Continuous Aeration Research Articles

Characterization of the Microbial Community in A Continuous Garbage Treatment Process

Previously, we developed a “static type” garbage treatment system whose performance exceeds that of conventional garbage treatment systems. However, we could not explain the system’s excellent performance especially from a microbial ecosystem’s stand point (Matsuda et al, 2017). Microbial activity causes the decomposition of organic materials in a garbage treatment process. However, we do not know which microbes are effective in garbage decomposition and what relationship exists between the succession of a microbial community and the decomposition of organic materials in a garbage composting process. 
 This study analyzed the relationship between a continuous operation garbage treatment system’s microbial community and the decomposition of organic matter and evaluated for effective microbes in the same garbage treatment system. Although many research articles have been published on the composting processes throughout the world, most of them employ batch processes and not continuous processes. Conversely, most real-world practical composting plants adopt a continuous operation system in which fresh feed is usually input once a day with continuous aeration and intermittent mixing. 
 To comprehensively analyze the microbial community, three different approaches were adopted in this study; 1) colony observation, 2) DNA analysis, and 3) the enzymatic activities of each colony.
 In our experiment, the working volume was 10 L of leaf mold and 40 g/(day L) of garbage (the organic load) was input to the reactor every day at a fixed time. Dog food with 70 % moisture content was used as a model garbage substrate. The reactor’s internal temperature, the total reactor’s weight and the sampled residue’s weight, moisture content and pH were measured before inputting garbage. Additionally, the reactor’s internal temperature was measured six hours later. The internal temperature was about 55 ℃ at the highest without heating. The organic matter decomposition rate was about 50 % and the weight reduction rate was over 90 %, implying successful garbage decomposition was achieved.
 The microbial composition and the number of the colonies seen on the medium plate changed every day and did not realize a “steady state.” Thus an extremely efficient microbe does not exist. Only eleven microbes were isolated; yet many more microbes must exist in the system but were not counted due to a high dilution rate.
 From our DNA analysis, the PCR-DGGE profile of the microbial community in the garbage residue showed that bands of isolated colonies were detected in the same positions as the bands of garbage residue, which contained all kinds of microbes. Nine microbes were identified using 16S rRNA genome from eleven isolated ones. The identified microbes were of different bacterial species and their characteristics were examined from the stand point of nutritional property and enzymatic activity. 
 The garbage decomposition process consists of two steps, solubilization and metabolization. Extracellular enzymes act during solubilization of solid garbage residue, and intracellular enzymes work when water-soluble substances are taken up into bacterial cells and metabolized. Protease and amylase activity were measured to assess extracellular enzymatic activity and dehydrogenase activity was measured to evaluate intracellular enzymatic activity. The enzyme activities of bacterial strains significantly differed by strain. Results from this study suggest complementary microbial activity and that Bordetella trematum, Bacillus cereus, Bacillus subtills subtills and Streptomyces thermocarboxydus effectively decompose garbage.

Biochemical Composition of Chlorella vulgaris Grown on Sugarcane Molasses

The quest for green and sustainable biofuel to serve as alternative to the conventional fossil fuel have remained a grey area in biotechnology. The Chlorella vulgaris was isolated from the African Regional Aquacultural Centre Aluu, Port Harcourt, Nigeria. Sugarcane Molasses modified Bold Basal medium was used to cultivate the Microalgae mixotrophically. The algal culture was incubated at room temperature for 15 days with continuous aeration and 12:12 hour photoperiod under artificial illumination of 2000 lux. The proximate composition of the biomass showed 6.28%wt, 67.37% wt and 11.35%wt of moisture, volatile organic matter and Fixed carbon content respectively. The ultimate composition of Chlorella biomass revealed that Carbon was 42.46% while Oxygen content was 27.93%. Nitrogen content was 6.62% while Sulphur content was 0.82% while hydrogen content was 6.74%. The study further identified that algal biomass from C. vulgaris has the potential of serving as both nutraceuticals and bioenergy feedstock. There is need for further studies around the algae oil oriented optimization as a veritable tool for biotechnological advancements.

