Biological Aerated Filter Reactor Research Articles

Safe purification of rural drinking water by biological aerated filter coupled with ultrafiltration

Water resources of many rural areas are usually lakes or reservoirs, which can be easily affected by run-off, non-point source pollution and are often of poorer quality compared with urban water sources. Drinking water supply in remote rural areas usually suffers from various challenges, such as the high cost of construction and maintenance of centralized drinking water treatment plants and pipe networks, due to the dispersed nature of villages, which are often located in varied and complex topographies. In this study, a combined process comprising biological aerated filter (BAF) combined with ultrafiltration was developed to treat polluted reservoir water. Organic matter indexes, turbidity, and chroma were used as indicators for the evaluation of the system performance. In a long-term experiment lasting 260 days, the combined process was tested under different values of critical operational parameters, including filler types and empty bed contact time (EBCT). Furthermore, the microbial communities in different BAF reactors were carefully evaluated at different times, finding that microorganisms with specific functions were enriched in the various BAF reactors. The combined process reached 85.5 % removal rate of DOC with an EBCT of 45 min and using granule active carbon (GAC) as filler. Most of the effluents of BAF reactors met the requirements for drinking water in China. The combined system showed practical potential for polluted water treatment in some rural areas.

Advanced treatment of effluent extended aeration process using biological aerated filter (BAF) with natural media: modification in media, design and backwashing process

Biological aerated filters (BAFs) have high filtration efficiency due to their tolerance of hydraulic and organic shocks are suitable for the treatment of complex and sanitary wastewater. In this study, for the first time, natural media of date kernel from Bam city was used as the BAF reactor media, with a meshing sand filter separated by a standard metal grid from the natural filter section used at the end of the reactor. This can be considered an innovation in the media and filtration. Aeration in the related reactor with 160 cm height was performed bilaterally as up-flow and continuously by nozzles throughout the reactor media. In this work, the actual effluent of the hospital wastewater treatment plant was employed as the inflow wastewater to the reactor, and its organic and inorganic parameters were measured before and after the treatment by the BAF reactor. The backwashing process was also studied in three ways: bottom backwashing (TB), top backwashing (BB), and top and bottom backwashing (TBBS), to determine the amount of water consumed and to achieve the desired result. According to the results obtained in this study, the removal efficiencies of inorganic and microbial contaminants, amoxicillin and azithromycin were obtained as follows: BOD5: 98.48%, COD: 92.42%, {text{NO}}_{3}^{ - }: 99.4%, P: 93.3%, Coliforms: 97%, Color: 42.8%, Turbidity: 95%, Sulphate: 30%, TSS: 98.9%, Amoxicillin: 20% and azithromycin: 13%. In the backwashing process, the amount of water consumed in these three TB, BB, and TBBS methods were obtained 300, 164, and 118 L, respectively, So, TBBS method was selected as the optimal method. Based on the results obtained in this study, it is concluded that the BAF process with natural date kernel has a high efficiency in removing organic and inorganic contaminants from hospital wastewater, also the concentration of most of the effluent parameters was less or in accordance with EPA standard.

Advanced treatment of secondary effluent organic matters (EfOM) from an industrial park wastewater treatment plant by Fenton oxidation combining with biological aerated filter

