部分负荷工况下多台冷水机组的冷量分配

以两台相同冷量冷水机组并联运行的空调系统为例分析了部分负荷工况下机组的性能,指出如果不对机组的冷水出水温度进行重设,系统冷量只能是平均分配,而无法实现主从控制.     

Characterisation and application of a novel positively charged nanofiltration membrane for the treatment of textile industry wastewaters

The present study demonstrates the high potential for the application of a novel self assembled positively charged nanofiltration membrane, PA6DT-C, in processes such as the recovery of valuable cationic macromolecules in the bioprocess and pharmaceutical industries or removal of multi-valent cations such as dyes and heavy metals in the paper and pulp, textiles, nuclear, and automotive industries. The nanofiltration membrane, prepared in this laboratory, is further characterised and then tested for the removal and recovery of Methylene Blue from a synthetic dye house wastewater. The characterisation process involved the construction of a rejection profile for NaCl over a wide range of pH and concentration, which illustrates that the optimal process conditions for the removal of small cations using this membrane is in the region pH <8.0 and concentration less than 15 mol m⁻³. The salt rejection data was used to calculate the magnitude of the effective membrane charge density and this was found to be significantly higher for the PA6DT-C membrane than two commercially available membranes (Desal-DK and Nanomax-50). The membrane flux for this new membrane is also superior to the commercial membranes with an approximate increase of 3-4 fold. The PA6DT-C membrane was successful in removal of Methylene Blue dye from synthetic dye house wastewaters achieving 98% rejection and a membrane flux of ∼17 LMH bar⁻¹. Thus, this new membrane both adds to and complements the existing short supply of positively charged NF membranes.     

Microbial community structure and dynamics in a pilot-scale submerged membrane bioreactor aerobically treating domestic wastewater under real operation conditions

A pilot scale submerged ultra-filtration membrane bioreactor (MBR) was used for the aerobic treatment of domestic wastewater over 9 months of year 2006 (28th March to 21st December). The MBR was installed at a municipal wastewater facility (EMASAGRA, Granada, Spain) and was fed with real wastewater. The experimental work was divided in 4 stages run under different sets of operation conditions. Operation parameters (total and volatile suspended solids, dissolved oxygen concentration) and environmental variables (temperature, pH, COD and BOD₅ of influent water) were daily monitored. In all the experiments conducted, the MBR generated an effluent of optimal quality complying with the requirements of the European Law (91/271/CEE 1991). A cultivation-independent approach (polymerase chain reaction-temperature gradient gel electrophoresis, PCR-TGGE) was used to analyze changes in the structure of the bacterial communities in the sludge. Cluster analysis of TGGE profiles demonstrated significant differences in community structure related to variations of the operation parameters and environmental factors. Canonical correspondence analysis (CCA) suggested that temperature, hydraulic retention time and concentration of volatile suspended solids were the factors mostly influencing community structure. 23 prominent TGGE bands were successfully reamplified and sequenced, allowing gaining insight into the identities of predominantly present bacterial populations in the sludge. Retrieved partial 16S-rRNA gene sequences were mostly related to the α-Proteobacteria, β-Proteobacteria and γ-Proteobacteria classes. The community established in the MBR in each of the four stages of operation significantly differed in species composition and the sludge generated displayed dissimilar rates of mineralization, but these differences did not influence the performance of the bioreactor (quality of the permeate). These data indicate that the flexibility of the bacterial community in the sludge and its ability to get adapted to environmental changes play an important role for the stable performance of MBRs.     

The potential of wastewater heat and exergy: Decentralized high-temperature recovery with a heat pump

There is a large potential in the heat losses from the wastewater leaving a building. We present a novel concept for recovering this heat. Instead of recovering it in a mixed state, the recovery immediately after use is evaluated. This allows the exploitation of the higher temperatures found at the points of warm water usage. By integrating a heat pump to utilize this heat, we can produce a higher temperature heat supply while maintaining a low temperature-lift requirement. This leads to the possibility of directly regenerating the hot water supply through wastewater heat recovery. The concept is a result of research into low exergy building systems, and is part of the IEA ECBCS Annex 49. We have modeled the annual performance of two different system scenarios, which result in a potential average annual coefficient of performance (COP) of over 6. The first scenario supplies up to 4400 kWh of heat for all hot water events with only 790 kWh of electricity, while the second scenario regenerated directly the hot water supply just for bathroom fixtures at 2400 kWh with just 410 kWh of energy. This is a significant reduction in the demand for hot water supply of a building compared to most modern installations.     

