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-An existing analytical pore-scale model is adapted in order to predict the pressure drop over a biofilter. The difference compared to a conventional packed bed is the effect of biofilm growth that has to be incorporated. Being able to predict the pressure drop and also the specific surface area of the packing material over several days of biofilter operation, aids in the optimization of the biofiltration process. The proposed model is validated against available experimental data of a biofilter with schist as packing material. The data includes measured pressure drop values, flow rates and porosity for 7 different days over a 106 day period. Two methods are proposed to predict the biofilm affected specific surface area. The first method is based on a relationship available in the literature in which the biofilm thickness and biofilm affected porosity are incorporated into the biofilm affected specific surface area. A second method is proposed in which the specific surface area can be determined if measured pressure drop and superficial velocity values are provided. The analytical pressure drop prediction is compared to an empirically adapted model proposed in the literature, with satisfactory results. The advantage of the analytical model is that it can provide physical meaning to the adaptations made.

Liabilities play a very important financial role in business operations, professional service providers as well as in the personal lives of people. It is possible that a single claim may even lead to the bankruptcy of the defendant. The claims handling process of liability insurance by short-term insurers is therefore very important to these parties as it should be clear that liability claims may have enormous and far-reaching financial implications for them. The objective of this research paper embodies the improvement of financial decision-making by short-term insurers with regard to the claims handling process of liability insurance. Secondary data was initially studied which provided the basis to compile a questionnaire for the empirical survey. The leaders of liability insurance in the South African short-term insurance market that represented 69.5% of the annual gross written premiums received for liability insurance in South Africa were the respondents of the empirical study. The perceptions of these short-term insurers provided the primary data for the vital conclusions of this research. This paper pays special attention to the importance of the claims handling factors of liability insurance, how often the stipulations of liability insurance policies are adjusted by the short-term insurers to take the claims handling factors into consideration, as well as the problem areas which short-term insurers may experience during the claims handling process. Feasible solutions to address the problem areas are also discussed.

In this study, experimental pressure drop data obtained for a biofilter containing expanded schist as packing material is used in order to characterize the packed bed properties. The biofilter was operated over a period of 106 days. Two modelling approaches were used: an empirical and an analytical approach. In the empirical approach the pressure drop prediction of the modified-Macdonald model, Representative Unit Cell (RUC) model and the model of Comiti and Renaud are used to determine the biofilm affected porosity, specific surface area and tortuosity. This was done by using Excel  Solver which is based on an optimization method. In the analytical approach the biofilm thickness is incorporated into the RUC model and used to predict the specific surface area, as well as the pressure drop. The effect of particle sphericity on the pressure drop is also investigated. The results obtained by the two modelling approaches are compared and analysed. The suitability of the three models used in the biofilter analysis is also determined based on the accuracy of predictions compared to the experimental data.