好氧颗粒污泥研究进展

介绍了好氧颗粒污泥的特征及形成机制,并对影响好氧颗粒污泥形成的因素如水力剪切力、胞外聚合物（EPS）、投加多价阳离子或载体、溶解氧（DO）、C／N比、反应器构型、底物组成、有机负荷率、污泥表面疏水性进行了分析,通过对好氧颗粒污泥的简介,提出了好氧颗粒污泥的发展趋势。     

Characterization of alginate-like exopolysaccharides isolated from aerobic granular sludge in pilot-plant

To understand functional gel-forming exopolysaccharides in aerobic granular sludge, alginate-like exopolysaccharides were specifically extracted from aerobic granular sludge cultivated in a pilot plant treating municipal sewage. The exopolysaccharides were identified by the FAO/WHO alginate identification tests, characterized by biochemical assays, gelation with Ca²⁺, blocks fractionation, spectroscopic analysis as UV-visible, FT-IR and MALDI-TOF MS, and electrophoresis. The yield of extractable alginate-like exopolysaccharides was reached 160 ± 4 mg/g (VSS ratio). They resembled seaweed alginate in UV-visible and MALDI-TOF MS spectra, and distinguished from it in the reactions with acid ferric sulfate, phenol-sulfuric acid and Coomassie brilliant blue G250. Characterized by their high percentage of poly guluronic acid blocks (69.07 ± 8.95%), the isolated exopolysaccharides were capable to form rigid, non-deformable gels in CaCl₂. They were one of the dominant exopolysaccharides in aerobic granular sludge. We suggest that polymers play a significant role in providing aerobic granular sludge a highly hydrophobic, compact, strong and elastic structure.     

The contribution of exopolysaccharides induced struvites accumulation to ammonium adsorption in aerobic granular sludge

Aerobic granular sludge from a lab-scale reactor with simultaneous nitrification/denitrification and enhanced biological phosphorus removal processes exhibited significant amount of ammonium adsorption (1.5 mg NH₄⁺-N/g TSS at an ammonium concentration of 30 mg N/L). Potassium release accompanied ammonium adsorption, indicating an ion exchange process. The existence of potassium magnesium phosphate (K-struvite) as one of potassium sources in the granular sludge was studied by X-ray diffraction analysis (XRD). Artificially prepared K-struvite was indeed shown to adsorb ammonium. Alginate-like exopolysaccharides were isolated and their inducement for struvite formation was investigated as well. Potassium magnesium phosphate proved to be a major factor for ammonium adsorption on the granular sludge. Struvites (potassium/ammonium magnesium phosphate) accumulate in aerobic granular sludge due to inducing of precipitation by alginate-like exopolysaccharides.     

Behavior of polymeric substrates in an aerobic granular sludge system

Particulate and slowly biodegradable substrates form an important fraction of industrial wastewater and sewage. To study the influence of suspended solids and colloidal substrate on the morphology and performance of aerobic granular sludge, suspended and soluble starch was used as a model substrate. Degradation was studied using microscopy, micro-electrode measurements, batch experiments and long term laboratory scale reactor operation. Starch was removed by adsorption at the granule surface, followed by hydrolysis and consumption of the hydrolyzed products. Aerobic granules could be maintained on starch as sole influent carbon source, but their structure was filamentous and irregular. It is hypothesized that this is related to the low starch hydrolysis rates, leading to available substrate during the aeration period (extended feast period) and resulting in increased substrate gradients over the granules. The latter induces a less uniform granule development. Starch adsorbed and was consumed at the granule surface instead of being accumulated inside the granules as occurs for soluble substrates. Therefore the simultaneous denitrification efficiencies remained low. Moreover, many protozoa and metazoans were observed in laboratory reactors as well as in pilot- and full-scale Nereda^® reactors, indicating an important role in the removal of suspended solids too.     

