Mixotrophic denitrification of waste activated sludge fermentation liquid as an alternative carbon source for nitrogen removal: Reducing N2O emissions and costs.

Heterotrophic-sulfur autotrophic denitrification (HAD) has been proposed to be a prospective nitrogen removal process. In this work, the potential of fermentation liquid (FL) from waste-activated sludge (WAS) as the electron donor for denitrification in the HAD system was explored and compared with other conventional carbon sources. Results showed that when FL was used as a carbon source, over 99% of NO3--N was removed and its removal rate exceeded 14.00 mg N/g MLSS/h, which was significantly higher than that of methanol and propionic acid. The produced sulfate was below the limit value and the emission of N2O was low (1.38% of the NO3--N). Microbial community analysis showed that autotrophic denitrifiers were predominated in the HAD system, in which Thiobacillus (16.4%) was the dominant genus. The economic analysis showed the cost of the FL was 0.062 €/m3, which was 30% lower than that in the group dosed with methanol. Our results demonstrated the FL was a promising carbon source for the HAD system, which could reduce carbon emission and cost, and offer a creative approach for waste-activated sludge resource reuse.

Distinct effects of typical sludge pretreatment approaches on the antibiotic resistance genes variations, associated bacterial community dynamics and metabolic activities during anaerobic fermentation process.

Anaerobic fermentation is effective for waste activated sludge (WAS) disposal to realize resource generation and pollutants reduction, and various pretreatments were commonly applied to improve the performance. This work mainly investigated the effects of typical WAS pretreatment approaches on the antibiotic resistance genes (ARGs, as emerging contaminants) removal during anaerobic fermentation processes and unveiled the underlying mechanisms. The results indicated that all the pretreatment strategies exhibited evident effects on the overall ARGs removal with the order of Fe2+ activated persulfate (PS/Fe2+) > pH 10 > Ultrasonication > Heat, and showed selective removal tendency for the specific ARGs (namely easily removed (aadA1 and sul1) and persistent ARGs). Mechanistic analysis demonstrated that the pretreatments disrupted the extracellular polymeric substances (EPS) and rose the cell membrane permeability (particularly for PS/Fe2+ and Heat). Then the increased ARGs release benefitted the subsequent reduction of mobile genetic elements (MGEs) and extracellular ARGs (especially for PS/Fe2+ and pH10), resulting the ARGs attenuation. Pretreatments significantly shifted the microbial community structure and the abundances of potential ARGs hosts (i.e., Sulfuritalea, and Denitratisoma). Also, the different pretreatments exhibited distinct effects on the microbial metabolic traits related with ARGs proliferation (i.e., ABC transporters, two-component system and bacterial secretion systems), which also contributed to the ARGs attenuations during WAS fermentation. The partial least-squares path modeling (PLS-PM) analysis indicated that the bacterial community (total effects = 0.968) was key factor determining ARGs fates.

Revealing the mechanism of quartz sand seeding in accelerating phosphorus recovery from anaerobic fermentation supernatant through vivianite crystallization.

The recovery of phosphorus (P) through vivianite crystallization offers a promising approach for resource utilization in wastewater treatment plants. However, this process encounters challenges in terms of small product size and low purity. The study aimed to assess the feasibility of using quartz sand as a seed material to enhance P recovery and vivianite crystal characteristics from anaerobic fermentation supernatant. Various factors, including seed dosage, seed size, Fe/P ratio, and pH, were systematically tested in batch experiments to assess their influence. Results demonstrated that the effect of seed enhancement on vivianite crystallization was more pronounced under higher seed dosages, smaller seed sizes, and lower pH or Fe/P ratio. The addition of seeds increased P recovery by 4.43% in the actual anaerobic fermentation supernatant and also augmented the average particle size of the recovered product from 19.57 to 39.28 µm. Moreover, introducing quartz sand as a seed material effectively reduced co-precipitation, leading to a notable 12.5% increase in the purity of the recovered vivianite compared to the non-seeded process. The formation of an ion adsorption layer on the surface of quartz sand facilitated crystal attachment and growth, significantly accelerating the vivianite crystallization rate and enhancing P recovery. The economic analysis focused on chemical costs further affirmed the economic viability of using quartz sand as a seed material for P recovery through vivianite crystallization, which provides valuable insights for future research and engineering applications.

