Effect Of Intermittent Aeration Research Articles

“Cattle dung biochar-packed vertical flow constructed wetland for nutrient removal”: Effect of intermittent aeration and wastewater COD/N loads on the removal process

The effect of varying COD/N ratio (1:1, 3:1, 5:1, 8:1, 10:1) of wastewater and intermittent aeration on treatment efficiency of biochar (BC)-packed (with 10% V/V biochar) vertical flow constructed wetland (VFCW), planted with Colocasia esculenta was assessed in this study. Three setups of VFCW were prepared in two sets: aerated (with an airflow rate of 1.0 ± 0.6 L min−1 for 6 h d−1) and non-aeration, and changes in COD, NH4+-N, NO3-N, TN, and TP (total phosphorous) in the effluent was investigated. In VFCWS with intermittent aeration, COD, NH4+-N, NO3-N, TP removal was 99.0, 97.0, 81.0, and 89.0%, significantly higher (p < 0.05) than non-aerated VFCW setups as 91.3, 70.9, 86.97 and 64.4%, respectively. In non-aerated VFCWs, BC addition in combination with plantation was advantageous in the nutrient removal process than setups without BC. COD/N ratio of wastewater did not show a significant impact on the working of VFCWs if amended with BC and intermittent aerations, suggesting slow adsorption rate and fast aerobic degradation of organic matter. The study suggests that oxygen supply management and BC addition in VFCWs could be an effective strategy to treat wastewater with a high organic load. Apart from that study results will be useful for refinement of the operational strategy with varying organic load.

Effect of Intermittent Aeration in a Hybrid Vertical Anaerobic Biofilm Reactor (HyVAB) for Reject Water Treatment

Water from anaerobic sludge dewatering (reject water that is recycled to the inlet main process treatment) from the Knarrdalstrand municipal wastewater treatment plant in Porsgrunn, Norway, contains 2.4 g/L of total chemical oxygen demand (TCOD) and 550 mg/L NH4-N (annual average). The high concentration of ammonium causes disturbances in the mainstream physical and chemical processes, while only a small fraction of the organics is biodegradable. A pilot-scale hybrid vertical anaerobic biofilm (HyVAB) reactor combining anaerobic and aerobic treatment was tested for reject water treatment to reduce process disturbances. The pilot HyVAB was prepared for the study with continuous aeration of the aerobic part of the reactor for 200 days, while two intermittent aeration schemes were applied during the three-month test period. Ammonium removal efficiency increased from 8% during the continuous aeration period to 50% at the end of the test when a short (7 min) aeration cycle was applied. COD removal was close to 20%, which was mainly obtained in the anaerobic stage and not significantly influenced by the aerations schemes. Simultaneous partial nitrification and denitrification were established in the biofilm that alternated between aerobic and anoxic conditions. The observed high ammonium removal is explained by two alternative shortcut processes via nitrite. The lack of biodegradable organics in the aerated stage suggests that most of the nitrogen removal was via the anammox pathway (autotrophic denitrification). The HyVAB, combining an anaerobic sludge bed and an intermittently aerated biofilm, appears to be an efficient process to treat high ammonium containing reject water.

Effect of Intermittent Aeration and Step-Feed on Nitrogen Removal Performance in Anoxic-aerobic Sequencing Batch Reactor

In this study, it was investigated the effect intermittent aeration and step-feed on nitrogen removal&#x0D; by providing anoxic-aerobic, anoxic-aerobic-anoxic-aerobic and step-feed anoxic-aerobic-anoxicaerobic working conditions. Chemical oxygen demand (COD) removal efficiency was the same in&#x0D; all three working conditions and was found to be 91%. The NH4&#x0D; +&#x0D; -N removal efficiency is almost&#x0D; the same. The NH4&#x0D; +&#x0D; -N removal efficiencies in the W1, W2 and W3 are 92%, 93% and 95%,&#x0D; respectively. Total inorganic nitrogen (TIN) removal efficiency increased by 4% when intermittent&#x0D; aeration was applied. Increasing the efficiency of TIN removal by 24% was achieved by applying&#x0D; the step-feed intermittent aeration. Experimental results show that the effect of intermittent aeration&#x0D; on TIN removal was limited and that TIN removal performance with step-feed intermittent aeration&#x0D; was significantly increased.

