Seasonal changes of coliphages, an auxiliary indicator of fecal coliforms for indexing enteric viral pollution, in septic tank sludge and night soil sludge were investigated. Relatively abundant coliphages, 1 × 102−1 × 104 [PFU/ml], were detected in the night soil sludge. Most of the phages, 0−1 × 103 [PFU/ml], found in the septic tank sludge were adsorbed on suspended solids. On the other hand, phages in the night soil sludge were found both suspending in the liquid medium and attaching on the solid matter. Aerobic treatment of this sludge reduced concentration of suspending phages, indicated this treatment might effective to reduce pathogenic viruses, too. On the other hand, aerobic conservation at 4°C did not reduce phage concentration. To investigate the factors influencing transduction frequency, P1 phage mediated tetracycline resistance marker DNA transfer was analyzed as a model system. The frequency increased according to the increase of multiplicity of infection (MOI) and reached maximum at MOI = 1.6, then started to decrease. Multiple infection of the phages on the single cell decreased viability of the host cell, followed by the decrease of transduction frequency. Mathematical model based on the kinetics of phage-host cell interaction was developed to predict transduction frequency.
Total organic carbon (TOC) removals of the synthetic wastewater and of the raw industrial wastewater discharged from LSI photo-resist processing of which main component is 1,2-naphthoquinone-2-diazido-5-sulfonic acid sodium salt (abbreviation naphthoquinone-5), have been carried out by using hydrogen peroxide and ultraviolet irradiation (H2O2/UV). Experiments were carried out in a batch reactor with a low pressure UV lamp (500 W) irradiating ultraviolet of 254 nm and of 185 nm (5% of energy). The following results were obtained. (1) TOC removals of the synthetic wastewater and of the raw industrial wastewater are pseudo-first-order processes, and TOC shows zero in about ten and several hours. (2) The TOC removal rate of the wastewater was governed by the concentration of hydrogen peroxide initially added and by the maximum pseudo-first-order rate constant and the optimum initial hydrogen peroxide concentration both existed in the synthetic wastewater and in the raw industrial wastewater. (3) The relation between the initial TOC concentration and the optimum initial hydrogen peroxide concentration exhibited linear both in the synthetic wastewater and in the raw industrial wastewater. The optimum initial hydrogen peroxide concentration in TOC removal of the raw industrial wastewater is same as that in the synthetic wastewater at the given initial TOC concentration. (4) The maximum pseudofirst-order rate constant increases with the decrease in the initial TOC concentration both in the synthetic wastewater and in the raw industrial wastewater. (5) A theoretical consideration was carried out and could explain with experimental results.
A waste recycling technique using sub- and supercritical water was developed for obtaining useful materials from marine wastes. As a preliminary work, the effect of reaction parameters was investigated using various types of reactors and samples. In order to obtain amino acids effectively, two main reactions (i.e. hydrolysis of proteins to amino acids and decomposition of amino acids) should be considered. The highest amount of amino acids was obtained at 523 K in reaction time of 60 min. The reaction temperature of 523 K was in agreement with the temperature indicating the maximum ion product of water at saturated vapor pressure. At 573 K, the amount of amino acids produced was low since amino acid decomposition rate was higher compared to production of amino acids from protein hydrolysis. Proper control of reaction parameters is necessary in order to obtain high yield of amino acids efficiently. The technique could be useful in establishing a material recycling system across various industries and production processes, with the goal to curtail waste emissions into the environment.
Metallic iron was selected as a new reductant for chemical reductive removal of nitrate from water in this study. The effect of pH on the reduction rate and products of nitrate was investigated with a fixed dosage of iron powder (size: 80 mesh) of 12 mol-Fe·mol-N-1 under acidic (pH = 2-5) and aerobic conditions. The reduction of nitrate by metallic iron was a pseudo-first order reaction under our experimental conditions. The reduction rate of nitrate was increased with decreasing pH of the reaction solution, and the pseudo-first order reaction rate constants were 0.49, 0.40, 0.05 and 0.01 h-1 at pH = 2, 3, 4 and 5, respectively. The reduction products of nitrate were ammonia and nitrogen gas, and their yields were strongly affected by pH. The yields of nitrogen gas were 30, 31 and 45% at pH = 3, 4 and 5, respectively, but no formation of nitrogen was found at pH = 2. It was also demonstrated that the indirect reduction of nitrate by hydrogen generated from the reaction between proton and metallic iron may be a major mechanism for the reduction of nitrate under the experimental conditions.