Recovery of phosphorus from wastewater containing humic substances through vivianite crystallization: Interaction and mechanism analysis.

Vivianite crystallization has been regarded as a suitable option for recovering phosphorus (P) from P-containing wastewater. However, the presence of humic substances (HS) would inevitably affect the formation of vivianite crystals. Therefore, the influences of HS on vivianite crystallization and the changes in the harvested vivianite crystals were investigated in this study. The results suggested the inhibition effect of 70 mg/L HS on vivianite crystallization reached 12.24%, while it could be attenuated by increasing the pH and Fe/P ratio of the solution. Meanwhile, the addition of HS altered the size, purity, and morphology of recovered vivianite crystals due to the blockage of the growth sites on the crystal surface. Additionally, the formation of phosphate ester group, hydrogen bonding, and COOH-Fe2+ complexes are the potential mechanisms of HS interaction with vivianite crystals. The results obtained herein will help to elucidate the underlying mechanism of HS on vivianite crystallization from P-containing wastewater.

Metagenomic insight into the prevalence and driving forces of antibiotic resistance genes in the whole process of three full-scale wastewater treatment plants.

The spread of antibiotic resistance genes (ARGs) is an emerging global health concern, and wastewater treatment plants (WWTPs), as an essential carrier for the occurrence and transmission of ARGs, deserves more attention. Based on the Illumina NovaSeq high-throughput sequencing platform, this study conducted a metagenomic analysis of 18 samples from three full-scale WWTPs to explore the fate of ARGs in the whole process (influent, biochemical treatment, advanced treatment, and effluent) of wastewater treatment. Total 70 ARG subtypes were detected, among which multidrug, aminoglycoside, tetracycline, and macrolide ARGs were most abundant. The different treatment processes used for three WWTPs were capable of reducing ARG diversity, but did not significantly reduce ARG abundance. Compared to that by denitrification filters, the membrane bioreactor (MBR) process was advantageous in controlling the prevalence of multidrug ARGs in WWTPs. Linear discriminant analysis Effect Size (LEfSe) suggested g_Nitrospira, g_Curvibacter, and g_Mycobacterium as the key bacteria responsible for differential ARG prevalence among different WWTPs. Meanwhile, adeF, sul1, and mtrA were the persistent antibiotic resistance genes (PARGs) and played dominant roles in the prevalence of ARGs. Proteobacteria and Actinobacteria were the host bacteria of majority ARGs in WWTPs, while Pseudomonas and Nitrospira were the most crucial host bacteria influencing the dissemination of critical ARGs (e.g., adeF). In addition, microbial richness was determined to be the decisive factor affecting the diversity and abundance of ARGs in wastewater treatment processes. Overall, regulating the abundance of microorganisms and key host bacteria by selecting processes with microbial interception, such as MBR process, may be beneficial to control the prevalence of ARGs in WWTPs.

Insight into the interaction between trimethoprim and soluble microbial products produced from biological wastewater treatment processes.