This study investigated the advanced treatment of secondary effluent organic matters (EfOM) from an industrial park wastewater treatment plant (IPWTP) by Fenton oxidation process and its combination with biological aerated filter (BAF). The constituents of EfOM were characterized by using fluorescence excitation-emission matrix, and the results showed that the major components included aromatic proteins, soluble microbial products, humic and fulvic acid-like substances, and compounds associated with fluorescent region of Ex 250–300 nm/Em 600–700 nm. The EfOM was strongly resistant to biodegradation (biochemical oxygen demand (BOD5):chemical oxygen demand (COD) ratio at 0.11), resulting in less than 15% dissolved organic carbon (DOC) removal efficiency by the BAF reactor. The advanced treatment of EfOM by Fenton oxidation process led to maximum ~50% mineralization efficiency of EfOM under the optimal conditions of 2.0 mM FeII, 10 mM H2O2, pH 3.0 and 3.0 h of the reaction time. Particularly, Fenton oxidation treatment effectively improved the biodegradability of EfOM in the IPWTP secondary effluents, e.g., increasing the BOD5:COD ratio from 0.11 to 0.42. A synergistic combination of Fenton oxidation process with the BAF reactor offered desirable mineralization efficiencies of EfOM (>70%) at lower dosages of Fenton's reagents. The present results suggest that Fenton oxidation process combining with the BAF reactor can be a promising strategy for the advanced treatment of EfOM in IPWTP secondary effluents. This study provides guidance for the characterization and advanced treatment of EfOM in IPWTP secondary effluents for practical purpose.

Effects of hydraulic retention time on nitrous oxide production rates during nitrification in a laboratory-scale biological aerated filter reactor

This study investigated the effects of hydraulic retention time (HRT) on nitrous oxide (N2O) production during nitrification in a laboratory-scale biological aerated filter (BAF) reactor. Furthermore, its underlying mechanisms were explored by microelectrode technology and PCR-denaturing gradient gel electrophoresis (PCR-DGGE). The results showed that the N2O production rate was at its maximum at HRT of 4 h and at its minimum at HRT of 6 h. And there was only a little increase in N2O production rate at HRT of 8 h compared to HRT of 6 h. The average N2O production rates were 0.2258, 0.0872, and 0.1015 mg/h for HRT of 4, 6, and 8 h, respectively. Results of analysis of the internal biofilm microenvironment were consistent with the results of the N2O production rate. Production of N2O decreased sharply when HRT was increased from 4 to 6 h, whereas a slight increase in N2O production was observed when HRT was further increased from 6 to 8 h. Determination of DO, ORP, and nitrogen by microelectrode also demonstrated that the internal microenvironment of the biofilm was responsible for N2O generation. DNA analysis showed that Proteobacteria and Bacteroidetes might be responsible for N2O emission in the biofilm. These results indicate that HRT significantly affects the microbial community structures between the seed sludge and BAF biofilm, thereby affecting N2O production ability and rates, and hence, should be taken into consideration during BAF application.

Characteristics of the extracellular polymeric substance composition in an up-flow biological aerated filter reactor: The impacts of different aeration rates and filter medium heights

In this study, the compositional characteristics of extracellular polymeric substances (EPS) were systematically explored to reveal their relationship with microbial community under different conditions in an up-flow biological aerated filter reactor. The aeration rates had a significant positive correlation (0.898 ≤ R ≤ 0.979) with the tightly bound (TB)-EPS contents, but basically showed an opposite trend (R < −0.631) with the loosely bound (LB)-EPS. Moreover, the filter medium heights also affected EPS distribution. The microbial biofilm produced more LB-EPS and TB-EPS to withdraw from the extreme environment. Five fluorescent substances were identified in the EPS by EEM-PARAFAC modeling; namely, two protein-like components (protein-like C1 and tryptophan-like C2) and three humic-like components (UVA marine humic-like C3, hydrophobic humic acid-like C4, and humic acid-like C5). Under different conditions, the relative abundance of Proteobacteria and Nitrospirae had a significant positive correlation with C5 and C4, respectively. These results demonstrated that microbial community distribution could affect EPS composition.