The sulfur capacity of metallurgical dusts from blast furnace ironmaking processes was measured in the temperature range from 298 to 923 K. The experimental results show that the sulfur capacity of metallurgical dusts is considerably increased with the increase of temperature from 298 to 923 K. The desulfurization ability of metallurgical dusts is mainly depend on its content of oxides of ZnO, PbO, CaO and MnO when the temperature is lower than 623 K, but when the temperature is higher than 623 K the contributions of iron oxides become dominant. Carbon content, due to its absorption effect, has a positive effect on the desulfurization ability of metallurgical dusts below 623 K. If the temperature increased to higher than 623 K the absorption effect of carbon disappears and the role of desulfurization reaction between H2S and the metal oxide such as ZnO, PbO, Fe2O3, CaO and MnO as well as the H2S diffusion in intraparticle of metallurgical dusts seems more important.
Based on the data SO2 emission, urban air quality, and acid precipitation, the status and characteristics of acid rain and SO2 pollution in China were analyzed. To prevent the further deterioration of acid rain and SO2 pollution effectively, the Acid Rain Control Zones and SO2 Pollution Control Zones (Two Control Zones called for short) were designated. The range of Two Control Zones was 1.09 × 106 km2, 11.4% of the whole territory of China, with SO2 emissions of 14 million tons in 1995. The Acid Rain Control Zone involves 14 provinces, autonomous regions or municipalities, with total area of 0.806 × 106 km2. The SO2 Pollution Control Zone includes 63 cities with total area of 0.29 × 106 km2. The control policies to be implemented in the Two Control Zones were formulated by the method of life cycle analysis on sulfur-in-coal. The impacts of the policy implementation on energy industry, including coal industry and power industry, were calculated and analyzed. It was proved that the policy implementation would improve the thermal power mix and promote the sustainable development of energy industry. The paper also analyzed the decrease of SO2 emission and the improvement of air quality in the cities in recent years, which were achieved by the control efforts.
A mathematics model is proposal for simulating desulfurization process in a CaO activation reactor of a limestone injection FGD system. The effective factors, including particle motion, water evaporation, particle impact, and aqueous sorbent reaction, have been considered in this model. By use of calculating results and experimental results from a 3000 N·m3/h pilot plant experimental system of CaO activation reactor, the effect of flue gas temperature, particle size, water injection and Ca/S molar ratio on desulfurization efficiency is investigated in detail. It is found that desulfurization efficiency rises with the increase of Ca/S molar ratio, the amount of water injection and the decrease of particle size, flue gas temperature. A method to improve desulfurization efficiency in the CaO activation reactor is also given in this paper. The above results are a help for semi-dry FGD system design.
Toluene-degrading bacteria were isolated from the trickle bed air biofilter (TBAB), which had eliminated toluene efficiently for three months. Among the isolates, Acinetobacter genospecies Tol 5 demonstrated the highest efficiency in toluene removal. A. genospecies Tol 5 tended to adhere to hydrophobic materials showing water-repellent. When the bacterium was grown on toluene in the presence of polyurethane foam, almost all the cells adhered to the polymer support until the amount of 0.12 kg-cell/kg-polyurethane. Analyses of cell surface hydrophobicity by the microbial-adhesion-to-hydrocarbons test and contact angle measurements revealed that A. genospecies Tol 5 has a noteworthily hydrophobic cell surface compared with Escherichia coli. A TBAB inoculated with A. genospecies Tol 5 showed a sufficiently high ability in toluene elimination within 24 h after starting the operation without preliminary operation for immobilization, suggesting that this strain was effective to shorten the adaptation period, which had been considerably long on the TBAB inoculated with the original activated sludge.
