序批式生物膜反应器的生物膜特性研究

通过扫描电镜对具有除磷功能的序批式生物膜反应器中生物膜的形态结构进行了观察，并考察了容积负荷、曝气量和厌氧循环水量对生物膜量的影响。结果发现，生物膜主要由微生物及其胞外多聚物组成，大量的微生物及其胞外多聚物相互连结，形成稳定的缠结结构。平均每片填料上附着的生物膜质量为4．088g，挥发性生物膜质量与生物膜干质量的比值为0．861，表明活性生物量较高。填料上的生物膜量主要受曝气量和厌氧循环水量的影响，而容积负荷对填料上的生物膜量基本没有影响。     

Biofilm growth and characteristics in an alternating pumped sequencing batch biofilm reactor (APSBBR)

A novel biofilm reactor-alternating pumped sequencing batch biofilm reactor (APSBBR)-was developed to treat synthetic dairy wastewater at a volumetric chemical oxygen demand (COD) loading rate of 487 g COD m(-3) d(-1) and an areal loading rate of 5.4 g COD m(-2) d(-1). This biofilm reactor comprised two tanks, Tanks 1 and 2, with two identical plastic biofilm modules in each tank. The maximum volume of bulk fluid in the two-tank reactor was the volume of one tank. The APSBBR was operated as a sequencing batch biofilm reactor with five operational phases-fill (25 min), anoxic (9 h), aerobic (9 h), settle (6 h) and draw (5 min). The fill, anoxic, settle and draw phases occurred in Tank 1. In the aerobic phase, the wastewater was circulated between the two tanks with centrifugal pumps and aeration was mainly achieved through oxygen absorption by micro-organisms in the biofilms when they were exposed to the air. In this paper, the biofilm growth and characteristics in the APSBBR were studied in a 98-day laboratory-scale experiment. During the course of the study, it was found that the biofilm thickness (delta) in Tank 1 ranged from 1.2 to 7.2 mm and that in Tank 2 from 0.5 to 2.2 mm; the biofilm growth against time (t) can be simulated as delta=0.07t0.99 (R2 = 0.97, P = 0.002) in Tank 1 and delta = 0.08t0.66 (R2 = 0.81, P = 0.04) in Tank 2. The biomass yield coefficient, Y, was 0.18 g volatile solids (VS) g(-1) COD removal. The biofilm density in both tanks, X, decreased as the biofilm thickness increased and can be correlated to the biofilm thickness, delta .     

曝气量对SBBR生物除磷的影响研究

为了考察曝气量对序批式生物膜反应器（SBBR）除磷效果的影响,采用厌氧/好氧交替运行的方式,通过控制好氧反应过程中的曝气量,研究了不同曝气量时SBBR的好氧吸磷效果,以及不同曝气量对生物膜脱落量的影响,并推导了生物除磷过程中生物膜内溶解氧的扩散模型。结果表明,曝气量是影响生物除磷效果的一个重要因素,为了满足生物膜内聚磷菌对氧的需求量,加快氧的传递速率,增加活性生物膜的厚度,加快聚磷菌的好氧吸磷速率,必须提高液相主体中溶解氧的含量。选择适宜的曝气量能够促进生物膜的脱落与更新,起到调控污泥龄的作用,从而增强生物除磷的稳定性。     

Impact of shear force on the biofilm structure and performance of a membrane biofilm reactor for tertiary hydrogen-driven denitrification of municipal wastewater

Hydrogen-driven denitrification using a hollow-fiber membrane biofilm reactor (MBfR) was evaluated for operation in tertiary wastewater treatment. Specific objectives were to evaluate the impact of different levels of shearing stress caused by mixing and nitrogen sparging on the biofilm structure and denitrification rates. Applying high shear force proved to be effective in improving denitrification rates by reducing the thickness of the biofilm. With intensive mixing a biofilm thickness of approximately 800 microm was maintained, while additional nitrogen sparging could further reduce the biofilm thickness to approximately 300 microm. The highest denitrification rates of 0.93 gN/m(2)d were obtained when biofilm thickness was lower than 500 microm. Lower extracellular polymeric substances (EPS) accumulation and carbohydrates to protein ratio observed in thinner biofilms allowed for higher nitrate removal in the system. No significant sloughing of biomass or change in total and soluble COD in the final effluent was observed under steady-state conditions.     

