实际城市污水培养好氧颗粒污泥的中试研究

以普通絮体活性污泥为接种污泥,采用实际城市污水在普通序批式反应器(SBR)中培养好氧颗粒污泥。通过逐渐缩短沉降时间至5 min,好氧颗粒污泥在第27天形成,并在第52天趋于稳定,平均粒径达到0.706 mm。成熟的颗粒污泥MLSS在12.19 g/L左右,SV为0.26,SVI为21.31 m L/g,具有良好的沉降性能。采用光学显微镜(OM)和扫描电子显微镜(SEM)对好氧颗粒污泥的结构进行分析,发现成熟的颗粒污泥内部结构紧密,表面光滑,形状规则,呈褐黄色的球状、椭球状或杆状。在稳定运行阶段,反应器出水COD、氨氮、总氮、溶解性总磷浓度分别在60、0.2、15、1.0 mg/L以下,显示出对污染物具有良好的去除效果。     

好氧污泥颗粒化过程中污泥性质及净化能力的研究

研究好氧污泥颗粒化过程中污泥性质及对污染物的净化能力。采用进水负荷交替变化法培养好氧颗粒污泥,研究颗粒污泥形成过程中粒径、沉淀性能以及对COD、NH4~+-N、TN和TP的去除效果。结果表明:在SBR反应器中,污泥颗粒化中粒径由100μm的种泥逐渐凝聚成粒径为1.25mm的成熟颗粒污泥;污泥颜色从棕褐色变成淡黄色再逐渐形成金黄色;污泥由无明显分界形成外形轮廓清晰可见的颗粒污泥,呈圆形或椭圆形,成熟的颗粒污泥是肉眼可见的一个个独立个体。SBR反应器内混合液浓度由3000mg/L逐渐增长至5512mg/L,同时沉降性也逐渐变好,SVI稳定在20.68mg/L,对COD、NH4~+-N、TN和TP去除效果分别可达到96.47%,97.09%,85.72%和83.06%。     

外循环厌氧法处理啤酒废水的研究

采用外循环(EC)厌氧反应器处理啤酒废水,考察了其处理效果和颗粒污泥的形成及其性能.结果表明,以好氧剩余污泥为接种污泥,采用低负荷、高去除率的启动方式,可使污泥很快实现颗粒化,所形成的颗粒污泥沉降性能良好,粒径主要集中在0.8～2.0 mm.系统稳定运行期,当进水COD为2 000～4 000 mg/L、碱度为1000～1 500 mg/L、温度为30～32℃、容积负荷为10～12 kgCOD/(m3·d)时,系统对COD的去除率稳定在80%左右.外循环厌氧反应器处理啤酒废水的效果良好、运行稳定、抗冲击负荷能力强.     

基质匮乏对好氧污泥颗粒化的影响研究

分别采用人工模拟废水和实际生活污水接种污泥指数为51mL/g的普通活性污泥,并在SBR反应器中培养好氧颗粒污泥,反应器的运行周期为4h、表面气体流速为3.48cm/s。结果表明,在前72个周期的运行中,反应器的出水COD浓度均较高,即模拟废水系统的出水COD100mg/L、生活污水系统的出水COD200mg/L,反应器内均没有出现基质匮乏现象。运行72个周期后,反应器内形成了粒径为0.1～0.3mm的好氧颗粒污泥。由此可见,基质匮乏并不是好氧颗粒污泥形成的必要条件。     

铁碳微电解耦合好氧颗粒污泥处理制膜工业废水

针对难降解制膜工业废水,采用铁碳微电解/好氧颗粒污泥耦合工艺进行处理,铁碳微电解为连续流,好氧颗粒污泥为序批式反应器(SBR)。耦合工艺系统成功培育出具有优异沉降性能的好氧颗粒污泥,120 d时SVI30在30 m L/g左右、平均粒径为316μm;出水COD、NH_4~+-N和TN浓度分别为130.1、6.6、23.7 mg/L,处理效果优于对照组。铁碳微电解预处理不但能提高废水的B/C值,而且能促进生化处理段颗粒污泥的形成,有利于难降解工业废水的处理。     