Soluble microbial products (SMPs), dissolved organic matter excreted by activated sludge, can interact with antibiotics in wastewater and natural water bodies. Interactions between SMPs and antibiotics can influence antibiotic migration, transformation, and toxicity but the mechanisms involved in such interactions are not fully understood. In this study, integrated spectroscopy approaches were used to investigate the mechanisms involved in interactions between SMPs and a representative antibiotic, trimethoprim (TMP), which has a low biodegradation rate and has been detected in wastewater. The results of liquid chromatography-organic carbon detection-organic nitrogen detection indicated that the SMPs used in the study contained 15% biopolymers and 28% humic-like substances (based on the total dissolved organic carbon concentration) so would have contained sites that could interact with TMP. A linear relationship of fluorescent intensities of tryptophan protein-like substances in SMP was observed (R2>0.99), indicating that the fluorescence enhancement between SMP and TMP occurred. Fourier-transform infrared spectroscopy and X-ray photoelectron spectroscopy indicated that carboxyl, carbonyl, and hydroxyl groups were the main functional groups involved in the interactions. The electrostatic and π-π interactions were discovered by the UV-vis spectra and 1H nuclear magnetic resonance spectra. Structural representations of the interactions between representative SMP subcomponents and TMP were calculated using density functional theory, and the results confirmed the conclusions drawn from the 1H nuclear magnetic resonance spectra. The results help characterize SMP-TMP complexes and will help understand antibiotic transformations in wastewater treatment plants and aquatic environments.

Sludge reduction and microbial community evolution of activated sludge induced by metabolic uncoupler o-chlorophenol in long-term anaerobic-oxic process.

Excess sludge management is a restrictive factor for the development of municipal wastewater treatment plants. The addition of metabolic uncouplers has been proven to be effective in sludge reduction. However, the long-term effect of metabolic uncoupler o-chlorophenol (oCP) on the biological wastewater treatment system operated in anaerobic-oxic mode is still unclear. To this end, two parallel reactors operated in anaerobic-oxic mode with and without 10 mg/L of oCP addition were investigated for 91 days. The results showed that 56.1 ± 2.3% of sludge reduction was achieved in the oCP-added system, and the nitrogen and phosphorus removal ability were negatively affected. Dosing oCP stimulated the formation of microbial products and increased the DNA concentration, but resulted in a decrease in the electronic transport activity of activated sludge. Microbial community analysis further demonstrated that a significant reduction of bacterial richness and diversity occurred after oCP dosing. However, after stopping oCP addition, the pollutant removal ability of activated sludge was gradually increased, but the sludge yield, as well as species richness and diversity, did not recover to the previous level. This study will provide insightful guidance on the long-term application of metabolic uncouplers in the activated sludge system.

Mechanisms of allicin exposure for the sludge fermentation enhancement: Focusing on the fermentation processes and microbial metabolic traits.

As a frequently used product with antimicrobial activity, consumed allicin might be discharged and concentrated in waste-activated sludge (WAS). However, the influence of allicin (as an exogenous pollutant) on WAS fermentation has not been clearly revealed. This study aimed to disclose the impacts of allicin on volatile fatty acid (VFA) generation during WAS fermentation. The results showed that the appropriate presence of allicin (10 mg/g TSS) significantly enhanced the VFA yield (1894 versus 575 mg COD/L in the control) with increased acetate proportion (24.3%). Further exploration found that allicin promoted WAS solubilization, hydrolysis and acidification simultaneously. Metagenomic analysis revealed that the key genes involved in extracellular hydrolysis metabolism (i.e., CAZymes), membrane transport (i.e., gtsA and ytfT), substrate metabolism (i.e., yhdR and pfkC) and fatty acid synthesis (i.e., accA and accD) were all highly expressed. Allicin also induced the bacteria to produce more signalling molecules and regulate cellular functions, thereby enhancing the microbial adaptive and regulatory capacity to the unfavourable environment. Moreover, the variations in fermentative microbes and their contributions to the upregulation of functional genes (i.e., ytfR, gltL, INV, iolD and pflD) for VFA generation were disclosed. Overall, the simultaneous stimulation of functional microbial abundances and metabolic activities contributed to VFA production in allicin-conditioned reactors.

Catalytic ozonation treatment of papermaking wastewater by Ag-doped NiFe2O4: Performance and mechanism.