Chlorination of model drinking water biofilm: implications for growth and organic carbon removal

The influence of chlorine on biofilm in low organic carbon environments typical of drinking water or industrial process water was examined by comparing biomass and kinetic parameters for biofilm growth in a chlorinated reactor to those in a non-chlorinated control. Mixed-population heterotrophic biofilms were developed in rotating annular reactors under low concentration, carbon-limited conditions (< 2 mg/L as carbon) using three substrate groups (amino acids, carbohydrates and humic substances). Reactors were operated in parallel under identical conditions with the exception that chlorine was added to one reactor at a dose sufficient to maintain a free chlorine residual of 0.09-0.15 mg/L in the effluent. The presence of free chlorine resulted in development of less biofilm biomass compared to the control for all substrates investigated. However, specific growth and organic carbon removal rates were on the average five times greater for chlorinated biofilm compared to the control. Observed yield values were less for chlorinated biofilm. Although chlorinated biofilm's specific organic carbon removal rate was high, the low observed yield indicated organic carbon was being utilized for purposes other than creating new cell biomass. The impacts of free chlorine on mixed-population biofilms in low-nutrient environments were different depending upon the available substrate. Biofilms grown using amino acids exhibited the least difference between control and chlorinated kinetic parameters; biofilm grown using carbohydrates had the greatest differences. These findings are particularly relevant to the fundamental kinetic parameters used in models of biofilm growth in piping systems that distribute chlorinated, low-carbon-concentration water.     

投加有效微生物强化SBR和SBBR除污效果的研究

将有效微生物（EM）富集培养液分别引入序批式反应器（SBR）和序批式生物膜反应器（SBBR）,构成新型的EM—SBR和EM—SBBR污水处理系统,以不接种EM的SBR和SBBR为对照,分别考察了各反应器的除污效果。结果表明,当EM在SBR中形成稳定的优势菌群后,可显著提高活性污泥的浓度,并可改善污泥的沉降性能;EM—SBR在曝气时间为4 h时对COD和NH4^＋-N的去除率均大于94%,EM—SBBR对COD和NH4^＋-N的去除率比对照组均高出7%左右;EM—SBR因菌种随出水流失造成除污效果下降而需要周期性投菌,EM—SBBR因附着性生物膜的存在有效减少了菌种的流失量,从而使其投菌周期较EM—SBR的大为延长,EM—SBBR除污效果周期性下降的主要原因为菌种退化。     

Nematodes in wastewater biofilms--appearance and density of species in three biofilter reactors

Population dynamics of nematode species in biofilms of three different biofilter reactors, differing in size (pilot/laboratory scale), operation mode and biofilm carrier, were studied over a period of 1 year. In the biofilm suspension of the pilot system mean nematode density was 118individuals/ml and average biomass 15microg wet weight/ml. Higher mean abundance was found in the two laboratory systems with 2380 and 4411individuals/ml. Mean biomass in the laboratory systems ranged from 209 to 330microg wet weight/ml. There were marked temporal differences in appearance and density of nematode species in all three biofilters. Number of species observed was 3 in the laboratory systems and 5 in the pilot system. The fastest growing species (Paroigolaimella bernensis and Diplogasteritus nudicapitatus) were observed in the pilot reactor in contrast to the more slowly growing species (Diploscapter coronatus and Acrostichus sp.), which dominated in the laboratory reactors. Sexual reproduction was found for all species but of Diploscapter coronatus. When comparing life history traits of the different species with the environmental conditions in the reactors, it seems that the unstable conditions in the pilot reactor favor the fast growing species whereas the stable environment in the laboratory systems allows the growth of species with longer generation times.     