Enhanced phosphorus removal in intermittently aerated constructed wetlands filled with various construction wastes.

Phosphorus (P) loss by various pathways in constructed wetlands (CWs) is often variable. The effects of intermittent aeration and different construction waste substrates (gravel, red brick, fly-ash brick) on P processing using six batch-operated vertical flow constructed wetlands (VFCWs) were studied for decentralized domestic wastewater treatment. Average removal of total phosphorus (TP) in three aerated CWs was markedly higher (21.06, 24.83, and 27.02mgm-2day-1, respectively) than non-aerated CWs (10.64, 18.16, and 25.09mgm-2day-1, respectively). Fly-ash brick offered superior TP removal efficiency in both aerated and non-aerated batch-operated VFCWs, suggesting its promising application for P removal in CWs. Aeration greatly promoted plant growth and thusly increased plant uptake of P by 0.57-1.45 times. Substance storage was still the main P sink accounting for 23.92-59.47% of TP removal. Other process including microbial uptake was revealed to be a very important P removal pathway (accounting for 14.86-34.84%). The contribution of microbial uptake was also indicated by microbial analysis. Long-term results suggested that the contribution of microbial P uptake could be always ignored and underestimated in most CWs. A combination of intermittent aeration and suitable substrates is effective to intensify P transformation in CWs.

Effect of intermittent aeration on microbial diversity in an intermittently aerated IFAS reactor treating municipal wastewater: A field study

ABSTRACTIn the present study, the effect of three intermittent aeration (IA) cycles on treatment performance and microbial diversity was investigated in an integrated fixed film activated sludge (IFAS) reactor treating municipal wastewater. The results showed that IA strategies were able to achieve efficient removal of organics and nitrogen ranging between 90 and 95% and 70 and 80%, respectively, however the phosphorus removal was found to be inversely proportional to the duration of aeration off time in each IA cycle. The microscopic analysis revealed that the suspended and attached biomass had compact morphology and open floc structure, respectively. For each gram of volatile suspended solids, 165 and 148 mg of extracellular polymeric substances (EPS) were extracted from attached and suspended biomass, respectively, constituting carbohydrates (∼24%), proteins (∼31%), humic acids (∼28%), DNA (∼2%) and unknown substances (∼12%). The microbial diversities of suspended biomass in IFAS reactor were investigated using culture-dependent approach, which confirmed the presence of Clostridium spp., Pseudomonas spp., Bacillus spp., Escherichia coli spp., Nitrosococcus spp., Streptococcus spp., Acinetobacter spp., Betaproteobacteria outliers, Klebsiella pneumoniae, Klebsiella aerogenes, Serratia marcescens, Micrococcus, Proteus vulgaris spp., Actinomycetes spp., and Actinobacteria including Micromonospora spp. and Streptomyces spp. Molecular tools for diversity analyses were used for ammonia and nitrite oxidizer identification, such as Nitrospira and Nitrosococcus species. Denitrifiers include the species of Pseudomonas, Betaproteobacteria and Flavobacterium. Acinetobacter, Betaproteobacteria and Gammaproteobacteria were responsible for the phosphorus removal in the present system. Overall, the system performed efficiently showing Proteobacteria (59%), Acinetobacter (12%) and Bacteroidetes (11%) as the dominant bacterial groups. However, the dominance of the bacterial diversity varied with the IA cycle time numerating the maximum percentage of bacterial species during IA1 phase i.e. 2.5 h aeration/0.5 h non-aeration.

