Improvement of the settling properties of Anammox sludge in an SBR

Biological systems for the treatment of wastewater have to provide optimum sludge retention to achieve high removal efficiencies. In the case of slow‐growing micro‐organisms, such as anaerobic ammonia‐oxidizing (Anammox) bacteria, episodes of flotation involving biomass wash‐out are especially critical. In this study a strategy based on the introduction of a mix period in the operational cycle of the Anammox Sequencing Batch Reactor (SBR) was tested for its effects on biomass retention and nitrite removal. Using this new cycle distribution the biomass retention inside the reactor improved as the solids concentration in the effluent of the SBR decreased from 20–45 to 5–10 mg VSS dm^?3 and the biomass concentration inside the reactor increased from 1.30 to 2.53 g VSS dm^?3 in a period of 25 days. A decrease of the sludge volume index (SVI) from 108 to 60 cm³ g VSS^?1 was also observed. Complete depletion of nitrite was achieved in the reactor only with the new cycle distribution treating nitrogen loading rates (g N‐NO₂^? + g N‐NH₄⁺ dm^?3 d^?1) up to 0.60 g N dm^?3 d^?1. Copyright © 2004 Society of Chemical Industry     

Enrichment of Anammox biomass from municipal activated sludge: experimental and modelling results

Anaerobic Ammonia Oxidising (Anammox) biomass was enriched from sludge collected at a municipal wastewater treatment plant, employing a Sequential Batch Reactor (SBR). After 60 days Anammox activity started to be detected, by consumption of stoichiometric amounts of NO₂^? and NH₄⁺ in the system. Fluorescence In Situ Hybridisation analysis confirmed the increase of Anammox bacteria concentration with time. A final concentration of enriched biomass of 3–3.5 gVSS dm^?3 was obtained, showing a Specific Anammox Activity of 0.18 gNH₄⁺‐N gVSS^?1 d^?1 The reactor was able to treat nitrogen loading rates of up to 1.4 kgN m^?3 d^?1, achieving a removal efficiency of 82 %. On the other hand, the start‐up and operation of the Anammox SBR reactor were consequentially modelled with the Activated Sludge Model nr 1, extended for Anammox. The simulations predicted quite well the experimental data in relation to the concentrations of nitrogenous compounds and can be used to estimate the evolution of Anammox and heterotrophic biomass in the reactor. These simulations reveal that heterotrophs still remain in the system after the start‐up of the reactor and can protect the Anammox microorganisms from a negative effect of the oxygen. Copyright © 2004 Society of Chemical Industry     

The shear force amendments on the slugging behavior of upflow Anammox granular sludge bed reactor

The granulation of Anammox sludge plays an important role in improving the efficiency of high-rate Anammox bioreactors. The present study involved the use of anaerobic granular sludge to start up the Anammox process to accomplish granulation in Anammox reactor. The accumulation of nitrogen gas and subsequent slugging behavior were observed in the upflow Anammox granular sludge bed (AGSB) reactor, resulting in deteriorated effluent quality. Based on shear force analysis of the gas column under the quasi-steady state, the liquid-induced shear force was increased by progressively shortening of hydraulic residence time (HRT) and implementing effluent recycling. It appeared to be the right strategy to eradicate the slugging behavior which disappeared completely when HRT was shortened to 1.10 h with liquid upflow velocity of 1.30 cm min⁻¹. The application of high shear stress enhanced the nitrogen removal performance to 15.40 kg-N m⁻³ d⁻¹. Thus the amendments in the liquid-induced shear force by shortening HRT may be an appropriate strategy to overcome slugging behavior of the Anammox reactor.     

