A novel perfusion system for animal cell cultures by two step sequential sedimentation

A novel perfusion system was developed for high density culture of animal cells. The system consists of an airlift bioreactor, a setting tank and a flat settler. Both the settling tank and flat settler have two connecting pipes for transporting the cells from and back to the reactor, respectively. Thus, the cell flow in the settlers can be controlled in uni-direction, avoiding the countercurrent flow of the cells. During perfusion cultures, the cells firstly settled in the settling tank, then, unsettled cells in the tank were transferred to the flat settler for re-settling. With the application of the system to hybridoma cell cultures, it was found that the maximum viable cell density, monoclonal antibody concentration and average productivity were 1.31 x 107 cells ml-1, 400 mg l-1 and 461 mg l-1 d-1, respectively, which were much higher than those of a batch culture. Both theoretical analysis and experimental results showed a much higher separation efficiency in such a two-step sedimentation system than that in a conventional one-step sedimentation system. In addition, the volumetric ratio of the sedimentation devices to the culture volume in our developed system is much lower, which may be potentially useful on an industrial-scale.     

An innovative membrane bioreactor (MBR) system for simultaneous nitrogen and phosphorus removal

Membrane filtration was integrated with a post-denitrification process to form an innovative membrane bioreactor (MBR) system for effective organic degradation and nutrient (N and P) removal. The system comprised of an aerobic tank, an anoxic tank, an intermediate sedimentation tank, and a membrane filtration tank. The sedimentation tank functioned not only as a rough settler for sludge–water separation before membrane filtration but also as an anaerobic chamber for P release. While half of the influent flowed into the aerobic tank, the other half was fed into the anoxic tank to favor the proliferation of phosphorus accumulating organisms (PAOs). The experiment was conducted continuously for about 430 days. With a short overall treatment time of less than 10 h for municipal wastewater, the MBR-based process could achieve the total organic carbon, total nitrogen, and total phosphorus removals of around 94%, 85%, and 87%, respectively. The growth and activity of PAOs in the MBR system were evidenced by the significant P release in the anaerobic chamber followed by the luxury P uptake in the membrane tank. With the DAPI and PAO_mix probe staining, the increases of PAOs and polyhydroxybutyrate (PHB) in sludge during the experiment were well observed under the fluorescent microscope.     

The use of vertical flow constructed wetlands for on-site treatment of domestic wastewater: New Danish guidelines

Official guidelines for the on-site treatment of domestic sewage have recently been published by the Danish Ministry of Environment as a consequence of new treatment requirements for single houses and dwellings in rural areas. This paper summarises the guidelines for vertical constructed wetland systems (planted filter beds) that will fulfil demands of 95% removal of BOD and 90% nitrification. The system can be extended with chemical precipitation of phosphorus with aluminium polychloride in the sedimentation tank to meet requirements of 90% phosphorus removal. The necessary surface area of the filter bed is 3.2 m²/person equivalent and the effective filter depth is 1.0 m. The filter medium must be filtersand with a d₁₀ between 0.25 and 1.2 mm, a d₆₀ between 1 and 4 mm, and a uniformity coefficient (U = d₆₀/d₁₀) less than 3.5. The sewage is, after sedimentation, pulse-loaded onto the surface of the bed using pumping and a network of distribution pipes. The drainage layer in the bottom of the bed is passively aerated through vertical pipes extending into the atmosphere in order to improve oxygen transfer to the bed medium. Half of the nitrified effluent from the filter is recirculated to the first chamber of the sedimentation tank or to the pumping well in order to enhance denitrification and to stabilise the treatment performance of the system. A phosphorus removal system is installed in the sedimentation tank using a small dosing pump. The mixing of chemicals is obtained by a simple airlift pump, which also circulates water in the sedimentation tank. The vertical flow constructed wetland system is an attractive alternative to the common practice of soil infiltration and provides efficient treatment of sewage for discharge into the aquatic environment.     