Assessment of total uncertainty in cocaine and benzoylecgonine wastewater load measurements

To check the effectiveness of campaigns preventing drug abuse or indicating local effects of efforts against drug trafficking, it is beneficial to know consumed amounts of substances in a high spatial and temporal resolution. The analysis of drugs of abuse in wastewater (WW) has the potential to provide this information. In this study, the reliability of WW drug consumption estimates is assessed and a novel method presented to calculate the total uncertainty in observed WW cocaine (COC) and benzoylecgonine (BE) loads. Specifically, uncertainties resulting from discharge measurements, chemical analysis and the applied sampling scheme were addressed and three approaches presented. These consist of (i) a generic model-based procedure to investigate the influence of the sampling scheme on the uncertainty of observed or expected drug loads, (ii) a comparative analysis of two analytical methods (high performance liquid chromatography-tandem mass spectrometry and gas chromatography-mass spectrometry), including an extended cross-validation by influent profiling over several days, and (iii) monitoring COC and BE concentrations in WW of the largest Swiss sewage treatment plants. In addition, the COC and BE loads observed in the sewage treatment plant of the city of Berne were used to back-calculate the COC consumption. The estimated mean daily consumed amount was 107 ± 21 g of pure COC, corresponding to 321 g of street-grade COC.     

Mechanical behavior of sandy facies of Opalinus Clay under different load conditions

The mechanical behavior of sandy facies of Opalinus Clay at the Mont Terri underground rock laboratory(URL)in Switzerland was investigated with drained and undrained triaxial compression and extension,cyclic compression,and creep tests.Samples were taken from boreholes drilled parallel to bedding.Most of the samples were reconditioned to minimize sampling effects of desaturation and micro-cracking.The compression was accomplished by increasing axial stress at constant radial stress.The extension was carried out by increasing radial stress at constant axial stress.Moreover,extension was also achieved by simultaneously increasing radial stress and decreasing axial stress under constant mean stress.The test results showed elastoplastic stress-strain behavior with volumetric compaction until onset of dilatancy at high deviatoric stresses above 80%-90%of the peak failure strength.The strength is dependent upon load path and mean stress.The strength under triaxial compression is higher than that under extension.The respective strength increases with increasing mean stress.Desaturation enhances the stiffness and strength of the claystone.The deformation and strength of the elaystone are time-dependent.Under constant deviatoric stress,the claystone crept continuously with time,which can be characterized by a transient phase and a following stationary phase,and even a tertiary phase at high deviatoric stresses to rupture.     

Experimental study of performance of digital variable multiple air conditioning system under part load conditions

An experimental study on performance of digital variable multiple air conditioning system under part load conditions in hot summer and cold winter zone was conducted in this paper. The effects of outdoor air temperature and on-unit ratio on total power consumption in 1 h, hourly heating performance factor or hourly energy efficiency ratio were analyzed by experiments. The variations of hourly heating performance factor (or hourly energy efficiency ratio) and total power consumption in 1 h with part load value under different outdoor air temperature were obtained. The results indicate that digital variable multiple air conditioning system can keep economical and reliable operation under part load conditions. And it is necessary to study the index which may reflect the seasonal energy consumption of digital variable multiple air conditioning system.     

Biodegradation potential of pure and mixed bacterial cultures for removal of 4-nitroaniline from textile dye wastewater

Environmentally toxic aromatic amines including nitroanilines are commonly generated in dye contaminated wastewater in which azo dyes undergo degradation under anaerobic conditions. The aim of this study was to develop a process for biological treatment of 4-nitroaniline. Three bacteria identified as Acinetobacter sp., Citrobacter freundii and Klebsiella oxytoca were isolated from enrichment cultures of activated sludge on 4-nitroaniline, after which the isolates and the mixed culture were studied to determine optimal conditions for biodegradation. HPLC analyses showed the mixed culture was capable of complete removal of 100 μmol/L of 4-nitroaniline within 72 h under aerobic conditions. There was an inverse linear relationship (R² = 0.96) between the rate of degradation (V) and 4-nitraoaniline concentrations [S] over 100-1000 μmol/L. The bacterial culture was also capable of decolorizing structurally different azo dyes (Acid Red-88, Reactive Black-5, Direct Red-81, and Disperse Orange-3) and also degraded nitrobenzene. Our findings show that enrichment cultures from activated sludge can be effective for the removal of dyes and their toxic intermediates, and that treatment may best be accomplished using an anaerobic-aerobic process.     