The catalytic ozonation treatment of secondary biochemical effluent for papermaking wastewater by Ag-doped nickel ferrite was investigated. Ag-doped catalysts prepared by sol-gel method were characterized, illustrating that Ag entirely entered the crystalline of NiFe2O4 and changed the surface properties. The addition of catalyst enhanced the removal efficiency of chemical oxygen demand and total organic carbon. The results of gas chromatography-mass spectrometer, ultraviolet light absorbance at 254 nm and three-dimensional fluorescence excitation-emission matrix suggested that aromatic compounds were efficiently degraded and toxic substances, such as dibutyl phthalate. In addition, the radical scavenging experiments confirmed the hydroxyl radicals acted as the main reactive oxygen species and the surface properties of catalysts played an important role in the reaction. Overall, this work validated potential applications of Ag-doped NiFe2O4 catalyzed ozonation process of biologically recalcitrant wastewater.

Impacts of environmental factors on AHL-producing and AHL-quenching activities of aerobic granules.

Aerobic granule is widely recognized as a promising biological wastewater treatment technique. Acyl-homoserine lactone (AHL)-mediated quorum sensing and quenching are reported to be involved in the formation of aerobic granules. However, little is known about how environmental factors affect the AHL-producing and AHL-quenching communities and their activities in aerobic granules. Therefore, in this work, the bacterial community of aerobic granules was explored and the impacts of substrate, electron acceptor, sludge concentration, pH, and temperature on the AHL-related communities and activities of aerobic granules were examined. These factors were found to affect the AHL-related activities, and thereby change the AHL level. The AHL-producing activities were observed to be more sensitive to the variation of these factors than the AHL-quenching activities. These findings help to establish the links between environmental factors and AHL-related activities and thus provide useful guides for the operation of aerobic granule systems.

Study on the interaction mechanism between cefradine and Chlamydomonas reinhardtii in water solutions under dark condition.

Our research investigated the hormesis effect of cefradine on the specific growth rates (µ) of single-celled algae (Chlamydomonas reinhardtii) from aqueous solutions. We found the specific growth rate of C. reinhardtii slightly increased with cefradine concentrations within the range 0.5-10 mg/L. Effects of algae density, initial solution pH, and temperature on the adsorption batch assays were investigated. The optimum conditions for cefradine adsorption occurred at a density of 5 × 106 algae cells/mL, a solution pH of 7.0, and a temperature of 25.0 °C. A Box-Behnken design was employed to evaluate correlations between influential factors and cefradine adsorption. The results showed a significant interaction between algae density and temperature. The maximum removal rate could reach 50.13% under the optimal conditions. Additionally, the adsorption mechanisms were explored through Langmuir and Freundlich isotherm equations, adsorption kinetics, and thermodynamics. The results suggested that the adsorption process was monolayer, spontaneous, and endothermic with an increase in randomness at the algae-solution interface, which followed a pseudo-second-order model. All the data indicated that the alga performed a better removal capacity in the antibiotic-containing wastewater treatment process. This study lays the groundwork for a better understanding of the interaction mechanism between cefradine and Chlamydomonas reinhardtii in water solutions under dark condition.

Synergistic reduction of pollution and carbon mitigation in constructed wetlands-microbial fuel cell using sludge-derived biochar.

Integrating microbial fuel cells (MFC) into constructed wetland systems (CW) has been an efficient wastewater treatment to improve the pollutants removal and regenerate power energy. This study fabricated a sludge biochar material (SBM) to sequestrate the carbon of residual sludge. Thereafter used SBM and modified SBM as the substrate materials to construct three groups of CW-MFC for decreasing the greenhouse gas (GHG) emission. The water quality improvement in removal efficiency achieved (2.59 %, 3.10 %, 5.21 % for COD; 3.31 %, 3.60 %, 6.71 % for TN; 1.80 %, 7.38 %, 4.93 % for TP) by the application of MFC, SBM, and modified SBM in wastewater treatment, respectively. Additionally, the reduction in global warming potential (GWP) realized 17.2 %, 42.2 %, and 64.4 % resulting from these applications. The carbon flow and fate diagrams showed MFC shifted the gas phase­carbon flow from CH4 to CO2, and SBM promoted this shift trends. Microbial diversity indicated enrichment of electrochemically active bacteria (EAB), denitrifying bacteria, and phosphate accumulating organisms (PAOs) by SBM. Metabolic pathways analysis showed that introduction of MFC and SBM exhibited significant increases of key functional genes in metabolic pathway of anaerobic oxidation of methane (AOM). This study highlights the benefit of CW-MFC in and provides a new strategy for removing pollutants and abating GHG emissions in wastewater treatment.

