Enhancing biological dissolved organic nitrogen removal in landfill leachate wastewater: The role of sodium acetate co-metabolism

Dissolved organic nitrogen (DON) comprises approximately 25% of dissolved nitrogen in landfill leachate wastewater (LLW), posing potential risks such as stimulating algal growth and forming disinfection by-products if not treated properly. While DON characterization and removal by physicochemical methods in wastewater treatment systems have been examined, biological strategies for effective DON removal remain less developed. This study explores the influence of sodium acetate addition during denitrification process on LLW DON removal. With sodium acetate addition (Stage I), we achieved 99% ammonia removal, 94% total inorganic nitrogen (TIN) removal, and 45% DON removal. Fourier-transform ion cyclotron resonance mass spectrometry (FTICR-MS) results suggested the majority of sulfur-containing DON molecules were eliminated in Stage I. Conversely, in the absence of sodium acetate (Stage II), while 99% ammonia removal was maintained, TIN removal dropped to around 10%, and DON concentrations (largely sulfur-containing DON) increased by approximately 22%. Cycle tests revealed similar DON reductions in the aerobic phase across both stages, whereas in the anoxic phase, DON concentrations decreased in Stage I but increased in Stage II. Functional gene prediction indicated higher expression of decarboxylase and deaminase genes in Stage I compared to Stage II. Consequently, this study posits that sodium acetate addition enhances DON removal, potentially via co-metabolism.</p

Enhancing anammox process with granular activated carbon: A study on Microbial Extracellular Secretions (MESs)

Granular activated carbon (GAC), a porous carbon-based material, provides increased attachment space for functional microorganisms and enhances nitrogen removal by facilitating extracellular electron transfer in the anammox process. This study investigates the effects of GAC on the biosynthesis of microbial extracellular secretions (MESs) and explores the roles of these secretions in anammox activities. Four lab-scale reactors were operated: two downstream UASB reactors (D1 and D2) receiving effluents from the upstream UASB reactors (U1: no-GAC, U2: yes-GAC). Our results indicate that MESs were enhanced with the addition of GAC. The effluent from U2 exhibited a 59.62 % higher amino acid content than that from U1. These secretions contributed to an increase in the nitrogen loading rate (NLR) in the downstream reactors. Specifically, NLR in D1 increased from 130.5 to 142.7 g N/m3/day, and in D2, it escalated from 137.5 to 202.8 g N/m3/day, likely through acting as cross-feeding substrates or vital nutrients. D2 also showed increased anammox bacterial activity, enriched Ca. Brocadia population and hao gene abundance. Furthermore, this study revealed that D2 sludge has significantly higher extracellular polymeric substances (EPS) (48.71 mg/g VSS) and a larger average granule size (1.201 ± 0.119 mm) compared to D1 sludge. Overall, GAC-stimulated MESs may have contributed to the enhanced performance of the anammox process.</p

Deciphering the role of granular activated carbon (GAC) in anammox: Effects on microbial succession and communication

Anaerobic ammonium oxidation (anammox) offered an energy-efficient option for nitrogen removal from wastewater. Granular activated carbon (GAC) addition has been reported that improved biomass immobilization, but the role of GAC in anammox reactors has not been sufficiently revealed. In this study, it was observed that GAC addition in an upflow anaerobic sludge blanket (UASB) reactor led to the significantly shortened anammox enrichment time (shortened by 45 days) than the reactor without GAC addition. The nitrogen removal rate was 0.83 kg N/m3/day versus 0.76 kg N/m3/day in GAC and non-GAC reactors, respectively after 255 days’ operation. Acyl-homoserine lactone (AHL) quorum sensing signal molecule C8-HSL had comparable concentrations in both anammox reactors, whereas the signal molecule C12-HSL was more pervasive in the reactor containing GAC than the reactor without GAC. Microbial analysis revealed distinct anammox development in both reactors, with Candidatus Brocadia predominant in the reactor that did not contain GAC, and Candidatus Kuenenia predominant in the reactor that contained GAC. Denitrification bacteria likely supported anammox metabolism in both reactors. The analyses of microbial functions suggested that AHL-dependent quorum sensing was enhanced with the addition of GAC, and that GAC possibly augmented the extracellular electron transfer (EET)-dependent anammox reaction.</p

Enhancing anammox process at moderate temperature via employing anammox granular sludge reactor effluent addition