Electro-dewatering of wastewater sludge: influence of the operating conditions and their interactions effects

Electric field-assisted dewatering, also called electro-dewatering (EDW), is a technology in which a conventional dewatering mechanism such a pressure dewatering is combined with electrokinetic effects to realize an improved liquid/solids separation, to increase the final dry solids content and to accelerate the dewatering process with low energy consumption compared to thermal drying. The application of these additional fields can be applied to either or both dewatering stages (filtration and/or compression), or as a pre-or post-treatment of the dewatering process. In this study, the performance of the EDW on wastewater sludge was investigated. Experiments were carried out on a laboratory filtration/compression cell, provided with electrodes, in order to apply an electrical field. The chosen operating conditions pressure (200-1200 kPa) and voltage (10-50 V) are sufficient to remove a significant proportion of the water that cannot be removed using mechanical dewatering technologies alone. A response surface methodology (RSM) was used to evaluate the effects of the processing parameters of EDW on (i) the final dry solids content, which is a fundamental dewatering parameter and an excellent indicator of the extent of EDW and (ii) the energy consumption calculated for each additional mass of water removed. A two-factor central composite design was used to establish the optimum conditions for the EDW of wastewater sludge. Experiments showed that the use of an electric field combined with mechanical compression requires less than 10 and 25% of the theoretical thermal drying energy for the low and moderate voltages cases, respectively.     

不同地质条件下地源热泵取热方式技术经济性分析

以保定市某地源热泵项目为研究对象,详细分析了钻孔设置竖直埋管换热器方式和地下水抽灌井方式的系统设计方案、资源条件、初投资及运行成本。结果表明地下水抽灌井方式取热方案的初投资是钻孔设置竖直埋管换热器方式的1/2以下,但其总运行费用要远高于钻孔设置竖直埋管换热器方式。     

Decolorization and toxicity of reactive anthraquinone textile dyes under methanogenic conditions

Reductive decolorization of two anthraquinone reactive dyes (Reactive Blue 4, RB4; Reactive Blue 19, RB19) under methanogenic conditions was performed using a mixed, methanogenic culture. Decolorization of the two anthraquinone dyes was investigated to evaluate the rate and extent of color removal as well as to assess possible toxic effects of the dyes and their decolorization product(s) on the methanogenic culture as a function of initial dye concentration ranging from 50 to 300 mg x L(-1). A dextrin/peptone mixture was used as the carbon and electron source. A high rate and extent of color removal was achieved ranging from 4.3 to 29.9 mg x L(-1)h(-1) and 73-91% for RB4, and 13.0-74.4 mg x L(-1)h(-1) and 90-95% for RB19. Initial RB4 concentrations up to 100 mg x L(-1) did not result in any significant inhibition. Both the 200 and 300 mg x L(-1) RB4-amended cultures, and all RB19-amended cultures resulted in severe inhibition of both acidogenesis and methanogenesis. Sequential dye addition at 300 mg x L(-1) for both RB4 and RB19 resulted in accumulation of volatile fatty acids (VFAs) and a very low methane production at the end of the first dye addition after 44 days of incubation. However, at the end of the second dye addition, after a relatively long incubation (384 days), recovery of methanogens in the RB4-amended culture was observed in contrast to the complete inhibition of methanogenesis in the RB19-amended culture. Therefore, RB19 resulted in a higher degree of inhibition of both acidogenesis and methanogenesis than RB4. Addition of dextrin/peptone to dye-inhibited cultures resulted in acidogenesis and a gradual recovery of methanogenesis (mainly aceticlastic methanogenesis) in the RB4-inhibited culture, and a slow recovery of acidogenesis but no recovery of methanogenesis in the RB19-inhibited culture. In contrast, addition of 80% H(2)-20% CO(2) gas to dye-inhibited cultures resulted in recovery of hydrogenotrophic methanogenesis in both the RB4- and RB19-inhibited cultures. In spite of the relatively severe inhibition of the two anthraquinone dyes on the mixed, methanogenic culture, a high extent of color removal was achieved.     