N2O and NO emission from a biological aerated filter treating coking wastewater: Main source and microbial community

Nitrous oxide (N2O) and nitric oxide (NO) emissions from domestic wastewater treatment had been widely investigated due to their severe greenhouse effect and stratospheric ozone depletion. Researches concerning N2O and NO emissions from industrial wastewater treatment which usually contain high concentrations of nitrogen and refractory organics were still limited. In this study, N2O and NO emissions from a biological aerated filter (BAF) for coking wastewater treatment were investigated that achieved efficient nitrogen and chemical oxygen demand (COD) removal efficiency through short-cut nitrification and denitrification. Notably, emission factor of N2O and NO reached 23.58% and 0.09% respectively, much higher than those emitted from most domestic wastewater treatment plants. Moreover, batch experiments revealed that nitrifier denitrification contributed as high as 97.17% and 93.89% of the total generated N2O and NO, which was supposed to be the main source of green-house gases (GHGs) during coking wastewater treatment. The inhibition of denitrifying reductase by the toxic components in coking wastewater and the severe nitrite accumulations were key factors promoting the high emission of N2O and NO. Microbial community analysis based on high throughput sequencing of 16S rRNA gene revealed that ammonia-oxidizing bacteria and denitrifying bacteria distributed abundantly in the BAF reactor, while nitrite-oxidizing bacteria was almost absent. The huge imbalance between NO and N2O reductase was an underlying explanation for the high N2O emission in the present coking wastewater treatment according to Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt) result. This study is of great significance to understanding the high N2O and NO emission and developing the control strategy when treating industrial wastewater with high-strength nitrogen and refractory organics.

Effect of Aeration Rates and Filter Media Heights on the Performance of Pollutant Removal in an Up-Flow Biological Aerated Filter

The biological aerated filter (BAF) is an effective biological treatment technology which removes the pollutants in municipal wastewater secondary treatment. However, we still know little about the interaction between the pollutants removal and microbes within the BAF. In this study, we used an up-flow BAF (UBAF) reactor to investigate the relationships between the pollutants removal and microbial community structure at different aeration rates and filter media heights. The microbial community of biofilm was analyzed by Illumina pyrosequencing. Our results showed that the UBAF achieved a better removal efficiency of chemical oxygen demand (COD), NH4+-N, NO3−-N, and total phosphorus (TP) at an aeration rate of 65 L/h. In addition, the COD and NH4+-N removal mainly occurred at 0–25 cm height of filter media. The microbial community structure in the UBAF demonstrated that the relative abundance of the Planctomycetes and Comamonadaceae at 10 cm height of filter media were 11% and 48.1%, respectively, proportions significantly higher than those under others treatments. Finally, the changes in relative abundance of Proteobacteria, Planctomycetes, and Nitrospirae likely explained the mechanism of nitrogen and phosphorus removal. Our results showed that suitable conditions could enhance the microbial community structure to achieve a high pollutants removal in the UBAF.

Correlating microbial community structure with operational conditions in biological aerated filter reactor for efficient nitrogen removal of municipal wastewater

In this study, the combination of strengthen circulation anaerobic (SCA) and biological aerated filter (BAF) reactor was employed to treat municipal wastewater. Different reflux percentages or gas/water ratios were selected for evaluating the removal performance of contaminants in SCA-BAF system and sequential nitrification and denitrification process in BAF reactor. In general, reflux percentage (200%) and gas/water ratio (3:1) were a relatively suitable operational condition for BAF reactor. The COD, NH3-N, TN concentrations of effluents collected from BAF reactor varied in the ranges of 18–80, 0.2–7.2, 9.1–33.0 mg L−1, respectively. A higher NO3-N concentration in effluents of BAF reactor resulted from the lack of organic carbon resource in wastewater. High throughput sequencing analysis indicated that different nitrification and denitrification bacteria thrived in the BAF reactor. The DO, NO2-N and NO3-N concentrations showed a strong correlation with Nitrospira and Nitrosomonas in bacterial samples outlet (c and e) under gas/water ratio of 3:1.