Aerobic granulation in a sequencing batch airlift reactor

Aerobic granular sludge was cultivated in an intensely mixed sequencing batch airlift reactor (SBAR). A COD loading of 2.5 kg Acetate-COD/(m3 d) was applied. Granules developed in the reactor within one week after inoculation with suspended activated sludge from a conventional wastewater treatment plant. Selection of the dense granules from the biomass mixture occurs because of the differences in settling velocities between granules (fast settling biomass), and filaments and flocs (slow settling biomass). At 'steady state' the granules had an average diameter of 2.5 mm, a biomass density of 60g VSS/I of granules, and a settling rate of > 10 m/h. The biomass consisted of both heterotrophic and nitrifying bacteria. The reactor was operated over a long period during which the granular sludge proved to remain stable. The performance of the intermittently fed SBAR was compared to that of the continuously fed biofilm airlift suspension reactor (BASR). The most importance difference was that the density of the granules in the SBAR was much higher than the density of the biofilms in the BASR. It is discussed that this could be due to the fact that the SBAR is intermittently fed, while the BASR is continuously fed.     

序批式生物膜法处理微污染河水的效果

采用序批式生物膜法处理实际河道中的微污染原水,考察了不同气水比下对污染物的去除效果和陶粒载体上生物膜的特征.结果表明:系统启动速度快,9 d后对污染物的去除率即达稳定;稳定运行时对COD<,Mn>、浊度和NH<,4><'+>-N的平均去除率分别为33.7%、83.4%和84.3%;气水比为4:1时,对COD<,Mn>和NH<,4><'+>-N的容积去除率分别为61.1和83.9 g/(m<'3>·d);此外,系统还具有较强的抗冲击负荷能力.生物膜构造均匀、极薄且致密;PCR-DGGE分析表明,相对于河道底泥和反应器内部松散的沉积物而言,该生物膜具有种群更丰富和多样的特点.     

Spatial distribution and physiological state of bacteria in a sand column experiment during the biodegradation of toluene

Toxic organic contaminants frequently serve as growth substrates for bacteria. However, long-term exposure to the organic contaminants can result in significant stress or "injury" to bacterial cells such that bacteria may lose, either temporarily or permanently, their capacity to degrade a specific toxic organic contaminant. In order to understand the relationship between biodegradability and physiological conditions of bacteria after a prolonged exposure to a contaminant, biomass samples collected from a sand column experiment, with toluene as the carbon source, were analyzed for bacterial physiology and spatial population distribution in the porous media. The column was seeded with three bacterial isolates that perform aerobic (Pseudomonas putida F1), denitrifying (Thauera aromatica T1), and facultative (Ralstonia pickettii PKO1) degradation of toluene were analyzed. Total, viable but not culturable with toluene, and toluene-culturable cells were enumerated using 4'6-diamidino-2-phenylindole (DAPI) staining and plate counting methods. Comparison of three types of cell counts showed that toluene-culturable cells were less than 40% of the total cell numbers. However, viable colonies transferred to a toluene media after cultivation on rich media regained their ability to degrade toluene. This implies that the temporary loss of their toluene degradation capacity is either due to an intracellular accumulation of degradation by-products, which have to be consumed in order for the cells to degrade toluene, or it is possible that cells have shifted to degrade other substrates such as toluene degradation intermediates or organic materials resulting from cell turnover. Comparison of cell counts with toluene concentration showed no exponential increase in total and viable cell numbers, as reported for flat bed biofilm reactor experiments. The overall fraction of toluene-culturable cells was highest at the highest toluene concentration near the column inlet, which indicates that the observed temporary loss of toluene culturability was not solely caused by a direct toxic effect from the long-term exposure to toluene.     

Visualization of active biomass distribution in a BGAC fluidized bed reactor using GFP tagged Pseudomonas putida F1

A favorable microenvironment for biofilm growth on GAC particles was shown using green fluorescent protein (GFP) as a marker for a phenol degrading bacterium, Pseudomonas putida F1. The dispersion of P. putida F1 in a biofilm covering granulated activated carbon (GAC) particles was monitored and compared to a biofilm on non-activated granular carbon particles. Laser scanning confocal microscopy (LSCM) micrographs of the biofilms taken from two fluidized bed reactors operating under identical conditions, showed higher fluorescent green areas in the GAC biofilm, especially close to the GAC surface. Quantitative analysis of the biofilm by COMSTAT, a three-dimensional biofilm structure analysis program, showed higher biomass concentration and higher viability in the GAC covered biofilm vs. the non-activated carbon biofilm. In addition, better effluent quality was measured for the BGAC reactor, which strongly suggests a significantly larger biofilm surface area available to the substrate, as opposed to that of the non-activated carbon carrier reactor.     