Colloidal gas aphrons (CGAs) were first proposed by Sebba (1971) as micro bubles (10-100 μm), composed of a gaseous inner core surrounded by a thin surfactant film. CGAs are created by intense stirring (usually over 5000 r·min-1) of a surfactant solution. Flotation of Cu(II) by colloidal gas aphrons has been conducted in order to explore a new method for separating heavy metal ions from dilute solution. The effects of CGA flow rate, amounts of CGA introduced to the system, surfactant concentration on the flotation efficiency have been investigated. The results show that the flotation efficiency at pH = 5-6 has an optimum value to CGA flow rate and amount. When pH is greater than 7, the flotation efficiency can be as high as 99% at the optimum condition.
It is easy to remove bubbles from a liquid phase using their buoyancy under the gravitational field on the ground. However, bubble removal from the liquid phase is difficult under microgravity. In this study, bubble breakage on an air-water interface by centrifugal force was experimentally investigated under microgravity for the design of a space station bioreactor. Under our experimental conditions, the mean bubble breakage time of the air-water system at 1G was 0.16 s, with a standard deviation of 0.023 s. The bubble breakage time at the air-water interface in a centrifugal force field under microgravity ranged from 0.27 to 1.27 s. Under our experimental conditions, bubble frequency had no effect on the bubble breakage time at 0.047G. The mean bubble breakage time under microgravity increased with decreasing centrifugal acceleration. Although the bubble breakage time at the air-water interface under microgravity is longer than at 1G, the bubbles at the air-water interface were often broken by centrifugal force.
The primary purpose of this work is to construct a new method how to define the turbulent flow structures effective for heat transfer augmentation. The flow field consists of a submerged liquid jet issuing from a convergent slot nozzle and a circular cylinder for heat transfer placed perpendicular to and on the jet centerline. Two small cylinders were inserted into the jet stream to examine the effectiveness of heat transfer augmentation. Time-series data of the jet centerline velocities were analyzed by a wavelet transformation. The information entropy and expectation can successfully extract the intermittent turbulent structures effective for the impingement heat transfer augmentation from the developing jet structures.
A multi-effect batch distillation system, MEBAD, which separates multiple components simultaneously, has higher energy effeciency compared with an ordinary batch distillation column. In this paper, in order to make the characteristics of the MEBAD clearer, the energy consumption of the MEBAD is compared with that of a conventional continuous distillation system for various feed conditions. Results of the exhaustive simulations show that the MEBAD has the potential for having a higher energy efficiency than a continuous system when the number of components is increased or relative volatilities among the components are decreased. Furthermore, it is shown that there is little relationship between the number of column stages and the energy consumption at the reboiler of the MEBAD while the number of stages strongly affects the energy consumption of the continuous system. The reason why the number of stages does not affect the energy consumption of the MEBAD is explained from the relationship between the operating line and the VLE curve.
Evaluating a chemical process commonly has several criteria consisting of not only the economic aspects but also social and technical ones; hence multi-dimensional evaluation becomes an important problem. Usually the different criteria, each has a distinct scale, which can hardly be unified to single one. Moreover, the frequently emerging unquantifiable parameters will make the problem more complex. Fuzzy mathematic methods have been put into use to deal with such difficulties. In order to overcome the shortcoming lying in current methods, based on the fuzzy reasoning, a multi-level evaluation approach using if-then rules is proposed in this paper. It decomposes a multi-dimensional evaluation problem to several problems belonging to different levels with fewer dimensions. The appropriate steps to establish the rule sets in different levels are provided, and a Mass Exchange Networks and a wastewater treatment plant are evaluated by using the proposed method. Satisfactory and reliable results in case studies prove the effectiveness and the efficiency of this method.