The anaerobic ammonium oxidation (anammox) application on mainstream wastewater treatment is limited by the ambient environment and slow growth rate of anammox bacteria. Bulk liquid in established anammox granular sludge bioreactors naturally contains active factors that could potentially boost anammox process under suboptimal conditions. In this study, effluent of a granular sludge-based anammox up-flow anaerobic sludge blanket treating ammonium-rich wastewater was harvested (the effluent is named as UAE) and continuously added into a bioreactor treating low-strength wastewater at 25 °C to study the effects and mechanisms on enhancing the anammox process. The NH4+-N removal efficiencies increased from 6.5% - 32.5% to 89.7% – 93.8%, and anammox genera accounted from 0.1% to 12.1% of microbial community in the receiving reactor with UAE addition. Coupled partial denitrification and dissimilatory nitrate reduction to ammonium (DNRA) processes with anammox were stimulated by UAE addition. Metagenomic analysis showed that the acyl-homoserine lactone-dependent quorum sensing molecules synthesis pathway was enhanced and an increased concentration of C8-HSL from 2.59 ng/L to 4.62 ng/L was observed in the UAE-receiving reactor. Selective amino acid transportation, amino acids biosynthesis and energy metabolic pathways of microbial community were upregulated with UAE addition. We demonstrate UAE as anammox biocatalyst and facilitate a deeper understanding for synergistic effect of active factors in UAE modified microhabitat for anammox metabolism in the UAE-receiving reactor.</p

Rapid enrichment of anammox bacteria for low-strength wastewater treatment: Role of influent nitrite and nitrate ratios in sequencing batch reactors (SBRs)

Anaerobic ammonium oxidation (Anammox) bacteria (AnAOB) have a long doubling time, which represents one of the key challenges for starting up anammox-based reactors. This study investigated the effect of varied nitrite/nitrate ratios on the anammox reactor startup process using five lab-scale anammox sequencing batch reactors (SBRs) (R1-R5). Nitrate addition significantly accelerated AnAOB enrichment startup, particularly during nitrite accumulation phase. The total start-up time was shortened by 55–71 days, compared to the reactor without nitrate. In R1 (nitrite/nitrate=10:0), anammox contributed the highest nitrogen removal percentage (91%), while R2 (nitrite/nitrate=7:3), with nitrate added, exhibited the highest anammox activity (53.84 mg NH4+-N/g VSS/day) in the steady-state phase. As nitrate proportions increased (R3-R5), anammox activity gradually declined due to limited available COD required for the conversion of NO3- to NO2-. Furthermore, it was found that nitrate-added improved the sludge settleability, with lower SVI30. 16S rRNA gene revealed that Ca. Brocadia was the predominant AnAOB in R1, R2 and R3, where nitrite was the primary NOx--N species (≥50%) in the influent. While in the reactor with low concentration of nitrite (R4: nitrite/nitrate=3:7), Ca. Kuenenia was the dominant AnAOB. This study successfully established a complex and balanced ecosystem with multi-species coexistence, where AnAOB served as the primary functional group on nitrogen removal, supported by denitrification bacteria and dissimilatory nitrate reduction to ammonium (DNRA) bacteria. This study proposes a rapid start-up strategy for the anammox process, which overcomes the bottleneck of long start-up time and helps to promote the application of anammox in wastewater treatment.</p

Reservoir quality prediction of deeply buried tight sandstones in extensively faulted region: A case from the middle-Upper Jurassic Shishugou Group in central Junggar Basin, NW China

The reservoir quality of tight sandstones is generally determined by the depositional environment, burial depth and diagenesis. However, the relationship between reservoir quality of tight sandstones and the controlling factors are very complicated. Deeply buried Middle-Upper Jurassic Shishugou Group sandstones are important tight oil sandstone reservoirs in the central Junggar Basin of NW china. The individual sandstones are thin (2–20m, av.7.8m), overlain by an unconformity and directly connected to the source rock by a well-developed fault system. The diagenetic system and reservoir quality of the Shishugou Group sandstones in the Central Junggar Basin was investigated using petrology, mineralogy, pore characteristics, sedimentary facies, burial and thermal history, knowledge of hydrocarbon charging, fault/fracture system, diagenetic reactions and sequence, controlling factors of reservoir quality, paleo-porosity reconstruction and formation mechanism of high-quality reservoir. The thin-section observation, scanning electron microscope (SEM and BSD), granularity analysis, Xray diffraction (XRD) and fluorescence microscope, 3D seismic and well logging analysis were used in this research. The top unconformity and faults system were the pathways for water and hydrocarbon migration. Organic acids and meteoric water with high concentrations of CO2 were the main fluids that caused dissolution of volcanic rock fragments, feldspar, analcime cement and early calcite cement. The paleo-porosity variation of Shishugou Group sandstones was analyzed quantitatively by the inversion and back stripping with the constrain of diagenetic evolution history and theoretical compaction models. The comprehensive researches including the origin of pore waters, origin of acidic fluids, fault/fracture system and hydrocarbon charging history, show that near-surface or meteoric diagenetic reactions of Shishugou Group sandstones closely beneath top unconformities were in open (geochemical) diagenetic systems, and that diagenetic (geochemical) systems were relatively open, especially in the faults-developed zone during burial process. The central sandstone body of the point bar, underwater distributary channel and distributary channel, which were cut through by the oil source fault, retained high-quality reservoir. The reservoir quality can be mostly predicted as a function of sedimentary environment (sedimentary facies and provenance), diagenetic reactions and burial history with the constrain of source rocks, diagenetic system and fault system

