Occurrence and removal of priority pollutants by lamella clarification and biofiltration

This study investigates the occurrence of all priority substances (n = 41) listed in the Water Framework Directive and additional substances (n = 47) in raw sewage, as well as the removal performance of lamella clarification and biofiltration techniques. Once the efficiency of both types of techniques has been assessed for typical wastewater parameters, the differences in each technique's ability to remove pollutants becomes obvious; nevertheless, pollutant removal in quantitative terms still depends on the physico-chemical properties of the compounds used and operating conditions within the selected facility. For lamella clarification, the removal of organic chemicals was found to be primarily correlated with their sorption potential and, hence, strongly dependent upon log K_ow of the compound under study. Compounds with a strong hydrophobic character (log K_ow > 4.5) are removed to a significant extent (approx. 85%), while hydrophilic compounds (log K_ow < 3.5) are poorly removed (<20%). For biofiltration, the removal of chemicals appears to be compound-dependent, although this outcome involves several mechanisms, namely: i) physical filtration of total suspended solids, ii) volatilisation, iii) sorption, and iv) biotransformation of substances. Even if the complex processes within a biofilter system do not yield an accurate prediction of pollutant removal, two groups of chemicals can still be clearly identified: i) hydrophobic or volatile compounds, for which moderate to high removal rates are observed (from 50% to over 80%); and ii) hydrophilic, non-volatile and refractory compounds for which a low removal rate would be expected (<20%).     

Construction,application and validation of selection evaluation model (SEM) for intelligent HVAC control system

Design teams are confronted with the quandary of choosing apposite building control systems to suit the needs of particular intelligent building projects, due to the availability of innumerable ‘intelligent’ building products and a dearth of inclusive evaluation tools. This paper is organised to develop a model for facilitating the selection evaluation for intelligent HVAC control systems for commercial intelligent buildings. To achieve these objectives, systematic research activities have been conducted to first develop, test and refine the general conceptual model using consecutive surveys; then, to convert the developed conceptual framework into a practical model; and, finally, to evaluate the effectiveness of the model by means of expert validation. The results of the surveys are that ‘total energy use’ is perceived as the top selection criterion, followed by the ‘system reliability and stability’, ‘operating and maintenance costs’, and ‘control of indoor humidity and temperature’. This research not only presents a systematic and structured approach to evaluate candidate intelligent HVAC control system against the critical selection criteria (CSC), but it also suggests a benchmark for the selection of one control system candidate against another.     

Some Views on the Contribution of Design Theory to Engineering Education

This paper aims at presenting the organisation,the findings and the lessons learnt of a design casestudy workshop organized in the context of UB1-HIT joint master programme.After presenting the content and the evolution of this workshop over the years,findings and lessons learnt are discussed and final conclusions and perspectives are being proposed at the end of the paper.     

A Note on the Ladyženskaja-Babuška-Brezzi Condition

The analysis of finite-element-like Galerkin discretization techniques for the stationary Stokes problem relies on the so-called LBB condition. In this work we discuss equivalent formulations of the LBB condition.     

Minimizing the normalized sum of square for workload deviations on m parallel processors

In many organizations, it is desirable to distribute workload as equally as possible among a group of employees or machines. This paper proposes a performance measure, that we call the Normalized Sum of Square for Workload Deviations (NSSWD), and studies the problem of how to schedule a set of n jobs on m parallel identical processors in order to minimize the NSSWD. The NSSWD criterion is relevant where uniformity of wear to machines or of workload to employees is desirable. An algorithm, called Workload Balancing (WB), is proposed for solving this problem. Moreover, we perform a simulation experiment to evaluate WB against several well-known heuristics in the literature. Lastly, we discuss the computational results obtained from the simulation experiment.