好氧颗粒污泥的培养及实现同步脱氮

采用厌氧颗粒污泥和少量活性污泥为种泥,进水为人工配水,在SBR反应器中采用逐渐减少污泥沉降时间的方法造成选择压,培养出了好氧颗粒污泥,颗粒污泥粒径在2 mm左右、SVI值为20 mL/g左右、MLSS为10 g/L左右。结果表明:成熟的好氧颗粒污泥对COD、NH4+-N和TN的平均去除率分别为94%、97.5%和68.6%,出水COD、NH4+-N和TN平均浓度分别为64.74、1.92和27.53 mg/L,出水NO3--N和NO2--N平均浓度分别为18.01和4.44 mg/L。结合微生物相观察,可以判断好氧颗粒污泥实现了同步脱氮。     

不同进水浓度下好氧颗粒污泥的培养及其除污性能

好氧颗粒污泥技术作为一种新型的污水处理方法日渐成为研究的热点。采用SBR反应器培养好氧颗粒污泥,在两种进水浓度下均培养出了好氧颗粒污泥。在培养过程中,对R1、R2中污泥的外观、粒径、沉降特性等指标进行了测定,R1中污泥的平均粒径为600μm,R2中污泥的平均粒径为550μm,即进水浓度对好氧颗粒污泥的形态有影响。同时还发现,在高进水浓度下培养出的好氧颗粒污泥对COD、氨氮和磷的去除效果比在低进水浓度下培养出的好且稳定。     

好氧SBR反应器中污泥颗粒化过程的成核研究

采用人工配制的模拟生活污水,以好氧絮状污泥为接种污泥,通过调控运行条件,在低高径比、纯好氧曝气的序批式反应器(SBR)中成功培养出了高活性的好氧颗粒污泥晶核,并对其性能、除污效果和成核影响因素进行了研究.结果表明:成熟好氧颗粒污泥晶核平均粒径为0.5mm,沉降性能较好,SVI为77mL/g;成熟好氧颗粒污泥晶核对COD和NH3-N都有较高的去除率,分别达到了90%和97%;水力剪切力是影响污泥成核的关键因素.     

基于复合铁碳材料的好氧颗粒污泥培养及脱氮研究

通过投加复合铁碳材料,经过70 d,在序批式活性污泥反应器(SBR)内培养出粒径为0. 5～4 mm、具有良好脱氮效果的成熟好氧颗粒污泥。在此过程中复合铁碳材料在提高污泥沉降性、加快颗粒化进程、提高脱氮效率等方面发挥了积极的作用。成熟好氧颗粒污泥的脱氮性能会受到pH值、DO浓度、C/N值的影响,最佳pH值为7. 0、DO为(2. 0±0. 1) mg/L、C/N值为8,相应的NH_4~+-N去除率分别为95. 60%、95. 78%、97. 87%,TN去除率分别为93. 64%、94. 28%、96. 28%。     

颗粒/絮体共存的生物除磷系统的特性研究

以颗粒/絮体共存的SBR生物除磷系统为研究对象,考察了生物除磷污泥的形成过程、颗粒/絮体共存及各自单独存在下的污泥特性和除污性能。在40 min的沉淀时间下,以厌氧/好氧交替方式运行的SBR反应器中有白色颗粒污泥出现,随着运行则系统处于颗粒和絮体共存的状态。运行至第60天,污泥的平均粒径为553μm,颗粒(粒径200μm)占污泥总量的比例为67%。颗粒/絮体共存的形式可以提高絮体污泥的沉降性能,同时降低颗粒污泥解体所导致的出水SS浓度的增加。另外,颗粒/絮体共存系统对COD、PO3-4-P、NH+4-N的去除率分别为80%、98.5%、100%。而单独颗粒系统的出水NH+4-N为7.63 mg/L,单独絮体系统的出水PO3-4-P为5.87 mg/L。颗粒与絮体共存更有利于对污染物的去除及污泥沉降性能的改善。     

不同流态对好氧污泥颗粒化的影响

采用圆柱形、球形和方柱形序批式反应器,在摇床内培养好氧颗粒污泥,应用粒子成像测速(PIV)系统进行分析和Flow-3D软件模拟,考察不同流态对好氧污泥颗粒化的影响.结果表明:三个反应器均能培养出好氧颗粒污泥;方柱形反应器内的颗粒污泥粒径相对较小、密实、数量多且均匀;在反应器内形成具有漩涡流特性的二次流和一定强度的紊动性,有利于形成密实和强度高的好氧颗粒污泥.     

