Inflow based investigations on the efficiency of a lamella particle separator for the treatment of stormwater runoffs.

The present design of stormwater tanks is based on the creation of storage volume to retain stormwater and the prevention or reduction of stormwater overflows. The treatment of stormwater is often improved with mechanical equipment. The general layout rules do usually not include the appropriate choice of design inflow related to the chosen treatment equipment. In the following investigations it was the task to analyze the hydraulic efficiency and the overflow behaviour of a lamella particle separator inside a stormwater tank under different design approaches regarding the chosen design inflow. Therefore six scenarios with different precipitation yield approaches were chosen and applied to a given constant sized catchment to calculate the design inflows. For a given minimum particle size, the necessary number of lamellas were determined for the scenarios and standard stormwater tanks were dimensioned. These stormwater tanks were modelled in the hydrologic model SMUSI to investigate the overflow behaviour of the different tank sizes. The number of overflow events, their duration and maximum flow rates were the results of the modelling. Comparisons to the design inflows were carried out. The treated particles sizes at the overflow events were determined reversible and compared to the original chosen minimum particle sizes.

Biocompatibility of mannuronic acid-rich alginates.

Highly purified algin preparations free of adverse contaminants with endotoxins and other mitogens recently became available by a new purification process (Klöck et al., Appl. Microbiol. Biotechnol., 1994, 40, 638-643). An advantage of this purification protocol is that it can be applied to alginates with various ratios of mannuronic acid to guluronic acid. High mannuronic acid alginate capsules are of particular practical interest for cell transplantation and for biohybrid organs, because mannuronate-rich alginates are usually less viscous, allowing one to make gels with a higher alginate content. This will increase their stability and reduce the diffusion permeability and could therefore protect immobilized cells more efficiently against the host immune system. Here we report the biocompatibility of purified, mannuronic acid-rich alginate (68% mannuronate residues) in a series of in vitro, as well as in vivo, assays. In contrast to raw alginate extracts, the purified product showed no mitogenic activity towards murine lymphocytes in vitro. Its endotoxin content was reduced to the level of the solvent. Animal studies with these new, purified algin formulations revealed the absence of a mitogen-induced foreign body reaction, even when the purified material (after cross-linking with Ba2+ ions) is implanted into animal models with elevated macrophage activity (diabetes-prone BB/OK rat). Thus, alginate capsules with high mannuronic acid content become available for applications such as implantation. In addition to the utilization as implantable cell reactors in therapy and biotechnology, these purified algins have broad application potential as ocular fillings, tissue replacements, microencapsulated growth factors and/or interleukins or slow-release dosage forms of antibodies, surface coatings of sensors and other invasive medical devices, and in encapsulation of genetically engineered cells for gene therapy.

[Immunologic isolation of transplanted islets of Langerhans: microcapsules with defined molecular limits]. / Immunisolation transplantierter Langerhansscher Inseln: Mikrokapseln mit definierter molekularer Ausschlussgrenze.

Immunoisolated transplantation of islets of Langerhans in barium alginate microcapsules is a promising therapeutic approach to cure diabetes. An improved membrane for the coating of barium alginate microcapsules has been developed. Chemically stable barium alginate microcapsules with a controlled molecular weight cutoff between 9400 and 40,500 D were obtained after coating of barium alginate capsules in Polybrene solutions. Microcapsules prepared by this new method were still freely permeable to low molecular weight substances.