Effects of low temperature on sludge settleability and nutrients removal performance treating domestic wastewater

In order to investigate the effect of temperature on activated sludge systems,sludge settleability,nitrogen and phosphorus removal processes were investigated by changing temperature variation patterns using 4 sequencing batch reactors (SBR).The results showed that no matter temperature changes in the range of 15-22 ℃ (decrease or increase) gradually or sharply,it has little effect on nitrogen and phosphorus removal processes.But when temperature decreases to 12 ℃,biochemical reactions will be inhibitted obviously.At least 1 sludge retention time (SRT) is needed for nitrification adapt to new temperature envirionment,and more time is necessary for phosphorus removal process.When temperature increases from 12 ℃ to 22 ℃ sharply,nitrification process deteriorates seriously,but phosphorus removal process shows no change.In addition,sludge settleability deteriorates when temperature changes sharply (decrease or increase),but the reasons are different.Under temperature decrease condition,it is mainly caused by the increase of accumulated extracellular polymeric substances (EPS).Under temperature increase condition,the loosing sludge flocs' configuration is the main reason.It should be pointed out that the filamentous bacteria content during the entire experiment keeps almost constant,and the sludge settleability variations are the reflection of the change of sludge physicochemical characteristics.

Growth,Dislocation and Morphology of Nd∶GdVO_4 Single Crystal

The neodymium ions doped gadolinium vanadate （Nd∶GdVO4） single crystals were successfully grown by Czochralski method. Chemical etching technique was used to reveal the dislocation structure of the crystals. An average dislocation density of （100） plane is 600 pits/mm 2. The crystal-morphology can be used to determine crystal orientation accurately with simple optical method.

Ecological and Low-carbon Technology in Urban Decentralized Treatment and Reclamation of Wastewater

China's water shortage situation is grim.Deep exploration of non-traditional water resources and relief of contradiction between China's economic development and water resources shortage is the only way to ensure the sustainable development of China.Urban sewage treatment and reclamation is a more stable and widely used method of non-traditional water resources development and utilization.However,urban centralized reclaimed water treatment faces many problems such as high transportation cost and difficulty in laying reusing pipe network.Relatively speaking,decentralized reclaimed water treatment technology has obvious advantages and is gradually getting more attention.In this research,three types of wastewater treatment process featured with urban decentralized low-carbon ecological technology have been mainly introduced.In addition,the operating data of relevant domestic and foreign engineering cases were analyzed from the perspectives of treatment effect,energy consumption level,applicable scale and occupied area,etc.This study considers that these three new sewage processes based on the principle of ecological engineering have the advantages of compact structure,small footprint,low water consumption,stable effluent quality,beautiful appearance and large applicable scale,and are worthy of researching and importing.

Competition for Single Carbon Source Between Denitrification and Phosphorus Release in Sludge under Anoxic Condition

In order to investigate the competition for carbon source between denitrification and phosphorus release processes,simultaneous phosphorus release and denitrification in sludge operated in anoxic,aerobic mode are investigated by varying the ratio of influent COD to nitrogenous compound concentration under anoxic condition using a lab-scale sequencing batch reactor(SBR).The results show that the nitrate reduction rate is nearly independent of the ratio of influent COD to nitrate under anoxic condition.More NOx--N in the influent leads to less 3 4PO --P release during the feeding period.However, 3 4PO--P release proceeds at a low rate simultaneously with denitrification even when the influent NOx--N concentration is as large as 20 mg·L-1and its rate is increased obviously when NOx--N is denitrified to a concentration lower than 0.5 mg·L-1.The variation of pH during anoxic period gives some information about the biochemical reactions of denitrification and3 4PO--P release.When more nitrate is present in the influent,more acetate uptake in feeding period is used for direct microorganism growth.

Formation of multiple trimethylsilyl derivatives in the derivatization of 17α-ethinylestradiol with BSTFA or MSTFA followed by gas chromatography-mass spectrometry determination

N,O-bis(trimethylsily)triffuoroacetamide (BSTFA) and N-methyl-N(trimethylsily) triffuoroacetamide (MSTFA) are common derivatization reagents used in the GC-MS analysis of estrogen steroids such as estrone (E1) and 17α-ethinylestradiol (EE2). In this study, three trimethylsilyl (TMS) steroid derivatives, mono-and di-trimethylsilyl EE2 and mono-trimethylsilyl E1, were observed during the derivatization of EE2 with BSTFA or MSTFA andor GC separation. Factors inffuencing the production of multiple TMS derivatives and their relative abundance were examined. It was found that both methanol and bisphenol A competed with estrogenic esteroids when reacting with silylation reagents, and thus affected the formation of TMS derivatives and their relative abundance in the derivatization products. Methanol was found to be more reactive than bisphenol A with the BSTFA reagent. None of the three solvents tested in this study could prevent the generation of multiple TMS derivatives during the derivatization of EE2 with BSTFA, followed by GC analysis. A similar result was observed using MSTFA as the derivative reagent followed by GC analysis. Thus, the suitability of BSTFA or MSTFA as the derivatization reagent for the determination of E1 and EE2 by GC-MS, under the conditions reported here, is questionable. This problem can be solved by adding trimethylsilylimidaz (TMSI) in the BSTFA reagent as recommended, and the performance of the method has been proved in this study.

