Advanced low-strength wastewater treatment, side-stream phosphorus recovery, and in situ sludge reduction with aerobic granular sludge.

Modern paradigm has upgraded wastewater treatment plants (WWTPs) to water resources recovery facilities (WRRFs), where aerobic granular sludge (AGS) is a sewage treatment technology with promising phosphorus recovery (PR) potential. Herein, the AGS-based simultaneous nitrification, denitrification, and phosphorus removal coupling side-stream PR process (AGS-SNDPRr) was developed with municipal wastewater. Results revealed that AGS always maintained good structural stability, and pollutant removal was unaffected and effective after 40 days of anaerobic phosphorus-rich liquid extraction (fixed rate of 30%). The AGS-SNDPRr achieved a stable phosphorus recovery efficiency of 63.40%, and the side-stream PR further exaggerated in situ sludge reduction by 7.7-10%. Apart from responses of extracellular polymeric substances (EPS), the Matthew effect of typical denitrifying glycogen accumulating organisms (DGAOs) Candidatus_Competibacter up to 67.40% mainly contributed to enhanced performance of this new process. This study demonstrated a new approach for simultaneous advanced wastewater treatment, phosphorus recovery, and excess sludge minimization.

Performance of anaerobic/oxic/anoxic simultaneous nitrification, denitrification and phosphorus removal system overwhelmingly dominated by Candidatus_Competibacter: Effect of aeration time.

The anaerobic/oxic/anoxic simultaneous nitrification, denitrification and phosphorus removal process (AOA-SNDPR) is a promising technology for enhanced biological wastewater treatment and in situ sludge reduction. Herein, effects of aeration time (90, 75, 60, 45, and 30 min, respectively) on the AOA-SNDPR were evaluated including simultaneous nutrients removal, sludge characteristics, and microbial community evolution, where the role of a denitrifying glycogen accumulating organisms, Candidatus_Competibacter, was re-explored given its overwhelming dominance. Results revealed that nitrogen removal was more vulnerable, and a moderate aeration period of 45-60 min favored nutrients removal most. Low observed sludge yields (Yobs) were obtained with decreased aeration (as low as 0.02-0.08 g MLSS/g COD), while MLVSS/MLSS got increased. The dominance of Candidatus_Competibacter was identified as the key to endogenous denitrifying and in situ sludge reduction. This study would aid the low carbon- and energy-efficient aeration strategy for AOA-SNDPR systems treating low-strength municipal wastewater.

Pachymic Acid Inhibits Growth and Metastatic Potential in Liver Cancer HepG2 and Huh7 Cells.

Pachymic acid (PA), exacted from Polyporaceae, has been known for its biological activities including diuretic, dormitive, anti-oxidant, anti-aging, anti-inflammatory and anticancer properties in several types of diseases. Recently, studies have demonstrated that PA could suppress cell growth and induce cell apoptosis in different kinds of cancer cells. But the underlying mechanisms remain poorly elucidated. In the current study, we investigated the effect of pachymic acid on liver cancer cells and its underlying mechanisms. Our results evidenced that pachymic acid effectively inhibited the cell growth and metastatic potential in HepG2 and Huh7 cells. Mechanistically, we revealed that pachymic acid triggered cell apoptosis by increasing caspase 3 and caspase 9 cleavage, upregulating Bax and cytochrome c expression, while reducing the expression of Bcl2. Besides, pachymic acid could markedly inhibit the cell invasion and migration and cell metastatic potential by mediating epithelial-to-mesenchymal transition (EMT) markers and metastasis-associated genes in HepG2 and Huh7 cells. In addition, we demonstrated that FAK-Src-Jun N-terminal kinase (JNK)-matrix metalloproteinase 2 (MMP2) axis was involved in PA-inhibited liver cell EMT. Together, these results contribute to our deeper understanding of the anti-cancer effects of pachymic acid on liver cancer cells. This study also provided compelling evidence that PA might be a potential therapeutic agent for liver cancer treatment.

Rapid start-up and stable operation of an aerobic/oxic/anoxic simultaneous nitrification, denitrification, and phosphorus removal reactor with no sludge discharge.

An anaerobic/aerobic/anoxic mode simultaneous nitrification, denitrification, and phosphorus removal system was visited for enhanced low-strength wastewater treatment and dramatic in situ sludge reduction. Results showed that rapid start-up was achieved with conventional activated sludge after 15 days, with effluent ammonia nitrogen, total nitrogen, total phosphorus, and chemical oxygen demand being 0.25, 7.89, 0.12, 24.37 mg/L, respectively. A two-stage biomass growth rate was observed with the sludge yield of 0.285 (day 1-50) and 0.017 g MLSS/g COD (day 51-110) without sludge discharge. Dynamics of bacterial community has been identified with outstanding accumulation of Candidatus_Competibacter up to 29.06 %, which contributed to both simultaneous nutrients removal and sludge reduction. Further analysis via PICRUSt2 revealed the main pathway of nitrogen metabolism, while proposed mechanism for phosphorus removal with no sludge discharge was analyzed from the intracellular and extracellular perspectives. Overall, this study provided guidance and reference for the development and application of A/O/A-SNDPR technology.