Modeling of recycling oxic and anoxic treatment system for swine wastewater using neural networks

A recycling reactor system operated under sequential anoxic and oxic conditions for the treatment of swine wastewater has been developed, in which piggery slurry is fermentatively and aerobically treated and then part of the effluent is recycled to the pigsty. This system significantly removes offensive smells (at both the pigsty and the treatment plant), BOD and others, and may be cost effective for small-scale farms. The most dominant heterotrophic were, in order,Alcaligenes faecalis, Brevundimonas diminuta andStreptococcus sp., while lactic acid bacteria were dominantly observed in the anoxic tank. We propose a novel monitoring system for a recycling piggery slurry treatment system through the use of neural networks. In this study, we tried to model the treatment process for each tank in the system (influent, fermentation, aeration, first sedimentation and fourth sedimentation tanks) based upon the population densities of the heterotrophic and lactic acid bacteria. Principal component analysis (PCA) was first applied to identify a relationship between input and output. The input would be microbial densities and the treatment parameters, such as population densities of heterotrophic and lactic acid bacteria, suspended solids (SS), COD, NH₄ ⁺-N, or-tho-phosphorus (o-P), and total-phosphorus (T-P). Then multi-layer neural networks were employed to model the treatment process for each tank. PCA filtration of the input data as microbial densities was found to facilitate the modeling procedure for the system monitoring even with a relatively lower number of input. Neural networks independently trained for each treatment tank and their subsequent combined data analysis allowed a successful prediction of the treatment system for at least two days.     

Effect of sludge recycle on performance of a rotating biodisc contactor treating saline wastewater

A rotating biodisc contactor (RBC) was used for biological treatment of synthetic saline wastewater with and without sludge (cell) recycle. Synthetic wastewater composed of diluted molasses, urea, KH_zPO₄, MgSO₄ and 3% salt (NaCl) was fed to the RBC unit with different flow rates. Underflow from a sedimentation tank placed at the end of RBC unit was recycled to the RBC unit with a constant flow rate. COD removal rates and efficiencies were determined for the cases of with and without sludge recycle and compared. COD removal efficiencies and rates obtained with sludge recycle were higher than those obtained without sludge recycle at low A/Q ratios (high flow rate) because of extra residence time provided by sedimentation tank. However, no significant difference was observed in the performance of RBC with and without sludge recycle at high A/Q ratios (low flow rates). Because of poor sedimentation characteristics of the culture no significant increase in biomass concentration in the RBC was observed when the system was operated with sludge recycle.     

Performance evaluation and phylogenic analysis of a full-scale subsurface cobble-bed biofilm system

The purpose of this study is to evaluate the efficiency of municipal wastewater treatment by a subsurface cobble-bed biofilm system (SCBS) in Taipei, Taiwan. In contrast to traditional wastewater treatment facilities, SCBS uses cobbles as the contact media in the biofilm treatment unit. In this study, the SCBS consists of a series of underground treatment units, including a sedimentation tank, a grit chamber, two bar screens, a pumping station, a distribution tank, a collection tank and an effluent tank. At the flowrate of 4000 m³/day, the average influent concentrations for biochemical oxygen demand, suspended solid, ammonium nitrogen, and total phosphorus were 66.99 mg/L, 26.14 mg/L, 17.33 mg/L, and 1.96 mg/L, respectively. After 39 months of operation, the measured influent and effluent results show that the treatment efficiencies obtained from the SCBS for biochemical oxygen demand, suspended solid, ammonium nitrogen, and total phosphorus are 91.3%, 84.0%, 84.0%, and 26.0%, respectively. The result of a first-order kinetic analysis shows that the NH₃-N degradation constant is greater than the BOD degradation constant in this cobble-bed biofilm unit. Probability analysis revealed that the SCBS may be an attractive alternative from the perspectives of treatment efficiency for municipal wastewater treatment. Klebsiella spp. were found to be the predominant species in the biofilm system in the SCBS.     