UASB颗粒污泥性质研究

介绍了UASB反应器处理高浓度葡萄糖有机废水的试验材料及方法，分析了UASB的运行过程及结果，对不同运行时期UASB反应器内颗粒污泥的性质进行了研究，以促进UASB的应用。     

Simultaneous nitrogen and phosphate removal in aerobic granular sludge reactors operated at different temperatures

The main biological conversions taking place in two lab-scale aerobic granular sludge sequencing batch reactors were evaluated. Reactors were operated at different temperatures (20 and 30 °C) and accomplished simultaneous COD, nitrogen and phosphate removal. Nitrogen and phosphate conversions were linked to the microbial community structure as assessed by fluorescent in situ hybridization (FISH) analysis. Anoxic tests were performed to evaluate the contribution of anoxic phosphate uptake to the overall phosphate removal and to clarify the denitrification pathway. Complete nitrification/denitrification and phosphate removal were achieved in both systems. A considerable fraction of the phosphate removal was coupled to denitrification (denitrifying dephosphatation). From the results obtained in anoxic batch experiments dosing either nitrite or nitrate, denitrification was proposed to proceed mainly via the nitrate pathway. Denitrifying glycogen-accumulating organisms (DGAOs) were observed to be the main organisms responsible for the reduction of nitrate to nitrite. A significant fraction of the nitrite was further reduced to nitrogen gas while being used as electron acceptor by denitrifying polyphosphate-accumulating organisms (PAO clade II) for anoxic phosphate uptake.     

Formation of aerobic granules and conversion processes in an aerobic granular sludge reactor at moderate and low temperatures

Temperature changes can influence biological processes considerably. To investigate the effect of temperature changes on the conversion processes and the stability of aerobic granular sludge, an aerobic granular sludge sequencing batch reactor (GSBR) was exposed to short-term and long-term temperature changes. Start-up at 8 degrees C resulted in irregular granules that aggregated as soon as aeration was stopped, which caused severe biomass washout and instable operation. The presence of COD during the aerobic phase is considered to be the major reason for this granule instability. Start-up at 20 degrees C and lowering the temperature to 15 degrees C and 8 degrees C did not have any effect on granule stability and biomass could be easily retained in the system. The temperature dependency of nitrification was lower for aerobic granules than usually found for activated sludge. Due to decreased activity in the outer layers of granules at lower temperatures, the oxygen penetration depth could increase, which resulted in a larger aerobic biomass volume, compensating the decreased activity of individual organisms. Consequently the denitrifying capacity of the granules decreased at reduced temperatures, resulting in an overall poorer nitrogen removal capacity. The overall conclusion that can be drawn from the experiments at low temperatures is that start-up in practice should take place preferentially during warm summer periods, while decreased temperatures during winter periods should not be a problem for granule stability and COD and phosphate removal in a granular sludge system. Nitrogen removal efficiencies should be optimized by changes in reactor operation or cycle time during this season.     

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.     

A model for autothermic aerobic digestion: Effects of scale depending on aeration efficiency and sludge concentration

Autothermic thermophilic (40–50°C) aerobic digestion will progressively substitute traditional “cold” aerobic sludge digestion in practical applications in medium sized sewage treatment plants (for populations of 10,000–30,000). This latter system has never given satisfactory results in the frigid winters of Northern and Central European countries, while the aerobic autothermic process gives a good sludge stabilization even in cold climates, and a higher grade of hygienic improvement than with the anaerobic process. This article proposes a single stage process with an 8-day retention time and diffused aeration, for the sole purpose of a good sludge stabilization. The calculated results indicate that: the effect of variations in the efficiency of the aerators is negligible in winter conditions with small reactors and solid concentrations below 2%; the effect of scaling up is considerable for solid concentrations less than 2% and is appreciable for solid concentrations of 5% and reactor volumes of less than 5 m³; even in winter conditions and solid concentrations of below 2%, a reactor temperature of 20°C is obtained with ordinary aeration systems; higher temperatures can be reached by using particular aeration systems available on the market with oxygenation efficiencies around 20%.     

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.     

Identification of trigger factors selecting for polyphosphate- and glycogen-accumulating organisms in aerobic granular sludge sequencing batch reactors