厌、好氧周期循环下的污泥颗粒化过程

为研究厌氧／好氧周期循环条件下厌氧快速吸收工艺中的污泥颗粒化过程、成因及影响因素，分别采用葡萄糖、乙酸钠人工配水及实际城市污水进行了试验。结果发现，形成的好氧颗粒污泥呈球形或椭球形，致密且边界清晰，其中葡萄糖配水的污泥粒径为0．5～0．8mm，最大可达1．0mm，SVI值为25～30mL／g；乙酸钠配水的污泥粒径为0．2～0．4mm，SVI值为40mL／g左右；实际城市污水的污泥经过短期运行即开始出现小颗粒，SVI值为60mL／g左右。3种污泥均具有良好的厌氧COD吸收活性。     

Microbial population dynamics during aerobic sludge granulation at different organic loading rates

Laboratory experiments were carried out to investigate the evolution of the bacterial community during aerobic sludge granulation. The experiments were conducted in three 2.4L sequencing batch reactors (SBRs) that were seeded with activated sludge and fed with glucose-based synthetic wastewater. Three different influent organic concentrations were introduced into the three SBRs, R1, R2 and R3, resulting in chemical oxygen demand (COD) loading rates of 1.5 (R1), 3.0 (R2) and 4.5 (R3)kg/m(3)d, respectively. Changes in bacterial diversity throughout the granulation process were monitored and analysed using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. The experimental results demonstrate that glucose-fed aerobic granules could be formed without significant presence of filamentous bacteria. Granules formed at different loading rates had different morphology, structural properties and bacterial species. A higher loading rate resulted in faster formation of larger and loose granules, while a lower loading rate resulted in slower formation of smaller and more tightly packed granules. The biomass underwent a dynamic transformation in terms of bacterial species richness and dominance during the granulation process. The reactor with the highest substrate loading rate had the lowest species diversity, while the reactor with the lowest substrate loading rate had the highest species diversity. Different dominant species of beta- and gamma-Proteobacteria and Flavobacterium within the granule communities from the three different SBRs were confirmed by analysis of 16S rDNA sequences of the PCR products separated by DGGE. It is apparent that a few common bacterial species play an important role in the formation and growth of aerobic granules and help sustain the granular sludge structure in the bioreactors.     

碳源对好氧颗粒污泥物理性状及除磷性能的影响

采用气提升内循环序批式反应器，分别以葡萄糖、乙酸钠、乙醇为碳源培养好氧颗粒污泥，考察了3种颗粒污泥的物理性状、除磷性能及除磷机理。结果表明：3种颗粒污泥在结构和处理效果上均能长时间保持稳定，其中以乙酸钠和葡萄糖为碳源培养出的颗粒污泥具有较密实的内部结构和较好的沉降性能；在进水COD为600mg／L、TP为15mg／L时，以葡萄糖、乙酸钠、乙醇为碳源培养出的好氧颗粒污泥对TP的去除率分别为82％、88％、52％，其中对TP去除效果较好的两种好氧颗粒污泥（以乙酸钠、葡萄糖为碳源培养的）在反应初期均有较明显的释磷现象发生；以乙酸钠为碳源培养出的颗粒污泥在进水COD浓度为800mg／L时对TP的去除率达到最高（为92％）．进一步加大COD负荷会使好氧颗粒污泥的除磷能力迅速下降。     

Effects of oxygen concentration on N-removal in an aerobic granular sludge reactor

In order to optimise nitrogen removal in an aerobic granular sludge system, short- and long-term effects of decreased oxygen concentrations on the reactor performance were studied. Operation at decreased oxygen concentration is required to obtain efficient N-removal and low aeration energy requirement. A short-term oxygen reduction (from 100% to 50%, 40%, 20% or 10% of the saturation concentration) did not influence the acetate uptake rate. A lower aerobic acetate uptake at lower oxygen concentrations was obviously compensated by anoxic acetate uptake. Nitrogen removal was favoured by decreased oxygen concentrations, reaching a value of 34% for the lowest oxygen concentration tested. Long-term effects were evaluated at two oxygen saturation levels (100% and 40%). Nitrogen removal increased from 8% to 45% when the oxygen saturation was reduced to 40%. However, the granules started to disintegrate and biomass washout occurred. It was impossible to obtain stable granular sludge at this decreased oxygen concentration under applied conditions. A solution to obtain stable aerobic granular sludge at low oxygen concentrations is needed in order to make aerobic granular sludge reactors feasible in practice.     

