Applications of Anammox based processes to treat anaerobic digester supernatant at room temperature

The supernatant of an anaerobic digester was treated at 20 °C in two systems. The first one is a two units configuration, conformed by two sequencing batch reactors (SBR), carrying out partial nitrification and Anammox processes, respectively. Partial nitrification was achieved by granular biomass with a mean diameter of 3 mm, operating at a dissolved oxygen concentration of 2.7 mg/L. The combined system allowed the removal of nitrogen loading rates around 0.08 g N/(L d).     

好氧和缺氧条件下游离亚硝酸对氨氧化菌和亚硝酸盐氧化菌的选择性抑制

【背景】稳定短程硝化是实现城市污水厌氧氨氧化技术的瓶颈,目前国内外关于游离亚硝酸(Free nitrous acid,FNA)对硝化菌活性的影响大多是在曝气条件下进行研究,鲜有关于缺氧条件下FNA对硝化菌活性影响的报道。【目的】探究好氧和缺氧下FNA对氨氧化菌(Ammonia oxidizing bacteria,AOB)和亚硝酸盐氧化菌(Nitrite oxidizing bacteria,NOB:Nitrospira和Nitrobacter)活性的抑制影响。【方法】采用序批式反应器(Sequencing batch reactor,SBR),基于混合液悬浮固体浓度(Mixed liquid suspended solids,MLSS)为8 300 mg/L的全程硝化污泥条件,通过批次试验分别考察好氧和缺氧下FNA(初始浓度为1.16 mg/L)处理48 h后,AOB和NOB活性的变化情况。【结果】好氧FNA处理活性污泥48 h后,FNA浓度维持在1.16-1.17 mg/L,游离氨(Free ammonia,FA)浓度小于0.017 mg/L,AOB、Nitrospira、Nitrobacter丰度均未发生明显变化;过曝气至99 h时,与空白组相比,比氨氮氧化速率(r~+_(NH4-N))、比亚硝酸盐氮氧化速率(r_(NO2-N))均出现小幅下降,分别由3.5、4.828 mg N/(g VSS·h)降至3.3、4.668 mg N/(g VSS·h),且亚硝酸盐氮累积率(Nitrite accumulation rate,NAR)始终低于33.2%。缺氧FNA处理活性污泥48 h后,FNA浓度维持在0.64-1.16 mg/L,FA浓度低于0.039 mg/L,AOB丰度变化较小,而Nitrospira、Nitrobacter丰度均明显下降,分别由3.002 9×10~9、4.245×10~8 copies/g VSS降至1.666 5×10~8、5.163 8×10~7 copies/g VSS;过曝气至99 h时,与空白组相比,r~+_(NH4-N)值下降幅度较小,而r_(NO2-N)值明显降低,由4.828 mg N/(g VSS·h)降至0.007 mg N/(g VSS·h),且在过曝气0-292 h内,NAR均大于94%。【结论】好氧FNA处理活性污泥48 h后对AOB和NOB无明显抑制作用,但缺氧FNA处理活性污泥48 h后对AOB具有轻微抑制作用,而对NOB具有强烈的抑制作用,可以实现稳定的短程硝化。     

A comparative study on the formation and characterization of aerobic 4-chloroaniline-degrading granules in SBR and SABR

The formation and characterization of the aerobic 4-chloroaniline-degrading granules in the three column-type sequencing batch reactors were investigated in this paper. The granular sludge was observed since 15 days after start-up in R2 and R3 which had the high ratio of height to diameter (H/D). Since then and within the subsequent 75 days, the granulation of aerobic sludge was apparently developed by the decreased settling time and gradually increased 4-chloroaniline (4-ClA) concentration to above 400 mg.L(-1) in R1 to R3. The aerobic granules tended to be mature in all reactors continuously operated with 4-ClA loading rates of around 800 g.m(-3).d(-1), and the removal efficiencies of chemical oxygen demand, total nitrogen, and 4-ClA were maintained above 93%, 70%, and 99.9%, respectively. Mature aerobic granules in R1 to R3 featured with the average diameter of 0.78, 1.68, and 1.25 mm, minimal settling velocity of 20.5, 70.1 and 66.6 m.h(-1), specific 4-ClA degradation rates of 0.14, 0.21, and 0.27 g.gVSS(-1).d(-1), and the ratio of proteins to polysaccharides of 8.2, 10.8, and 13.7 mg.mg(-1), respectively. This study demonstrates that the reactor with a high H/D ratio and internal circulation favors the granulation and stabilization of aerobic sludge.     

