Aeration Mode Research Articles

Enhancing nitrogen removal from digested swine wastewater by anammox with aeration optimization coupling real-time control strategy

The nitrogen removal of anaerobically digested swine wastewater (ADSW) through partial nitritation and anammox is hindered by the challenge of balancing aeration between ammonia oxidizing bacteria (AOB) and anammox bacteria (AnAOB). This study focused on optimizing aeration through a real-time control strategy in an integrated fixed-film activated sludge reactor for treating ADSW. The system implemented a dual aeration mode that included both low dissolved oxygen (DO) (< 0.4 mg/L) and short-term high DO (0.6–1.2 mg/L), with pH, oxidation–reduction potential, and NH4+-N electrode values as real-time control parameters. NH4+-N removal rate increased from 3.37 to 12.82 mgN/(gVSS·h), and total nitrogen (TN) removal rate enhanced from 0.14 to 0.25 kgN/(m3·d). Increasing DO stimulated AOB activity by 31 % and provided sufficient NO2−-N for AnAOB. The r-strategist AnAOB (Candidatus Kuenenia) proliferated well in the biofilm (0.25 % in flocs vs. 1.86 % in biofilm). The enrichment of denitrifiers improved organic matter and TN removal.

Revealing the impacts of intermittent aeration on nitrogen and phosphorus removal in powder carrier system from interfacial thermodynamics and metagenomic analysis

Intermittent aeration strategy has attracted significant attention due to its benefits of low oxygen and carbon source consumption. However, the feasibility of intermittent aeration in the powder carrier process and its effect on micro-granule formation remain unclear. This study investigated the impacts of intermittent aeration on the powder carrier system through interfacial thermodynamics and metagenomic analysis. The results demonstrated that total nitrogen removal efficiency increased from 61.1 ± 2.6 % to 89.7 ± 3.7 % under intermittent aeration, while the PO43-–P removal efficiency increased from 47.6 ± 4.7 % to 81.6 ± 3.9 %. The interfacial free energy of micro-granules was reduced from –4.85 mJ/m2 to –16.03 mJ/m2 due to aeration mode, resulting in a larger micro-granule size (185.24 ± 15.25 μm) and enhanced aggregation ability. Significant enhancements in tryptophan-like substances and hydrophobic functional groups (β-sheet, protonated amines, and C-(C/H)) in EPS under intermittent aeration likely contributed to the increased hydrophobicity and reduced interfacial free energy. The abundances of norank_NS9_marine_group (4.17 %), norank_Comamonadaceae (4.57 %), and Terrimonas (3.44 %) were increased, further driving the synergy of nitrogen removal of simultaneous partial nitrification and denitrification and endogenous denitrification. Correlation analysis confirmed that intermittent aeration primarily affected gene expression involved in the partial nitrification process, and that denitrification genes were enriched by increased hydrophobic components and micro-granule size. These results provide deeper insights into the key influencing factors and mechanisms of the powder carrier system, and offer a theoretical basis for process optimization.

Establishing mainstream partial nitrification in the membrane aerated biofilm reactor by limiting the oxygen concentration in the biofilm

The proliferation of nitrite oxidizing bacteria (NOB) still remains as a major challenge for nitrogen removal in mainstream wastewater treatment process based on partial nitrification (PN). This study investigated different operational conditions to establish mainstream PN for the fast start-up of membrane aerated biofilm reactor (MABR) systems. Different oxygen controlling strategies were adopted by employing different influent NH4+-N loads and oxygen supply strategies to inhibit NOB. We indicated the essential for NOB suppression was to reduce the oxygen concentration of the inner biofilm and the thickness of aerobic biofilm. A higher NH4+-N load (7.4 g-N/(m2·d)) induced higher oxygen utilization rate (14.4 g-O2/(m2·d)) and steeper gradient of oxygen concentration, which reduced the thickness of aerobic biofilm. Employing closed-end oxygen supply mode exhibited the minimum concentration of oxygen to realize PN, which was over 46% reduction of the normal open-end oxygen mode. Under the conditions of high NH4+-N load and closed-end oxygen supply mode, the microbial community exhibited a comparative advantage of ammonium oxidizing bacteria over NOB in the aerobic biofilm, with a relative abundance of Nitrosomonas of 30–40% and no detection of Nitrospira. The optimal fast start-up strategy was proposed with open-end aeration mode in the first 10 days and closed-end mode subsequently under high NH4+-N load. The results revealed the mechanism of NOB inhibition on the biofilm and provided strategies for a quick start-up and stable mainstream PN simultaneously, which poses great significance for the future application of MABR.