Effect of Different Salinity Levels on Population Dynamics and Growth of the Cyclopoid Copepod Oithona nana

Copepods are one of the most abundant and diverse live food sources for mesopelagic and bathypelagic fishes and crustaceans. They could contribute to the overlap of the transition period from live feed to an artificial weaning diet in marine larvae production. However, the culture conditions still need optimization to provide sufficient production to cover the increasing demand for marine hatcheries. Therefore, the present study investigated the effects of different salinity levels (5, 10, 15, 20, 25, and 30 ppt) on the population growth, growth rate, and population composition (males, females, copepodite, and nauplii ratio) of the marine copepod, Oithona nana. The experiment continued for 15 days, under laboratory-controlled conditions of temperature (27 ± 1 °C), pH (7.7 ± 0.15), and continuous gentle aeration in 30 L glass aquaria. The copepod culture aquaria were supplemented with a mixture of soybean and yeast (0.5 g 10−6 individual−1 24-h−1) as a feed source. The highest significant population growth and population growth rate of O. nana were achieved with a salinity level of 20 ppt. Regarding population composition, O. nana cultured at the salinity level of 20 ppt recorded the highest significant percentages of copepodite and nauplii. The results concluded that copepod, O. nana, is capable of withstanding abrupt changes in the salinity, but there are limits to their tolerance, with an optimal salinity level of 20 ppt. This salinity level achieved the highest population growth and the highest percentages of copepodite and nauplii of marine Copepoda, O. nana.

Solid-state culture of Azospirillum brasilense: a reliable technology for biofertilizer production from laboratory to pilot scale.

A biofertilizer of Azospirillum brasilense was produced in solid-state culture (SSC) from laboratory to pilot scale. Similar operation conditions (continuous aeration and mild intermittent mixing) and two dimensionless numbers with similar L/D ratio and a similar working volume were applied to reach a scale-up factor of 75. An innovative bioreactor with rotating helical ribbons (15kg wet matter) was used at pilot scale. A mathematical model was proposed and validated to evaluate the respirometry trends at laboratory and pilot scale exhibiting similar behavior. The cell viability was (1.3 ± 0.4) × 109 and (1.3 ± 0.3) × 109 colony-forming units per gram of initial dry mass at laboratory and pilot scale, at 36 and 43h, respectively. A. brasilense maintains its viability twelve months of storage at 4 and 30°C. This is the first report of A. brasilense being cultivated in SSC under controlled conditions. SSC processes involving unicellular microorganisms with tolerance to agitation are a promising technology to produce biofertilizers.

Effect of first-stage aeration on treatment of domestic sewage in different hybrid constructed wetlands.

Two sets of hybrid constructed wetlands (HCWs) with the first-stage aeration were used to treat actual domestic sewage in this paper, where the effects of three important factors of aeration mode, hydraulic loading rates (HLR), and aeration volume on the removal of pollutants in both HCWs were studied in contrasts. In addition, the pollutant removal efficiency, the contribution of plants, and the characteristics of biofilm in both HCWs were explored. The results of 250-day experiment showed that the TN removal capacity of HCW combining vertical flow CW with horizontal flow CW (VF-HF) was better than HCW's converse combination (HF-VF) in treatingsewage, while the removal efficiency of COD and NH4+-N were similar, and the concentrations of TN and COD in the effluent of VF-HF could successfully meet the National discharge requirements. Compared with the continuous aeration, the intermittent aeration only had a little effect on the removal of COD and NH4+-N, but could improve TN removal performance in both HCWs. Meanwhile, increasing the aeration volume was beneficial to remove NH4+-N but not TN in HCWs. In addition, although the pollutant removal performances in both HCWs were impacted, the removal capacity of TN in VF-HF was only affected a little, when HLR was increased by 50%. The contribution of plants' uptake accounted for about 10% to nitrogen removal and 20% to phosphorus removal in both HCWs. The biomass at the filler surface near the plant rhizosphere was greater than that in the non-rhizosphere zones, and the impact of plant rhizosphere on the nitrification activity of biofilm was significantly greater than that on denitrification activity in both HCWs.