Novel calcium oxide activated peroxymonosulfate system for methylene blue removal: Identification of key influencing factors, transformation pathway and toxicity assessment.

The activation of peroxymonosulfate (PMS) has gained significant interest in the removal of organic pollutants. However, traditional methods usually suffer from drawbacks such as secondary contamination and high energy requirements. In this study, we propose a green and cost-effective approach utilizing calcium oxide (CaO) to activate PMS, aiming to construct a simple and reliable PMS based advanced oxidation processes (AOPs). The proposed CaO/PMS system achieved fast degradation of methylene blue (MB), where the degradation rate of CaO/PMS system (0.24 min-1) was nearly 2.67 times that of PMS alone (0.09 min-1). Under the optimized condition, CaO/PMS system exhibited remarkable durability against pH changes, co-exists ions or organic matters. Furthermore, singlet oxygen (1O2) was identified as the dominant reactive oxygen species by electron paramagnetic resonance (EPR) and quenching tests. Accordingly, the degradation pathways of MB are proposed by combing the results of LC/MS analysis and density functional theory (DFT) calculations, and the predicted ecotoxicity of the generated byproducts evaluated by EOCSAR could provide systematic insights into the fates and environmental risks of MB. Overall, the study provides an eco-friendly and effective strategy for treating dyeing wastewater, which should shed light on the application of PMS based AOPs.

Dynamic microbiome disassembly and evolution induced by antimicrobial methylisothiazolinone in sludge anaerobic fermentation for volatile fatty acids generation.

In the post-COVID-19 pandemic era, various antimicrobials have emerged and concentrated in waste-activated sludge (WAS), affecting the biological treatment of WAS. However, there is still a knowledge gap in the dynamic response and adaptive mechanism of anaerobic microbiome under exogenous antimicrobial stress. This study found that methylisothiazolinone (MIT, as a typic antimicrobial) caused an interesting lag effect on the volatile fatty acids (VFAs) promotion in the WAS anaerobic fermentation process. MIT was effective to disintegrate the extracellular polymeric substances (EPS), and those functional anaerobic microorganisms were easily exposed and negatively impacted by the MIT interference after the loss of protective barriers. Correspondingly, the ecological interactions and microbial metabolic functions related to VFA biosynthesis (e.g., pyruvate metabolism) were downregulated at the initial stage. The syntrophic consortia gradually adapted to the interference and attenuated the MIT stress by activating chemotaxis and resistance genes (e.g., excreting, binding, and inactivating). Due to the increased bioavailable substrates in the fermentation systems, the dominant microorganisms (i.e., Clostridium and Caloramator) with both VFAs production and MIT-tolerance functions have been domesticated. Moreover, MIT disrupted the syntrophic interaction between acetogens and methanogens and totally suppressed methanogens' metabolic activities. The VFA production derived from WAS anaerobic fermentation was therefore enhanced due to the interference of antimicrobial MIT stress. This work deciphered dynamic changes and adaptive evolution of anaerobic syntrophic consortia in response to antimicrobial stress and provided guidance on the evaluation and control of the ecological risks of exogenous pollutants in WAS treatment.

Genetic characteristics of lung adenocarcinoma with ground-glass opacity component.

