Solids handling can contribute to a significant portion of the operational costs of a wastewater treatment plant, contributing up to 50% of the total expenses in certain instances. Sludge dewatering and drying therefore become necessary not only from the operational perspective, but also from the economical viewpoint. The J-Vap process combines the above-mentioned processes, by pressure filtration of sludge followed by application of vacuum and heat. However, when cationic polymer conditioned sludge is dewatered in the J-Vap, the polymer is suspected to interact with the filter media at high temperatures, resulting in the formation of a skin layer that hinders efficient dewatering. The first part of the study has looked at various digestion processes and how they affect the skin formation phenomenon. The results showed that temperature played a significant role in determining the amount of polymer that adhered to the filter media. The second part of the study focused on different kinds of digestion processes and their effects on extracellular polymeric substances, bound water content and dewatering. Bound water tests were used to determine the maximum achievable solids concentration on dewatering. Bound water content of solids obtained from field centrifuges run at different torques and g values were evaluated and fitted on a standard graph obtained from lab pressed sludge with different solids concentration. The bound water was seen to decrease with increasing solids content till 20%, after which a nearly constant 1.0 g of bound water was present for every gram of dry solids seen. The results indicate that nearly 50% solids concentration could be achieved on mechanical dewatering. In reality, only 30 to 35% solids concentration was attained both in the lab and on the field. It was determined that dilatometry attributed the increase in cake solids to the decrease in bound water. However, the use of bound water as a predictive tool for determining cake solids was not practical since the bound water calculations use the solids content in the calculations. / Master of Science

One of the most important aspects for all life on this planet is the act to keep their biological processes in a state where they do not reach equilibrium. One part in the upholding of this imbalanced state is the barrier between the cells and their surroundings, created by the cell membrane. Additionally, terrestrial animal life often requires a barrier that protects the organism's body from external hazards and water loss. As an alternative to experiments, the investigation of the processes occurring at these barriers can be performed by using molecular dynamics simulations. Through this method we can obtain an atomistic description of the dynamics associated with events that are not accessible to experimental setups.  In this thesis the first paper presents an improved particle-mesh Ewald method for the calculation of long-range Lennard-Jones interactions in molecular dynamics simulations, which solves the historical performance problem of the method. The second paper demonstrate an improved implementation, with a higher accuracy, that only incurs a performance loss of roughly 15% compared to conventional simulations using the Gromacs simulation package. Furthermore, the third paper presents a study of cholesterol's effect on the permeation of six different solutes across a variety of lipid bilayers. A laterally inhomogeneous permeability in cholesterol-containing membranes is proposed as an explanation for the large differences between experimental permeabilities and calculated partition coefficients in simulations. The fourth paper contains a coarse-grained simulation study of a proposed structural transformation in ceramide bilayer structures, during the formation of the stratum corneum. The simulations show that glycosylceramides are able to stabilize a three-dimensionally folded bilayer structure, while simulations with ceramides collapse into a lamellar bilayer structure. / <p>QC 20160308</p>