Based on pinch analysis, the regeneration process in the carbon dioxide removing system of a fertilizer plant is suitable to use thermal vapor recompression heat pump. To obtain economically optimal conditions, calculation and analysis have been done for the energy saving cost and economical benefit of each design with varying temperature drop of the potassium carbonate solutions. Moreover, the feasible energy saving design and the type of the equipment are chosen according to the practical situation of the plant.
In order to save energy and protect the environment, a high efficiency gas turbine cogeneration system has been proposed. The new technologies of two-stage combustion and steam addition are combined into this proposed system. Natural gas is used as a fuel. In this system, a key technology is to add a large quantity of steam to a gas turbine system that has two-stage combustor on the premise of flammable. It is thermodynamically proved that the turbine output is improved by steam addition. However, there is a risk to quench flame in the second stage combustion under the conditions of the low oxygen and high steam concentration.For application of this system, we have examined the combustion characteristics and NOx formation of two-stage combustion by means of experiments and numerical simulations using detailed chemical kinetics. The results provide data useful for establishing the optimal combusion conditions in this gas turbine cogeneration system.
Reactive distillation was researched for the synthesis of ethyl tert-butyl ether from ethanol and tert-butyl alcohol. A dynamic mathematical model for this process was developed. The model incorporated reaction kinetics, vapor-liquid non-idealities and the distillation process. The rapid solution for this model can be obtained by overrelexation method. Simulation results are in good agreements with the literature results.
Three kinds of temperature-sensitive gels are synthesized from a photo-crosslinkable prepolymer, ENTP-4000 or ENT-3400, and a functional monomer, and their potentiality as an adsorbent for temperature-swing adsorption is investigated. The ENT-type hydrophilic gels show reversible swelling-shrinking behavior in response to thermal stimulus, while the ENTP-type hydrophobic gel shows no volume change. The adsorbed amount of nonionic surfactant Triton X-102 on the ENTP-type gel drastically increased with shifting temperature from 283 to 293 K. Considerable change in the adsorbed amount of the surfactant on the ENT-type gels is also observed. These results confirm the high potentiality of the photo-crosslinked gels as an adsorbent for temperature-swing adsorption process.
Composite particles composed of solid powders and a polymer were prepared by semi-chemical recycle of wasted plastics. Wasted expanded polystyrene was used as a raw material. Also, both of magnetite and silicon carbide powders were used as solid powders. In the experiment, the oil phase dissolving expanded polystyrene was dispersed as much fine droplets in the continuous water phase. Two kinds of powders were added at the same time or separately in the O/W dispersion. The mean diameter of composite particles was strongly affected by the addition time when silicon carbide powder was added into the dispersion. Composite particles were found to have the structure that a polymer particle was covered with solid powders. Furthermore, it was found that the gradient adhesion layer due to two solid powders was able to be formed on the surface of a polymer particle.
Biodegradable microcapsules entrapping water soluble materials such as potassium nitrate, bovine serum albumin, and egg yolk proteins are prepared by the solvent evaporation method in a (W/O/W) complex emulsion system. Effects of preparation conditions of a (W/O/W) emulsion on the capsule morpholoy and the entrapment efficiency of the core materials are investigated. The entrapment efficiency of the core material is improved by decreasing in the volume fraction and the concentration of salt in the inner aqueous phase, by the irradiation of ultrasonic wave to (W/O) emulsion, and by increasing in the concentration of salt in the outer aqueous phase. The entrapment efficiency decreases by releasing of the core material in the course of wall formation of the microcapsules.
The biodegradable plastic poly-β-hydroxybutyrate (PHB) was synthesized by a unicellular cyanobacterium, Synechocystis sp. PCC6803. The cell growth and PHB accumulation were inspected comprehensively. Nitrogen starvation was favorable for cyanobacterial PHB accumulation, while the final biomass of nitrogen-starved culture decreased to one-third of that in nitrogen-sufficient condition. A two-step culture, a balanced mixotrophic culture followed by a nitrogen-starved culture, was developed to improve the cyanobacterial PHB production efficiency. To adapt the large-scale outdoor culture that has the natural light/dark cycle, modification to the culture method was put forward based on the studies on the heterotrophic culture.