Effect of pre- and post-UV disinfection conditions on photoreactivation of fecal coliforms in wastewater effluents

Photoreactivation of microorganisms following UV disinfection can represent a disadvantage to using UV technology for wastewater treatment since recovery may, in some cases, reach several logs. Thus, decreasing photoreactivation can lead to considerable savings in capital and operating costs. Objectives of this study were to determine pre- and post-UV irradiation conditions which could decrease fecal coliform (FC) photoreactivation in wastewater effluents. Results indicated that delaying exposure to photoreactivating light for 3 h suppressed photoreactivation after relatively low UV doses of 10 and 20 mJ/cm². Moreover, at least 440 lux (0.065 mW/cm²) of visible light was needed to initiate photoreactivation. Additionally, photoreactivation decreased significantly when samples were exposed to visible light simultaneously or prior to UV irradiation. This was more significantly observed for winter samples, where photoreactivation decreased by nearly 50%. Finally, summer FC populations were more sensitive to inactivation and less able to photoreactivate than winter populations. The effect of visible light on photoreactivation levels may be explained by several photo-mechanisms of FC photolyase, such as photodecomposition of the MTHF co-factor and reduction of FAD.     

Distribution of antidepressant residues in wastewater and biosolids following different treatment processes by municipal wastewater treatment plants in Canada

The fate of 14 antidepressants along with their respective N-desmethyl metabolites and the anticonvulsive drug carbamazepine (CBZ) was studied in 5 different sewage treatment plants (STPs) across Canada. Using two validated LC-MS/MS analytical methods, the concentrations of the different compounds were determined in raw influent, final effluent and treated biosolids samples. Out of the 15 compounds investigated, 13 were positively detected in most 24-h composite raw influent samples. Analysis showed that venlafaxine (VEN), its metabolite O-desmethylvenlafaxine (DVEN), citalopram (CIT), and CBZ were detected at the highest concentrations in raw influent (up to 4.3 μg L⁻¹ for DVEN). Cumulated results showed strong evidence that primary treatment and trickling filter/solids contact has limited capacity to remove antidepressants from sewage, while activated sludge, biological aerated filter, and biological nutrient removal processes yielded moderate results (mean removal rates: 30%). The more recalcitrant compounds to be eliminated from secondary STPs were VEN, DVEN and CBZ with mean removal rates close to 12%. Parent compounds were removed to a greater degree than their metabolites. The highest mean concentrations in treated biosolids samples were found for CIT (1033 ng g⁻¹), amitriptyline (768 ng g⁻¹), and VEN (833 ng g⁻¹). Experimental sorption coefficients (K_d) were also determined. The lowest K_d values were obtained with VEN, DVEN, and CBZ (67-490 L kg⁻¹). Sorption of these compounds on solids was assumed negligible (log K_d ≤ 2). However, important sorption on solids was observed for sertraline, desmethylsertraline, paroxetine and fluoxetine (log K_d > 4).     

黏性土在不同温度下干缩裂缝的发展规律及形态学定量分析

通过试验,研究了黏性土干缩裂缝的发生和发展与温度之间的关系,运用计算机图像处理和编程技术,对不同温度下形成的黏性土干缩裂缝的表面结构特征进行了描述和定量分析。结果表明:土样裂缝的发生和发展过程基本上分三个阶段,在裂缝出现时,土样失水率有上升趋势;温度对黏性土表面裂缝节点个数、裂缝长度、裂缝条数、块区个数、块区的最可几面积、裂缝率和裂隙网络的分维数等参数有重要影响;块区面积分布函数的峰值随温度的升高而减小。     

Viability of six species of larval and non-larval helminth eggs for different conditions of temperature, pH and dryness

Helminth eggs are the most difficult biological parasites to inactivate in wastewater and sludge. In developing countries, in particular, they are present in high concentrations and are the cause of many diseases that impact seriously on the human population. The process conditions for affordable inactivation are very variable, leading to different inactivation efficiencies. Temperature, dryness, pH and the developmental stage of the eggs must be taken into consideration to achieve complete inactivation. The objective of this research was to study the inactivation of six species of larval and non-larval helminth eggs of medical importance in developing countries under controlled conditions of temperature, pH, dryness and contact time. Results showed considerable differences in inactivation conditions among helminth eggs and a high level of resistance was confirmed for the eggs of Ascaris lumbricoides and Ascaris suum. The appropriate conditions for inactivation of all types of eggs were found by applying combinations of pH, temperature and dryness. At 45 °C it was possible to inactivate all species with a pH of 5.3 and 90% dryness within 6 days. If alkalization was applied, a pH of 12.7 was sufficient over 19 days at the same conditions of dryness and temperature. From these results it is proposed that both Ascaris spp. and Taenia solium may be used as indicators of biological contamination in wastewater and sludge.     