Growth and storage processes in aerobic granules grown on soybean wastewater

Aerobic granules in a sequencing batch reactor (SBR) are subjected to alternative feast and famine conditions, and are able to take up carbon substrate in wastewater rapidly and to store it as intracellular storage products when the substrate is in excess. This phenomenon could not be described by the widely used activated sludge model No.3 (ASM3). In this work, taking adsorption process, microbial maintenance, and substrate diffusion into account, the simultaneous growth and storage processes occurring in an aerobic-granule-based SBR are investigated with experimental and modeling approaches. A new model is established and successfully validated with the experimental results of an SBR fed with soybean-processing wastewater. Simulation results show that our approach is appropriate for elucidating the fates of major model components. Comparison between ASM3 and the model established in this work demonstrates that the latter is better to describe the substrate removal mechanisms and simultaneous growth and storage processes in aerobic granules.     

High levels of nitrifying bacteria in intermittently aerated reactors treating high ammonia wastewater

Changes in the fractions of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria in two laboratory-scale reactors were investigated using 16S rRNA probe hybridizations. The reactors were operated in intermittent aeration mode and different aeration cycles to treat anaerobically digested swine wastewater with ammonia concentrations up to 175 mg NH(3)-N/L. High ammonia removals (>98.8%) were achieved even with increased nitrogen loads and lower aeration: non-aeration time ratios of 1h:3h. Nitrosomonas/Nitrosococcus mobilis were the dominant ammonia-oxidizing bacteria in the reactors. Nitrospira-like organisms were the dominant nitrite-oxidizing bacteria during most of the investigation, but were occasionally outcompeted by Nitrobacter. High levels of nitrifiers were measured in the biomass of both reactors, and ammonia-oxidizing bacteria and nitrite-oxidizing bacterial levels adjusted to changing aeration: non-aeration time ratios. Theoretical ammonia-oxidizer fractions, determined by a mathematical model, were comparable to the measured values, although the measured biomass fractions were different at each stage while the theoretical values remained approximately constant. Stable ammonia removals and no nitrite accumulation were observed even when rRNA levels of ammonia oxidizers and nitrite-oxidizers reached a minimum of 7.2% and 8.6% of total rRNA, respectively. Stable nitrogen removal performance at an aeration: non-aeration ratio of 1h:3h suggests the possibility of significant savings in operational costs.     

Effective and robust partial nitrification to nitrite by real-time aeration duration control in an SBR treating domestic wastewater

Achieving sustainable partial nitrification to nitrite has been proven difficult in treating low strength nitrogenous wastewater. Real-time aeration duration control was used to achieve efficient partial nitrification to nitrite in a sequencing batch reactor (SBR) to treat low strength domestic wastewater. Above 90% nitrite accumulation ratio was maintained for long-term operation at normal condition, or even lower water temperature in winter. Partial nitrification established by controlling aeration duration showed good performance and robustness even though encountering long-term extended aeration and starvation period. Process control enhanced the successful accumulation of ammonia oxidizing bacteria (AOB) and washout of nitrite oxidizing bacteria (NOB). Scanning electron microscope observations indicated that the microbial morphology showed a shift towards small rod-shaped clusters. Fluorescence in situ hybridization (FISH) results demonstrated AOB were the dominant nitrifying bacteria, up to 8.3 ± 1.1% of the total bacteria; on the contrary, the density of NOB decreased to be negligible after 135 days operation since adopting process control.     

Stoichiometric analysis of dissolved organic carbon flux into storage and growth in aerobic granules culture

This study attempted to address a fundamental question of whether metabolic behaviors of aerobic granules are different from their counterparts, such as activated sludge and biofilms. A series of respirometric experiments were carried out using mature aerobic granules with mean sizes of 0.75–3.4 mm. Results suggested that metabolism of aerobic granules comprised three consecutive phases: (i) conversion of external dissolved organic carbon to a poly-β-hydroxybutyrate-like substance; (ii) growth of aerobic granules on the stored poly-β-hydroxybutyrate-like substance derived from phase I, and (iii) subsequent endogenous metabolism of aerobic granules. The stoichiometric analysis revealed that the conversion yields of external dissolved organic carbon to the poly-β-hydroxybutyrate-like substance, the growth yields of biomass on storage, and the overall growth yields of biomass on external dissolved organic carbon were not significantly correlated to the sizes of aerobic granules, i.e., the metabolism of aerobic granules would be size independent. The conversion coefficients and growth rates of aerobic granules were found to be comparable with those reported in the activated sludge and biofilms cultures, indicating that there would not be significant difference in the metabolisms of aerobic granules over activated sludge and biofilms. This information will be useful for modeling and designing aerobic granular sludge processes.     