Pathways of nitrobenzene degradation in horizontal subsurface flow constructed wetlands: Effect of intermittent aeration and glucose addition

Intermittent aeration and addition of glucose were applied to horizontal subsurface flow constructed wetlands in order to investigate the effect on pathways of nitrobenzene (NB) degradation and interactions with microbial nitrogen and sulphur transformations. The experiment was carried out in three phases A, B and C consisting of different NB loading and glucose dosing. For each phase, the effect of aeration was assessed by intermittently aerating one wetland and leaving one unaerated. Regardless of whether or not the wetland was aerated, at an influent NB concentration of 140 mg/L, both wetlands significantly reduced NB to less than 2 mg/L, a reduction efficiency of 98%. However, once the influent NB concentration was increased to 280 mg/L, the aerated wetland had a higher removal performance 82% compared to that of the unaerated wetland 71%. Addition of glucose further intensified the NB removal to 95% in the aerated wetlands and 92% in the unaerated. Aeration of wetlands enhanced NB degradation, but also resulted in higher NB volatilization of 6 mg m−2 d−1. The detected high concentration of sulphide 20–60 mg/L in the unaerated wetland gave a strong indication that NB may act as an electron donor to sulphate-reducing bacteria, but this should be further investigated. Aeration positively improved NB removal in constructed wetlands, but resulted in higher NB volatilization. Glucose addition induced co-metabolism to enhance NB degradation.

Effects of intermittent aeration on pollutants removal in subsurface wastewater infiltration system

In this study, the pollutant removal performances in two pilot-scale subsurface wastewater infiltration systems (SWISs) with and without intermittent aeration were investigated. Matrix oxidation reduction potential (ORP) results showed that intermittent aeration well developed aerobic conditions in upper matrix and anoxic or anaerobic conditions in the subsequent sections, which resulted in high NH4+-N and TN removal. Moreover, intermittent aeration increased removal rates of COD and TP. Microbial populations and enzyme activities analysis proved that intermittent aeration not only obviously boosted the growth and reproduction of bacteria, fungus, actinomyces, nitrifying bacteria and denitrifying bacteria, but also successfully increased nitrate reductase (NR) and nitrite reductase (NIR) in the depth of 80 and 110cm. The results suggest that the intermittent aeration could be a widespread research and application strategy for achieving the high removal performance in SWISs.

Pilot scale experiment with MBR operated in intermittent aeration condition: Analysis of biological performance

The effect of intermittent aeration (IA) on a MBR system was investigated. The study was aimed at analyzing different working conditions and the influence of different IA cycles on the biological performance of the MBR pilot plant, in terms of organic carbon and ammonium removal as well as extracellular polymeric substances (EPSs) production. The membrane modules were placed in a separate compartment, continuously aerated. This configuration allowed to disconnect from the filtration stage the biological phenomena occurring into the IA bioreactor. The observed results highlighted good efficiencies, in terms of organic carbon and ammonium removal. It was noticed a significant soluble microbial products (SMPs) release, likely related to the higher metabolic stress that anoxic conditions exerted on the biomass. However, the proposed configuration, with the membranes in a separate compartment, allowed to reduce the EPSs in the membrane tank even during the non-aerated phase, thus lowering fouling development.

Influence of operating conditions on nitrous oxide formation during nitritation and nitrification.

Nitrous oxide (N2O), a strong greenhouse gas, can be produced by ammonium-oxidizing bacteria (AOB) as a by-product of ammonium oxidation and can potentially be formed in all types of nitrification processes. However, partial nitritation has been reported to cause significantly higher N2O emissions than complete nitrification. In the study presented here, the mechanisms and factors that drive N2O formation by AOB were investigated with respect to different operational strategies to achieve nitrite accumulation base on combined evaluation of oxygen uptake rate (OUR) and N2O formation rate. On the one hand, N2O formation during partial nitritation and nitrification in a continuously stirred tank reactor (CSTR) with continuous aerobic conditions was observed. On the other hand, the effect of intermittent aeration on N2O formation during nitrification was investigated. The presence of nitrite, the extend of sludge-specific ammonium loading, low oxygen concentration, and transition from aerobic to anoxic conditions significantly increased N2O formation in this reactor independently from each other, indicating that different formation pathways, supposedly via nitrite or hydroxylamine, were active.