Influence of filtration conditions on membrane fouling and scouring aeration effectiveness in submerged membrane bioreactors to treat municipal wastewater

Membrane fouling and scouring aeration effectiveness were studied using three large pilot-scale submerged membrane bioreactors (MBRs) operated at a series of permeate fluxes, scouring aeration intensities and cyclic aeration frequencies to treat municipal wastewater. The results showed that when operated at the sustainable conditions, the MBRs had a stable reversible fouling resistance. At unsustainable conditions, the reversible fouling resistance increased exponentially as filtration progressed. For each of above two cases, the fouling ratios newly defined by Eqs. (7) and (8) were calculated from the transmembrane pressure increases to compare the relative reversible fouling rates. With the range of sustainable filtration conditions, the fouling ratios at the same reference scouring aeration intensity were found to be proportional to permeate flux. Similarly, the fouling ratios calculated with the same reference permeate flux decreased exponentially with increasing scouring aeration intensity. Moreover, the effects of scouring aeration intensity and permeate flux on the fouling ratios were found to be independent of one another. As a result, an empirical relationship was derived to relate the stable reversible fouling resistance to sustainable permeate fluxes and scouring aeration intensities. Its application was demonstrated by constructing transmembrane pressure contours overlaid with scouring aeration effectiveness contours to aid in the selection of optimal MBR filtration conditions.     

Seismic stability of embankments with different densities and upstream conditions related to the water level

Modeling an embankment by subjecting it to different upstream conditions in a centrifuge is challenging. However, the response of an embankment to shaking under different upstream conditions needs to be studied to ensure that the necessary precautions are taken during its construction and maintenance. Herein, the influence of different upstream conditions and embankment densities are investigated. The pore water pressure values at different locations in an embankment were recorded during seepage and under induced shaking. Accelerometers recorded the response of the embankment to shaking, and a linear variable differential transformer (LVDT) measured the settlement at the top of the embankment as a result of the shaking. An image analysis was used to trace the resulting deformation of the embankment due to the shaking. The results indicate that the upstream conditions of the embankment determine the failure mechanism of the embankment in cases of lower density. In addition, the distribution of the water content within the embankment was found to have a greater influence on its response to shaking than the water level height on its upstream side.     

Laccase-catalyzed conversion of natural and synthetic hormones from a municipal wastewater

The Trametes versicolor-derived laccase-catalyzed oxidation of natural estrogens (estrone--E1; 17beta-estradiol--E2; and estriol--E3) and a synthetic estrogen (17alpha-ethinylestradiol--EE2) was studied in synthetic water and municipal wastewater to optimize the process for steroid estrogen removal in wastewater. The optimal pH for each studied steroid estrogen oxidation was approximately 6 in synthetic water. This research also focused on the wastewater matrix effect on developed enzymatic treatment. At pH 7.0 and 25+/-1 degrees C, the experiments showed that the laccase-catalyzed system for the removal of steroid estrogens was not significantly affected by the municipal wastewater matrix. Laccase activity of 20 U/ml was sufficient to achieve complete removal of studied steroid estrogens in both synthetic water and municipal wastewater. Moreover, 1-hydroxy-benzotriazole, when used as a mediator, improved laccase-catalyzed system efficiency, thus decreasing the overall cost of the enzymatic system.     

不同连接形式下GRC构件荷载试验及结果分析

通过对GRC外装饰构件在不同连接形式下进行荷载试验,从结果上分析了不同连接方式及锈胀裂缝对GRC外装饰构件承载力、变形性能、安全性的影响,以促进GRC构件的研究。     

多国荷载规范中平屋盖及球形屋盖体型系数取值探讨

风荷载体型系数一直是风工程和风荷载规范研究专家关注的主要问题之一.本文首先总结了各国荷载规范中风荷载规定的差异,并就平屋盖和球形屋盖的风载体型系数对比了中国规范(GB50009-2001)、美国规范(ASCE7-98)、加拿大规范(NBC-1995)和日本规范(AIJ-2004)中的规定.最后结合大跨度平屋盖与球形屋盖的风洞试验,给出了球形屋盖和平屋盖的风载体型系数取值建议,为大跨屋盖结构的抗风设计提供了参考资料.