Oxygen diffusion and consumption in active aerobic granules of heterogeneous structure

The interior structure of aerobic granules is highly heterogeneous, hence, affecting the transport and reaction processes in the granules. The granule structure and the dissolved oxygen profiles were probed at the same granule in the current work for possible estimation of transport and kinetic parameters in the granule. With the tested granules fed by phenol or acetate as carbon source, most inflow oxygen was consumed by an active layer thickness of less than 125 μm on the granule surface. The confocal laser scanning microscopy scans also revealed a surface layer thickness of approximately 100 μm consisting of cells. The diffusivities of oxygen transport and the kinetic constant of oxygen consumption in the active layers only were evaluated. The theoretical models adopted in literature that ignored the contributions of the layered structure of aerobic granule could have overlooked the possible limitations on oxygen transport.     

Substrate uptake,loss, and reserve in ammonia-oxidizing bacteria (AOB) under different substrate availabilities

The controversial arguments on the true substrate in nitritation kinetics might be due to the cells' dual substrate-transport system. Our experiments revealed that, under ammonia-rich environments, it diffused into the membrane (ammonia was the direct substrate); but, under oligotrophic, ammonium ion was actively transported (ammonium was the direct substrate). Facilitating this change-over, the bacterial composition in the sludge was altered, although the predominant was Nitrosomonas eutropha in most of the six chemostats. Also, the substrate affinity constant (K_s) fell resulting in partial compensation for the reduced availability of substrate. When the environmental ammonia concentration was lower than the cytoplasmic one, a backward diffusion appeared to take place, which probably had the cells accelerate its energy-consuming ammonium transport. The % ammonium oxidizing bacteria (AOB) to the total number of bacteria in the sludge remarkably decreased when cells were grown under oligotrophic environments. This could be evidence of the cellular energy dissipation caused by ammonia loss and recovery. Intracellular total ammonium nitrogen (TAN) accumulations were observed, which gradually increased from a basal value of ∼1 M (for AOB grown under copious environments) to much higher values (grown under oligotrophic environment). It did not affect the reaction kinetics but potentially served as a reserve against famine.     

Differential distribution of ammonia- and nitrite-oxidising bacteria in flocs and granules from a nitrifying/denitrifying sequencing batch reactor

A lab-scale sequencing batch reactor was operated with alternating anoxic/aerobic conditions for nitrogen removal. Flocs and granules co-existed in the same reactor, with distinct aggregate structure and size, for over 180 days of reactor operation. Process data showed complete nitrogen removal, with temporary nitrite accumulation before full depletion of ammonia in the aerobic phase. Microbial quantification of the biomass by fluorescence in situ hybridisation showed that granules contained most of the nitrite-oxidising bacteria (NOB) whereas the ammonium-oxidising bacteria (AOB) seemed to be more abundant in the flocs. This was supported by microsensor measurements, which showed a higher potential of NO₂⁻ uptake than NH₄ uptake in the granules. The segregation is possibly linked to the different growth rates of the two types of nitrifiers and the reactor operational conditions, which produced different sludge retention time for flocs and granules. The apparent physical separation of AOB and NOB in two growth forms could potentially affect mass transfer of NO₂⁻ from AOB to NOB, but the data presented here shows that it did not impact negatively on the overall nitrogen removal.     

盐分对生物脱氮工艺中硝化反应的影响与机理

高盐废水来源广泛,在利用生物脱氮法处理高盐含氮废水时,盐分会对生物脱氮产生抑制作用.硝化反应是生物脱氮工艺中的关键过程,研究盐分对硝化反应的影响机理具有重要意义.本文概述了盐分对废水生物脱氮过程中硝化反应影响的研究进展,总结了盐胁迫对好氧氨氧化过程、亚硝酸盐氧化过程中硝化效率和反应特性的影响规律,并分析了盐分对硝化微生物细胞形态、生物絮体结构和胞外聚合物特性变化以及菌群结构的影响,系统阐述了盐胁迫下的硝化反应机理,为高盐分高铵氮废水生物脱氮工艺设计提供理论指导.
     