Influence of aeration modes and DO on simultaneous nitrification and denitrification in treatment of hypersaline high-strength nitrogen wastewater using sequencing batch biofilm reactor (SBBR)

Sequencing batch biofilm reactor (SBBR) has the potential to treat hypersaline high-strength nitrogen wastewater by simultaneous nitrification-denitrification (SND). Dissolved oxygen (DO) and aeration modes are major factors affecting pollutant removal. Low DO (0.35–3.5 mg/L) and alternative anoxic/aerobic (A/O) mode are commonly used for municipal wastewater treatment, however, the appropriate DO concentration and operation mode are still unknown under hypersaline environment because of the restricted oxygen transfer in denser extracellular polymeric substances (EPS) barrier and the decreased carbon source consumption during the anoxic phase. Herein, two SBBRs (R1, fully aerobic mode; R2, A/O mode) were used for the treatment of hypersaline high-strength nitrogen wastewater (200 mg/L NH4+-N, COD/N of 3 and 3% salinity). The results showed that the relatively low DO (2 mg/L) could not realize effective nitrification, while high DO (4.5 mg/L) evidently increased nitrification efficiency by enhancing oxygen transfer in denser biofilm that was stimulated by high salinity. A stable SND was reached 16 days faster with a ∼10% increase of TN removal under A/O mode. Mechanism analysis found that denser biofilm with coccus and bacillus were present in A/O mode instead of filamentous microorganisms, with the secretion of more EPS. Corynebacterium and Halomonas were the dominant genera in both SBBRs, and HN-AD process might assist partial nitrification-denitrification (PND) for highly efficient TN removal in biofilm systems. By using the appropriate operation mode and parameters, the average NH4+-N and TN removal efficiency could respectively reach 100% and 70.8% under the NLR of 0.2 kg N·m−3·d−1 (COD/N of 3), which was the highest among the published works using SND-based SBBRs in treatment of saline high-strength ammonia nitrogen (low COD/N) wastewater. This study provided new insights in biofilm under hypersaline stress and provided a solution for the treatment of hypersaline high-strength nitrogen (low COD/N) water.

Interactions between bacteria and microalgae in microalgal-bacterial symbiotic wastewater treatment systems: mechanisms and influencing factors

Microalgal-bacterial symbiotic wastewater treatment systems (MBSWTSs) have received widespread attention due to their capacity to achieve high pollutant removal efficiency during wastewater treatment, with low energy consumption requirements, efficient carbon sequestration, and wastewater resource utilization. This paper provides an overview of the treatment performance and current research status of MBSWTSs, including a detailed summary of the mechanisms of nitrogen, phosphorus, and carbon removal by MBSWTSs and the interactions between bacteria and microalgae. In particular, this review focuses on the influence of operational parameters on the regulation of the symbiotic system, such as the microalgal:bacterial ratio, N:P ratio, external carbon source, dissolved oxygen concentration, aeration mode, and light availability. Among these factors, the microalgal:bacterial ratio, carbon source, and light availability have an important influence on microalgal-bacterial competition, as well as the trophic mode of the system, biomass production, and the capacity for the process to be practically applied on a large scale. MBSWTSs still have some challenging aspects that have hindered their development and application, such as the unknown mechanism of microalgal-bacterial co-metabolism, limited previous practical applications, algal contamination, and harvesting difficulties. To overcome these challenges, future research requires a multidisciplinary approach, incorporating life sciences, material science, and other disciplines. Comprehensive research should be conducted on the metabolic mechanisms of MBSWTSs, the optimization of process performance and waste resource utilization, providing a theoretical and practical foundation for the practical application of MBSWTSs.

Effects of aeration modes and rates on nitrogen conversion and bacterial community in composting of dehydrated sludge and corn straw.