Preparation of Nicotinic Acid from Oxidation of 3-Picoline with Oxygen Under Catalysis of T(o-Cl)PPMn

The oxidation of 3-picoline to nicotinic acid took place efficiently in an ethanol solution with O2 as the oxidant under the catalysis of T(o-Cl)PPMn at 40―150 °C and 0.5―3.0 MPa oxygen pressure. The influences of temperature, oxygen pressure, reaction time, concentration of 3-picoline, concentration of sodium hydroxide, and concentration of T(o-Cl)PPMn catalyst, etc. on the production of nicotinic acid were investigated. The results show that T(o-Cl)PPMn presented excellent catalytic activity in the oxidation of 3-picoline to nicotinic acid and the yield of nicotinic acid varied greatly with the reaction temperature, oxygen pressure, T(o-Cl)PPMn concentration, etc.

Electromagnetic anti-fouling technology for prevention of scale

An electromagnetic anti-fouling technology(EAFT) was developed further. The operating principle of the EAFT was presented using fundamental physics laws. To validate the effect of EAFT and identify the mechanism, a circulating flow setup was built. A series of fouling tests were carried out with and without EAFT, measuring fouling thermal resistance as function of time, making scanning electron microscope images and analyzing the particles size distribution in solution by dynamics light scattering technology. The main results were as follows: 1) All the precipitated crystals in solution were calcite and there were little differences between with EAFT and without EAFT in the experimental range. 2) The number of precipitate nucleation in solution was small and the particle growth was slow without EAFT. In opposition to the case untreated, a rapid particle growth was observed and the number of nucleation was expected to be large, due to the fact that the EAFT effectively increases the ions and crystals collision frequency and effectiveness by utilizing the induced electric field. It is indicated that the particle growth is promoted mainly by coagulation process but not nucleation growth. 3) The EAFT could prolong the delay time of fouling greatly, and after the delay time, the thermal resistance quickly increased. Therefore, in order to mitigate scale significantly, the floccules in solution should be deposited beforehand in a low-lying area of the exchangers and let off in time.

Disposal methods for used passenger car tires: One of the fastest growing solid wastes in China

With the rapid growth in the number of passenger cars(PCs)in China over the past decades,more than ten million tons of used tires have already become solid wastes and subsequently caused serious environmental issues.Due to the presence of synthetic rubber in PC tires,waste PC tires cannot be disposed through rubber reclaiming technology.Thus,waste PC tires have become one of fastest growing solid wastes in China.First,the current disposal capacity of the pyrolysis method,regarded as a promising technology for the disposal of waste PC tires,is surveyed and compared with other disposal methods mentioned in previous papers.Second,this work establishes a model to predict the total number of waste PC tires in the next five years depending on the rate of PC growth and current waste tire disposal capacity.Moreover,pyrolysis is evaluated on 15 collected waste PC tires selected from the most representative tire brands in the Chinese market.The corresponding results imply that~68.5%of S was into oil and~44.3%N and large amount of heavy metals resided in solid carbon which severely limit further applications.Finally,a new pyrolysis technology is introduced that may represent a solution to the limits in the application of tire disposal methods and relief for the coming waste tire crisis.

Preparation of ceria-zirconia solid solution with enhanced oxygen storage capacity and redox performance

A new method called ultrasonic-assisted membrane reaction(UAMR)was reported for the fabrication of ceria-zirconia solid solution.A series of ceria-zirconia solid solutions with different Ce/Zr molar ratios were prepared by the UAMR method and characterized by Xray diffraction(XRD),N2 adsorption,hydrogen temperature-programmed reduction(H2-TPR),scanning electron microscope(SEM),and transmission electron microscopy(TEM)techniques.The UAMR method proved to be superior,especially when the Ce/Zr molar ratio was lower than 1,in fabricating ceria-zirconia solid solutions with large BET surface area,high oxygen storage capacity(OSC),and low reduction temperature.