Start up of a pilot scale aerobic granular reactor for organic matter and nitrogen removal

Aerobic granulation is a promising technology for the removal of nutrients in wastewater. Since research to date is mainly focused at laboratory scale, a pilot‐scale sequencing batch reactor (100 L) was operated to obtain granular sludge in aerobic conditions grown on acetate as organic carbon substrate. Selective pressure created by means of decreasing settling time and increasing organic loading rate (OLR) enhanced the formation of aerobic granular sludge. Granules appeared after 6 days and reached an average diameter around 3.5 mm. The settling velocity value should be higher than 11 m h^?1 in order to remove flocculent biomass. The reactor treated OLRs varying between 2.5 and 6.0 g COD L^?1 d^?1 reaching removal efficiencies around 96%, which demonstrates the high activity and the ability of the system to withstand high OLR. Nevertheless, a rapid increase in the OLR produced a loss of biomass in the reactor due to breakage of the granules. Copyright © 2011 Society of Chemical Industry     

Simultaneous removal of organic substances and nitrogen using amembrane bioreactor seeded with anaerobic granular sludge under oxygen-limited conditions

An innovative process, the oxygen-limited membrane bioreactor seeded with anaerobic granular sludge, wasproposed and its performance investigated for concurrent removal of organic substances and nitrogen from synthetic domestic wastewaters. An air diffuser was installed just above the granular sludge bed to supply air to the reactor at an intermittent mode. The internal recycle from the upper part of the reactor to the bottom was introduced to provide the granular sludge bed under the oxygen-limited conditions. The oxygen addition rates were controlled at 3-4 g O₂ 1⁻¹d⁻¹. The total COD removal efficiency of more than 94% was achieved throughout the whole operation period. N was removed through the simultaneous nitrification and denitrification process that took place in the granular sludge bed. TN levels decreased with the decrease of ammonium levels, indicating that nitrification was the rate-limiting step. The TN removal efficiency reached 80-91% at an hydraulic retention time of 15 h. Nitrate was scarcely detected and nitrite was the main NO_x-N species in the effluent, indicating that nitrite oxidizers were inhibited in the system.     

协同调控C/N负荷提升好氧颗粒污泥亚硝化性能

以异养颗粒污泥为接种污泥启动SBR反应器,通过协同调控进水碳、氮负荷比值,成功获得了具备短程亚硝化功能的自养型颗粒污泥。基于对粒径分布、胞外聚合物（EPS）和功能菌动力学活性的分析,系统阐述了影响污泥性状与功能演化的关键因素。结果表明,随着氨氧化菌（AOB）活性（μ_NO3-N）的持续增强和对亚硝酸盐氧化菌（NOB）活性（μ_NO3-N）的有效抑制,反应器对亚硝态氮（NO₂^--N）的累积速率可达1.34 kg·（m³·d）^-1。污泥平均粒径由1.4 mm增至2.2 mm,颜色变为红棕色,沉降性能明显改善。得益于EPS的不断累积,颗粒污泥在高选择压条件下（沉淀时间3 min）,仍能有效截留、固定AOB。曝气反应期间,游离氨（FA）和游离亚硝酸（FNA）对NOB的选择性抑制也是实现稳定亚硝化反应的重要原因。     

自养脱氮工艺有机物去除段与硝化段精确分离的实现与实时控制

为了实现城市污水处理过程中的节能降耗,提出了三段式城市污水自养脱氮工艺,阐述了除有机物SBR在整套工艺中的重要地位,探讨了不同曝气量与污泥浓度条件下,除有机物SBR中有机物的去除特征与规律。结果表明,在不同的曝气量及污泥浓度条件下,COD降解结束前NO₂^--N与NO₃^--N的浓度均低于0.1 mg·L^-1,反应器进入COD难降解阶段后,NO₂^--N与NO₃^--N的浓度快速提高,可以认为在除有机物SBR内有机物的去除和硝化过程是分步进行的,即先进行有机物的去除,而后进行硝化过程。DO曲线与pH曲线的突越点与除有机物过程的终点始终保持一致,可将其作为实时控制参数监测有机物的去除终点,对好氧曝气过程进行实时控制。     

Simultaneous organic carbon and nitrogen removal in an SBR controlled at low dissolved oxygen concentration

