Photosynthetic oxygen-supported algal-bacterial aerobic granular sludge can facilitate carbon, nitrogen and phosphorus removal from wastewater: Focus on light intensity selection.

Photosynthetic O2 is a promising alternative for mechanical aeration, the major energy-intensive unit in wastewater treatment plants. This study aimed to investigate the effects of light intensity varied from 190 to 1400 µmol·s-1·m-2 on photosynthetic O2-supported algal-bacterial aerobic granular sludge (AGS) system. Results indicate photosynthetic O2 can implement aerobic phosphorus (P) uptake and ammonia oxidation under the test illumination range even at dissolved oxygen concentration < 0.5 mg/L. An obvious O2 accumulation occurred after 60-90% nutrients being removed under 330-1400 µmol·s-1·m-2, and highly efficient ammonia removal, P uptake, and dissolved inorganic carbon removal were achieved under 670-1400 µmol·s-1·m-2. On the other hand, photosynthesis as O2 supplier showed little effect on major ions except for K+. This study provides a better understanding of the roles of light intensity on photosynthetic O2-supported algal-bacterial AGS system, targeting a sustainable wastewater industry.

Highly efficient carbon assimilation and nitrogen/phosphorus removal facilitated by photosynthetic O2 from algal-bacterial aerobic granular sludge under controlled DO/pH operation.

Reducing CO2 emission and energy consumption is crucial for the sustainable management of wastewater treatment plants (WWTPs). In this study, an algal-bacterial aerobic granular sludge (AGS) system was developed for efficient carbon (C) assimilation and nitrogen (N)/phosphorus (P) removal without the need for mechanical aeration. The photosynthetic O2 production by phototrophic organisms maintained the dissolved oxygen (DO) level at 3-4 mg/L in the bulk liquid, and an LED light control system reduced 10-30% of light energy consumption. Results showed that the biomass assimilated 52% of input dissolved total carbon (DTC), and the produced O2 simultaneously facilitated aerobic nitrification and P uptake with the coexisting phototrophs serving as a C fixer and O2 supplier. This resulted in a stably high total N removal of 81 ± 7% and an N assimilation rate of 7.55 mg/(g-MLVSS∙d) with enhanced microbial assimilation and simultaneous nitrification/denitrification. Good P removal of 92-98% was maintained during the test period at a molar ∆P/∆C ratio of 0.36 ± 0.03 and high P release and uptake rates of 10.84 ± 0.41 and 7.18 ± 0.24 mg/(g- MLVSS∙h), respectively. Photosynthetic O2 was more advantageous for N and P removal than mechanical aeration. This proposed system can contribute to a better design and sustainable operation of WWTPs using algal-bacterial AGS.

Revealing calcium ion behavior during anaerobic phosphorus release process in aerobic granular sludge system.

Calcium ions (Ca2+) are important for biological phosphorus (P) removal from wastewater, but its behavior has not been well documented during the anaerobic P release process. This study is aimed to explore the mechanisms of Ca2+ release in bacterial aerobic granular sludge (AGS) system. During the non-aeration (anaerobic) phase, nearly 40 % increase in Ca2+ concentration was detected at the bottom of AGS reactor where decrease in pH and increase in Mg2+ concentration occurred. The pH decrease due to anaerobic P release caused CaCO3 dissolution inside the granules, leading to Ca2+ release. In addition, the increased Mg2+ ions from hydrolysis of polyphosphates were detected to reversibly exchange with Ca2+ in granules at a molar ΔCa/ΔMg ratio of 0.51-0.65. Results from this work revealed that dissolution of CaCO3 and ions exchange between Ca2+ and Mg2+ were the two major contributors to Ca2+ release during anaerobic P release process.

Neuroprotective Effects of the Psychoactive Compound Biatractylolide (BD) in Alzheimer's Disease.

Mitochondria play a central role in the survival or death of neuronal cells, and they are regulators of energy metabolism and cell death pathways. Many studies support the role of mitochondrial dysfunction and oxidative damage in the pathogenesis of Alzheimer's disease. Biatractylolide (BD) is a kind of internal symmetry double sesquiterpene novel ester compound isolated from the Chinese medicinal plant Baizhu, has neuroprotective effects in Alzheimer's disease. We developed a systematic pharmacological model based on chemical pharmacokinetic and pharmacological data to identify potential compounds and targets of Baizhu. The neuroprotective effects of BD in PC12 (rat adrenal pheochromocytoma cells) and SH-SY5Y (human bone marrow neuroblastoma cells) were evaluated by in vitro experiments. Based on the predicted results, we selected 18 active compounds, which were associated with 20 potential targets and 22 signaling pathways. Compound-target, target-disease and target-pathway networks were constructed using Cytoscape 3.2.1. And verified by in vitro experiments that BD could inhibit Aß by reducing oxidative stress and decreasing CytC release induced mPTP opening. This study provides a theoretical basis for the development of BD as an anti-Alzheimer's disease drug.

Energy saving and rapid establishment of granular microalgae system from tiny microalgae cells: Effect of decrease in upflow air velocity under intermittent aeration condition.

