Comparison of denitrifying nitrite accumulation performance when sludge fermentation liquid progressively replaced acetate

• Published in: Journal of water process engineering 2024-12, Vol.68, p.106572, Article 106572
• Main Authors: Nie, Jiaxiang, Zhao, Ji, Kong, Desheng, Wu, Yuzhe, Shi, Liangliang, Yu, Deshuang, Qiu, Yanling, Feng, Juan, Wang, Xiaoxia
• Format: Article
• Language: English
• Subjects: Denitrifying nitrite accumulation; Microbial community; Partial denitrification; Progressive replacement; Sludge fermentation liquid
• ISSN: 2214-7144; 2214-7144
• DOI: 10.1016/j.jwpe.2024.106572

Sludge fermentation liquid (SFL), rich in volatile fatty acids, is supposed to be the promising organic carbon source to substitute acetate for driving partial denitrification (PD). However, it did not guarantee a comparable nitrate-to-nitrite transformation rate (NTR) when compared with using acetate due to its complicated composition. This study compared the PD performance of SFL and acetate in two parallel reactors (R1 and R2, respectively) and used progressive replacement to enhance the robustness of SFL. At first, PD was rapidly established in R1 and R2 within 21 days by using acetate and setting the carbon-to-nitrate ratio at 5. Then, after SFL progressively and completely replaced acetate in R1, the NTR of 64.7 ± 8.5 % and nitrate reduction rate of ∼39.7 mg/(L∙h) was obtained, which was comparable to those in R2 (58.7 ± 6.2 % and 50.9 mg/(L∙h)). Furthermore, the adopted long famine time caused extra nitrite soaking duration, leading to the system's quick startup but low biomass yield. According to high-throughput sequencing analyses of 16S rRNA, Thauera, a speculative PD contributor, was dominant in both reactors, and its relative abundance was ∼4.6 %. [Display omitted] •SFL showed its potential as an acetate substitute for PD via progressive replacement.•After SFL completely replaced acetate, a higher NTR0.5 of 64.7 ± 8.5 % was obtained.•A high NRR of ∼ 39.7 mg/(L×h) was achieved at a low MLSS of ∼1820 mg/L.•Extended famine and NO2− soaking time led to quick start-up and low biomass yield.•Thauera defeated indigenous GAOs and dominated with the relative abundance of ∼4.6 %.