Ammonium adsorption in aerobic granular sludge, activated sludge and anammox granules

The ammonium adsorption properties of aerobic granular sludge, activated sludge and anammox granules have been investigated. During operation of a pilot-scale aerobic granular sludge reactor, a positive relation between the influent ammonium concentration and the ammonium adsorbed was observed. Aerobic granular sludge exhibited much higher adsorption capacity compared to activated sludge and anammox granules. At an equilibrium ammonium concentration of 30 mg N/L, adsorption obtained with activated sludge and anammox granules was around 0.2 mg NH₄-N/g VSS, while aerobic granular sludge from lab- and pilot-scale exhibited an adsorption of 1.7 and 0.9 mg NH₄-N/g VSS, respectively. No difference in the ammonium adsorption was observed in lab-scale reactors operated at different temperatures (20 and 30 °C). In a lab-scale reactor fed with saline wastewater, we observed that the amount of ammonium adsorbed considerably decreased when the salt concentration increased. The results indicate that adsorption or better ion exchange of ammonium should be incorporated into models for nitrification/denitrification, certainly when aerobic granular sludge is used.     

Extracellular polymeric substances (EPS) in upflow anaerobic sludge blanket (UASB) reactors operated under high salinity conditions

Considering the importance of stable and well-functioning granular sludge in anaerobic high-rate reactors, a series of experiments were conducted to determine the production and composition of EPS in high sodium concentration wastewaters pertaining to anaerobic granule properties. The UASB reactors were fed with either fully acidified substrate (FAS) consisting of an acetate medium (reactor R1) or partly acidified substrate (PAS) consisting of acetate, gelatine and starch medium (reactors R2, R3, and R4). For EPS extraction, the cation exchange resin (CER) method was used. Strength and particle size distribution were determined by assessing the formation of fines sludge under conditions of high shear rate and by laser diffraction, respectively. Batch tests were performed in 0.25 L bottles to study Ca²⁺ leaching from anaerobic granular sludge when incubated in 20 g Na⁺/L in the absence of feeding for 30 days. Results show a steady increase in the bulk liquid Ca²⁺ concentration during the incubation period. UASB reactor results show that the amounts of extracted proteins were higher from reactors R2 and R3, fed with PAS compared to the sludge samples from reactor R1, fed with FAS. Strikingly, the amount of extracted proteins also increased for all reactor sludges, irrespective of the Na⁺ concentration applied in the feed, i.e. 10 or 20 gNa⁺/L. PAS grown granular sludges showed an important increase in particle size during the operation of the UASB reactors. Results also show that, addition of 1 gCa²⁺/L to the high salinity wastewater increases the granules' strength.     

Biomass characteristics in three sequencing batch reactors treating a wastewater containing synthetic organic chemicals

The physical and biochemical characteristics of the biomass in three lab-scale sequencing batch reactors (SBR) treating a synthetic wastewater at a 20-day target solids retention time (SRT) were investigated. The synthetic wastewater feed contained biogenic compounds and 22 organic priming compounds, chosen to represent a wide variety of chemical structures with different N, P and S functional groups. At a two-day hydraulic retention time (HRT), the oxidation-reduction potential (ORP) cycled between -100 (anoxic) and 100 mV (aerobic) in the anoxic/aerobic SBR, while it remained in a range of 126+/-18 and 249+/-18 mV in the aerobic sequencing batch biofilm reactor (SBBR) and the aerobic SBR reactor, respectively. A granular activated sludge with excellent settleability (SVI=98+/-31 L mg(-1)) developed only in the anoxic/aerobic SBR, compared to a bulky sludge with poor settling characteristics in the aerobic SBR and SBBR. While all reactors had very good COD removal (>90%) and displayed nitrification, substantial nitrogen removal (74%) was only achieved in the anoxic/aerobic SBR. During the entire operational period, benzoate, theophylline and 4-chlorophenol were completely removed in all reactors. In contrast, effluent 3-nitrobenzoate was recorded when its influent concentration was increased to 5 mg L(-1) and dropped only to below 1 mg L(-1) after 300 days of operation. The competent (active) biomass fractions for these compounds were between 0.04% and 5.52% of the total biomass inferred from substrate-specific microbial enumerations. The measured competent biomass fractions for 4-chlorophenol and 3-nitrobenzoate degradation were significantly lower than the influent COD fractions of these compounds. Correspondent to the highest competent biomass fraction for benzoate degradation among the test SOCs, benzoate oxidation could be quantified with an extant respirometric technique, with the highest specific oxygen uptake rate (SOUR(benzoate), 0.026 g O2 h(-1) g(-1) XCOD) in the anoxic/aerobic SBR. These combined results suggest that operating SBRs with alternative anoxic/aerobic cycles might facilitate the formation of granular sludge with good settleability, and retain comparable removal of nitrogen and synthetic organic compounds. Hence, the practice of anoxic/aerobic cycling should be considered in wastewater treatment systems whenever possible.     

