Organic matter release in low temperature thermal treatment of biological sludge for reduction of excess sludge production.

Thermal treatment applied in association with a biological system allows for a significant reduction in excess sludge production (approximately 50%). In general, heat treatment is described as a sludge disintegration technique. This paper offers a thorough study on the impact of heat treatment, at temperatures below 100 degrees C, on the solubilisation of the sludge COD and its biodegradability. Discontinuous heating experiments were performed on activated and digested sludge. At all temperatures tested the released COD for digested sludge was systematically higher than that for activated sludge (15 and 40%, respectively, at 95 degrees C for 40 min of contact time). For the first 30 min, a 1st order kinetic, with respect to the residual COD, was systematically found. In the range of 40-95 degrees C, digested sludge had a lower activation energy than activated sludge (26 kcal/mol compared to 70-160 kcal/mol). COD solubilisation is thus more positively influenced by temperature in the case of activated sludge. This may be due to the significant difference in the ratio of protein/carbohydrate in digested and activated sludge (1-5 and 0.2-0.7, respectively). The increase in the COD/TKN ratio in the solubilised fraction after thermal treatment of activated sludge suggests a preferential solubilisation of proteins over carbohydrates. Respirometric tests performed on the solubilised COD showed that whatever the sludge origin, only 40-50% of released COD is biodegradable at a conventional hydraulic retention time (i.e., 24 h). Hence, heat treatment would act more through organic matter solubilisation rather than by a biodegradability increase.     

Use of electrochemical oxidation process as post-treatment for the effluents of a UASB reactor treating cellulose pulp mill wastewater.

The main purpose of this study was to evaluate the performance of the electrochemical oxidation process as a post-treatment for the effluents of a bench-scale UASB reactor treating simulated wastewater from an unbleached pulp plant. The oxidation process was performed using a single compartment cell with two plates as electrodes. The anode was made of Ti/Ru0.3Ti0.7O2 and the cathode of stainless steel. The following variables were evaluated: current density (75, 150 and 225 mA cm(-2)) and recirculation flow rate in the electrochemical cell (0.22, 0.45 and 0.90 L h(-1)). The increase in current density from 75 to 225 mA cm(-2) did not increased the color removal efficiency for the tested flow rates, 0.22, 0.45 and 0.90 L h(-1), however the energy consumption increased significantly. The results indicated the technical feasibility of the electrochemical treatment as post-treatment for UASB reactors treating wastewaters from pulp and paper plants.     

Application of a leakage model to assess exfiltration from sewers.

The exfiltration of wastewater from sewer systems in urban areas causes a deterioration of soil and possibly groundwater quality. Beside the simulation of transport and degradation processes in the unsaturated zone and in the aquifer the analysis of the potential impact requires the estimation of quantity and temporal variation of wastewater exfiltration. Exfiltration can be assessed by the application of a leakage model. The hydrological approach was originally developed to simulate the interactions between the groundwater and surface water, it was adapted to allow for modelling of interactions between groundwater and sewer system. In order to approximate the exfiltration specific model parameters infiltration specific parameters were used as a basis. Scenario analysis of the exfiltration in the City of Dresden from 1997 to 1999 and during the flood event in August 2002 shows the variation and the extent of exfiltration rates.     

JETS,PLUMES AND BUOYANT JETS IN STATIC ENVIRONMENT

Turbulence represents an essential aspect in atmospheric and oceanic circulations.In particu-lar,it is a preponderant factor in the dispersion of pollutants of artificial or natural origin.Thevertical turbulent jets,plumes and buoyant jets discharging into static environment is one of themost important and basic flow patterns related with the environment pollution.These flows havenumerous important applications,for example,thrust augmentors,waste disposal plumes fromstacks and combustion systems,and significant problems of turbulent diffusion.     