Simultaneous organic carbon and nitrogen removal was studied in a sequencing batch reactor (SBR) fed with synthetic municipal wastewater and controlled at a low dissolved oxygen (DO) level (0.8 mg dm^?3). Experimental results over a long time (120 days) showed that the reactor achieved high treatment capacities (organic and nitrogen loading rates reached as high as 2.4 kg COD m^?3 d^?1 and 0.24 kg NH₃‐N m³ d^?1) and efficiencies (COD, NH₃‐N and total nitrogen removal efficiencies were 95%, 99% and 75%). No filamentous bacteria were found in the sludge even though the reactor had been seeded with filamentous bulking sludge. Instead, granular sludge, which possessed high activity and good settleability, was formed. Furthermore, the sludge production rate under low DO was less than that under high DO. Significant benefits, such as low investment and less operating cost, will be obtained from the new process. © 2001 Society of Chemical Industry     

短程硝化颗粒污泥SBR的快速启动与维持

为探究短程硝化污泥快速颗粒化的最佳条件,采用SBR反应器,在温度28℃,曝气量0.2m3.h-1,溶解氧(DO)2.0mg·mL-1,污泥龄(SRT)为15d的运行工况下,缩短沉降时间为2min,通过以pH作为氨氧化过程的控制参数,优化曝气时间,防止过曝气,经过80周期(19d)成功实现短程硝化絮状污泥的颗粒化,并维持稳定。形成的颗粒污泥粒径在1.5～2.0mm之间,对COD和氨氮的去除率分别达到80%和95%,亚硝酸盐积累率(NO2--N/NOx--N)平均达到95%。分子生物学FISH技术对颗粒污泥菌群结构的定量分析表明,AOB依旧是优势菌群,约占17.8%左右,NOB占0.6%。曝气初期FA的抑制和实时控制是启动和维持颗粒污泥短程硝化性能的主要原因。     

Modelling a sequencing batch reactor to treat the supernatant from anaerobic digestion of the organic fraction of municipal solid waste

In this study, a lab‐scale sequencing batch reactor (SBR) has been tested to remove chemical oxygen demand (COD) and NH₄⁺‐N from the supernatant of anaerobic digestion of the organic fraction of municipal solid waste. This supernatant was characterized by a high ammonium concentration (1.1 g NH₄⁺‐N L^?1) and an important content of slowly biodegradable and/or recalcitrant COD (4.8 g total COD L^?1). Optimum SBR operating sequence was reached when working with 3 cycles per day, 30 °C, SRT 12 days and HRT 3 days. During the time sequence, two aerobic/anoxic steps were performed to avoid alkalinity restrictions. Oxygen supply and working pH range were controlled to promote the nitrification over nitrite. Under steady state conditions, COD and nitrogen removal efficiencies of more than 65% and 98%, respectively, were achieved. A closed intermittent‐flow respirometer was used to characterize and model the SBR performance. The activated sludge model ASM1 was modified to describe the biological nitrogen removal over nitrite, including the inhibition of nitrification by unionized ammonia and nitrous acid concentrations, the pH dependency of both autotrophic and heterotrophic biomass, pH calculation and the oxygen supply and stripping of CO₂ and NH₃. Once calibrated by respirometry, the proposed model showed very good agreement between experimental and simulated data. Copyright © 2007 Society of Chemical Industry     

Study of saline wastewater influence on activated sludge flocs through automated image analysis

BACKGROUND: In activated sludge systems, sludge settling ability is considered a critical step in effluent quality and determinant of solid–liquid separation processes. However, few studies have reported the influence of saline wastewater on activated sludge. This work aims the evaluation of settling ability properties of microbial aggregates in a sequencing batch reactor treating saline wastewaters of up to 60 g L^?1 NaCl, by image analysis procedures. RESULTS: It was found that the sludge volume index (SVI) decreased with salt content up to 20 g L^?1, remaining somewhat stable above this value. Furthermore, it was found that between the first salt concentration (5 g L^?1) and 20 g L^?1 aggregates suffered a strong deflocculation phenomenon, leading to a heavy loss of aggregated biomass. Regarding SVI prediction ability, a good correlation coefficient of 0.991 between observed and predicted SVI values was attained. CONCLUSION: From this work the deflocculation of aggregated biomass with salt addition due to pinpoint floc formation, dispersed bacteria growth and protozoa absence could be established. With respect to SVI estimation, and despite the good correlation obtained, caution is advisable given the low number of SVI data points. Copyright © 2008 Society of Chemical Industry     