Aeration is an important factor to regulate composting efficiency and nitrogen loss. This study is aimed to compare the effects of different aeration modes (continuous and intermittent) and aeration rate on nitrogen conversion and bacterial community in composting from dehydrated sludge and corn straw. Results showed that the intermittent aeration mode at same aeration volume was superior to the continuous aeration mode in terms of NH3 emission reduction, nitrogen conversion and germination index (GI) improvement. Intermittent aeration mode with 1200 L/h (aeration 5 min, stop 15 min) [K5T15 (V1200)] and 300 L/h of continuous aeration helped to the conservation of nitrogen fractions and accelerate the composting process. However, it was most advantageous to use 150 L/h of continuous aeration to reduce NH3 emission and ensure the effective composting process. The aeration mode K5T15 (V1200) showed the fastest temperature rise, the longer duration of thermophilic stage and the highest GI (95%) in composting. The cumulative NH3 emission of intermittent aeration mode was higher than continuous aeration mode. The cumulative NH3 emission of V300 was 23.1% lower than that of K5T15 (V1200). The dominant phyla in dehydrated sludge and corn straw composting were Firmicutes, Proteobacteria, Actinobacteria, and Bacteroidetes. The dominant phylum in the thermophilic stage was Firmicutes (49.39%~63.13%), and the dominant genus was Thermobifida (18.62%~30.16%). The relative abundance of Firmicutes was greater in the intermittent aeration mode (63.13%) than that in the continuous aeration mode (57.62%), and Pseudomonas was dominant in composting with lower aeration rate and the lowest NH3 emission. This study suggested that adjustment to the aeration mode and rate could affect core bacteria to reduce the nitrogen loss and accelerate composting process.

The effect of aeration mode (intermittent vs. continuous) on nutrient removal and greenhouse gas emissions in the wastewater treatment plant of Corleone (Italy)

The paper reports the results of an experimental study aimed at comparing two configurations of a full-scale wastewater treatment plant (WWTP): conventional activated sludge (CAS) and oxic-settling-anaerobic process (OSA) with intermittent aeration (IA). A comprehensive monitoring campaign was carried out to assess multiple parameters for comparing the two configurations: carbon and nutrient removal, greenhouse gas emissions, respirometric analysis, and sludge production. A holistic approach has been adopted in the study with the novelty of including the carbon footprint (CF) contribution (as direct, indirect and derivative emissions) in comparing the two configurations. Results showed that the OSA-IA configuration performed better in total chemical oxygen demand (TCOD) and ortho-phosphate (PO4-P) removal. CAS performed better for Total Suspended Solids (TSS) removal showing a worsening of settling properties for OSA-IA. The heterotrophic yield coefficient and maximum growth rate decreased, suggesting a shift to sludge reduction metabolism in the OSA-IA configuration. Autotrophic biomass showed a reduced yield coefficient and maximum growth yield due to the negative effects of the sludge holding tank in the OSA-IA configuration on nitrification. The OSA-IA configuration had higher indirect emissions (30.5 % vs 21.3 % in CAS) from additional energy consumption due to additional mixers and sludge recirculation pumps. The CF value was lower for OSA-IA than for CAS configuration (0.36 kgCO2/m3 vs 0.39 kgCO2/m3 in CAS).

A multistep (semi)-continuous biocatalytic setup for the production of polycaprolactone.

Biocatalysis has gained increasing importance as an eco-friendly alternative for the production of bulk and fine chemicals. Within this paradigm, Baeyer Villiger monoxygenases (BVMOs) serve as enzymatic catalysts that provide a safe and sustainable route to the conventional synthesis of lactones, such as caprolactone, which is employed for the production of polycaprolactone (PCL), a biocompatible polymer for medicinal applications. In this work, we present a three-step, semi-continuous production of PCL using an entirely biocatalytic process, highlighting the merits of continuous manufacturing for enhancing biocatalysis. First, caprolactone is produced in batch from cyclohexanol using a coenzymatic cascade involving an alcohol dehydrogenase (ADH) and BVMO. Different process parameters and aeration modes were explored to optimize the cascade's productivity. Secondly, the continuous extraction of caprolactone into an organic solvent, needed for the polymerization step, was optimized. 3D-printed mixers were applied to enhance the mass transfer between the organic and the aqueous phases. Lastly, we investigated the ring-opening polymerization of caprolactone to PCL catalyzed by Candida antarctica lipase B (CAL-B), with a focus on eco-friendly solvents like cyclopentyl-methyl-ether (CPME). Space-time-yields up to 58.5 g L-1 h-1 were achieved with our overall setup. By optimizing the individual process steps, we present an efficient and sustainable pathway for PCL production.

