h) has been proved to be effective to maintain stable nitritation.