Stimulation effect of electric current density (ECD) on microbial community of a three dimensional particle electrode coupled with biological aerated filter reactor (TDE-BAF)

Improving the stimulation effect of electric current density (ECD) on microbial community is critical in designing and operating TDE-BAF. This study investigated the effect of ECD at 0.00, 4.08, 6.12, 12.20, 14.25, 16.30 and 20.20A·m−2 on the removal performance, diversity and structure of microbial community in TDE-BAF. Results indicated that the ECD of 14.25A·m−2 exhibited the highest COD, TOC and NH4+-N average removal rates with 93.33%, 91.26% and 93.87%, respectively; Under high ECD, especially exceeding 14.25A·m−2, the inhibition of growth and activity because of plasmatorrhexis was in agreement with the sharp biomass decline; there was no significant relation between community richness and diversity and removal efficiency below optimum ECD, while above optimal ECD, it was just the opposite; Microbial communities mainly including Hydrogenophaga, Saprospiraceae_uncultured, Delftia, Enterobacter, Pseudomonas, Pseudoxanthomonas, and Nitrosospira and physicochemical properties well explained the excellent removal performance at the optimum ECD.

Effect of backwashing on the microbial community structure and composition of a three dimensional particle electrode coupled with biological aerated filter reactor (TDE-BAF)

The impact of backwashing on recovery capacity and microbial diversity of the TDE-BAF by comparing with single BAF was investigated. Results showed that the effluent concentrations of CODcr, TOC, NH4+N and Turbidity after backwashing all revealed initial peak and gradually decreased to a steady state. TDE-BAF has a slightly better backwashing recovery capacity than single BAF. Regarding to backwashing recovery of CODcr, TOC, NH4+N and Turbidity, TDE-BAF needs approximately 4h, 3h, 2h, 4h, however, single BAF spends around 6h, 4h, 3h, 5h, respectively. Miseq pyrosequencing was used to investigate microbial diversity of TDE-BAF. The microbial community structures at phylum level were different between TDE-BAF and single BAF. Flavobacterium, Methylophilus, Saprospiraceae_uncultured, Sphaerotilus, Prosthecobacter and Comamonadaceae_unclassified were ubiquitous and distinct phyla. The diversity of the microbial community in the upper part of two reactors greatly raised from before-backwashing to after-backwashing biofilm samples, but in contrast it decreased on the lower part of two reactors. The microbial community structures at genus level were different between TDE-BAF and single BAF. The relative abundance of after backwashing in the TDE-BAF indicated that most genus in the upper part gradually rose, while the majority of genus is decreased rather than increased in the lower part.

Effects of C/N ratio on nitrous oxide production from nitrification in a laboratory-scale biological aerated filter reactor.

Emission of nitrous oxide (N2O) during biological wastewater treatment is of growing concern. This paper reports findings of the effects of carbon/nitrogen (C/N) ratio on N2O production rates in a laboratory-scale biological aerated filter (BAF) reactor, focusing on the biofilm during nitrification. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and microelectrode technology were utilized to evaluate the mechanisms associated with N2O production during wastewater treatment using BAF. Results indicated that the ability of N2O emission in biofilm at C/N ratio of 2 was much stronger than at C/N ratios of 5 and 8. PCR-DGGE analysis showed that the microbial community structures differed completely after the acclimatization at tested C/N ratios (i.e., 2, 5, and 8). Measurements of critical parameters including dissolved oxygen, oxidation reduction potential, NH4+-N, NO3--N, and NO2--N also demonstrated that the internal micro-environment of the biofilm benefit N2O production. DNA analysis showed that Proteobacteria comprised the majority of the bacteria, which might mainly result in N2O emission. Based on these results, C/N ratio is one of the parameters that play an important role in the N2O emission from the BAF reactors during nitrification.

Production of unburned calcium silicon filter material (UCSFM) from oyster shell and its performance investigation in an A/O integrated biological aerated filter reactor (A/O-BAF)

A considerable amount of the oyster shells as a waste product of mariculture is produced every year, which leads to a major disposal problem with coastal regions of China.