EXPERIMENTAL STUDIES AND NUMERICAL CALCULATION ON TURBULENT BOUNDARY LAYER OF WATER FLOW ALONG CURVED SURFACE

This paper will introduce experimental studies and numerical calculation onturbulent boundary layer of water flow along curved surface in our country in recent years.Onthe basis of the experimental studies,the effects of curvature and roughness on velocitydistribution and pressure distribution and the change of turbulent flow boundary layer onoverflow bucket concave surface is discussed.We proposed the empirical formula of velocity,pressure and the change of turbulent flow boundary layer on outlet bucket concave.According tothe momentum principle,we have deduced the momentum integral equation full water depthboundary layer and using the element as control unit inside the boundary layer on concavesurface of bucket.Combining with continuity equation,we have computed the boundary layerdevelopment on the bucket of a spillway.Compared with the field experimental data,thecalculation results are available.Under polar coordinates,a mathematical model for simulatingtime-averaged flow characteristics in concave surface of bucket is established.The turbulent flowfield on concave surface of bucket is calculated by SIMPLE method and this mathematicalmodel.The flow velocity field,pressure field,distribution of turbulent kinetic energy,distribution of turbulent energy dissipating rate and distribution of shear stress are available.Thecalculation value is consistent with measured test data.     

The dynamics of economic systems,or how to transform a failed socialist economy

How to transform a failed socialist economy raises questions about the processes of structural and institutional changes, which standard economics is inadequately equipped to study. An economic theory that can study both these processes is suggested and applied to the actual debate of how the transformation should be conducted. Standard notions of institutional roles (R) and organizational structures (S) are seen in a non-standard way as outcomes of two interrelated but distinct evolutions. Comparing different given Rs for their influence on S-evolution throws new light on which R should be the target of the transformation. Compared to standard analysis, the case against socialism on the supply side is strengthened, whereas the case against a redistributive welfare society on the demand side is weakened. S-evolution is shown to require more time and be more difficult to be helped by government than R-evolution. This clarifies several controversial points about the speed and the sequencing of the transformation policies. The study of R-evolution discloses an important cognitive constraint on these policies, which teaching of economics can help to soften. Standard economics, shown to be a special case of the suggested theory, is rehabilitated as the best subject by which such teaching should start.     

An exploratory study of exclusive dealing in channel relationships

The channel literature has paid little attention to issues related to exclusive dealing governance arrangements. Consequently, there is only limited knowledge about how exclusive dealing impacts various channel processes and outcomes. This gap is especially regrettable since exclusive dealing, in addition to being one of the most commonplace governance formats within the distribution channels, is also one of the best exemplars of viable unilateral governance formats. In this initial investigation, the authors explore the linkages among the constructs of exclusive dealing, relationalism, communication, and performance. Empirical data for the study were drawn from the photocopier industry. He obtained his M.B.A. and D.B.A. degrees from Boston University. His primary research interest includes channels of distribution, franchisor-franchisee relationships, and consumer purchase behavior in international contexts. He has published articles inJournal of Marketing Channels and the proceedings of several marketing conferences. This article was crafted when Rajiv Dant was at Boston University. He received his M.B.A. from Bombay University and his Ph.D. from Virginia Polytechnic Institute and State University. His research focuses on channels of distribution, with primary emphasis on franchise structure, franchisee-franchisor relationships, and public policy aspects of franchising growth and ownership topics. His research has been published inJournal of Marketing, Journal of Public Policy & Marketing, Research in Marketing, Journal of Retailing, Journal of Business Research, Journal of Business Venturing, Journal of the Operations Research Society, Marketing Letters, Journal of Small Business Management, Journal of Economic Psychology, Southern Business & Economics Journal, Philosophical and Radical Thought in Marketing, Journal of Healthcare Marketing, Journal of Marketing Channels, andInternational Small Business Journal.     

Low Income Dynamics in 1990s Britain

This paper analyses low income dynamics in Britain using the first four waves of the British Household Panel Survey. There is much low income turnover: although there is a small group of people who are persistently poor, more striking is the relatively large number of low income escapers and entrants from one year to the next. Simulations using estimated low income exit and re-entry rates demonstrate the importance of repeated low income spells for explaining a person's experience of low income over a given period. We also document the characteristics of low income stayers, escapers and entrants.     

The Economic Benefits of Australian University Degrees: Bachelor and Research Higher Degrees

The investment in Australian bachelor and research degrees results in significant economic benefits for the individual and for society.