Nitrogen removal performance of intermitTENTly aerated membrane bioreactor treating black water

The study investigated the effect of intermitTENT aeration on the nitrogen removal performance of a membrane bioreactor (MBR) treating black water. A pilot-scale MBR with an effective volume of 630 L operating as a sequencing batch reactor (SBR) with intermitTENT aeration was used in the experiments. Substrate feeding was limited to the initial non-aerated phase. The MBR unit was sustained at a steady state at a sludge age of 60 d with a biomass concentration of around 10,000 mg/L for 3 months. The treated black water could be characterized with an average COD of 950 mg/L and total nitrogen of 172 mg/L, corresponding to a low COD/N ratio of 5.5. The selected MBR scheme was quite effective, reducing COD down to 26 mg/L, providing effective nitrification and yielding a total oxidized nitrogen concentration under 10 mg N/L. The nitrogen removal performance was substantially better than the level predicted by process stoichiometry, due to multiple anoxic configuration inducing additional nitrogen removal. Dissolved oxygen profiles associated with the cyclic operation of the system suggested that the incremental nitrogen removal could be attributed to simultaneous nitrification-denitrification, a commonly observed mechanism in MBR systems sustained at high biomass concentrations.

Study and Analysis of the Impacts and Mechanisms of Intermittent Aeration and Movement Degree of Membrane on the Permeate Flux in a Submerged Membrane System

This task studies the impacts and mechanisms of intermittent aeration and movement degree of membrane on the permeate flux in a submerged membrane system. The contents includes: Analysis of the effects of intermittent aeration on the membrane performance, modelling the experimental results and find out the mechanisms; Analysis of the effects of different movement degree of membrane on the permeate flux during the intermittent aeration process, modelling the experimental results and find out the mechanisms; Determination of the optimum membrane running conditions, including the most effective intensity of gas sparging, the most effective intermittent aeration cycle time and the most effective movement degree of membrane, etc. It shows that intermittent aerations between backwashing processes can significantly improve the membrane performance; the change of the movement degree (L/H),which means the ratio of the effective length and the effective vertical height) of membrane can affect the influences of intermittent aeration on the membrane performance significantly; the most effective intensity of gas sparging is 1.5L/h; the most effective intermittent aeration cycle time is 30min; the most effective movement degree of membrane is 1.07.The result of the research is good for the selection of operation condition and determination of running parameters of ultrafiltration membrane water supply process.

Effect of intermittent aeration on the microbial community structure of activated sludge in a submerged membrane bioreactor

AbstractLow removal rate for total nitrogen (TN) is the main limitation of a membrane bioreactor (MBR). The effects of intermittent aeration on the removal of TN and the microbial community structure of activated sludge from a submerged membrane bioreactor (SMBR) operating at three different aeration on/off times (run 1, continuous aeration; run 2, 60/60 min aeration on/off time; and run 3, 60/75 min aeration on/off time) were studied. The results showed that the removal rates for TN under different operation conditions were 26.2% (run 1), 59.5% (run 2) and 70.7% (run 3), respectively, and significant improvements were achieved. Monounsaturated phospholipid fatty acids (PLFAs) and saturated PLFAs were dominant PLFA types in activated sludge, followed by branched PLFAs; cyclopropane fatty acid were relatively small in amount. The highest ratio of the characteristic fatty acid representing the abundance of bacteria in activated sludge was found in run 2. Aerobic prokaryotes were the predominant groups under all three operation conditions, followed by the anaerobic bacteria and the Gram‐positive bacteria group; sulphate‐reducing bacteria (SRB) and other anaerobic bacteria occupied the lowest proportion. Intermittent aeration can be used as a possible means to improve the treatment performance in an MBR.

Effect of intermittent aeration on the treatment performance in a submerged membrane bioreactor

In order to improve removal for nitrogen in a pilot-scale submerged membrane bioreactor (SMBR), intermittent aeration was conducted, and the effect on the treatment performance under four kinds of operation condition (run 1, continuous aeration; run 2, 60/60 min aeration on/off time; run 3, 60/90 min aeration on/off time; run 4, 60/75 min aeration on/off time) was evaluated. The results showed that depending on the specific on/off of the aeration time ratio, removal efficiency of nitrogen could be improved significantly, and the removal rates of total nitrogen (TN) under different operation conditions were 28.0%, 59.5%, 66.8% and 70.7%, respectively. There were no obvious differences for removal rates for CODCr and ammonia among different operation conditions. In general, intermittent aeration could be used as a feasible way to improve treatment performance for nitrogen in the SMBR.