Organic Substances Reduction in Palm Oil Mill Effluent (POME) After Cultivation with Locally Isolated Microalgae

This work aims to study the ability of locally isolated microalgae to reduce organic substances in Palm Oil Mill Effluent (POME) which was carried out on a laboratory scale. Inoculum with a concentration of 20% was cultivated into POME media with various concentration of LP100 (without dilution), LP75 (25% dilution), and LP50 (50% dilution) using aeration and continuous lighting for 15 days in vessels with a lighting intensity of 1300 lux. Biomass of microalgae were observed daily and analyzed in dry weight by means of spectrophotometry using 624 nm wavelength to get their growth by determining the content of algae biomass. The reduction of organic substances in POME was observed by measuring the COD, BOD phosphate, ammonium, nitrate, and fatty oil parameters every 3 hours with the standard method. Results show that the growth of microalgae occurred well in POME media at LP75 and LP50 concentrations with inoculum concentration of 20% under 1300 lux lighting intensity conditions with a continuous 24-hour lighting and aeration cycle that obtained biomass content of 0.92 and 1.08 g-DW/L, respectively. The presence of microalgae in POME at concentration of LP75 for 12 days reduced organic substances and nutrients reaching 80.74% - 99.70%. Some parameters that were reduced include BOD (99.35%), COD (89.57%), TSS (89.68%), Phosphate (97.70%), Ammonium (95.08%), Fatty Oil (99.70%), and Nitrates (80.74%). This study concludes that locally isolated microalgae have ability to treat POME safely for environment and as a growing medium for microalgae followed by a decrease in organic substances.

Pollutants removal, greenhouse gases emission and functional genes in wastewater ecological soil infiltration systems: influences of influent surface organic loading and aeration mode.

The influences of influent surface organic loading rate (SOLR) and aeration mode on matrix oxygen, organic matter, nitrogen, phosphorus removal, greenhouse gases emission and functional gene abundances in lab-scale wastewater ecological soil infiltration systems (WESISs) were investigated. In WESISs, intermittent or continuous aeration improved oxygen supply at 50 cm depth and hardly changed anaerobic condition below 80 cm depth, which enhanced chemical oxygen demand (COD), NH4+-N, total nitrogen (TN) removal, the abundances of bacterial 16S rRNA, amoA, nxrA, narG, napA, nirK, nirS, qnorB, nosZ genes and reduced CH4, N2O conversion efficiencies with SOLR of 16.9 and 27.6 g BOD/(m2 d) compared with non-aeration. Increased SOLR resulted in high TN removal, low N2O emission in aeration WESIS, which was different from non-aeration WESIS. High average COD removal efficiency of 90.7%, NH4+-N removal efficiency of 87.0%, TN removal efficiency of 84.6%, total phosphorus (TP) removal efficiency of 93.1% and low average N2O emission rate of 12.8 mg/(m2 d) were achieved with SOLR of 16.9 g BOD/(m2 d) in intermittent aeration WESIS. However, continuous aeration WESIS obtained high average removal efficiencies of 90.1% for COD, 87.5% for NH4+-N, 84.1% for TN, 92.9% for TP and low average emission rate of 13.1 mg/(m2 d) for N2O with SOLR of 27.6 g BOD/(m2 d). Aeration could be an optional strategy for WESISs to achieve high pollutants removal and low CH4, N2O emission when treating wastewater with high SOLR.

Boosting pharmaceutical removal through aeration in constructed wetlands

This work evaluated the removal efficiency of 13 wastewater-borne pharmaceuticals in a pilot constructed wetland (CW) operated under different aeration strategies (no aeration, intermittent and continuous). Aeration improved the removal of conventional wastewater parameters and the targeted micropollutants, compared to the non-aerated treatment. Reduction of chemical oxygen demand (COD) and total nitrogen (TN) was slightly higher applying intermittent aeration than applying continuous aeration, the opposite was observed for the investigated pharmaceuticals. Seven targeted compounds were found in influent wastewater, and five of them (acetaminophen, diclofenac, ketoprofen, bezafibrate and gemfibrozil) were efficiently removed (> 83%) in the aerated systems. The overall risk of the investigated samples against aquatic ecosystems was moderate, decreasing in the order influent > no aeration > intermittent aeration > continuous aeration, based on the hazard quotient approach. Lorazepam, diclofenac and ketoprofen were the pharmaceuticals that could contribute the most to this potential environmental impact of the CW effluents after discharge. To the authors' knowledge this is the first sound study on the removal and fate of ketoprofen, bezafibrate, and lorazepam in aerated CWs, and provides additional evidence on the removal and fate of acetaminophen, diclofenac, gemfibrozil, and carbamazepine in this type of bioremediation systems at pilot plant scale.