Nutrient removal performances of sequencing batch reactors using granular sludge for intensified biological wastewater treatment rely on optimal underlying microbial selection. Trigger factors of bacterial selection and nutrient removal were investigated in these novel biofilm systems with specific emphasis on polyphosphate- (PAO) and glycogen-accumulating organisms (GAO) mainly affiliated with Accumulibacter and Competibacter, respectively. In a first dynamic reactor operated with stepwise changes in concentration and ratio of acetate and propionate (Ac/Pr) under anaerobic feeding and aerobic starvation conditions and without wasting sludge periodically, propionate favorably selected for Accumulibacter (35% relative abundance) and stable production of granular biomass. A Plackett-Burman multifactorial experimental design was then used to screen in eight runs of 50 days at stable sludge retention time of 15 days for the main effects of COD concentration, Ac/Pr ratio, COD/P ratio, pH, temperature, and redox conditions during starvation. At 95% confidence level, pH was mainly triggering direct Accumulibacter selection and nutrient removal. The overall PAO/GAO competition in granular sludge was statistically equally impacted by pH, temperature, and redox factors. High Accumulibacter abundances (30–47%), PAO/GAO ratios (2.8–8.4), and phosphorus removal (80–100%) were selected by slightly alkaline (pH > 7.3) and lower mesophilic (<20 °C) conditions, and under full aeration during fixed 2-h starvation. Nitrogen removal by nitrification and denitrification (84–97%) was positively correlated to pH and temperature. In addition to alkalinity, non-limited organic conditions, 3-carbon propionate substrate, sludge age control, and phase length adaptation under alternating aerobic-anoxic conditions during starvation can lead to efficient nutrient-removing granular sludge biofilm systems.     

Integration of anammox into the aerobic granular sludge process for main stream wastewater treatment at ambient temperatures

Anaerobic ammonium oxidation, nitrification and removal of COD was studied at ambient temperature (18 °C ± 3) in an anoxic/aerobic granular sludge reactor during 390 days. The reactor was operated in a sequencing fed batch mode and was fed with acetate and ammonium containing medium with a COD/N ratio of 0.5 [g COD/gN]. During influent addition, the medium was mixed with recycled effluent which contained nitrate in order to allow acetate oxidation and nitrate reduction by anammox bacteria. In the remainder of the operational cycle the reactor was aerated and controlled at a dissolved oxygen concentration of 1.5 mg O₂/l in order to establish simultaneous nitritation and Anammox. Fluorescent in-situ hybridization (FISH) revealed that the dominant Anammox bacterial population shifted toward Candidatus “Brocadia fulgida” which is known to be capable of organotrophic nitrate reduction. The reactor achieved stable volumetric removal rates of 900 [g N₂-N/m³/day] and 600 [g COD/m³/day]. During the total experimental period Anammox bacteria remained dominant and the sludge production was 5 fold lower than what was expected by heterotrophic growth suggesting that consumed acetate was not used by heterotrophs. These observations show that Anammox bacteria can effectively compete for COD at ambient temperatures and can remove effectively nitrate with a limited amount of acetate. This study indicates a potential successful route toward application of Anammox in granular sludge reactors on municipal wastewater with a limited amount of COD.     

Evaluating the solid retention time of bacteria in flocculent and granular sludge

The specific solid retention time for different bacteria within flocculent and granular sludge was determined. Samples were collected from reactor and effluent sludge and the number of a specific bacterial group was evaluated in respect to the total bacterial community with quantitative polymerase chain reaction (qPCR). The ratio of the relative presence of a specific bacterial group in the reactor sludge and wasted sludge was established to observe if preferential wash-out occurred. From the data also the solid retention time for different microbial groups can be estimated. Using this tool, we were able to show that the SRT of populations found on the exterior of granules is slightly lower than the SRT for population in the interior. Archaea were not found in the flocculent system but were present in small amounts within the granular system. It was further observed that protozoa were grazing on the bacterial community within the system indicating that they have the potential to shorten the specific SRT of bacteria.     

采用CSTR反应器培养好氧颗粒污泥的研究

以醋酸盐作碳源的人工配水为原水,在常温(25~30℃)条件下采用连续流完全混合反应器(CSTR)培养好氧颗粒污泥。结果表明,通过采用逐步缩短HRT和提高有机负荷的方法,在60 d内培养出了成熟的好氧颗粒污泥;好氧颗粒污泥反应器的运行高效而稳定,在水力停留时间为2.82 h、有机负荷为3~4.24 kgCOD/(m3.d)的条件下,对COD、NH+4-N和PO34--P的去除率分别可达90%、90%和70%,具有明显的脱氮除磷效果。     

Laboratory studies of virus survival during aerobic and anaerobic digestion of sewage sludge

The survival of three enteroviruses (polio 1, coxsackie B3 and echo 1) and a rotavirus (SA-11) was studied under laboratory conditions. The effects of temperature, dissolved oxygen, detention time, sludge source and virus type on virus inactivation were determined. Temperature was the single most important factor influencing the rate of virus inactivation. No significant differences were found for virus inactivation rates at dissolved oxygen levels between 0.9 and 5.8 mg/l. However, the inactivation rate of the viruses under aerobic conditions was found to be significantly greater than the inactivation rate under anaerobic conditions (−0.77log₁₀/day vs −0.33 log₁₀/day). Sludge source, detention time and virus type did not significantly influence the rate of virus inactivation.     