The novel type of microalgae granules (MGs) derived from tiny microalgae cells has received extensive attention due to its great potential for nutrient remediation and resource recovery in wastewater treatment whereas the long start-up time with increased labor expenses remains a bottleneck. In this study, an operation strategy at reduced upflow air velocity (UAV = 0.49 cm/s in RA) under intermittent aeration mode was proposed and compared with RB at a higher UAV (0.98 cm/s) in terms of MGs formation, maintenance, and energy consumption. Although the formation of MGs in RA was delayed for 12 days compared to RB, 40.78 % increase in chlorophyll-a content was detected in MGs in RA along with more cost-effective carbon, nitrogen, and phosphorus removals due to efficient microalgae assimilation and energy reduction. Results from this study provide new insight into minimizing energy input for rapid establishment and stable operation of MG systems towards environmentally sustainable wastewater management.

A comparative study on simultaneous recovery of phosphorus and alginate-like exopolymers from bacterial and algal-bacterial aerobic granular sludges: Effects of organic loading rate.

The effects of organic loading rate (OLR) on simultaneous phosphorus (P) and alginate-like exopolymers (ALE) recovery from bacterial aerobic granular sludge (AGS) and algal-bacterial AGS were examined and compared during 70 days' operation. With the increase of OLR (0.6-1.2 g COD/(L·day)), both AGS showed good settleability and granular strength with P bioavailability > 92% (Stage III). The moderate increase in OLR had a positive influence on simultaneous recovery of P and ALE. On day 60, the contents of ALE and guluronic acid/guluronic acid (GG) blocks reached the highest in algal-bacterial AGS, about 13.37 and 2.13 mg/g-volatile suspended solids (VSS), respectively. Meanwhile, about daily 0.55 kg of P is estimated to be recovered from the wastewater treatment plant with a treatment capacity of 10,000 m3/day. P mass balance analysis during ALE extraction from both AGS was conducive to further evaluation of P removal pathway and its application potentials.

Insight into aerobic phosphorus removal from wastewater in algal-bacterial aerobic granular sludge system.

This study aimed to figure out the main contributors to aerobic phosphorus (P) removal in the algal-bacterial aerobic granular sludge (AGS)-based wastewater treatment system. Kinetics study showed that aerobic P removal was controlled by macropore (contributing to 64-75% P removal) and micropore diffusion, and the different light intensity (0, 4.0, 12.3, and 24.4 klux) didn't exert significant (p > 0.05) influence on P removal. On the other hand, the increasing light intensity did promote microalgae metabolism, leading to the elevated wastewater pH (8.0-9.8). The resultant pH increase had a strongly negative relationship (R2 = 0.9723) with P uptake by polyphosphate-accumulating organisms, while promoted chemical Ca-P precipitation at a molar Ca/P ratio of 1.05. Results from this work could provide an in-depth understanding of microalgae-bacteria symbiotic interaction, which is helpful to better design and operate the algal-bacterial AGS systems.

Effect of traditional chinese medicine (TCM) and its fermentation using Lactobacillus plantarum on ceftriaxone sodium-induced dysbacteriotic diarrhea in mice.

BACKGROUND: Buzhongyiqi decoction (BD), Sijunzi decoction (SD), and Shenlingbaizhu decoction (SHD) have been extensively used clinically for the treatment of diseases caused by spleen-Qi deficiency and microbial fermentation has historically been utilized in traditional Chinese medicine (TCM). This study aimed to investigate the mitigative effect of TCM and fermented TCM (FTCM) with Lactobacillus plantarum (LP) on antibiotic-associated diarrhea, and to select an optimal formula and then identify its compounds. METHODS: Dysbacteriosis in mice was induced by ceftriaxone sodium (CS). The mice were then treated with LP, BD, SD, SHD, fermented BD, fermented SD (FSD), and fermented SHD. Diarrhea indexes, the abundances of gut bacteria, intestinal morphometrics, and mRNA expressions of genes related to intestinal barrier function were assessed. Then, ultra-high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UHPLC-Q-TOF/MS) were employed to identify and relatively quantify the compounds in the selected decoctions. RESULTS: CS significantly increased the fecal output weight, the total number of fecal output, and fecal water content, indicating the occurrence of diarrhea. Bacterial culture tests showed that the above symptoms were accompanied by the disruption of specific intestinal flora. TCM, LP, and FTCM alleviated the diarrhea index and recovered the intestinal microbiota. FTCM showed more advantageous than TCM or LP alone. The mRNA expressions of aquaporins (AQPs) and tight junctions (TJs) decreased by CS were enhanced by TCM, LP, and FTCM. In addition, through UHPLC-Q-TOF/MS, (S)-(-)-2-hydroxyisocaproic acid, L-methionine, 4-guanidinobutyric acid (4GBA), and phenyllactate (PLA) in SD and FSD were identified and relatively quantified. CONCLUSIONS: TCM, LP, and TCM fermented with LP alleviated CS-induced diarrhea symptoms, and improved the intestinal flora and barrier function. Four compounds including (S)-(-)-2-hydroxyisocaproic acid, L-methionine, 4GBA, and PLA in FSD, which were identified by UHPLC-Q-TOF/MS, might function in modulating intestinal flora and improving villi structure.