Control of sludge settleability and nitrogen removal under low dissolved oxygen condition

低溶解的氧() 是在激活的污泥的一个 energysaving 条件过程。在定序批反应堆(SBR ) 调查有限细丝状的 bulking (LFB ) 的可能的申请，二实验室规模 SBR 被用来分别地对待合成国内废水和真实市政的废水。结果显示出那延长低做通风持续时间和背景 pre 缺氧(厌氧) 阶段是有效策略分别地导致并且禁止细丝状的污泥 bulking。根据污泥 settleability， LFB 能被调整操作模式稳定地维持。细丝状的细菌内容和污泥体积索引(SVI ) 多半被相关。SVI 在一些周期以内戏剧性地波动什么时候约 200 mL 爠瑡潩漠 ? 湩汦敵瑮愠浭湯畩 ? 潴渠瑩楲整眠獡洠楡瑮楡敮 ? 瑡愠潢瑵ㄠ ? 愠 ?? 潣据湥牴瑡潩 ? 敢潬 ?? ‰杭 ???? 庑 ???? o 景挠牨浯畩 ? 湩琠敨猠楯? 慷 ?污潳攠桮湡散

Uniform design ray in the assessment of combined toxicities of multi-component mixtures

Multi-component mixture(MCM) is a complicated chemical system that contains a great deal of mixture rays with various mixture ratios, and each ray includes many mixtures with different concentration levels.Currently, in combined toxicity field, almost all studies on MCM focus on the mixtures designed by the equivalenteffect concentration ratio(EECR) procedure. However, the EECR mixtures cannot represent the whole mixture system because the EECR mixtures are located on one mixture ray in concentration space formed by multiple components. In our view, some optimal experimental design such as the uniform design(UD) should be used to effectively select many representative mixture rays from the MCM system,instead of single EECR ray. The uniform design ray(UDray) integrating UD idea with fixed-ratio ray design can systematically and comprehensively measure the combined toxicity changes in the MCM system. This review introduces the operation method, construction of uniform table and corresponding usable table, and some cases of application of the UD-ray to help readers easily use UD-ray in their MCM toxicity assessment.

Implementation of a microcanonical variational transition state theory for direct dynamics calculations of rate constants

An implementation of the variational quantum RRKM program is presented to utilize the direct ab initio dynamics approach for calculating k(E, J ), k(E ) and k(T ) within the framework of the microcanonical transition state (mTST) and microcanonical variational TST (mVT) theories. An algorithm including tunneling contributions in Beyer-Swinehart method for calculating microcan-onical rate constants is also proposed. An efficient piece-wise interpolation method is developed to evaluate the Boltzmann integral in calculation of thermal rate constants. Calculations on several test reactions, namely the H(D)2CO→H(D)2 + CO, CH2CO→CH2 + CO and CH4 + H→CH3 + H2 reactions, show that the results are in good agreement with the previous rate constants calcula-tions. This approach would require much less computational resource.

Experimental research of a novel vortex generator for solar absorption chiller

In this study,a novel generator for the single-effect LiBr-H2O absorption chiller using solar energy was investigated.A dual-chamber vortex generator(DCVG)consisted of a lower chamber and an upper chamber.The hot weak LiBr-H2O liquid entered the lower chamber tangentially through a small nozzle to create a strong vortex flow.Due to the rotating flow,the pressure was reduced toward the central portion of the lower chamber.Experiments were conducted under different solution flow rates and temperatures.The experimental results showed that the lower pressure developed in the lower cham-ber could reduce the saturated temperature and help the evaporation in the generator that is more heat could be utilized to generate more refrigerant vapor.When the inlet temperature was 90℃,the COP of a solar absorption chiller using the DCVG could reach 0.83,which was higher than of the conventional absorption chiller by 22%.

Sub-Atmospheric Pressure Coupled with Width Effect on Downward Flame Spread over Energy Conservation Material Polyurethane Foam

Rigid polyurethane(PUR)foam,a sustainable thermosetting building facade porous polymer material,has been widely applied in the construction industry for energy conservation.Additional knowledge of the fire safety performance of PUR foam at different altitudes and sample widths is required.Comparative lab-scale experiments were conducted in the Lhasa plateau(66.5 kPa)and the Hefei plain(99.8 kPa)in China.Flame propagation characteristics(average flame spread rate and flame height)were measured at different widths and atmospheric pressures of the test locations.Experimental results show that the dependence of dimensionless flame heights on sample width shows negative power law relationships with index of−w/5.4 to−w/5.8.Both flame height and flame spread rate were lower under low ambient pressure conditions as H f P0.26~0.33 and Vf P0.057~0.568.Flame spread rate decreased with increasing sample width in the convection regime before a critical width of 4 cm–8 cm,after which the flame spread rate increased in the radiation regime.Results of this study contribute to the science of combustion,fire safety and energy conservation,and provide a basis for fire safety protocols for historical heritage buildings in the Lhasa plateau.