The Effects of Intermittent Aeration on the Characteristics of Bio-Cake Layers in a Membrane Bioreactor

The effects of a sequencing variation for dissolved oxygen (DO) concentrations on the membrane permeability in a submerged membrane bioreactor (MBR) were studied. An MBR was continuously operated under alternating DO conditions, e.g., 36 h of an aerobic phase, followed by 36 h of an anoxic phase. The rate of increase in transmembrane pressure (TMP) in the anoxic phase was always steeper than that in the aerobic phase, indicating that the fouling rate was higher in the anoxic than in the aerobic condition. Regardless of the phases, the rate of TMP increase became steeper as the cycles were repeated. However, this trend became less important as the cycle numbers increased. Even in identical microbial communities, the number of colloidal particles and soluble extracellular polymeric substances (EPS) in the bulk solution were increased during the anoxic condition, which caused a reduction in the porosity of the bio-cake. During analysis of the bio-cake profile along the cake depth, the temporal variation of the bio-cake structure was attributed to the temporal change in the number of colloidal particles as well as the change in compression forces acting on the bio-cake. The influence of the latter was found to be more important than that of the former, which was verified by comparing the various structures of bio-cake formed in differing DO environments.

Nitrogen removal from on-site treated anaerobic effluents using intermittently aerated moving bed biofilm reactors at low temperatures

On-site post-treatment of anaerobically pre-treated dairy parlour wastewater (DPWW e; 10 °C) and mixture of kitchen waste and black water (BWKW e; 20 °C) was studied in moving bed biofilm reactors (MBBR). The focus was on removal of nitrogen and of residual chemical oxygen demand (COD). Moreover, the effect of intermittent aeration and continuous vs. sequencing batch operation was studied. All MBBRs removed 50–60% of nitrogen and 40–70% of total COD (COD t). Complete nitrification was achieved, but denitrification was restricted by lack of carbon. Nitrogen removal was achieved in a single reactor by applying intermittent aeration. Continuous and sequencing batch operation provided similar nitrogen and COD removal, wherefore simpler continuous feeding may be preferred for on-site applications. Combination of pre-treating upflow anaerobic sludge blanket (UASB) -septic tank and MBBR removed over 92% of COD t, 99% of biological oxygen demand (BOD 7), and 65–70% of nitrogen.

Effect of intermittent aeration on the decrease of biological sludge amount

As a biochemical approach to decrease the amount of biological sludge, the sludge solubilization by repeatedly changing the microbial environments from aerobic to anaerobic was studied. The sludge reduction amount in batch operation was related to the degradation of intracellular materials released through sludge solubilization. The shorter the operation cycle time was, the more effective the sludge amount reduction was. On the other hand, under the cycle time of 3–24 h, longer anaerobic period compared to aerobic period was effective in removing nitrogenous compounds. This was partly ascribed to the excretion of enzyme such as protease and lipase.

Composting Process Optimization – Using On/Off Controls

Despite the commercialization of a variety of different composting systems, the design and operation of composting systems to minimize the cost of producing compost remains a major goal. Evaluation of how system design and management affects the time required to stabilize compost is critical to optimizing the process. In this study, analytical equations relating biological and physical factors and compost temperature, moisture, oxygen level and decomposition rates for aerobic composting are developed. The study focused on the effects of intermittent aeration on the composting operation. A multi-parameter kinetic model in conjunction with heat and mass balance equations were used to predict and optimize the performance of composting systems. Equations evaluating airflow and on/off fan cycle times on composting temperature, oxygen and moisture were developed. Kinetic data from pilot scale experiments using three different feedstocks: municipal solid waste, biosolids/woodchips, and grass/leaves/brush were used in the derived equations to evaluate the composting systems operation.