Breakage and growth towards a stable aerobic granule size during the treatment of wastewater

To better understand granule growth and breakage processes in aerobic granular sludge systems, the particle size of aerobic granules was tracked over 50 days of wastewater treatment within four sequencing batch reactors fed with abattoir wastewater. These experiments tested a novel hypothesis stating that granules equilibrate to a certain stable granule size (the critical size) which is determined by the influence of process conditions on the relative rates of granule growth and granule breakage or attrition. For granules that are larger than the critical size, granule breakage and attrition outweighs granule growth, and causes an overall reduction in granule size. For granules at the critical size, the overall growth and size reduction processes are balanced, and granule size is stable. For granules that are smaller than the critical size, granule growth outweighs granule breakage and attrition, and causes an overall increase in granule size. The experimental reactors were seeded with mature granules that were either small, medium, or large sized, these having respective median granule sizes of 425 μm, 900 μm and 1125 μm. An additional reactor was seeded with a mixture of the sized granules to represent the original source of the granular sludge. The experimental results were analysed together with results of a previous granule formation study that used mixed seeding of granules and floccular sludge. The analysis supported the critical size hypothesis and showed that granules in the reactors did equilibrate towards a common critical size of around 600–800 μm. Accordingly, it is expected that aerobic granular reactors at steady-state operation are likely to have granule size distributions around a characteristic critical size. Additionally, the results support that maintaining a quantity of granules above a particular size is important for granule formation during start-up and for process stability of aerobic granule systems. Hence, biomass washout needs to be carefully managed to optimize granule formation during the reactor start-up.     

Alternating anoxic feast/aerobic famine condition for improving granular sludge formation in sequencing batch airlift reactor at reduced aeration rate

In this study the influence of a pre-anoxic feast period on granular sludge formation in a sequencing batch airlift reactor is evaluated. Whereas a purely aerobic SBR was operated as a reference (reactor R2), another reactor (R1) was run with a reduced aeration rate and an alternating anoxic-aerobic cycle reinforced by nitrate feeding. The presence of pre-anoxic phase clearly improved the densification of aggregates and allowed granular sludge formation at reduced air flow rate (superficial air velocity (SAV) = 0.63 cm s⁻¹). A low sludge volume index (SVI₃₀ = 45 mL g⁻¹) and a high MLSS concentration (9–10 g L⁻¹) were obtained in the anoxic/aerobic system compared to more conventional results for the aerobic reactor. A granular sludge was observed in the anoxic/aerobic system whilst only flocs were observed in the aerobic reference even when operated at a high aeration rate (SAV = 2.83 cm s⁻¹). Nitrification was maintained efficiently in the anoxic/aerobic system even when organic loading rate (OLR) was increased up to 2.8 kg COD m⁻³ d⁻¹. In the contrary nitrification was unstable in the aerobic system and dropped at high OLR due to competition between autotrophic and heterotrophic growth. The presence of a pre-anoxic period positively affected granulation process via different mechanisms: enhancing heterotrophic growth/storage deeper in the internal anoxic layer of granule, reducing the competition between autotrophic and heterotrophic growth. These processes help to develop dense granular sludge at a moderate aeration rate. This tends to confirm that oxygen transfer is the most limiting factor for granulation at reduced aeration. Hence the use of an alternative electron acceptor (nitrate or nitrite) should be encouraged during feast period for reducing energy demand of the granular sludge process.