Achieving simultaneous nitrification and endogenous denitrifying phosphorus removal in anaerobic/intermittently-aerated moving bed biofilm reactor for low carbon-to-nitrogen ratio wastewater treatment

In this study, an anaerobic/intermittently-aerated moving bed biofilm reactor (AnIA-MBBR) was proposed to realize simultaneous nitrification and endogenous denitrifying phosphorus removal (SNEDPR) in treating low carbon-to-nitrogen (C/N) ratio wastewater. The effect of different intermittent aeration modes (short and long aeration) on nutrients’ removal was investigated. With the C/N ratio around 3, the removal efficiencies of total nitrogen and phosphorus were 90% and 74%, 88% and 59%, respectively, for short aeration and long aeration. The different aeration time also altered the nutrients’ degradation pathway, biofilm characteristics, microbial community, and functional metabolic pathways. The results confirmed the occurrence of aerobic denitrifiers, anoxic denitrifiers, phosphorus accumulating organisms, glycogen accumulating organisms in AnIA-MBBR systems and their synergistic performance induced the SNEDPR. These results indicated that the application of AnIA in MBBR systems was an effective strategy to achieve SNEDPR, providing better simultaneous removal performance of nitrogen and phosphorus from low C/N ratio wastewater.

Study on Enhancement of Denitrification Performance of Alcaligenes faecalis

Nitrogen pollution in water bodies presents a serious threat to ecosystems due to its role in eutrophication. In this study, the aerobic denitrifying bacterium Alcaligenes faecalis was used as a model microorganism to investigate the optimal operating conditions for nitrogen removal from nitrogen-containing wastewater by Alcaligenes faecalis under different aeration modes, microbial dosages and C/N ratios. The results showed that the optimal aeration mode for efficient bacterial denitrification was 10 min of aeration with a 30 min interval, and the total nitrogen removal reached 87.82%. At different bacterial doses, NO3−–N was completely denitrified and NO2−–N accumulation levels were reduced, all of which resulted in significant denitrification, and the final total nitrogen removal efficiencies reached 86.39–98.50%. With an increase in the C/N ratio, the pollutant removal performance of denitrifying bacteria increased. When the C/N ratio was 17, the final rates of NO3−–N, TN and COD removal were 100%, 98.50% and 96.13%, respectively. At lower C/N ratios, the growth and metabolism of microorganisms were inhibited and fewer electron acceptors were available during the denitrification process, which seriously affected denitrification performance. In this study, the denitrification performance of aerobic denitrifying bacterium Alcaligenes faecalis was explored in experiments using changes in aeration mode, microbial dosage and C/N ratio, and the optimal operating conditions of Alcaligenes faecalis for treating nitrogenous wastewater were indicated. This provides technical support for Alcaligenes faecalis in improving the remediation effect of nitrogenous wastewater and provides a theoretical basis for further in-depth research on the performance of Alcaligenes faecalis in the future.

Effect of hydrodynamic aeration on bioelectricity generation from photoautotrophic Spirulina platensis in biophotovoltaic devices

A biophotovoltaic (BPV) device is a type of bioelectrochemical cell that shows potential for renewable energy production using photosynthetic exoelectrogenic microorganisms. However, the technology currently has limitations due to its relatively low power output and high dependence on biofilm attachment. Thus, this paper examines the effect of hydrodynamic aeration on the bioelectricity generation of BPV devices. Aeration is widely applied in microalgae cultivation to improve the mixing effect between microalgae cells, culture medium, and air bubbles. The methodology involves the cultivation of Spirulina platensis, device fabrication, voltage measurement in both non-aeration and aeration modes, and the use of polarization curves to determine the device performance under a gradually rising external load. The BPV devices are affected by abnormal voltage drop under high external loads, which is called power overshoot. The use of aeration successfully solved the power overshoot issues over time, but it also resulted in a gradual reduction in the voltage output and power density of the BPV devices. During aeration, the BPV devices produced a peak power density of 0.121 ± 0.056 mWm−2 on Day 1, which declined to 0.048 ± 0.025 mWm−2 on Day 13. The blowing of air bubbles had some side effects on BPV devices, including causing the attachment of Spirulina cells to the container walls and accelerating the evaporation of the culture medium. This study emphasizes the role of hydrodynamic aeration in the bioelectricity generation process and opens up possibilities for wider application of BPV devices in renewable energy production.