Artificial aeration promotes better zootechnical performance and physiological balance of tambaqui (Colossoma macropomum) cultivated in a system without continuous water flow (Amazon: Brazil)

The aimed of the study was to evaluate the effect of continuous artificial aeration on zootechnical performance, hematological characteristics and glucose concentration of tambaqui (Colossoma macropomum) cultivated in a system without water flow. The study was conducted with two treatments, with aeration and without artificial aeration. Were 600 tambaqui juveniles with an average initial weight of 15 ± 0.15g were distributed in two excavated tanks. Thirty fish were captured per cultivation unit to perform monthly biometric measurements and were subjected to blood collection to determine hematological parameters. There was no difference between hematological variables (p<0.05). However, the continuous use of artificial aeration provided fish with more comfortable conditions, resulting in greater performance (p<0.05) in up to 90 days of cultivation, with an average daily weight gain of 4.82 g compared to 4.49g to the system without artificial aeration. It can be inferred that fish grown in a system without artificial aeration presented, when compared to those raised in a system with continuous artificial aeration, smaller values (p<0.05) of growth, both in weight and in length, consequently the continuous use of the aerator provided favorable conditions for the fish, resulting in average daily weight gain and total biomass gain.

Stochastic dynamic model analysis of the effect of stocking density on the monosex production of male redclaw crayfish Cherax quadricarinatus reared in commercial gravel-lined ponds

The potential for commercial Australian redclaw crayfish culture is considered very significate. However, information on maximization of pond carrying capacity that provides consistent production of commercial sizes is limited. A stochastic model was used to study the dynamics of commercial male redclaw production in 2500 m2 gravel-lined ponds with continuous aeration, when reared at 1, 2, 4, and 6 pre-adults m−2. After 119 days, the individual weight ranged from 80.9 to 90.5 g, survival averaged 74.0%, yields varied from 0.68 to 3.2 ton ha−1, depending on density, and the feed conversion ratio fell within the 0.75–0.87 range, indicating good production performance of male redclaw when compared with other reports. Three commercial whole-body size ranges were considered for evaluation: 40–60, 61–90 and over 90 g. The commercial category including males weighing 90 g or more was the most productive in terms of biomass, followed by the groups integrated by 61–90 and 40–60 g individuals. Production distributions inferred using the stochastic model resulted in mean yields approximating the crops in the database, with differences ranging from 0.9–7.1% and coefficient of variation values from 0.03 (1 m−2) to 0.81 (6 m−2) indicating higher uncertainty in the expected production at the highest density. The random variability of the 40–60 category and mean individual weight during rearing were the main factors affecting yields. We conclude that it is feasible to produce up to 3.2 ton ha−1 male redclaw crayfish in gravel-lined ponds, and that the stochastic model is useful for redclaw production analysis, establishing the relationships among commercial categories from a dynamic perspective, and to identify and assess production variability.

Consecutive bacterial cellulose production by luffa sponge enmeshed with cellulose microfibrils of Acetobacter xylinum under continuous aeration.

The bacterial cellulose production (BCP) process, using cellulose microfibrils (CM) of Acetobacter xylinum enmeshed on luffa sponge matrices (LSM) as LSM-CM starter, has been successfully developed where the LSM-CM production process can be recycled through consecutive cycles in limited dissolved oxygen (DO) under continuous aeration. In this study, incremental aeration rates impacted the consecutive cycles. Gluconic acid production, during the process, resulting in the reduction of BCP, was increasingly generated at high aeration from 0.28 to 0.34% at 3 L/min to 0.83-0.97% and 1.52-1.99% at 6 and 9 L/min after 7 d culture at 30 ± 2°C. To compensate for the negative impact of aeration, 0.10 and 0.15% (w/v) carboxymethyl cellulose (CMC) was found to create a microenvironment for recycled LSM-CM at both high aeration (6 and 9 L/min, respectively). Under nine consecutive BCP cycles, acceptable BC yields (from 5.54 ± 0.5 to 5.89 ± 0.5g/L) were associated with high biomass at 6 L/min aeration. These results confirm that LSM-CM, combined with CMC called as LSM-CM-CMC, created microenvironments low in DO under high aeration rates and that the recycled LSM-CM-CMC with aeration is an alternative, sustainable, economic process that could be applied for mass BCP.