自絮凝颗粒酵母乙醇连续发酵耦合酵母回用工艺的研究

模拟现有酒精发酵行业普遍采用的多级发酵罐串联系统,建立了一套由三级串联操作的搅拌式发酵罐和两个沉降罐组成的反应器系统,以脱胚脱皮玉米粉双酶法制备的糖化液为发酵底物,培养基初始还原糖浓度为220g/L,添加(NH4)2HPO41.5g/L和KH2PO42.5g/L,以0.057h-1的恒定稀释速率流加,将自沉降浓缩后的酵母乳先后经活化和不活化两种方式处理并循环至第一级发酵罐,系统在两种操作条件下分别达到了拟稳态。实验结果表明活化处理对改善发酵工艺技术指标方面发挥了显著的作用,发酵终点乙醇浓度达到101g/L,还原糖和残总糖分别在3.2和7.7g/L左右,发酵系统的设备生产强度指标为5.77g/(L.h),与无酵母回用的搅拌式反应器系统中自絮凝颗粒酵母乙醇发酵工艺相比,提高了70%。     

Application of life cycle inventory analysis to fuel tank system design

Life Cycle Assessment is becoming an important tool for guiding environmental design improvements in the automotive industry. This paper reports the life cycle inventory profiles for two fuel tank systems based on a collaborative effort between the National Pollution Prevention Center at the University of Michigan, General Motors Research and Development, and the National Risk Management Research Laboratory of the U.S. Environmental Protection Agency. Two 31 gallon functionally equivalent fuel tank systems used on a 1996 light duty vehicle were investigated: a multi-layer HDPE tank with a steel shield and PVC coated steel straps, and a steel tank with a HDPE shield and painted steel straps. Overall, the HDPE fuel tank system is environmentally preferable to the steel tank system based on the set of inventory results presented in this investigation. The Life Cycle Inventory analysis indicated lower energy burdens for the HDPE tank system and comparable solid waste burdens for both systems. The total life cycle energy consumption for the steel and HDPE tank systems were 4.9 GJ and 3.6 GJ per tank, respectively. The energy consumption and most of the air pollutants inventoried occurred as a consequence of the use phase. The solid wastes were generated primatily during the material production phase for the steel tank (13 kg) and during the end-of-life management phase for the HDPE tank (14 kg). This study also highlights data analysis and modeling challenges, including manufacturing and use phase allocation methods.     

The “azotopure” process for treating nitrogen-deficient aqueous wastes

Many chemical and food processing wastes are deficient in nitrogen, and must therefore be supplemented with domestic sewage or ammonia to dispose of them by conventional biological treatment. A more economical treatment, especially of strong wastes, is possible by maintaining a semipure culture of nitrogen-fixing bacteria in a stirred aerated tank. When operated as a chemostat with 4 to 6 hr detention time, removal of 85% of the COD is possible in a single step without the need for clarifiers or digesters. A clarified effluent could also be produced by flotation or sedimentation of the flocculated bacteria. In that case there would be 99% removal of COD and a reduction in the amount of sludge by two-thirds over the conventional activated sludge process.     

Automatic gas tank switching system for CO2 incubators.

The use and construction of an automatic gas tank switching system are described. This device monitors the gas pressure in a CO2 incubator gas system and automatically switches to a reserve tank when the main supply tank is depleted. The unit contains an alarm system that signals either loss of power or gas pressure in the supply system.     

Upgrading of Existing Municipal Wastewater Treatment Plants with the “Non‐Conventional Low MLSS MBR Technology”

In the future, upgrading of existing wastewater treatment plants (wwtps) will be more important than the erection of entirely new plants, as most of the plants necessary in Germany already exist. Thus far, membrane bioreactor (MBR) technology is not used as an alternative for plant upgrading in Germany. However, at several locations the preconditions indicate that the application of the MBR technology for upgrading of plants may be favorable. These preconditions include the need for a substantial enlargement of the aeration tank volume and/or the need to improve the efficiency of the final sedimentation tanks, and also require that the existing tanks be in a good state, so that the tanks can be used in the future. The relevant preconditions and the basic upgrading concept using the MBR technology were presented earlier. Depending on the local preconditions regarding the existing tank volume, a specific aspect of this application can be an operation mode using “non‐conventional low MLSS (mixed liquor suspended solids) concentrations” (5 kg MLSS/m³ through 7 kg MLSS/m³) due to the amount of the existing tank volume. Two research projects were carried out covering the operation of five pilot plants on a cubic meter scale to demonstrate the feasibility of this kind of MBR process. This paper presents the core results of this research work.     

