Microbial kinetic analysis of three different types of EBNR process

The disadvantages of developed biological nutrient removal (BNR) processes (additional energy for liquid circulation and addition of external carbon substrate for denitrification in anoxic zones) were improved by reconfiguring the process into (1) an anaerobic zone followed by multiple stages of aerobic-anoxic zones (TNCU3 process) or (2) anaerobic, oxic, anoxic, oxic zones in sequence (TNCU2 process). These two pilot plants were operated at a recycling sludge ratio of 0.5 without internal recycle of nitrified supernatant. The sludge retention time was maintained at 10 d. The main objective of this study is to analyze the kinetics of different microorganisms in these two processes and A2O process by using the Activated Sludge Model No. 2d. The effective removal efficiency of carbon, total phosphorus and total nitrogen at 87-98%, 92-100% and 63-80%, respectively, were achieved in the testing runs. According to model simulations, the microbial kinetics in the TNCU3 and TNCU2 processes would be affected by different operations. When the step feeding strategy was adopted, the HRT was longer due to the less influent flowrate in the front stages and the microbes would grow in quantities by about 6% in the aerobic reactors. In the followed anoxic reactors, the microbes would decrease in quantities by about 12% due to the dilution effect. The dilution effects in TNCU3 and TNCU2 processes did not take place in A2O process because the recycling mixed liquid from the aerobic reactor to the anoxic reactor still contained particulate components. The XH, XPAO, and XAUT concentrations in the effluent of the last tank were lower when the step-feeding mode was adopted. The TNCU3 and TNCU2 processes could be operated efficiently without nitrified liquid circulation and addition of external carbon substrate for denitrification.     

臭氧-曝气生物滤池处理酸性玫瑰红染料废水

在实验室配制含酸性玫瑰红染料的印染废水,采用臭氧氧化-曝气生物滤池工艺开展处理试验.试验运行结果表明,臭氧氧化处理能提高模拟废水的可生化性,BOD/COD值由原水的0.18上升到0.36.经组合工艺处理后出水COD＜40 mg/L,色度40倍以下,SS约50 mg/L,处理效果良好.     

絮凝体分形维数投药控制研究

依据分形理论，通过先进的图像分析处理技术，实现了对絮凝体分形维数的联机在线监测，试验证实分形维数可以很好地反映絮凝程度及其混凝处理效果，通过建立的混凝剂投加量、分形维数及沉后水浊度三者间的模糊控制模型，最终实现了对混凝剂投加量的自动控制与调节。     

Adsorption and desorption characteristics of semiconductor volatile organic compounds on the thermal swing honeycomb zeolite concentrator

The use of a honeycomb zeolite concentrator and an oxidation process is one of the most popular methods demonstrated to control volatile organic compound (VOCs) emissions from waste gases in semiconductor manufacturing plants. This study attempts to characterize the performance of a concentrator in terms of the removal efficiencies of semiconductor VOCs (isopropyl alcohol [IPA], acetone, propylene glycol methyl ether [PGME], and propylene glycol monomethyl ether acetate [PGMEA]) under several parameters that govern the actual operations. Experimental results indicated that at inlet temperatures of under 40 degrees C and a relative humidity of under 80%, the removal efficiency of a zeolite concentrator can be maintained well over 90%. The optimal rotation speed of the concentrator is between 3 and 4.5 rph in this study. The optimal rotation speed increases with the VOCs inlet concentration. Furthermore, reducing the concentration ratio helps to increase the removal efficiency, but it also increases the incineration cost. With reference to competitive adsorption, PGMEA and PGME are more easily adsorbed on a zeolite concentrator than are IPA and acetone because of their high boiling points and molecular weights.     

Assessment of sorbent/water ratio effect on adsorption using dimensional analysis and batch experiments

Many factors affect adsorption phenomena in solid-liquid systems. One of the most important factors is the sorbent/water (S/W) ratio in the system. However, the effect of varying S/W ratios on the adsorption is still unclear. In this study, batch experiments were examined to observe the adsorption of four contaminants (copper, cadmium, Butachlor, and Deltamethrin) in six soils with texture ranging from silty clay to loamy sand and with different S/W ratios. Dimensional analysis was used to assess the relationship between adsorption phenomena and S/W ratio. We have assumed that the total amount of sorbate sorbed in soil is a function of the equilibrium concentration, the volume of sorbate solution, and the sorbent amount in the system. A power function (Freundlich-like) model was obtained from the dimensional analysis. It can describe precisely the adsorption phenomena of different sorbents and sorbates in the moisture regime of paddy soils. Therefore, proper adsorption parameters can be obtained by this power function model regardless of the solids effect, which can then be utilized to describe the fate of solute in soil using solute transport models.     

A reevaluation of carbon monoxide: past trends,future concentrations,and implications for conformity "hot-spot" policies

Control of CO is one of the great air-quality management success stories of the past 20 years. This paper evaluates whether past progress will continue into the future and whether changes in microscale CO concentrations are comparable to reductions observed at the regional scale. Neighborhood and microscale CO concentrations were evaluated at six northern and southern California monitoring sites. The study also included a review of CO emission, concentration, and exposure trends and on-road motor vehicle-based CO emission control programs for California and the United States. Consistent with California and national trends, CO concentrations declined at each of the six study locations from 1988 through 1998. Microscale concentrations declined at the same rate as did neighborhood-scale concentrations. Rollback analyses demonstrated that microscale concentrations will continue to decline through at least 2010-2020. Within a few years, microscale violations of the CO National Ambient Air Quality Standards (NAAQS) will be unlikely in California except under extraordinary circumstances.     