Biological aeration filter post-treating effluent from Fenton oxidation process of wastewater containing rhodamine B

AbstractIn order to investigate the treatment of refractory organic pollutants in textile wastewater, Rhodamine B (RhB) was selected as a model pollutant to prepare the simulated wastewater. Aim to treat the effluent from Fenton oxidation process for wastewater containing RhB, biological aerated filter (BAF) was used as post-treatment process. The start-up process of the BAF reactor and the optimum operation conditions for the wastewater treatment process were investigated in this study. It was demonstrated by a series of bench-scale tests that the reactor could be successfully started up by exogenously inoculated activated sludge and gradual acclimation method. Operation condition experiments indicated that the BAF could achieve relatively high performance when gas–water ratio was 5–6, hydraulic retention time was controlled at 6–8 h and influent organic loading was within the range from 0.77 to 2.04 kgCOD/(m3 d).

생물학적 호기성필터를 이용한 소규모 하수처리시스템에 관한 연구

The biological aerated filter (BAF) reactor is regarded as an effective biological wastewater treatment method. It can remove pollutants by carrier filtration and biodegradation. Due to its advantages, which include high biomass retention, tolerance to toxicity, excellent removal efficiency, and slurry separation, BAF has been widely used to remove COD, NH4 + -N, phosphorus, and other harmful organic substances. In this study, the BAF reactor was used to remove organic contaminants of domestic wastewater of Korea at both the benchand pilot-scale. The main objectives of this study are to: (i) investigate the removal efficiency of organic contaminants (ex. COD, nitrate, phosphorus) in BAF reactors at both scales; (ii) characterize the small-scale wastewater treatment plant using the BAF reactor. The concentration of COD in the influent increased from 69 to 246 mg/L. During the operation period, the final effluent concentration of COD remained maximum 4.0 mg/L, and the average removal efficiency was above 88%. The present study investigated the removal efficiencies of COD, TN, TP and NH4 + -N from smelting wastewater by BAF system. When treating wastewater in both bench and pilot-scale reactors, the BAF worked well.

Impact of sorption functional media (SFM) from zeolite tailings on the removal of ammonia nitrogen in a biological aerated filter

Haydite and sorption functional media (SFM), made of clinoptilolite tailings, were used as filter media for biological aerated filter (BAF) to treat synthetic wastewater in parallel. The aim of this work was to evaluate impact of SFM on the removal of ammonia nitrogen in a biological aerated filter reactor under ammonium nitrogen shock loads. It could be demonstrated that: (1) the BAF with SFM presented higher ammonia nitrogen removal efficiency than that with haydite; (2) during the phase of higher influent concentrations SFMs were collecting ammonia nitrogen and can buffer ammonia nitrogen loads and dampen the effluent concentration of ammonia nitrogen; (3) when the influent concentration decreases ammonia nitrogen will desorb from the SFM and can be utilized by the nitrifying bacteria growing on the SFM. Therefore, with the SFM application existing BAF unites can be upgraded and the stability of the operation process of BAF can be improved significantly.

Construction and Calibration of Physical Filtration Equation of Biological Aerated Filter

To establish the physical filtration equation of Biological Aerated Filter (BAF), the porosity calculating model (Eq. 5) and SS concentration calculating model (Eq. 16) were constructed respectively by the way of infinitesimal element analysis. And then the BAF physical filtration equation had been derived by using the relationship among headloss, porosity and SS. The BAF physical filtration equation was shown as Eq. 19.Then the Kozeny-Carman coefficient in Eq. 19, kc, was confirmed to be 0.040 by experimental adjusting and domesticating. In the condition of kc=0.040, the predicted values of Eq. 19 fitted the experimental values of BAF reactor well, which illustrated that the BAF filtration equation constructed in this study was scientific and the parameters value adopted in this equation was reasonable.