Continuous monitoring of erythrocyte sedimentation process: a new possible mechanism of erythrocyte sedimentation

An automated system is constructed to record the complete course of erythrocyte sedimentation process. In this system a light source and a paired photodetector are employed to monitor the change of light transmittance at the junction of plasma and the sedimenting red blood cell column, thus providing a continuous record of erythrocyte sedimentation as a function of time. Differentiation of this sedimentation--time curve yields a velocity--time curve of erythrocyte sedimentation. Frequently recorded "spikes" on top of the velocity--time curve imply the episodes of very rapid fall of erythrocytes in the sedimentation tube that cannot be explained by the currently accepted theory of erythrocyte sedimentation based mainly on Stokes' law, and a new mechanism of rouleau coalescing and fracturing is proposed to account for them.     

Convection-free boundary sedimentation of dilute protein solutions

Use of the density gradient sedimentation velocity technique appears to be essential for the accurate determination of the mean sedimentation coefficients of dilute protein solutions. When performed on an analytical ultracentrifuge equipped with a photoelectric-scanning-absorption optical system, the density gradient sedimentation velocity technique has been shown to be particularly useful in studying the subunit association-dissociation equilibria of multisubunit enzyme systems. The time factor has been shown to be a major advantage of the density gradient sedimentation velocity technique, as opposed to the sedimentation equilibrium technique, in studying the subunit association-dissociation equilibria of multisubunit enzymes such as rabbit muscle apo-glyceraldehyde-3-phosphate dehydrogenase, which is very unstable in dilute solution.     

Anomalous sedimentation behaviour of the e-coli ribosomal system: 50S-30S ⇄ 50S + 30S

An experimental and theoretical study has been made into the effect of association-dissociation reactions on the sedimentation of the E. coli ribosomal system 50S-30S ⇄ 50S + 30S. It has been found that(a) the sedimentation pattern is strongly dependent on the rotor speed;(b) the ratio of components as measured using high-speed ultracentrifugation (30000–40000 r.p.m.) is independent of rotor speed; and(c) the speed of ultracentrifugation has a strong effect on the sedimentation coefficient of the ribosomal system as determined by the mean square second moment.The results of this paper demonstrate that ribosome sedimentation at low-speed ultracentrifugation is affected by some artefactual processes. A theoretical analysis of the experimental findings has shown that the observed effects cannot be attributed to the effect of the association-dissociation reaction not to the pressure dependence of the equilibrium constant of that reaction.On the other hand, at high-speed ultracentrifugation the ribosomal system sediments as a heterogeneous mixture of non-interacting components. Consequently, the shape of the boundary in this case will reflect the equilibrium composition of the ribosomal system.     

供水系统摇蚊污染的微生物控制实验研究

为了研究微生物防治对水厂摇蚊污染的控制效果,测定了一种苏云金杆菌以色列亚种(Bacillus thuringiensis subsp.israelensis,Bti)制剂对摇蚊的LC50,并利用其对某水厂沉淀池孳生的摇蚊进行了现场控制试验。结果表明,Bti粉剂对摇蚊的LC50为0.318mg/L,使沉淀池中摇蚊幼虫在24h得到了有效控制,成虫在36h后得以完全控制。该制剂对摇蚊的控制时效达10周,且控制成本是采用液氯费用的1/3,采用微生物手段能使供水系统的摇蚊污染得到高效、经济的治理。     

Automatic gas tank switching system for CO2 incubators

Summary The use and construction of an automatic gas tank switching system are described. This device monitors the gas pressure in a CO₂ incubator gas system and automatically switches to a reserve tank when the main supply tank is depleted. The unit contains an alarm system that signals either a loss of power or of gas pressure in the supply system. This research was supported by National Cancer Institute Contract No 1-CP-33226, grants CA 13058 and CA 14680 and an institutional grant to the Michigan Cancer Foundation by the United Foundation of Greater Detroit.     