Aeration strategies and total nitrogen removal in a hybrid aerated treatment wetland

Abstract This study investigates the impact of aeration strategy on the performance of total nitrogen (TN) removal in a compact hybrid aerated treatment wetland (TW), called Rhizosph'air®. The system combines a single-stage French vertical flow wetland with an aerated horizontal-flow wetland, offering a unique and flexible approach for optimizing TN removal. In total, seven experimental conditions were tested, with different aeration modes, hydraulic loading rates and ammonium addition. The wetland system demonstrated high performance in terms of chemical oxygen demand removal (&amp;gt;85%) and solids removal (&amp;gt;90%), regardless of the experimental condition. However, TN removal was found to be directly impacted by operational changes. Increasing the hydraulic loading rate from 0.15 to 0.25 m/day led to an improvement in TN removal, achieving over 60%. Furthermore, when ammonium was added to the inlet and when the aeration timing was synced with the timing of the influent batch load, the environmental conditions facilitated the denitrification process, resulting in TN removal of approximately 70% and the lowest effluent NO3-N concentrations (8.70 ± 4.40 mg/L). In summary, the timing of the aeration strategy according to influent batch loading improved TN removal, suggesting its potential for optimization in future studies.

Membrane Contamination Control in the Intermittent Aeration Mode of Operation of the C-MBR Process for Campus Wastewater Reuse

Filtration backwashing is necessary for the effective operation of membrane modules, and intermittent aeration helps to remove nutrients, which can save energy and effectively control the occurrence of membrane contamination. In this study, membrane contamination was controlled using an MBR in intermittent aeration operation mode and a filtration backwash cycle; difficult organic matter and nitrogen (COD and NH4+-N) were used as the main contamination indicators for this study; and the main membrane contamination components, extracellular polymers (EPs), and soluble microbial products (SMPs) were detected. The results show that the average removal of COD and NH4+-N could reach 86.45% and 92.47%, respectively, with a 2.0 day intermittent aeration time and 9/1 min filtration backwash cycle mode, and it also helped to reduce the membrane contamination, as shown by a decrease of 11.87% in bound EPs (EPSBound) and an increase of only 5.32% in SMPs. Microbiological analyses revealed that Proteobacteria and Acinetobacter, as dominant bacteria (50.90%), were the main causes of membrane contamination.

How do aeration mode and influent carbon/nitrogen ratio affect pollutant removal, gas emission, functional genes and bacterial community in subsurface wastewater infiltration systems?

Abstract This study investigated the influences of aeration mode and influent carbon/nitrogen ratio on matrix oxygen concentration, pollutant removal, greenhouse gas emission, functional gene abundances and bacterial community in subsurface wastewater infiltration systems (SWISs). Intermittent or continuous aeration enhanced oxygen supply at 0.6 m depth in the matrix, which improved organics removal, nitrogen removal, the abundances of bacterial 16S rRNA, amoA, nxrA, narG, napA, nirK, nirS, norB, nosZ genes, bacterial community Alpha diversity, the relative abundances of Actinobacteria at 0.6 m depth, the relative abundances of Chloroflexi, Gemmatimonadetes, Bacteroidetes and Firmicutes at 0.9 and 1.2 m depth and reduced CH4 and N2O conversion efficiencies, the abundance of mcrA gene with carbon/nitrogen ratio of 12 and 16 compared with non-aeration. Increased carbon/nitrogen ratio resulted in higher TN removal efficiencies and lower CH4 and N2O conversion efficiencies in aeration SWISs than those in non-aeration SWIS. Intermittent aeration SWIS obtained high removal efficiencies of 83.2, 85.4 and 90.8% for TN, NH4+ -N and COD and low conversion efficiency of 0.21 and 0.65% for N2O and CH4 with optimal carbon/nitrogen ratio of 12. However, high TN (82.6%), NH4+ -N (84.9%) and COD (92.2%) removal efficiencies and low CH4 (0.67%) and N2O (0.23%) conversion efficiencies were achieved in continuous aeration SWIS with carbon/nitrogen ratio of 16.