Diagenetic characteristics, evolution, controlling factors of diagenetic system and their impacts on reservoir quality in tight deltaic sandstones: Typical example from the Xujiahe Formation in Western Sichuan Foreland Basin, SW China

Deeply buried (3000–5000 m), deltaic sandstones of the Upper Triassic Xujiahe Formation are important tight gas reservoirs in the Sichuan Foreland Basin, China. The diagenesis of these tight sandstones was examined using a variety of petrographic and geochemical techniques, including thin section description, X-ray diffraction (XRD), whole-rock chemical analysis, scanning electron microscopy (SEM), Cathodoluminescence (CL) imaging, electron probe analysis, fluid inclusions and isotopic analysis. These integrated petrographic and geochemical techniques were used to determine the diagenetic history of the sandstones and its impact on the reservoir quality. The tight deltaic sandstones of the T3x2 and T3x4 (second and fourth members of Xujiahe Formation) have undergone a significant and complicated series of diagenetic alterations and changes in geochemical composition. Strong mechanical and chemical compaction together with carbonate cementation destroyed almost all the primary pores and the secondary dissolution pores now dominate the pore space. The T3x4 sandstones experienced a more open diagenetic system at near-surface and eodiagensis resulted in higher porosity than seen in the T3x2 sandstones. Both the T3x2 and T3x4 sandstones experienced closed-system diagenesis during middle-late mesodiagenesis. The early diagenetic dissolution, which mainly occurred in the open geochemical system, produced secondary pores and provided kaolinite and some K+ needed for the subsequent illitization of kaolinite and K-feldspar. The late dissolution of K-feldspar and illitization of K-feldspar in T3x4 sandstones and T3x2 sandstones during the mesodiagenesis, produced some effective secondary pores in the closed geochemical system or in the focused fluid flow zone along fractures. The diagenetic characteristics, size and evolution of (open vs closed) diagenetic system, which were constrained by the depositional environment, deep burial depth and tectonic activity, can be used to predict the reservoir quality ahead of drilling

Exploring interactions between quorum sensing communication and microbial development in anammox membrane bioreactor

The long duration required to enrich bacteria that perform anaerobic ammonium oxidation (anammox) limits their wide application in wastewater treatments. Anammox enrichment requires extensive microbial development, but the mechanisms involved are still being studied. Here, a total nitrogen removal rate of 1.22 kg N/m3/day was obtained over 280 days when anammox was enriched in a membrane bioreactor (MBR). Interactions between quorum sensing (QS) and microbial community development were investigated. Acyl-homoserine lactones (AHLs) were detected in the MBR effluent, with C8-HSL having the highest concentration (2.05 ng/L). The specific anammox activity (SAA) of the biomass increased from 335.8 (± 16.4) mg NH4+-N/g VSS/day to 382.9 (± 19.6) mg NH4+-N/g VSS/day with 0.1 μM C8-HSL addition. Anammox bacteria from the genus Candidatus Brocadia were enriched in the MBR. Metagenomic analysis suggested quorum sensing dependent on AHL and c-di-GMP (bis-[3′-5′]-cyclic dimeric guanosine monophosphate) contributed to microbial development. C-di-GMP-dependent quorum sensing may impact the formation of extracellular polymeric substances (EPS) and cell motility of biomass.</p

Photodriven Nanopump with Self-Augmented ROS Generation and Controllable Drug Release for Precisely Tuning Tumor Photodynamic-Chemotherapy

Although the stimulus-responsive nanoplatform shows excellent drug delivery preponderance in controlling drug release, its application is still inevitably restricted by exogenous uncontrollability, scarce biocompatibility, and a complex tumor microenvironment. Here, a photodriven self-augmented precision controllable nanoplatform was constructed by designing a novel pump-type switch cross-linker with 1O2-activation to covalently cross-link the topoisomerase I of 7-ethyl-10-hydroxycamptothecin (SN38) concurrently loading chlorin e6 (Ce6) to obtain the anticipative nanopump-CNs. After laser irradiation, the nanopump can be controllably unlocked, realizing the self-enhanced cascade amplification process of producing reactive oxygen species (ROS) while releasing the chemotherapy drug. Significantly, SN38 can effectively increase the sensitivity of tumor-related organelles to ROS while inducing DNA damage in tumor cells, thus, amplifying the efficacy of photodynamics caused by Ce6. This cascade self-enhanced drug nanosystem based on exogenous controlled chemotherapy and photodynamic therapy is expected to provide a new perspective for designing nanomedicine with a precise regulation model for malignant tumor therapy