Assessment of organic chlorinated compound removal from aqueous matrices by adsorption on activated carbon

Adsorption on activated carbon is currently the most frequently used technology to remove organic chlorinated pollutants from wastewaters. The present study examines the ability of five commercially available types of activated carbon to remove organic chlorinated compounds from the effluent of a chemical plant. The various types were tested on the basis of Freundlich adsorption isotherms for 14 pure organic chlorinated compounds, of molecular weight ranging from that of dichloromethane (MW=84.93 gmol(-1)) to hexachlorobenzene (MW=284.78 gmol(-1)). The best was selected and used in a laboratory fixed-bed column to assess its removal efficiency with respect to the tested organic chlorinated compounds. Removal efficiency was always higher than 90%. These results provide information necessary to optimize scale-up from the pilot plant to the real one.     

A statistical approach to the optimisation of membrane operation

A bench‐scale analysis has been conducted on the ultrafiltration of synthetic and real domestic wastewaters post‐biotreatment by a biological aerated filter. This paper presents a rigorous analytical technique to identify the process parameters that have a significant influence on a membrane system performance. By applying statistical techniques, the influence of each parameter and the level of uncertainty were quantified within a highly complex, interrelated and variable process. The results showed that the fouling propensity for real greywater was significantly variable, both during the trial and from one trial to the next. The variability was primarily due to the inherent variability of greywater quality and the extent of settling within the storage facility. However, the fouling propensity for real greywater was generally lower than for settled sewage. The results of the analysis were extended to produce a predictive model that can be used as a guide in the design of membrane systems and their operation. The methodology is readily transferable and adaptable to other membrane systems.     

Intra-storm variability in microbial partitioning and microbial loading rates

Association with particles in the water column can have a significant impact on microbial fate and transport. This study analyzed multiple stormwater samples taken throughout the duration of three separate storms (at two different sites) to evaluate the fraction of microbes partitioning to denser "settleable" particles and to examine how partitioning behavior varied over the course of a storm. Intra-storm sampling also allowed for estimates of microbial loading rates (both total and particle-associated) and cumulative storm-induced microbial load. Five different indicator organisms were examined, with the fraction of microbes associated with settleable particles assessed via a calibrated centrifugation method. Partitioning behavior varied across microorganism type, with an average of 40% of fecal coliforms, Escherichia coli, and enterococci associating with settleable particles, compared to approximately 65% of Clostridium perfringens spores and only 13% of total coliphage. Partitioning remained fairly constant for each type of organism throughout storm events. Nonetheless, higher concentrations of both settleable particles and microbes entering the water column soon after the onset of a storm led to higher loading rates of settleable microbes in the storm's earliest stages, a trend that could have important implications for the design of stormwater management structures (e.g., detention basins). Estimates of cumulative storm-induced microbial loading suggested that one day's worth of storm loading can be the equivalent of months, or even years, of dry-weather loading.     

Computer Simulation of IT-diagrams of Steel

PHASE transformation modeling is one of the mainchallenges in modeling of heat treatment[1].The mechanism of phase transformations is not fullyunderstood and interactive influence of differentelements,austenitizing temperature,etc.usually arenot taken in account.The mistakes in phase transformation calculationcould be extremely great if a model is based only ongrain size of prior austenite,austenitizing temperatureand elemental composition of steel.Phase transformation kinetic depends also o…     

Influence of Heat Treatment on the Bond Coat Cyclic Oxidation Behaviour in an Air-plasma-sprayed Thermal Barrier Coating System

THE METALLIC BOND COAT is an importantconstituent in a TBC system.It enhances the adhesionof the ceramic thermal barrier layer(the topcoat)to thesubstrate and also provides oxidation protection to thesubstrate metal.The composition of the bond coat,generalized as M-Cr-Al-Y,where M represents Ni,Coand/or Fe,generally allows a layer of alumina(A12O3)to form during high temperature exposure.If acontinuous scale of A12O3forms along the interfacebetween the bond coat and the ceramic to…     

Ni/Al Intermetallics Plasma Transferred Arc Processing

TAILORING COMPONENT SUFACES for elevatedtemperature operations has been a goal of researchersduring the last century.Process and material selectionare the key factors for this development.In particularlythe latter can be described to have started with thedevelopment of stainless steels.Ni and Co based alloys,the superalloys,attended the increasing technologicaldemands for higher service temperatures(1).Morerecently the higher operating temperatures ofequipments,such as gas turbines,r…     

Microstructure Transformation in the Welding Heat Affected Zone of 800MPa Grade Ultra Fine Structured Steel

The transformation behavior and microstructure development in the heat affected zone (HAZ) of 800MPa grade ultra fine structured steel was investigated. It was found that the HAZ has intermediate temperature transformation characteristics in a wide range of cooling rates, with the bainite sheaves consisting of bainite ferrite plates without carbide precipitation and retained austenite in the .fast cooling regime. At relatively high cooling rates, which corresponded to low heat inputs, the hardness o.f the simulated HAZ was above that of the base metal. When the cooling rate was below 9℃/s, the welding HAZ would have an obvious softening. The analysis of transformation rates in continuous cooling processes was completed by numerical differential method. The result indicated that the microstructure transformation rate o.f the HAZ in 800MPa grade ultra fine structured steel changed sharply to slow speeds when the cooling time t8/5 is longer than 7s.     

Effects of Thermal Cycle on Mechanical Properties and Fractography in HAZ of HQ130 Steel

The effect of different peak temperature (Tp) and cooling time (t8/5) on hardness, impact toughness and fracture morphology in the heat-affected zone (HAZ) of HQ130 steel was studied by using welding thermo-simulation test. Experimental results show that the impact toughness and hardness decrease with the decrease of Tp or increase of t8/5 under the condition of a single thermal cycle. There is a brittle zone in the vicinity of Tp=800℃, where the impact toughness is considerably low. There is softened zone in vicinity of Tp=700℃, Where the hardness decreases but the toughness increases. In the practical application of multi-layer and multi-pass welding, the welding heat input should be strictly limited (t8/5≥20s) so as to reduce the softness and brittleness in the HAZ of HQ130 steel.     

Numerical Simulation of Macro-Segregation in Steel Ingot During Solidification

A mathematical model coupling the momentum, energy and species conservation equations was proposed to calculate the macro-segregation of Fe-C alloy ingot during solidification. The corresponding simulation software which concurrently solves the macroscopic mass, momentum, energy and species conservation equations has been developed by applying the SIMPLE algorithm. The thermo-solutal convection in a NH4 Cl-H2O ingot is verified and the result shows good agreement with that reported. Then macro-segregation in a steel ingot is simulated by using the developed program. The steel ingot is in a rectangular mold with a riser. The fluid flow is mainly induced by the temperature field and the solid fraction. The macro-segregation pattern is mainly affected by the thermo-induced convection in the mushy zone. The negative segregation forms along the walls of the casting. The positive segregation forms at the top center of the casting into the riser. The species concentration reaches the peak in the center of the ingot where solidification ends lastly.