Enhancing completely autotrophic nitrogen removal over nitrite by trace NO2 addition to an AUSB reactor

BACKGROUND: Completely autotrophic nitrogen removal over nitrite (CANON) could decrease energy consumption and CO₂ release compared with conventional nitration–denitrification. Trace NO₂ addition could enhance the activities of aerobic and anaerobic ammonium oxidation. RESULTS: An aerated upflow sludge bed (AUSB) reactor inoculated simultaneously with aerobic and anaerobic ammonium oxidizing sludge was operated to cultivate granular sludge capable of carrying out CANON. The results showed that the efficiency and rate of total nitrogen (TN) removal reached 61% and 0.114 kgN, respectively (m^?3 day^?1) for DO = 0.5–0.6 mg L^?1. Batch tests indicated that trace NO₂ addition could increase the CANON activity of sludge. The TN removal rate and efficiency of the reactor was increased to 0.234 kgN m^?3 day^?1 and 63%, respectively, when the reactor was aerated with air containing 2.7–3.3 mmol m^?3 NO₂ and DO was at 0.5–0.8 mg L^?1. CONCLUSIONS: Trace NO₂ addition provides an alternative to increase the capacity of a CANON system at low DO concentration. Copyright © 2009 Society of Chemical Industry     

生活污水对成熟厌氧氨氧化颗粒污泥的影响

部分短程硝化和厌氧氨氧化技术的研究主要集中在高氨氮废水方面，对低氨氮浓度生活污水的研究相对较少。使经过除碳和部分短程硝化后的实际生活污水进入厌氧氨氧化UASB反应器，探究生活污水对成熟厌氧氨氧化颗粒污泥的影响。结果表明，当厌氧氨氧化UASB反应器的进水由配水变为生活污水后，反应器出水中氨氮浓度可降到5 mg·L^-1以下，亚硝态氮浓度可降到1 mg·L^-1以下，但是硝态氮的生成量高于理论值，可能是溶解氧被带入UASB反应器使硝化作用增强。UASB反应器内厌氧氨氧化污泥颜色由红色变为红黑色，T-EPS含量减少，PN/PS由1.13增大到3.66，沉降性变好，反应器内污泥中厌氧氨氧化菌Candidatus Brocadia所占比例由17.7%减少为14.4%，系统内AOB和NOB菌的含量增加，如果能够降低进入UASB反应器的溶解氧，有可能会减少出水硝氮，达到较好总氮去除效果。     

Autotrophic biological nitrogen removal from saline wastewater under low DO

BACKGROUND: This study was conducted to investigate the feasibility and performance of nitrogen removal through the complete autotrophic nitrogen removal over nitrite (CANON) process for saline wastewater in a continuous reactor, and to characterize microorganisms in the sludge from the reactor using DNA‐based techniques. RESULTS: The nitrogen removal experiment in the reactor was operated over five phases for 286 days treating a synthetic sewage of 1.2% salinity at 21–25 °C. At dissolved oxygen (DO) concentrations of 0.5–1.0 mg L^?1 and in the presence of glucose, NO₂^? was accumulated, indicating the activity of ammonia‐oxidizing bacteria (AOB). At DO concentration of 0.5 mg L^?1 without organic substrate, the anaerobic ammonium oxidation (Anammox) process was the major pathway responsible for nitrogen removal, with a total nitrogen removal of 70% and an ammonium conversion efficiency of 96%. A maximum ammonium removal rate of 0.57 kg‐N m^?3 d^?1 was achieved during the experimental period. The concentrations of AOB and Anammox bacteria were monitored over the operation of reactor using quantitative real‐time polymerase chain reaction (qRT‐PCR). CONCLUSION: In this study, autotrophic nitrogen removal process was achieved under salinity condition in a one‐reactor system. An over 100 fold increase of AOB was found due to the increased supply of ammonium at the beginning, then AOB concentration decreased temporarily in correspondence with the decreased DO, and the AOB resumed their concentration at the last phase. The Anammox bacteria abundance was about 150 fold higher than that at the beginning, indicating the successful enrichment of Anammox bacteria in the reactor. Copyright © 2010 Society of Chemical Industry     