Background: Increasing evidence suggests that ground-glass opacity featured lung adenocarcinoma (GGO-LUAD) and pure solid-LUAD have significantly different tumor biological behaviors; the former is usually indolent. Genetic variations fundamentally contribute to this distinct tumor behaviors. This study aims to investigate and compare the gene mutations using next-generation sequencing (NGS) technology in these two subtypes of LUAD. Methods: The clinical data and gene testing results of 46 patients suffering from LUAD with a histologically invasive subtype ≤3 cm and operated in the Thoracic Surgery Department of Beijing Tsinghua Changgung Hospital from May 2019 to December 2022 were retrospectively analyzed; a case-control study was performed to compare the pathological and genetic differences between LUAD with a GGO component and pure solid-LUAD. Results: Notable differences existed in vascular invasion, tumor spread through air spaces (STAS) and high-risk histological subtypes (micropapillary or solid subtypes) between the two types of LUAD with similar histologically invasive size. No significant difference was found in the mutation frequency of EGFR and KRAS. However, gene mutations were more prevalent in the cell cycle and TP53 signaling pathway for solid-LUAD. A significant difference was found in the mutation frequency of the tumor suppressor genes TP53 and CDKN2A between the two types. Conclusions: The wild-type TP53 and CDKN2A genes could potentially be used as molecular indicators for indolent LUAD characterized by GGO-featured.

Insights into integrated glycerol-driven partial denitrification-anaerobic ammonium oxidation system using bioinformatic analysis: The dominance of Bacillus spp. and the potential of nitrite producing via assimilatory nitrate reduction.

Partial denitrification-anaerobic ammonium oxidation (PD/A) was considered a novel technology for biological nitrogen removal. In this study, a glycerol-driven PD/A granular sludge reactor was constructed, and its nitrogen removal efficiency and microbial mechanisms were investigated systematically. After optimization, the PD/A reactor achieved 92.3 % of the nitrogen removal (~90 % by anammox) with the influent COD/NO3--N ratio of 2.6, and approximate 1.36 mol NO3--N was required for removing 1 mol NH4+-N. Granular sludge with layered structure (anaerobic ammonium oxidizing bacteria (AnAOB) was wrapped by the heterotrophic bacteria) was successfully developed, which resulted in the sludge floating. Bacillus was firstly found to be the dominant genus in PD/A system with an abundance of 46.1 %, whereas the AnAOB only accounted for 0.2-2.8 %. Metatranscriptomic analysis showed that the metabolic characteristics obviously changed during the operation, and the differential expressing genes mainly belonged to ABC transport and quorum sensing pathway. Further analysis about the expressing patterns of nitrogen metabolism related genes indicated that the anammox related genes (mainly from Candidatus Brocadia and Candidatus Jettenia) exhibited a much higher expressing level than other genes. Interestingly, the assimilatory nitrate reduction process in Bacillus showed great NO2--N producing potential, so it was considered to be an essential pathway participating in PD/A process. This study provided a comprehensive insight into the glycerol-driven PD/A system.

Influence of C/N ratio and ammonia on nitrogen removal and N2O emissions from one-stage partial denitrification coupled with anammox.

The development of low carbon treatment processes is an important issue worldwide. Partial denitrification coupled with anammox (PD/A) is a novel strategy to remove nitrogen and reduce N2O emissions. The influence of C/N ratio and NH4+ concentration on nitrogen removal and N2O emissions was investigated in batch reactors filled with PD/A coupled sludge. A C/N ratio of 2.1 was effective for nitrogen removal and N2O reduction; higher ammonia concentration might make anammox more active and indirectly reduce N2O emissions. Long-term operation further confirmed that a C/N ratio of 2.1 resulted in a minimum effluent N2O concentration (mean value of 0.94 µmol L-1); as the influent NH4+ concentration decreased to 50 mg L-1 (NH4+-N/NO3--N: 1), the nitrogen removal rate increased to 82.41%. Microbial analysis showed that anammox bacteria (Candidatus Jettenia and Ca. Brocadia) were enriched in the PD/A system and Ca. Brocadia gradually dominated the anammox community, with the relative abundance increasing from 1.69% to 18.44% between days 97 and 141. Finally, functional gene analysis indicated that the abundance of nirS/K and hao involved in partial denitrification and anammox, respectively, increased during long-term operation of the reactor; this change benefitted nitrogen metabolism in anammox, which could indirectly reduce N2O emissions.

ZFP36 loss-mediated BARX1 stabilization promotes malignant phenotypes by transactivating master oncogenes in NSCLC.