Biological treatment of fuel wastewater generated from a thermal power plant by continuous and discontinuous aeration

Biological treatment of fuel wastewater generated from a thermal power plant by continuous and discontinuous aeration

Effects of pH on filtration of freshwater pearl mussel Lamellidens marginalis, Lamarck (Bivalvia: Unionidae) under laboratory conditions

The study was conducted to evaluate the effects of pH on the filtration rate of freshwater pearlmussel Lamellidens marginalis under laboratory conditions. Three treatments were used in triplicate;treatment 1 (T1) at pH 7.5, treatment 2 (T2) at pH 8.0 and treatment 3 (T3) at pH 8.5. Ten mussels werestocked in each aquarium with continuous aeration. After 48 hours, 40 ml eutrophicated water having 34.75 x105 to 36.0 x 105 cells/ml of phytoplankton were provided in each aquarium. Initial concentration ofphytoplankton was 14400±360.55, 13900±360.55 and 14133± 404.14 cells/ml, whereas the finalconcentrations were 10300±100.00, 8300±200.00 and 10333±57.73 cells/ml in T1, T2 and T3, respectively.The reduction rate was consistently lower in T2 when compared to other treatments. Mussels of T2 (pH 8.0)exhibited significantly higher filtration rate (p<0.05) over T1 (pH 7.5) and T3 (pH 8.5) at all sampling times.The minimum filtration rate 58.03±32.79 ml/mussel/h was found in T3 after 1 h exposure, whereas thehighest filtration rate 110.94 ± 21.68 ml/mussel/h was obtained in T2 after 2 h exposure. The resultsconcluded that the pH has a clear effect on feeding habit of freshwater pearl mussel and pH 8 providesenvironment friendly to maximize the filtration of L. marginalis.

Genotype × Environment Interaction for Wheat Yield Traits Suitable for Selection in Different Seed Priming Conditions.

Different seed priming treatments are widely used in order to improve the nutritional status of wheat, as well as to improve its grain yield and yield- related traits. The present study aimed to evaluate the impact of seed priming with zinc oxide nanoparticles (ZnO NPs) on the yield related traits, such as, field emergence, plant height, spike length and grain yield per plant of four winter wheat genotypes (Triticum aestivum L.) during two vegetation seasons of 2018/2019 and 2019/2020. The seeds of each wheat genotypes were primed with different concentrations of ZnO NPs (0 mg L−1, 10 mg L−1, 100 mg L−1 and 1000 mg L−1) for 48 h in a dark box by continuous aeration and were sown in soil pots with 60–70% moisture content until full maturity. The additive main effects and multiplicative interaction (AMMI) models were used to study the genotype environment effects. The results indicated that the plants response to ZnO nanoparticles significantly increased all of the observed traits of the wheat, while its maximum rates reduced the traits of the wheat. The AMMI analysis revealed the very complex nature of the variation observed in the trial and showed the significant effect of the G×E interaction, in which the first main component was significant for all components.

Correlating scalants characteristic and air bubbling rate in submerged vacuum membrane distillation: A fouling control strategy

The feasibility of aeration for membrane scaling mitigation in submerged vacuum membrane distillation (S-VMD) system was evaluated. The effect of aeration rate in both intermittent and continuous modes were investigated. The flux decline rate due to fouling was reduced significantly with air bubbling. In the absence of aeration, larger salt crystals containing sodium chloride (NaCl) and magnesium sulphate (MgSO4) were deposited on the membrane. Continuous air bubbling at 30 LPM provides sufficient surface shear with noticeable reduction of scalants on the membrane surface. However, continuous bubbling at higher flow rate (60 LPM) caused rapid nucleation and smaller crystals on membrane that inferior the bubble scouring effect. Based on the theoretical analysis of hydrodynamic forces induced by the bubble flow, the net shear force generated by the bubbling at 60 LPM with velocity of 0.2 m/s (bubble size of 250–400 μm) is not effective to remove particle that is smaller than 1.09 μm. Continuous aeration at 30 LPM showed better cleaning efficiency and had almost constant specific energy consumption over long term operation. These results indicated that air bubbling is a feasible and effective method for alleviating membrane scaling in S-VMD system.