Nitrification and occurrence of salt-tolerant nitrifying bacteria in the Negev desert soils

Ammonia oxidation potential, major ammonia oxidizers and occurrence of salt-tolerant nitrifying bacteria were studied in soil samples collected from diverse ecosystems along the northern Negev desert. Great diversity in ammonia oxidation potential was observed among the soil samples, and ammonia oxidizers were the rate-limiting step of nitrification. Denaturing gradient gel electrophoresis and partial 16S rRNA gene sequences indicate that members of the genus Nitrosospira are the major ammonia oxidizers in the natural desert soil samples. Upon enrichment with different salt concentrations, salt-tolerant nitrifying enrichments were established from several soil samples. In two enrichments, nitrification was not inhibited by 400 mM NaCl. Electrophoretic analysis and partial 16S rRNA gene sequences indicate that Nitrosomonas species were dominant in the 400 mM salt enrichment. The results point towards the potential of the desert ecosystem as a source of stress-tolerant nitrifying bacteria or other microorganisms with important properties.     

固定化硝化菌群联合芽孢杆菌处理对虾养殖废水

【背景】高度集约化的对虾养殖业面临着日益严重的水污染问题,同步高效降解养殖废水中的有机物、氨氮和亚硝酸盐是对虾养殖业健康可持续发展的重要保障之一。【目的】通过分别固定化硝化菌群(Nitrifyingbacterialconsortia,NBC)和芽孢杆菌,优化菌群空间结构,提高菌群功能,实现同步高效降解对虾养殖废水中的有机物、亚硝酸盐和氨氮,保障南美白对虾养殖的可持续发展。【方法】采集养殖虾塘底泥进行硝化细菌自养富集和连续培养,利用16S rRNA基因高通量测序技术分析硝化菌群组成。从5株芽孢杆菌中筛选化学需氧量(Chemical oxygen demand,COD)降解能力最强的菌株。选用吸附和成球效果好的无毒包埋材料,通过正交实验优化固定化配方提高机械强度。选择硝化菌群和芽孢杆菌最适使用浓度进行分别固定化并联合应用于对虾养殖废水的处理。【结果】高通量分析结果显示硝化菌群中变形菌门(Proteobacteria,61.10%)占绝对优势,具有自养硝化功能的类群丰度达12.69%并呈高多样性。还包含丰度达47.44%的具有反硝化功能或者潜在反硝化功能的优势菌群和丰度达12.85%的光合细菌,是高有机负荷下硝化作用的重要补充,并可通过反硝化作用实现真正脱氮。COD降解能力最强的是解淀粉芽孢杆菌(Bacillusamyloliquefacien)YL-10,48h内COD降解率达100%。固定化最佳配方为贝壳粉5%、海藻酸钠3%、交联剂氯化钙为4%、优化后的固定化小球其机械强度可达129.68m N。固定化使硝化菌群的氨氮和亚硝酸盐降解率分别提高了128.13%和130.11%(P0.05),但对芽孢杆菌YL-10的COD降解率无明显提高。1×10~8 CFU/mL为硝化菌群和芽孢杆菌YL-10在养殖废水中最适使用浓度。在固定化硝化菌群和芽孢杆菌YL-10联合作用下,对虾养殖废水的氨氮、亚硝酸盐和COD浓度在48h内分别由初始的6.32±0.12、5.69±0.11和65.29±1.14 mg/L降至0.03±0.03、0.06±0.01和0 mg/L (P0.05),降解率分别为99.57%、99.03%和100%。【结论】通过优化固定化有效提高硝化菌群的硝化作用,联合COD降解能力强的芽孢杆菌,同步高效降解对虾养殖废水中的有机物、氨氮和亚硝酸盐,为规模化应用于南美白对虾高密度养殖提供科学依据。     

Structure and stability of aerobic granules cultivated under different shear force in sequencing batch reactors

The cultivation of stable aerobic granules as well as granular structure and stability in sequencing batch reactors under different shear force were investigated in this study. Four column sequencing batch reactors (R1–R4) were operated under various shear force, in terms of superficial upflow air velocity of 0.8, 1.6, 2.4, and 3.2 cm s⁻¹, respectively. Aerobic granules were formed in all reactors in the experiment. It was found that the magnitude of shear force has an important impact on the granule stability. At shear force of 2.4 and 3.2 cm s⁻¹, granules can maintain a robust structure and have the potential of long-term operation. Granules developed in low shear force (R1, 0.8 cm s⁻¹ and R2, 1.6 cm s⁻¹) deteriorated to large-sized filamentous granules with irregular shape, loose structure and resulted in poor performance and operation instability. Granules cultivated under high shear force (R3, 2.4 cm s⁻¹ and R4, 3.2 cm s⁻¹) stabilized to clear outer morphology, dense and compact structure, and with good performance in 120 days operation. Fractal dimension (D_f) represents the internal structure of granules and can be used as an important indicator to describe the structure and stability of granules. Due to the combined effects of shear force and growth force, the mature granules developed in R3 and R4 also displayed certain differences in granular structure and characteristics.     