Influence of adsorption and anaerobic granular sludge characteristics on long chain fatty acids inhibition process

The impact of LCFA adsorption on the methanogenic activity was evaluated in batch assays for two anaerobic granular sludges in the presence and absence of bentonite as synthetic adsorbent. A clear inhibitory effect at an oleate (C18:1) concentration of 0.5 g_C18:1 L⁻¹ was observed for both sludges. Palmitate (C16:0) was confirmed to be the main intermediate of C18:1 degradation in not adapted sludge and its accumulation was further evidenced by fluorescence staining and microscopy techniques. LCFA inhibition could be decreased by the addition of bentonite, reducing the lag-phase and accelerating the kinetics of LCFA degradation, concluding in the importance of the adsorptive nature of the LCFA inhibitory process. Granule morphology and molecular profiling of predominant microorganisms revealed that biomass adaptation to LCFA could modify the intermediates accumulation profiles and process rates.     

SBR系统同步脱氮除磷好氧颗粒污泥的培养

以普通絮状活性污泥为种泥,采用人工配制的模拟生活污水,在序批式反应器(SBR)中成功地培养出了具有同步脱氮除磷功能的好氧颗粒污泥.研究表明,通过提高COD负荷和逐步减少污泥沉降时间以造成选择压,可促进颗粒污泥的形成.成熟的颗粒污泥形态完整、结构致密、表面光滑、外观呈橙黄色,为近似球形或椭球形,粒径大多在0.5～1.0 mm之间,污泥体积指数为27.0 mL/g,MLSS为6 800 mg/L.该颗粒污泥对NH4 -N的去除率接近100%,对COD和PO3-4-P的平均去除率均在80%以上,而且颗粒污泥中的微生物种群具有多样性,所形成的微生态系统更稳定,抗外界干扰及自身恢复调节能力较强.     

利用好氧颗粒污泥实现同时除磷脱氮

为实现同时除磷脱氮,以单级SBR中的好氧颗粒污泥为研究对象,在温度为 25℃、pH值为 7~8、厌氧反应 80~90min、好氧反应 240min、曝气阶段的DO为 1~2mg/L、SRT为 20d的运行条件下进行了研究。结果表明,大量反硝化聚磷菌能够与硝化菌在颗粒污泥中共存并富集,反硝化聚磷菌占全部聚磷菌的 73. 1%;系统处于稳态时对氮、磷和有机碳具有非常稳定的去除效果。当进水氨氮、磷和乙酸碳浓度分别为 25~50、8~15、100~180mg/L,MLSS为 7. 0g/L,MLVSS为 6. 4g/L时,对氨氮、总无机氮、磷、乙酸碳的平均去除率分别为 97. 8%、89. 7%、96. 8%和98. 8%。     

Isolation, identification and utilization of thermophilic strains in aerobic digestion of sewage sludge

Two representative thermophilic bacterial strains (T1 and T2) were isolated from a one-stage autothermal thermophilic aerobic digestion pilot-scale reactor. 16S rRNA gene analysis indicated that they were Hydrogenophilaceae and Xanthomonodaceae. These isolated strains were inoculated separately and/or jointly in sewage sludge, to investigate their effects on sludge stabilization under thermophilic aerobic digestion condition. Four digestion conditions were tested for 480 h. Digestion without inoculation and inoculation with strain T2, as well as joint- inoculation with strains T1 and T2, achieved 32.6%, 43.0%, and 38.2% volatile solids (VS) removal, respectively. Removal in a digester inoculated with stain T1 only reached 27.2%. For the first 144 h, the three inoculated digesters all experienced higher VS removal than the digester without inoculations. Both specific thermophilic strains and micro-environment significantly affected the VS removal. DGGE profiles revealed that the isolated strains T1 and T2 can successfully establish in the thermophilic digesters. Other viable bacteria (including anaerobic or facultative microbes) also appeared in the digestion system, enhancing the microbial activity.