The study of fine and coarse particles, and metallic elements for the daytime and night-time in a suburban area of central Taiwan, Taichung

Daily average concentrations of fine and coarse particulates, and TSP samples have been measured simultaneously at daytime and night-time periods by using Universal and PS-1 sampler in a suburban area of central Taiwan from June to August 1998. The samples were analyzed by atomic absorption spectrometry to determine the fine and coarse particulate concentrations of metallic elements (Ca, Fe, Mn, Pb, Cu, Zn and Cr). The concentration of PM2.5 and TSP showed a decreased trend for the daytime period. The fine particle concentrations were about two times as that of coarse particulate concentrations. The averaged fine particulate concentrations at daytime are higher than at night-time. Ca and Fe were mostly in the coarse particulate mode. The correlation coefficients were 0.63 and 0.69 for elements Ca and Fe in the coarse particle mode for day and night periods. Pb showed a similar distribution ratio with Mn for the fine to coarse particle ratios at both day and night period. Pb and Mn are highly correlated for the day (R = 0.78) and night period (R = 0.61) at particle size <2.5 microm. Cu and Zn were mainly in fine particles at both day and night period. Fe and Ca consist of the major parts of all the elements. Elemental Mn is the lowest among the rest of the heavy metals.     

Assessing ozone-precursor relationships based on a smog production model and ambient data

A semi-empirical model, Johnson's smog production model (SPM), which relates precursor emissions to ozone levels and estimates the relative effectiveness of volatile organic compounds (VOC) and NOx emission controls, has been evaluated and a modified version of SPM has been introduced. Both versions have been applied to routine data from 1989-1991 in five areas in the United States. In particular, extent parameters, which reveal the relative merit of VOC and NOx controls in reducing high ozone levels, have been calculated. Preliminary applications of SPM reveal interesting features with respect to VOC vs. NOx controls in reducing high ozone levels. For hourly data with ozone > or =0.08 ppm, distributions of extent parameters resulting from the modified SPM show the effectiveness of VOC controls at more monitoring sites than those from Johnson's SPM; however, relative features between the two versions are similar. On the other hand, for hourly data with ozone > or =0.12 ppm, the two SPM versions show very similar relative effectiveness of VOC and NOx controls with chosen values of model parameters. To improve the credibility of SPM, the range of validity of relationships between maximum smog produced or maximum ozone and NOx concentrations must be determined, and the parameters in these relationships must be better determined for typical VOC mixtures. Another essential parameter, which determines the fractional loss of NOy (NO and its oxidation products) from the gas phase must be better determined.     

Compatibility analysis of material and energy recovery in a regional solid waste management system

The rising prices of raw materials and concerns about energy conservation have resulted in an increasing interest in the simultaneous recovery of materials and energy from waste streams. Compatibility exists for several economic, environmental, and managerial reasons. Installing an on-site or off-site presorting facility before an incinerator could be a feasible alternative to achieve both goals if household recycling programs cannot succeed in local communities. However, the regional impacts of presorting solid waste on a waste-to-energy facility remain unclear because of the inherent complexity of solid waste compositions and properties over different areas. This paper applies a system-based approach to assess the impact of installing a refuse-derived fuel (RDF) process before an incinerator. Such an RDF process, consisting of standard unit operations of shredding, magnetic separation, trommel screening, and air classification, might be useful for integrating the recycling and presorting efforts for a large-scale municipal incinerator from a regional sense. An optimization modeling analysis is performed to characterize such integration potential so that the optimal size of the RDF process and associated shipping patterns for flow control can be foreseen. It aims at exploring how the waste inflows with different rates of generation, physical and chemical compositions, and heating values collected from differing administrative districts can be processed by either a centralized presorting facility or an incinerator to meet both the energy recovery and throughput requirements. A case study conducted in Taipei County, which is one of the most densely populated metropolitan areas in Taiwan, further confirms the application potential of such a cost-benefit analysis.     

Pore structure effects on Ca-based sorbent sulfation capacity at medium temperatures: activated carbon as sorbent/catalyst support

The reaction between three different Ca-based sorbents and SO2 were studied in a medium temperature range (473-773 K). The largest SO2 capture was found with Ca(OH)2 at 773 K, 126.31 mg SO2 x g Ca(OH)2(-1), and the influence of SO2 concentration on the sorbent utilization was observed. Investigations of the internal porous structure of Ca-based sorbents showed that the initial reaction rate was controlled by the surface area, and once the sulfated products were produced, pore structure dominated. To increase the surface area of Ca-based sorbents available to interact with and retain SO2, one kind of CaO/ activated carbon (AC) sorbent/catalyst was prepared to study the effect of AC on the dispersion of Ca-based materials. The results indicated that the Ca-based material dispersed on high-surface-area AC had more capacities for SO2 than unsupported Ca-based sorbents. The initial reaction rates of the reaction between SO2 and Ca-based sorbents and the prepared CaO/AC sorbents/catalysts were measured. Results showed that the reaction rate apparently increased with the presence of AC. It was concluded that CaO/AC was the active material in the desulfurization reaction. AC acting as the support can play a role to supply O2 to increase the affinity to SO2. Moreover, when AC is acting as a support, the surface oxygen functional group formed on the surface of AC can serve as a new site for SO2 adsorption.