Nitrification in saline wastewater with high ammonia concentration in an activated sludge unit

A nitrifying activated sludge reactor fed with a high salinity medium was operated efficiently at ammonia loading rates between 1 and 4 g NH4+ -N l(-1) d(-1). The system became completely inefficient at inlet salt concentrations higher than 525 mM due to the mixed inhibition effect of salts and ammonia. The final product was mainly nitrate although dissolved oxygen limitations caused sporadic ammonia and nitrite accumulations. Specific nitrifying activity decreased due to the saline effect. A set of activity tests showed that in the continuous reactor non-adapted biomass is rather more sensitive than biomass to the saline effect. Physical properties of biomass in the reactor (sludge volumetric index and zone settling velocity) were not affected by the saline concentration, a biomass concentration of 20 gVSS l(-1) was achieved.     

Suspended biofilm carrier and activated sludge removal of acidic pharmaceuticals

Removal of seven active pharmaceutical substances (ibuprofen, ketoprofen, naproxen, diclofenac, clofibric acid, mefenamic acid, and gemfibrozil) was assessed by batch experiments, with suspended biofilm carriers and activated sludge from several full-scale wastewater treatment plants. A distinct difference between nitrifying activated sludge and suspended biofilm carrier removal of several pharmaceuticals was demonstrated. Biofilm carriers from full-scale nitrifying wastewater treatment plants, demonstrated considerably higher removal rates per unit biomass (i.e. suspended solids for the sludges and attached solids for the carriers) of diclofenac, ketoprofen, gemfibrozil, clofibric acid and mefenamic acid compared to the sludges. Among the target pharmaceuticals, only ibuprofen and naproxen showed similar removal rates per unit biomass for the sludges and biofilm carriers. In contrast to the pharmaceutical removal, the nitrification capacity per unit biomass was lower for the carriers than the sludges, which suggests that neither the nitrite nor the ammonia oxidizing bacteria are primarily responsible for the observed differences in pharmaceutical removal. The low ability of ammonia oxidizing bacteria to degrade or transform the target pharmaceuticals was further demonstrated by the limited pharmaceutical removal in an experiment with continuous nitritation and biofilm carriers from a partial nitritation/anammox sludge liquor treatment process.     

Sludge viability in a biological reactor

The volatile suspended solids (VSS) concentration cannot be used as a measure for the active biomass in a reactor which operates under a wide range of operating conditions since the viable organism content of the VSS is not constant. Using substrate saturation conditions the kinetic parameters maximum substrate removal rate ( ) and oxygen uptake rate (J)—both per mass of VSS—were determined in an experimental pulse fed batch biological reactor. It was found that and J both doubled during the experimental period (6 h). It was concluded that the increases in and J values were due to the increase in the sludge viability which are here defined as the percentage of VSS which is active biomass. Using the variations in and J values during each experiment, it was possible to calculate sludge viability. During a 6 h experimental period at substrate saturation level the sludge viability increased on average from 8.9 to 23.3%.In a loop type sewage conduits system operated as a plug flow reactor and enriched with biomass and air, it is possible to achieve high specific substrate removal rates when step feeding creates saturation conditions. This is further attenuated by a marked increase in the sludge viability.     

Anaerobic fixed-film reactors treating carbohydrate wastewater

Anaerobic downflow stationary fixed-film reactors operated at 35°C, successfully treated synthetic (sucrose-based) wastewater of different concentrations at high organic loading rates and short hydraulic residence times. Waste stabilization was due to the high concentration of active biomass retained in the biofilm. Biofilm biomass concentration increased with organic loading rate reaching a maximum of 8.7 kg VFS m⁻³ of reactor volume (0.112 kg VFS m⁻² support surface). The biofilm was found to be completely active and unaffected by diffusional limitations up to an average thickness of 2.6 mm.     

