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Deficiency of researches on biotic community-driven biofilm activity makes biofilm regulation lack of quantitative response for decades. Based on three full-scale aerobic bioreactors in wastewater treatment plants, this study for the first time linked microbial respiratory activity with phospholipid fatty acid (PLFA) of biofilm developed on fixed and suspended carriers. Results showed that C16:00, C18:00, C16:1, ω7c, C18:1, ω7c, C12:00 and C18:1ω9c were top six biomarkers of PLFA among different sources of samples and Gram-negative bacteria (G−) was more abundant than Gram-positive bacteria (G+) with average G−/G+ of 2.98. It’s interesting to find defective revealing of PLFA-based biofilm activity by specific oxygen uptake rate (SOUR). Further modeling indicated that C16:00 achieved the optimal quantitative response to STOUR with the best model of composite, growth, or exponential curve (R2 = 0.416, p = 0.005). This research was promising to provide important reference for biofilm regulation and accurate control of biofilm-based process.

Denitrification biofilters (DNBFs) are widely used in advanced nitrogen removal of wastewater with low C/N and effective biofilm formation is critical to their long-term operation. Hereby the influence of rhamnolipid addition in DNBFs was investigated for the first time. Gradient concentrations (0, 20, 40, 80, 120 mg/L) of rhamnolipid were applied to investigate nitrogen removal, biofilm properties and microbial community of lab-scale DNBFs. A significant increase of nitrogen removal was observed in rhamnolipid-treated DNBFs (p

The anaerobic ammonia oxidation (anammox) and sulfocompound-oxidizing autotrophic denitrification coupling system (A/SAD) was initiated in an expanded granular sludge bed (EGSB) reactor for nitrogen removal from high-strength wastewater. Owing to cooperation between anammox and partial sulfocompound-oxidation autotrophic denitrification coupling system (PSAD), the highest nitrogen removal efficiency (NRE) of 98.1% ± 0.4% achieved at the optimal influent conditions of conversion efficiency of ammonium (CEA) of 55% and S2O32−-S/NO3−-N (S/N) of 1.4 mol mol−1. The activity of the short-cut sulfocompound-oxidizing autotrophic denitrification (SSAD) was also regulated to cope with dynamic CEA in the influent by changing the S/N, which was demonstrated to be effective in alleviating nitrite accumulation when the CEA was between 57% and 61%. Both the anammox and SAD bacteria enriched in the reactor after long-term incubation. Candidatus Brocadia and Candidatus Jettenia might be potentially contributing the most to anammox, while the Thiobacillus was the dominant taxa related to SAD.

In this study, the feasibility of using excess activated sludge as carbon source for denitrification to remove low concentrations of nitrate from wastewater was investigated. With an optimized upflow anaerobic reactor, high denitrification performance for both synthetic wastewater and effluent from municipal wastewater treatment plant was achieved. The results showed that the nitrate nitrogen can be reduced down to

Carbon/nitrogen (C/N) ratios play an important role in biological wastewater treatment processes, with quorum sensing (QS) coordinating biological group behaviors. However, the relationship between them remains unclear. This study investigated the effects of varying C/N ratios and exogenous QS signals on the distribution characteristics of AHLs in Moving Bed Biofilm Reactors during the biofilm development process. Results show that C10-HSL and C12-HSL were the dominant AHLs, with the highest concentrations observed in the reactor with a C/N ratio of 10, followed by C/N ratios of 20 and 4. With varying C/N ratios, the biofilm microbial community structure changed significantly, which may contribute to significant differences in the distribution of AHLs. Furthermore, with the addition of a QS strain Sphingomonas rubra sp. nov., the pollutant removal efficiency of the reactor was not significantly improved and a reversible change in community composition was temporarily observed.

Three lab-scale membrane bioreactors (MBRs) were continuously operated to treat saline wastewater under 0%, 0.75% and 1.5% NaCl stress. 0.75% and 1.5% NaCl reduced the COD and NH4(+)-N removal at the beginning, while the removal efficiencies could be recovered along with the operation of MBRs. Also, the polysaccharide in extracellular polymeric substances (EPS) and soluble microbial products (SMP) played an important role in the membrane fouling. Illumina sequencing of 16S rRNA gene showed that the increasing level of salinity reduced the diversity of the microbial community, and a higher salinity stimulated the growth of Bacteroidetes. At genus level, Flavobacterium, Aequorivita, Gelidibacter, Microbacterium, and Algoriphagus increased with the increase of salinity, which are shown to be highly salt tolerant. The strength of salinity or the duration of salinity could stimulate the microorganisms with similar functions, and the changes of polysaccharide in EPS and SMP were closely related to the membrane fouling rate as well as correlated with some saline-resistance genera.