Effect of Aeration on the Performance of a Simulated Landfilling Reactor Stabilizing Municipal Solid Wastes

In this study, the effects of intermittent aeration on the anaerobic treatment of domestic solid waste and leachate characteristics were investigated in three simulated landfill anaerobic bioreactors. All of the reactors were operated with leachate recirculation and recirculation rate was 300 mL/d. All the reactors were loaded with solid waste having different operational mode. The first reactor was operated with recirculation (control-no aeration). The second reactor was aerated three days in a week during 1 h (Run 1) and the last reactor was aerated one day in a week during 1 h (Run 2). pH, chemical oxygen demand (COD), volatile fatty acids (VFA), ammonium nitrogen (NH4-N), nitrate nitrogen (NO3-N) concentrations, total, and methane gas productions in the leachate samples were regularly monitored. 96, 85, and 97% COD and 86, 77, and 93% VFA removals were obtained, in the leachate samples of the control, R1 and R2 reactors, respectively, after 79 days of anaerobic incubation. The TN, TP and NH4-N concentrations in MSW reduced to 4300, 1100, and 160 mg/g from 11,100, 2450, and 630 mg/g in R1 reactor by day 79. The values of pH were 6.98, 6.76, and 7.98, respectively, after anaerobic incubation, respectively in the aforementioned reactors. It was observed that the aeration decreased the methane percentage and the quantity in the simulated bioreactor. The maximum cumulative methane gas production was recorded as 11.2, 0.9, and 3.6 L in control, R1 and R2 reactors, respectively, at the end of 79 days. A BOD5/COD ratio of 0.23 achieved in the R2 reactor indicated the better MSW stabilization resulting in a high rate than that of R1 and control reactors. It was observed that the aerated reactor one day in a week during one hour (R2) reduced the COD and VFA concentrations in leachate samples. The aerated reactor three days in a week during 1 h (R1) reduced the waste quantity, the organic content of the solid waste. The final leachate quantities of aerated runs were lower than that of control reactor operated under strictly anaerobic conditions.

Effect of Aeration on the Performance of a Simulated Landfilling Reactor Stabilizing Municipal Solid Wastes

In this study, the effects of intermittent aeration on the anaerobic treatment of domestic solid waste and leachate characteristics were investigated in three simulated landfill anaerobic bioreactors. All of the reactors were operated with leachate recirculation and recirculation rate was 300 mL/d. All the reactors were loaded with solid waste having different operational mode. The first reactor was operated with recirculation (control-no aeration). The second reactor was aerated three days in a week during 1 h (Run 1) and the last reactor was aerated one day in a week during 1 h (Run 2). pH, chemical oxygen demand (COD), volatile fatty acids (VFA), ammonium nitrogen (NH4-N), nitrate nitrogen (NO3-N) concentrations, total, and methane gas productions in the leachate samples were regularly monitored. 96, 85, and 97% COD and 86, 77, and 93% VFA removals were obtained, in the leachate samples of the control, R1 and R2 reactors, respectively, after 79 days of anaerobic incubation. The TN, TP and NH4-N concentrations in MSW reduced to 4300, 1100, and 160 mg/g from 11,100, 2450, and 630 mg/g in R1 reactor by day 79. The values of pH were 6.98, 6.76, and 7.98, respectively, after anaerobic incubation, respectively in the aforementioned reactors. It was observed that the aeration decreased the methane percentage and the quantity in the simulated bioreactor. The maximum cumulative methane gas production was recorded as 11.2, 0.9, and 3.6 L in control, R1 and R2 reactors, respectively, at the end of 79 days. A BOD5/COD ratio of 0.23 achieved in the R2 reactor indicated the better MSW stabilization resulting in a high rate than that of R1 and control reactors. It was observed that the aerated reactor one day in a week during one hour (R2) reduced the COD and VFA concentrations in leachate samples. The aerated reactor three days in a week during 1 h (R1) reduced the waste quantity, the organic content of the solid waste. The final leachate quantities of aerated runs were lower than that of control reactor operated under strictly anaerobic conditions.

Nitrogen transformations during biological aerobic treatment of pig slurry: effect of intermittent aeration on nitrous oxide emissions

A laboratory scale aeration treatment system was built to study the fate of nitrogen during aeration of pig slurry. For each run evaluated, the nitrogen mass balance was determined including measurement of the nitrous oxide gas emissions. Intermittent aeration led to a nitrogen removal of about 53% of the total nitrogen content of the raw slurry. About 18% of the total nitrogen content of the raw slurry was emitted as N 2O during aeration with an aerobic to anoxic ratio equal to 0.625. In contrast, the extension of the anoxic period (aerobic to anoxic ratio=0.375) allowed complete denitrification and avoided N 2O emissions.