Distinct responses of aerobic granular sludge sequencing batch reactors to nitrogen and phosphorus deficient conditions.

The nutrients availability determines efficiency of biological treatment systems, along with the structure and metabolism of microbiota. Herein nutrients deficiencies on aerobic granular sludge were comparatively evaluated, treating wastewater with mass ratios of chemical oxygen demand : nitrogen : phosphorus being 200:20:4, 200:2:4, and 200:20:0.4 (deemed as nutrient-balanced, nitrogen-deficient, and phosphorus-deficient), respectively. Results revealed that both nitrogen and phosphorus deficiencies significantly raised the effluent qualities especially nitrogen removal. However, nitrogen deficiency aroused considerable growth of filamentous bacteria, while granules kept compact structure under phosphorus deficient condition. Extracellular polymeric substances (EPS) also varied in contents and structures in response to different wastewaters. Microbial community structure analysis demonstrated that nitrogen deficiency led to lower richness and higher diversity, while the reverse was observed under phosphorus deficient condition. Nitrogen deficiency mainly induced decrease of nitrifying bacteria, while similarly phosphorus deficiency led to loss of phosphorus accumulating organisms. Dramatic enrichment Candidatus_Competibacter and filamentous Thiothrix were found under nutrients deficiencies, in which the latter explained and indicated filamentous bulking potential especially under nitrogen limited condition. Bacterial metabolism patterns verified the functions of microbial community responding to nutrients via PICRUSt2 prediction mainly by up-regulating cell motility, and cellular processes and signaling. This study could aid understanding of long-term stability of aerobic granular sludge for low-strength wastewater treatment.

Insights into the simultaneous nitrification, denitrification and phosphorus removal process for in situ sludge reduction and potential phosphorus recovery.

A simultaneous nitrification-denitrification and phosphorus removal (SNDPR) system operated in an alternating anaerobic/aerobic/anoxic (A/O/A) mode was revisited from new perspectives of sludge reduction and potential phosphorus recovery. Reliable and robust removal performance was obtained even under winter temperatures, with average removal efficiency of COD, TP, NH4+-N and TIN being 89.68%, 93.60%, 92.15% and 79.01% at steady state, respectively. Inoculated sludge got enhanced in biomass density, settleability, and bioactivity. And relatively stable amounts of extracellular polymeric substances (EPS) with a stable protein/ polysaccharide (PN/PS) ratio were observed over operation. Meanwhile, a low observed sludge yield (Yobs) of 0.083 g MLSS/g COD (0.082 g MLVSS/g COD) was obtained. A maximum anaerobic phosphorus release up to 43.54 mg/L was found, thus providing phosphorus-rich and low-turbidity stream for further phosphorus recovery. Overall, the SNDPR system deserved attention for in situ sludge reduction and potential phosphorus recovery, beyond reliable and stable wastewater treatment.

Interaction and removal of oxytetracycline with aerobic granular sludge.

Aerobic granular sludge as a promising technology showed great resistance to adverse conditions. However, the interaction between oxytetracycline (OTC) and granular sludge was not studied sufficiently. This study therefore investigated OTC-tolerance ability of incomplete and complete granulation sludge from aspects of simultaneous nutrients removal, sludge characteristics, microbial activity, community changes, and vice versa OTC removal performance. Incomplete granulation sludge showed better denitrification performance and resistance. Whereas, denitrification and phosphorus removal of complete granulation sludge suffered a permanent collapse under 5 mg/L OTC. OTC could be removed by rapid adsorption and slow biodegradation via granular sludge. The EPS, especially TB-PS, played a significant role during the operational period subjected to OTC. The major genera of Lysobacter and Candidatus_Competibacter laid the biological basis for stability and functionality of granules, which acted as the putative contributors for resisting and removing OTC. This study showed that incomplete-granulated sludge qualified more promising application prospect.

Effects of phenol on extracellular polymeric substances and microbial communities from aerobic granular sludge treating low strength and salinity wastewater.

The effects of phenol on aerobic granular sludge including extracellular polymeric substances (EPS) and microbial community were investigated for low strength and salinity wastewater treatment. Elevated phenol over 20 mg/L stimulated biological phosphorus removal mainly via co-metabolism with nearly complete phenol degradation, whereas resulted in significant accumulation of nitrate around 4 mg/L. Aerobic granules kept structural stability via enhancing production of extracellular polymeric substances (EPS), especially folds of polysaccharides (PS) and varying functional groups identified through EEM, FTIR and XPS spectral characterizations at increasing phenol loads. Illumina MiSeq sequencing results indicated that elevated phenol decreased the bacterial diversity and richness, and caused remarkable variations in structural and compositions of microbial population. Multiple halophilic bacteria including Stappia, Luteococcus, and Formosa laid the biological basis for stability of aerobic granules and efficient biological nutrients and phenol removal. Redundancy analysis (RDA) suggested the key role of phenol in shaping the relative abundances and predominant genera. This study proved that aerobic granular sludge was feasible for low-saline and phenol-laden low-strength wastewater treatment.