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer, with high morbidity and mortality worldwide. Although the dysregulation of BARX1 expression has been shown to be associated with malignant cancers, including NSCLC, the underlying mechanism remains elusive. In this study, we identified BARX1 as a common differentially expressed gene in lung squamous cell carcinoma and adenocarcinoma. Importantly, we uncovered a novel mechanism behind the regulation of BARX1, in which ZFP36 interacted with 3'UTR of BARX1 mRNA to mediate its destabilization. Loss of ZFP36 led to the upregulation of BARX1, which further promoted the proliferation, migration and invasion of NSCLC cells. In addition, the knockdown of BARX1 inhibited tumorigenicity in mouse xenograft. We demonstrated that BARX1 promoted the malignant phenotypes by transactivating a set of master oncogenes involved in the cell cycle, DNA synthesis and metastasis. Overall, our study provides insights into the mechanism of BARX1 actions in NSCLC and aids a better understanding of NSCLC pathogenesis.

Prediction of biological nutrients removal in full-scale wastewater treatment plants using H2O automated machine learning and back propagation artificial neural network model: Optimization and comparison.

The effective control of total nitrogen (ETN) and total phosphorus (ETP) in effluent is challenging for wastewater treatment plants (WWTPs). In this work, automated machine learning (AutoML) (mean square error = 0.4200 âˆ¼ 3.8245, R2 = 0.5699 âˆ¼ 0.6219) and back propagation artificial neural network (BPANN) model (mean square error = 0.0012 âˆ¼ 6.9067, R2 = 0.4326 âˆ¼ 0.8908) were used to predict and analyze biological nutrients removal in full-scale WWTPs. Interestingly, BPANN model presented high prediction performance and general applicability for WWTPs with different biological treatment units. However, the AutoML candidate models were more interpretable, and the results showed that electricity carbon emission dominated the prediction. Meanwhile, increasing data volume and types of WWTP hardly affected the interpretable results, demonstrating its wide applicability. This study demonstrated the validity and the specific advantages of predicting ETN and ETP using H2O AutoML and BPANN model, which provided guidance on the prediction and improvement of biological nutrients removal in WWTPs.

Re-circulation of Fe/persulfate regulated sludge fermentation products for sewage treatment: Focus on pollutant removal efficiency, microbial community and metabolic activity.

Persulfate (PS)-based technologies have been demonstrated as efficient methods for enhancing the performance of waste activated sludge (WAS) anaerobic fermentation. Except for volatile fatty acids (VFAs), however, some exogenous substances would be also released during this process, which might affect its application as a carbon source for sewage treatment. To fill this knowledge gap, the feasibility of sludge fermentation liquid regulated by Fe/persulfate (PS) (PS-FL) as a carbon source for sewage treatment was investigated in this study. Results indicated that PS-FL exhibits distinct effects on the pollutants removal compared with commercial sodium acetate. It facilitates PO43--P removal but slightly inhibited COD removal & denitrification, and sludge settleability was also decreased. The mechanistic analysis demonstrated that PS-FL could stimulate the enrichment of phosphorus-accumulating bacteria (i.e. Candidatus Accumulibacter) and the enhancement of their metabolic activities (i.e. PKK), thereby enhancing the biological PO43--P removal. Moreover, Fe ions in PS-FL could combine with PO43--P to form a precipitate and thus further contributed to PO43--P removal. Conversely, the sulfate reduction process induced by SO42- in PS-FL inhibits denitrification by reducing the abundance of denitrifying bacteria (i.e. Dechloromonas) and metabolic activities (i.e. narG). Additionally, PS-FL also decreased the abundance of flocculation bacteria (i.e. Flavobacterium) and down-regulated the expression of functional genes responsible for COD removal, by which it exhibited certain negative effects on COD removal and sludge settleability. Overall, this work demonstrated that PS-FL can re-circulation as a carbon source for sewage treatment, which provides a new approach to recovering valuable carbon sources from WAS.