泉州西湖沉积物中硝化细菌的分布及其作用

比较研究泉州西湖沉积物中氨氧化细菌(AOB)和亚硝酸盐氧化细菌(NOB)的分布及氨氧化潜力和亚硝酸盐(NO2?)氧化潜力。结果表明: 西湖沉积物中存在高浓度的有机质(OM)、总氮(TN)和氨氮。AOB生物量为1.1×106?6.4×106 个/g干土, 显著高于NOB生物量4.2×105?7.4×105 个/g 干土(配对t-检验, P<0.05)。对于NOB, 硝化杆菌属(Nitrobacter)和硝化螺菌属(Nitrospira)同时存在于西湖沉积物中, 以Nitrobacter为优势种群。AOB和NOB生物量的差异一定程度上导致西湖沉积物中氨氧化潜力显著高于NO2?氧化潜力(配对t-检验, P<0.05), NO2?氧化过程成为硝化作用的限制步骤。另外, 西湖沉积物中存在的较高浓度氨氮, 一方面促进了AOB的生长和活性, 导致较高速率的氨氧化过程, 另一方面却对亚硝酸盐氧化过程产生选择性抑制, 这也是导致NO2?氧化潜力较低的主要原因之一。     

Biodegradation and kinetics of aerobic granules under high organic loading rates in sequencing batch reactor

Biodegradation, kinetics, and microbial diversity of aerobic granules were investigated under a high range of organic loading rate 6.0 to 12.0 kg chemical oxygen demand (COD) m⁻³ day⁻¹ in a sequencing batch reactor. The selection and enriching of different bacterial species under different organic loading rates had an important effect on the characteristics and performance of the mature aerobic granules and caused the difference on granular biodegradation and kinetic behaviors. Good granular characteristics and performance were presented at steady state under various organic loading rates. Larger and denser aerobic granules were developed and stabilized at relatively higher organic loading rates with decreased bioactivity in terms of specific oxygen utilization rate and specific growth rate (μ _overall) or solid retention time. The decrease of bioactivity was helpful to maintain granule stability under high organic loading rates and improve reactor operation. The corresponding biokinetic coefficients of endogenous decay rate (k _d), observed yield (Y _obs), and theoretical yield (Y) were measured and calculated in this study. As the increase of organic loading rate, a decreased net sludge production (Y _obs) is associated with an increased solid retention time, while k _d and Y changed insignificantly and can be regarded as constants under different organic loading rates.     

Ammonia biofiltration and community analysis of ammonia-oxidizing bacteria in biofilters

Biological removal of ammonia was investigated using compost and sludge as packing materials in laboratory-scale biofilters. The aim of this study is to characterize the composition of ammonia-oxidizing bacteria (AOB) in two biofilters designed to remove ammonia. Experimental tests and measurements included analysis of removal efficiency and metabolic products. The inlet concentration of ammonia applied was 20–100 mg m⁻³. Removal efficiencies of BFC and BFS were in the range of 97–99% and 95–99%, respectively. Periodic analysis of the biofilter packing materials showed ammonia was removed from air stream by nitrification and by the improved absorption of NH₃ in the resultant acidity. Nitrate was the dominant product of NH₃ transformation. Changes in the composition of AOB were examined by using nested PCR, denaturing gradient gel electrophoresis (DGGE) and sequencing of DGGE bands. DGGE analysis of biofilter samples revealed that shifts in the community structure of AOB were observed in the experiment; however, the idle phase did not cause the structural shift of AOB. Phylogenetic analysis revealed the population of AOB showed Nitrosospira sp. remains the predominant population in BFC, while Nitrosomonas sp. is the predominant population in BFS.     

Mathematical modeling of aerobic granular sludge: A review

Aerobic granulation may play an important role in the field of wastewater treatment due to the advantages of aerobic granules compared to the conventional sludge flocs, such as denser structure, better settleability and ensured solid-effluent separation, higher biomass concentration, and greater ability to withstand shock loadings, which is promising for a full-scale implementation. As an aid for this implementation, mathematical modeling would be an invaluable tool. In this paper, the existing mathematical models available in literature concerning aerobic granule systems are reviewed, including the modeling of the dynamic facets of the aerobic granulation process, the mass transfer and detachment in aerobic granules, the granule-based sequencing batch reactor, the fate of microbial products in granules, and the multi-scale modeling of aerobic granular sludge. An overview of the parameters used in the aerobic granular modeling approaches is also presented. Our growing knowledge on mathematical modeling of aerobic granule might facilitate the engineering and optimization of aerobic granular sludge technology as one of the most promising techniques in the biological wastewater treatment.