Effect of aeration on low-substrate CANON process

The completely autotrophic nitrogen removal over nitrite (CANON) is a new type of nitrogen removal process developed in recent years. The control of dissolved oxygen (DO) in this process is relatively stringent, especially in low-substrate wastewater treatment. However, the results of studies on the operation of the process in different aeration modes are still controversial, and investigations on biofilm type CANON reactors are limited. In this study, a pilot-scale CANON bioreactor filled with suspended carriers was investigated on the treatment of wastewater at low ammonium concentrations, and the effect of the aeration mode on autotrophic nitrogen removal was evaluated. Seven conditions with various aeration on/off times and DO levels were tested. The results showed that an intermittent aeration with a 20-min/20-min aeration on/off time and DO concentrations of 1.0–1.3 mg/L at the end of the aeration period was appropriate, potentially inhibiting nitrite oxidizing bacteria (NOB) and keeping the total nitrogen (TN) removal rate at a relatively high level of 76.7% ± 2.5%. In the optimal aeration mode, the reactor achieved effluent TN and NH4+-N concentrations of (11.1 ± 3.3) mg/L and (3.6 ± 2.3) mg/L, respectively, with a hydraulic retention time of 12 h and an influent NH4+-N concentration of (48.6 ± 9.4) mg/L at 30.1°C ± 2.2°C. The results of metagenomic sequencing for microorganisms on carriers indicated that the main nitrogen removal bacteria in the reactor were Proteobacteria, Planctomycetes, and Nitrospirae. The NOB genus Nitrospira was completely inhibited by intermittent aeration. Candidatus Kuenenia had strong adaptability to low-concentration wastewater.

Extracellular polymeric substances and microbial community shift during the start-up of a single-stage partial nitritation/anammox process.

A sequencing batch reactor (SBR) was operated to investigate variations of extracellular polymeric substances (EPS) and microbial community during the start-up of the single-stage partial nitritation/anammox (SPN/A) process at intermittent aeration mode. The SPN/A system was successfully started on day 34, and the nitrogen removal efficiency and total nitrogen loading rate were 82.29% and 0.31 kg N/(m3 ·d), respectively. Furthermore, the relationship between the protein secondary structures and microbial aggregation was strongly related. The α-helix/ (β-sheet + random coil) ratios increased obviously from 0.20 ± 0.03 to 0.23 ± 0.01, with the sludge aggregation mean size increased from 56 to 107 μm during the start-up of SPN/A. During the start-up of SPN/A, Candidatus Kuenenia was the primary anammox bacteria, whereas Nitrospira was the main functional bacteria of nitrite-oxidizing bacteria. Correlation between the microbial community and EPS components was performed. The EPS and microbial community played important roles in keeping stable nitrogen removal and the formation of sludge granules.

Compatible Solutes Accumulated by &lt;i&gt;Glutamicibacter&lt;/i&gt; sp. Strain SMB32 in Response to Abiotic Environmental Factors

Abstract—Proton magnetic resonance spectroscopy was used for investigation of the pool of compatible solutes accumulated in the cells of Glutamicibacter sp. strain SMB32 in response to abiotic environmental factors. The original habitat of the strain was anthropogenically salinated soil at the Verkhnekamsk deposit of potassium and magnesium salts (Perm krai, Russia). The strain grew within the temperature range from 5 to 35°C. At 5 and 32°C, the intracellular content of trehalose in the cells of Glutamicibacter sp. SMB32 was significantly higher than at 25°C. Glutamicibacter sp. SMB32 was able to grow both in the absence of NaCl and at its concentrations up to 11%. Glutamate predominated in the cells growth without NaCl. At high salinity (8% NaCl), predominant compounds in the studied strain cells were trehalose, proline, glutamine, and glutamate. Increasing salinity of the growth medium resulted in higher levels of intracellular proline. This is the first report of ability of a Glutamicibacter strain to synthesize mannitol; its accumulation was found to depend on the aeration mode. Thus, Glutamicibacter sp. strain SMB32 possesses high metabolic plasticity and is able to adapt to the action of unfavorable physicochemical factors.

Superior performance of a membrane bioreactor through innovative in-situ aeration and structural optimization using computational fluid dynamics.