Dynamics of drinking water biofilm in flow/non-flow conditions

Drinking water biofilm formation on polyvinyl chloride (PVC), cross-linked polyethylene (PEX), high density polyethylene (HDPE) and polypropylene (PP) was followed in three different reactors operating under stagnant or continuous flow regimes. After one week, a quasi-steady state was achieved where biofilm total cell numbers per unit surface area were not affected by fluctuations in the concentration of suspended cells. Metabolically active cells in biofilms were around 17-35% of the total cells and 6-18% were able to form colony units in R(2)A medium. Microbiological analysis showed that the adhesion material and reactor design did not affect significantly the biofilm growth. However, operating under continuous flow (0.8-1.9 Pa) or stagnant water had a significant effect on biofilm formation: in stagnant waters, biofilm grew to a less extent. By applying mass balances and an asymptotic biofilm formation model to data from biofilms grown on PVC and HDPE surfaces under turbulent flow, specific growth rates of bacteria in the biofilm were found to be similar for both materials (around 0.15 day(-1)) and much lower than the specific growth rates of suspended bacteria (around 1.8 day(-1)).     

Micropollutant removal by attached and suspended growth in a hybrid biofilm-activated sludge process

Removal of organic micropollutants in a hybrid biofilm-activated sludge process was investigated through batch experiments, modeling, and full-scale measurements. Batch experiments with carriers and activated sludge from the same full-scale reactor were performed to assess the micropollutant removal rates of the carrier biofilm under oxic conditions and the sludge under oxic and anoxic conditions. Clear differences in the micropollutant removal kinetics of the attached and suspended growth were demonstrated, often with considerably higher removal rates for the biofilm compared to the sludge. For several micropollutants, the removal rates were also affected by the redox conditions, i.e. oxic and anoxic. Removal rates obtained from the batch experiments were used to model the micropollutant removal in the full-scale process. The results from the model and plant measurements showed that the removal efficiency of the process can be predicted with acceptable accuracy (±25%) for most of the modeled micropollutants. Furthermore, the model estimations indicate that the attached growth in hybrid biofilm-activated sludge processes can contribute significantly to the removal of individual compounds, such as diclofenac.     

Specific activity of nitrifying biofilm in water nitrification process

The effect of the accumulation of fixed biomass on the specific activity of nitrifying biofilm was studied in a continuous flow reactor. The specific activity of nitrifying biofilm was described by the specific removal rate of ammonium-N (q_obs). The observed relationship between q_obs and the film thickness was apparent to an inverse V-shaped curve. The maximum specific activity of biofilm was attained at a film thickness in the range 15–25 μm, at which a steady state was established in the liquid phase for different influent ammonium-N concentrations (S₀). Beyond such a range, the specific activity began to decline significantly with the additional accumulation of biofilm. It was demonstrated from both experimental and theoretical approaches that reduction in the specific activity of biofilm was closely related to the ratio of active biomass to the accumulation of inactive materials within the biofilm.     

Physico-chemical factors affecting the E. coli removal in a rotating biological contactor (RBC) treating UASB effluent

The removal mechanism of E. coli from UASB effluent using a Rotating Biological Contractor (RBC) has been investigated. Preliminary batch experiments in a RBC indicate a first-order removal kinetics. Variation in the dissolved oxygen concentration and E. coli counts over the depth of the RBC has been recorded and indicates that the RBC is not a completely mixed reactor. Therefore batch experiments were carried out in a beaker where the different operating conditions can be controlled. Factors affecting the removal of E. coli via a biofilm system as stirring, dissolved oxygen concentration, pH, and addition of cationic polymer were investigated. The results obtained indicated that the most important removal mechanism of E. coli in the biofilm is the adsorption process, followed by sedimentation. Die-off is a relatively minor removal mechanism in an RBC system. Higher removal rate of E. coli was observed in an aerobic compared to an anaerobic biofilm system. Variation of dissolved oxygen concentration (3.3-8.7 mgl(-1)) and pH-values between 6.5 and 9.3 did not exert any significant effect on the removal rate of the E. coli by the heterotrophic biofilm. A rapid adsorption of E. coli to the biofilm occurred during the first days after adding the cationic polymer, after which the adsorption slowed down.