A detailed analysis of the mechanisms controlling the acceleration of 2,4-DCP monooxygenation in the two-tank suspended growth process

The mechanisms underlying the observed acceleration of monooxygenationreactions in two-tank accelerator/aerator suspended growth system are evaluatedin detail. The accelerator tank is characterized by a very high electron flow throughreduced nicotinamide adenine dinucleotide (NADH + H⁺), particularly when the retention-time ratio is small. Only a small fraction of the electron flow wasdiverted to oxygenation reactions, and the major sinks of NADH + H⁺ were respiration and biomass synthesis. The main producer of NADH + H⁺ is oxidation of acetate, a rapidly degraded electron-donor substrate. The half-maximum-rate concentration for oxygen used in respiration was 0.03 mg/L, while the half-maximum-rate concentration for oxygen used as a cosubstrate in monooxygenation was 0.18 mg/L. Thus, monooxygenations were more sensitive to oxygen limitation than was respiration. The NADH + H⁺ concentration had a direct effect on the monooxygenation kinetics. Therate coefficients for both monooxygenation reactions were directly proportional to thespecific growth rate in the accelerator, which supports that the accelerator tank causedan up-regulation of the monooxygenase content. Because the rate coefficients in theaerator tank were much larger than in the one-tank system, even though the specificgrowth rates were nearly the same, monooxygenases may have carried over from theaccelerator tank to the aerator tank. Its higher concentration of 2,4-dichlorophenol(2,4-DCP) and the higher specific growth rate were the main reasons why the accelerator had faster kinetics for 2,4-DCP utilization than did the aerator tank. The apparently higher levels of monooxygenase in both tanks of the two-tank system also appears be a primary reason why its performance was substantially superior to that of the one-tank system in terms of 2,4-DCP removal.     

Seasonal sedimentation trends in a mesotrophic lake: Influence of diatoms and implications for phosphorus dynamics

To quantify the extent to which biomass and phosphorus in particular is removed from an aquatic system via sedimentation as well as to identify factors that influence sedimentation of nutrient elements, various characterizations of suspended and settling particulate matter were made in Trout Lake, Wisconsin, USA. The proportion of water column phosphorus reaching sediment traps showed a seasonal component with a minimum during late summer. Biogenic silicon analysis indicated that relatively high rates of phosphorus removal were associated with the sedimentation of siliceous algae (diatoms) from the water column. Estimates of the impact of nutrient removal through diatom sedimentation indicate that this process can reduce primary production by decreasing the amount of nutrient remineralization in the water column during the stratified period.     

Management of sedimentation in centrifugal counter-current distribution of sperm cells in an aqueous 2-phase system.

It is generally assumed that centrifugal counter-current distribution (CCCD) in aqueous two-phase systems cannot be employed for analyzing or fractioning cell populations, due to large particles of sediment in the system caused by enhanced gravity. The present work was undertaken to find out whether addition of Percoll to a two-phase system would be a useful method to avoid this cell sedimentation. The results obtained show that bull spermatozoa partition as a unique peak in a CCCD using a Dextran T500-poly(ethylene glycol) 6000 system, and that sedimentation takes place significantly in the upper phase during the process. Addition of increasing concentrations of Percoll made this unique peak wider and two different populations of bull spermatozoa were finally obtained when Percoll concentration rose to 13.6%. This management of cell sedimentation in CCCD could be of great interest for analyzing cell heterogeneity, since the shortening of the time required for counter-current distribution should prevent the loss of cell viability during the separation process. Finally, the results obtained suggest that an increase of viscosity rather than of density is the phase feature which has greater influence on managing cell sedimentation in CCCD.     

猪场污水的A2/O-深度处理和中水回用

猪场污水采用A²/O-生物接触氧化-混凝沉淀-砂滤消毒组合方法处理,可以实行中水回用。原污水经过固液分离、调解池、竖流式初沉池、厌氧消化池、缺氧池、传统活性污泥曝气池、竖流式二沉池、接触氧化池、药剂混合池、斜板沉淀池、砂滤池、pH调解和消毒池处理后进入排放池,系统正常运行后处理废水可以达到GB8978-1996中规定的二级以上标准,处理水没有检测到病原微生物。中水引入中水塔,通过独立设计的中水道,可以应用到猪舍冲栏使用。而污泥通过污泥干化场得到干化。