The optimization of membrane bioreactors (MBRs) involves a critical challenge in structural design for mitigation of membrane fouling. To address this issue, a three-dimensional computational fluid dynamics (CFD) model was utilized in this study to simulate the hydrodynamic characteristics of a flat sheet (FS) MBR. The optimization of the membrane module configuration and operating conditions was performed by investigating key parameters that altered the shear stress and liquid velocity. The mixed liquor suspended solids (MLSS) concentration was found to increase the shear stress, leading to a more uniform distribution of shear stress. By optimizing the appropriate bubble diameter to 5mm, the shear stress on the membrane surface was optimized with relatively uniform distribution. Additionally, extending the side baffle length dramatically improved the uniformity of the shear stress distribution on each membrane. A novel in-situ aeration method was also discovered to promote turbulent kinetic energy by 200 times compared with traditional aeration modes, leading to a more uniform bubble streamline. As a result, the novel in-situ aeration method demonstrated superior membrane antifouling potential in the MBR. This work provides a new approach for the structural design and optimization of MBRs. The innovative combination of the CFD model, optimization techniques, and novel in-situ aeration method has provided a substantial contribution to the advancement of membrane separation technology in wastewater treatment.

Effects of different aeration strategies and ammonia-nitrogen loads on nitrification performance and microbial community succession of mangrove constructed wetlands for saline wastewater treatment

In highly salinized environments, nitrification is the process that limits the rate of nitrogen transformation and removal. Therefore, this study concentrated on the impacts of different aeration strategies and NH4+–N loads on the nitrification performance of mangrove constructed wetlands (CWs), as well as investigating the succession mechanism of ammonia-oxidizing microorganisms (AOMs). The results showed that both the CW with continuous aeration (CA-CW) and intermittent aeration (IA-CW) achieved a nitrification efficiency of more than 98% under an NH4+–N loading of 1.25–4.7 g/(m2·d). However, the total nitrogen removal rates of IA-CW under low and high ammonia-nitrogen loads (LAL, 20.09 ± 4.4% and HAL, 8.77 ± 1.35%, respectively) were higher than those of CA-CW (16.11 ± 4.7% and 3.32 ± 2.3%, respectively), especially under HAL (p < 0.05). Pearson correlation analysis showed that under different operating conditions, the differential secretion of Kandelia candel rhizosphere organic matter had a certain regulatory effect on nitrification and denitrification groups such as Candidatus Nitrocosmicus, Nitrancea, Truepera, Pontibacter, Halomonas, and Sulfurovum in the wetland root layer. The quantitative polymerase chain reaction revealed that the NH4+–N load rate was the primary factor driving the succession of the AOMs, with different aeration strategies exacerbating this process. Overall, this study revealed that the dominant AOMs in mangrove CWs could be significantly altered by regulating the aeration modes and pollution loads to adjust the rhizosphere organic matter in situ, thereby resulting in more efficient nitrification.

Insect Colonisation and the Decomposition Process in Aerated versus Watertight Burial Systems.

In recent years, burial systems have covered increasingly higher costs due to the pollution caused by decomposition products. These products are understood as chemicals and microorganisms in the surrounding soil and groundwater and represent a topical issue. The purpose of this research was to ascertain the extent of decomposition when pig carcasses are buried in two different burial systems ("aerated" vs. "watertight") and catalogue the arthropods associated with burials at different time-points of removal from niches (after 6, 12, 24, 36, and 60 months). Thirteen taxa were collected in aerated niches, whereas five were collected in watertight niches. The initial access or exclusion of insect colonisers affected overall functional activity. Two Diptera species, Hydrotaea capensis and Megaselia scalaris, were the most abundant, supporting the hypothesis that insects can colonise carcasses in aerated burial systems. Furthermore, some species of bacteria have been documented as facilitators of the initial decomposition process of the carcass. Most bacterial colonies develop only in aerated niches. The trial showed that the first enzymatic-bacterial and insect actions helped promote the process of cadaveric decomposition and later skeletonisation, mainly when associated with aeration modes of the tomb/mound. The results obtained provide essential information on the process of human decomposition and taphonomy in cemeteries. Moreover, these data could benefit forensic science by adding information on insect colonisation and body modification in medico-legal investigations concerning the post-mortem interval in exhumed bodies and illegal burials.