Study on Optimal Controlling Strategy of Backwashing Process in Biological Aerated Filter

Basing on comprehensive analysis of the existing backwashing modes of Biological Aerated Filter (BAF), air and water combined backwashing was taken as the most efficient and economic mode for BAF backwashing in this study to ensure operating stability and backwashing effect. Then the relevant parameters, involved in air flushing, air and water combined washing and water rinsing, were optimized reasonably. In this paper, the optimal backwashing control strategy was recommended as follows: air backwashing 3 minutes with air backwashing intensity of 10 L/m2·s,secondly, air and water combined backwashing 3 minutes with both air and water backwashing intensity of 10 L/m2·s,at last,water rinsing for 9 minutes with water rinsing intensity of 10 L/m2·s. To discuss the influence of backwashing process on treatment efficiency of BAF, the changes of headloss and contaminants concentration of BAF before and after backwashing was also investigated in this study. The experimental results revealed that under the optimal backwashing control strategy the water flux could be recovered soon after backwashing. Although the contaminants concentration in initial filtrated water increased slightly, the treatment efficiency of BAF reactors could be back to normal in 2 hours.

Impact of Substratum Surface on Microbial Community Structure and Treatment Performance in Biological Aerated Filters

The impact of substratum surface property change on biofilm community structure was investigated using laboratory biological aerated filter (BAF) reactors and molecular microbial community analysis. Two substratum surfaces that differed in surface properties were created via surface coating and used to develop biofilms in test (modified surface) and control (original surface) BAF reactors. Microbial community analysis by 16S rRNA gene-based PCR-denaturing gradient gel electrophoresis (DGGE) showed that the surface property change consistently resulted in distinct profiles of microbial populations during replicate reactor start-ups. Pyrosequencing of the bar-coded 16S rRNA gene amplicons surveyed more than 90% of the microbial diversity in the microbial communities and identified 72 unique bacterial species within 19 bacterial orders. Among the 19 orders of bacteria detected, Burkholderiales and Rhodocyclales of the Betaproteobacteria class were numerically dominant and accounted for 90.5 to 97.4% of the sequence reads, and their relative abundances in the test and control BAF reactors were different in consistent patterns during the two reactor start-ups. Three of the five dominant bacterial species also showed consistent relative abundance changes between the test and control BAF reactors. The different biofilm microbial communities led to different treatment efficiencies, with consistently higher total organic carbon (TOC) removal in the test reactor than in the control reactor. Further understanding of how surface properties affect biofilm microbial communities and functional performance would enable the rational design of new generations of substrata for the improvement of biofilm-based biological treatment processes.

Effects of Air/Liquid Ratio on Treatment Efficiency of Textile Wastewater in a Biological Aerated Filter Reactor

A biologically aerated filter (BAF) is a novel, flexible and effective bioreactor that provides a small footprint process option at various stages of wastewater treatment. Double layers of activated carbon and ceramsite were applied in the biological aerated filter reactor. An experiment was conducted under laboratory conditions to investigate the treatment efficiencies at different air/liquid ratios. The experimental results obtained showed that air/liquid ratio had a greater effect on NH4+–N removal than COD removal. More than 80% ammonia nitrogen was removed at 2 of air/liquid ratio. However, less than 50% COD was removed at 2 of air/liquid ratio.

A simultaneous removal of beryllium and ammonium–nitrogen from smelting wastewater in bench- and pilot-scale biological aerated filter

Heavy metal and NH4+–N co-contaminated wastewater are frequently found, and the presence of NH4+–N makes it extremely difficult to treat. In the present study, bench-scale and pilot-scale experiments were conducted to investigate the simultaneous removal of beryllium and NH4+–N from smelting wastewater by biological aerated filter (BAF) reactors. The results of the five-stage BAF reactors showed that the system could endure shock loadings. The average removal efficiency for beryllium and NH4+–N was 92.6% and 95.0%, respectively. Sequence extraction indicates that the primary removal mechanism in the first two reactors was precipitation, whereas the organic-bound fraction was predominant in the last three reactors due to the high accumulation rates of beryllium inside the microbial cells. Polymerase chain reaction and denaturing gradient gel electrophoresis (PCR–DGGE) and sequence analysis of 16S rDNA gene fragments showed that N-oxidizing bacteria (Nitrosomonas sp. and Beta proteobacterium CH24i) were primarily detected in the first two BAF reactors, in accordance with their high NH4+–N removal efficiencies, and metal-resistant bacteria (Actinobacteria sp.) were found in all BAF reactors.