Lignite Improved the Quality of Composted Manure and Mitigated Emissions of Ammonia and Greenhouse Gases during Forced Aeration Composting

Lignite amendment of livestock manure is considered a viable ammonia (NH3) emission mitigation technique. However, its impact on the subsequent composting of the manure has not been well studied. This work compared changes in biochemical parameters (e.g., organic matter loss and nitrogen (N) transformation) and also the emissions of NH3 and greenhouse gases (GHGs) between lignite-amended and unamended cattle manure during forced aeration composting. Amending manure with lignite did not alter the time to compost stability despite delaying the onset of the thermophilic temperatures. Lignite treatments retained N in the manure by suppressing NH3 loss by 35–54%, resulting in lignite-amended manure composts having 10–19% more total N than the unamended compost. Relative to manure only, lignites reduced GHG emissions over the composting period: nitrous oxide (N2O) (58–72%), carbon dioxide (CO2) (12–23%) and methane (CH4) (52–59%). Low levels of CH4 and N2O emissions were observed and this was attributed to the continuous forced aeration system used in the composting. Lignite addition also improved the germination index of the final compost: 90–113% compared to 71% for manure only. These findings suggest that lignite amendment of manure has the potential to improve the quality of the final compost whilst mitigating the environmental release of NH3 and GHGs.

Bio-mass Production of Chlorella vulgaris grown on date wastes under different stress conditions

A laboratory experiment was conducted to produce Chlorella vulgaris biomass grew on date wastes. The green microalgae were grown indoor on BG-11 medium in plexi glass columns with continuous fluorescent light and aeration. Date palm (Phoenix dactylifera) fruit wastes were washed and the flesh was oven dried at 55°C for 24h after removing the stones to obtain the flesh powder (0.9mm). Algal growth was performed under different stress conditions included (1) concentrations of 0.0, 10, 20, 30, 40 ml l-1 of wastes enriched growth media (2) NaCl concentration of 0.0, 0.5, 1.0,1.5, 2% and (3) nitrogen concentrations of 0, 25, 50, 75, 100%. The determinations included DW, total chlorophyll, carotenes and growth analysis. The obtained results showed that, the superior obtained net biomass was (0.215g l-1) with 20 ml l-1 of PDWE concentration. The net obtained chlorophyll was (34.515 mg l-1) with 30 ml l-1 of PDWE and highest carotenoid content (2.802 mg l-1) was recorded with the control. The dry weight and chlorophyll content decreased with increasing salinity, on contrary, the carotene content increased up to 1.5% and then back off again. The dry weight and chlorophyll content decreased with nitrogen decreasing while, the carotene content increased with nitrogen decreasing.

The connection between aeration regimes and EPS composition in nitritation biofilm

The effects of aeration regimes (intermittent and continuous aeration) on nitritation performance and biofilm EPS composition were evaluated in moving bed biofilm reactors (MBBRs), and a hypothesis that the aeration regimes affect EPS composition by affecting the microbial activity and sludge discharge content was proposed. The effluent NO2−/NH4+ ratio corresponded to that of an anammox reaction (1.07 ± 0.20) for the MBBR with continuous aeration (MBBRcon.), while that in the MBBR with intermittent aeration (20 min on/15 min off) (MBBRint.) was relatively lower (0.75 ± 0.19). Furthermore, the activity of ammonia-oxidizing bacteria in MBBRcon. was 0.4–7.9 mg-N·L−1·h−1 more than that in MBBRint., which was consistent with the lower proportion of dead cells in MBBRcon. compared with MBBRint. (9.4% vs. 31.8%). The higher microbial activity in MBBRcon. led to more sludge discharge than MBBRint., which was reflected in the higher biofilm detachment rate in MBBRcon. compared with MBBRint. (0.15 ± 0.02 vs. 0.11 ± 0.02 g m−2·d−1). The ratio of humic substances to polysaccharides in the EPS was high (0.96 ± 0.08) in the detachment biomass, while the ratios in the nitritation biofilm on carriers from MBBRcon. and MBBRint. were 0.52 ± 0.13 and 0.72 ± 0.16, respectively. We hypothesized that biofilm matrix with high ratios of humic substances to polysaccharides are structurally unstable and prone to fall off. In addition, the higher proportion of dead cells in MBBRint. made the proportion of humic substances in EPS high. Meanwhile, less sludge discharge in MBBRint. than MBBRcon. caused more humic substances to accumulate in the biofilm. These was responsible for the higher ratio of humic substances to polysaccharides in MBBRint. compared with MBBRcon. The findings elucidate the connection between aeration regimes and biofilm EPS composition, and guide the choice of aeration regimes in the design of biofilm reactors for partial nitritation.