SBR反应器中好氧颗粒污泥处理汽车涂装废水

为研究序批间歇式（SBR）反应器中好氧颗粒污泥处理汽车涂装废水的可行性,采用以生活污水培养出的好氧颗粒污泥作为接种体,逐步加入汽车涂装废水驯化,考察被驯化的颗粒污泥的形态、理化性质以及反应器内污染物的去除效果。结果表明：驯化5周后的颗粒污泥未有解体,结构更致密,平均粒径可达到1.5 mm,呈白色,MLSS为8000 mg/L,SVI30值为28 mL/g,其沉降性能、生物量都提高。反应器运行至45 d左右,除污性能明显且稳定,COD、NH4+-N、PO43－-P的出水浓度保持在100 mg/L、10 mg/L、1.0 mg/L以下,均达到GB 8978-1996《污水综合排放标准》二级标准,保持了良好的污染物同步去除效果。     

强化生物除磷体系中颗粒污泥的形成及机理探讨

以实验室小试SBR反应器为载体接种普通活性污泥,研究了强化生物除磷系统对颗粒污泥形成的促进作用并探讨了其形成机理。试验结果发现：在生物脱氮运行阶段,SBR中的活性污泥能维持较稳定的絮体状态,平均SVI为138.9 ml·g^-1;当系统转为生物除磷方式运行时,随着除磷效果的好转,反应器中的污泥逐渐转化为颗粒污泥,平均SVI降低至74.1 ml·g^-1,颗粒污泥的平均粒径为0.8 mm。因此,SBR生物除磷系统有利于颗粒污泥的形成。试验发现在强化生物除磷系统厌氧释磷的过程中会有带正电的微粒大量生成,它们可以作为颗粒污泥的晶核吸附带负电的细胞体,进而促进颗粒污泥的形成。强化生物除磷颗粒污泥系统有着较为稳定的磷去除性能,除磷效率接近100%。     

Coupling sequencing batch airlift reactor (SBAR) and membrane filtration: Influence of nitrate removal on sludge characteristics, effluent quality and filterability

This study investigates the sludge and effluent characteristics of a new process of coupling an aerobic granular sludge bioreactor with a membrane filtration. The effluent and mixed liquor of sequencing batch airlift reactor (SBAR) were analyzed at various aeration shear stresses when fed with high nitrate containing wastewater. The presence of nitrate nitrogen and aerobic/anoxic condition was able to improve the sludge characteristics in terms of biomass retention, density and settling ability in SBAR. MLSS and SVI could reach 9 g/L and 44 mL/g respectively at the aeration rate of 0.6 cm/s. The presence of nitrate and the denitrification process could minimize the fouling potential. The membrane fouling can be better correlated to SBAR sludge characteristics than biomass concentration. The high aeration rate in the reactor increased the fouling resistance due to production of large MW soluble microbial products (30-50 kDa). The soluble fraction of SBAR effluent contained mainly hydrophilic substances when nitrate is present in the wastewater.     