Simultaneous recovery of phosphorus and alginate-like exopolysaccharides from two types of aerobic granular sludge.

Wastewater treatment plants are expected to realize not only pollutants removal from wastewater but also resources recovery such as phosphorus (P) and alginate-like exopolysaccharides (ALE) from the produced sludge. In this study, ALE extraction and fractionation from the same activated sludge-derived bacterial aerobic granular sludge (AGS) and algal-bacterial AGS were performed in addition to P fate examination during ALE recovery. Results showed that the ALE content recovered from algal-bacterial AGS was 8.81 ± 0.02 mg/g-volatile suspended solids (VSS), about 2.8 times higher than that from bacterial AGS when fed with the same synthetic wastewater. Moreover, the mannuronic acid to guluronic acid (MG) blocks accounted for the largest proportion of ALE from the two granular sludges. In particular, the extracellular polymeric substances (EPS) extracted from bacterial and algal-bacterial AGS contained about 25.10 ± 1.85 and 19.53 ± 0.04 mg-P/g-SS, respectively, and both granular sludges possessed high P bioavailability of 97-99%.

Achieving stably enhanced biological phosphorus removal from aerobic granular sludge system via phosphorus rich liquid extraction during anaerobic period.

In order to sustainably manage wastewater treatment plants and the environment, enhanced biological phosphorus (P) removal (EBPR) was proposed to achieve P recovery through extracting P-rich liquid (i.e., Phostrip) from the bottom of aerobic granular sludge (AGS)-based sequencing batch reactors (SBRs) under no mixing during the anaerobic phase. Results showed both tested bacterial AGS (BAGS) and algal-bacterial AGS (A-BAGS) systems stably produced low effluent P (<0.05 mg-P/L) with little impact on their organics and NH4+-N removals (>99%). The collected P-rich liquids (55-83 mg-P/L) from both systems showed great potential for P recovery of about 83.85 ± 0.57 % (BAGS) or 83.99 ± 0.77% (A-BAGS), which were contributed by the influent P (>95%) and P reserves in granules based on P balance analysis. This study suggests that the AGS-based SBRs coupling the Phostrip holds great potentials for P recovery profit and further reduction in energy consumption.

Ionic response of algal-bacterial granular sludge system during biological phosphorus removal from wastewater.

Biological phosphorus removal (BPR) from wastewater can be generally realized through alternative non-aeration and aeration operation to create anaerobic and aerobic conditions respectively for P release and uptake/accumulation by polyphosphate accumulating organisms (PAOs), with P removal finally achieved by controlled discharge of P-rich sludge. In this study, the response of algal-bacterial aerobic granular sludge (AB-AGS) during BPR to main ions including Ac- (acetate), Cl-, SO42-, NH4+, K+, Mg2+, Ca2+ and Na+ in wastewater was investigated with conventional bacterial AGS (B-AGS) as control and acetate as the sole carbon source. Results show that BPR process mainly involved the changes of Ac-, K+, Mg2+, and Ca2+ rather than Cl-, SO42-, NH4+ and Na+. The mole ratio of ΔP/ΔAc kept almost unchanged during the non-aeration (P release) phase in both B-AGS and AB-AGS systems (ΔPB-AGS/ΔAcB-AGS > ΔPAB-AGS/ΔAcAB-AGS), and it was negatively influenced by the light in AB-AGS systems, in which 62% of acetate was not utilized for P release at the high illuminance of 81 k lux. During the entire non-aeration/aeration period, both ΔK/ΔP and ΔMg/ΔP remained constant, while ΔKAB-AGS/ΔPAB-AGS > ΔKB-AGS/ΔPB-AGS and ΔMgAB-AGS/ΔPAB-AGS ≈ ΔMgB-AGS/ΔPB-AGS. The presence of algae seemed not beneficial for PAOs to remove P, while more K+ and P uptake by algae in AB-AGS suggest its great potential for manufacturing biofertilizer.

Behavior of algal-bacterial granular sludge in a novel closed photo-sequencing batch reactor under no external O2 supply.

Algal-bacterial aerobic granular sludge (AB-AGS) as a symbiosis system possesses high potential for being operated without external O2 supply. In this study, a novel lab-scale closed photo-sequencing batch reactor (PSBR) was developed for AB-AGS operation under successively open (Phase Ⅰ) and closed (Phase Ⅱ) conditions. Results show that AB-AGS maintained almost 100% of organics removal, exhibiting higher removals of phosphate (63 ± 20%), K+ (19 ± 12%) and Mg2+ (26 ± 12%), and higher chlorophylls content during Phase II. Meanwhile, only O2 besides N2 was detectable in the headspace of PSBR. The change of granular structure and faster algae growth during Phase Ⅱ may contribute to the increase of microbial activity and phosphorus bioavailability, in which lower extracellular polymeric substances content may account for low biomass retention. Results from this closed PSBR imply that AB-AGS has the potential to reduce some greenhouse gases like CO2 and CH4 emission.