Effects of Aeration on the Formation of Arbuscular Mycorrhiza under a Flooded State and Copper Oxide Nanoparticle Removal in Vertical Flow Constructed Wetlands.

In this study, six vertical flow constructed wetlands (VFCWs) planted with Phragmites australis were operated at different aeration times (4h day-1 and 8h day-1), aeration modes (continuous and intermittent), and arbuscular mycorrhizal fungi (AMF) inoculation treatments (inoculation with Rhizophagus intraradices and no inoculation) to explore the effects of different aeration strategies on the formation of arbuscular mycorrhiza under a flooded state in VFCWs. In addition, these VFCWs were further used to treat copper oxide nanoparticle (CuO-NP) wastewater to evaluate the correlations among aeration, colonization, growth, and CuO-NP removal. The highest AMF 28S copy number (1.99×105) and colonization in reed roots, with values of 67%, 21%, and 1% for frequency (F%), intensity (M%), and arbuscule abundance (A%), were observed in the treatment with intermittent aeration for 4h day-1. Aeration significantly increased the dissolved oxygen (DO) concentration and AMF colonization in VFCWs, thereby promoting plant growth and the purification of the CuO-NPs. However, excessive and continuous aeration had little positive effect on AMF colonization. This study provides a theoretical basis for the application of AMF for improving pollutant removal performance in constructed wetlands.

Effect of Different Ratios of Anaerobic Time and Aeration Time on the Operation of a Continuous-Flow Reactor with Partial Nitrification Granules

A continuous flow reactor was inoculated at 25-28℃ with mature partial nitrification granular sludge. In order to avoid the granular sludge being crushed because of the sludge backflow through the peristaltic pump, a built-in sedimentation zone was used for internal backflow. The experiment investigated the influence of the different anaerobic time to aeration time ratio (1:1, 2:1, and 1:2) on the stability of a continuous-flow partial nitrification granular sludge system. The results showed that when the controlled anaerobic time to aeration time ratio was 1:1 and 2:1, the partial nitrification performance was good and the nitrite accumulation rates were 85.2% and 94.5%, respectively. When the controlled anaerobic time to aeration time ratio was 1:2, the partial nitrification performance gradually deteriorated, and the ammonia nitrogen removal rate and nitrite accumulation rate at the end of the stage decreased to 64.1% and 58.7%, respectively. Batch test results showed that intermittent aeration and continuous aeration can better inhibit the relative activity of NOB in the partial nitrification system to a certain extent. The longer the anaerobic time, the better the NOB activity inhibition. However, too long an anaerobic time will also lead to ammonia nitrogen removal rate. In the process of partial nitrification, the long-term stable operation of continuous flow partial nitrification process can be realized by 1:1 and coordinated control of other control conditions. An analysis of sludge performance indicated that in the anaerobic time to aeration time ratio range of 1:1-1:2, the longer the anaerobic time, the more stable the granular sludge structure. The shorter the anaerobic time, the smaller the selection pressure in the reactor, resulting in poor sludge sedimentation performance and partial disintegration of partial nitrification granular sludge. An EPS chemical analysis and a three-dimensional fluorescence spectroscopic analysis showed that the PN content was higher and the PN/PS value was higher when the anaerobic time and aeration time ratio was 2:1.