Start‐up and enrichment of a granular anammox SBR to treat high nitrogen load wastewaters

BACKGROUND: Landfill leachate is characterized by low biodegradable organic matter that presents difficulties for the complete biological nitrogen removal usually performed by conventional biological nitrification/denitrification processes. To achieve this, the anaerobic ammonium oxidation (anammox) process is a promising biological treatment. This paper presents an anammox start‐up and enrichment methodology for treating high nitrogen load wastewaters using sequencing batch reactor (SBR) technology. RESULTS: The methodology is based on the gradual increase of the nitrite‐to‐ammonium molar ratio in the influent (from 0.76 to 1.32 mole NO₂^?‐N mole^?1NH₄⁺‐N) and on the exponential increase of the nitrogen loading rate (NLR, from 0.01 to 1.60 kg N m^?3 d^?1). 60 days after start‐up, anammox organisms were identified by polymerase chain reaction (PCR) technique as Candidatus Brocadia anammoxidans. After one year of operation, NLR had reached a value of 1.60 kg N m^?3 d^?1 with a nitrogen (ammonium plus nitrite) removal efficiency of 99.7%. The anammox biomass activity was verified by nitrogen mass balances with 1.32 ± 0.05 mole of nitrite removed per mole of ammonium removed and 0.23 ± 0.05 mole of nitrate produced per mole of ammonium removed. Also, enrichment of anammox bacteria was quantified by fluorescence in situ hybridization (FISH) analysis as 85.0 ± 1.8%. CONCLUSIONS: This paper provides a methodology for the enrichment of the anammox biomass in a SBR to treat high nitrogen loaded wastewaters. Copyright © 2007 Society of Chemical Industry     

Performance assessment of a UASB–anoxic–oxic system for the treatment of tomato‐processing wastes

An upflow anaerobic sludge blanket (UASB)–anoxic–oxic system was used to achieve biochemical oxygen demand, NH₄ and total suspended solids (TSS) criteria of 15, 1 and 15 mg dm^?3 at 1.17 days of system hydraulic retention time during treatment of tomato‐processing waste. The incorporation of an anoxic tank was found to affect the improvement in sludge‐settling characteristics, as reflected by about 25–33% reduction in the sludge volume index, along with final effluent TSS and soluble biochemical oxygen demand concentrations of 13 and 9 mg dm^?3, respectively, which met the discharge criteria. Despite incomplete denitrification, sludge settleability was very good (sludge volume index < 60 cm³ g^?1) owing to reduction in volatile suspended solids/TSS ratio from 0.75 to 0.6 as a result of higher alkalinity in the UASB effluent. Also in this study, phosphorus release was observed in the anoxic tank, predominantly due to abundance of acetic acid in the UASB effluent. A phosphate release of 5.4 mg P dm^?3 was observed in the anoxic tank with subsequent P uptake in the following aerobic stage. Copyright © 2006 Society of Chemical Industry     

Development of a membrane‐assisted hybrid bioreactor for ammonia and COD removal in wastewaters

A new membrane‐assisted hybrid bioreactor was developed to remove ammonia and organic matter. This system was composed of a hybrid circulating bed reactor (CBR) coupled in series to an ultrafiltration membrane module for biomass separation. The growth of biomass both in suspension and biofilms was promoted in the hybrid reactor. The system was operated for 103 days, during which a constant ammonia loading rate (ALR) was fed to the system. The COD/N‐NH₄⁺ ratio was manipulated between 0 and 4, in order to study the effects of different organic matter concentrations on the nitrification capacity of the system. Experimental results have shown that it was feasible to operate with a membrane hybrid system attaining 99% chemical oxygen demand (COD) removal and ammonia conversion. The ALR was 0.92 kg N‐NH₄⁺ m^?3 d^?1 and the organic loading rate (OLR) achieved up to 3.6 kg COD m^?3 d^?1. Also, the concentration of ammonia in the effluent was low, 1 mg N‐NH₄⁺ dm^?3. Specific activity determinations have shown that there was a certain degree of segregation of nitrifiers and heterotrophs between the two biomass phases in the system. Growth of the slow‐growing nitrifiers took place preferentially in the biofilm and the fast‐growing heterotrophs grew in suspension. This fact allowed the nitrifying activity in the biofilm be maintained around 0.8 g N g^?1 protein d^?1, regardless of the addition of organic matter in the influent. The specific nitrifying activity of suspended biomass varied between 0.3 and 0.4 g N g^?1 VSS d^?1. Copyright © 2004 Society of Chemical Industry