Controlled release of growth factors using synthetic glycosaminoglycans in a modular macroporous scaffold for tissue regeneration.

Healthy regeneration of tissue relies on a well-orchestrated release of growth factors. Herein, we show the use of synthetic glycosaminoglycans for controlled binding and release of growth factors to induce a desired cellular response. First, we screened glycosaminoglycans with growth factors of interest to determine kon (association rate constant), koff (dissociation rate constant), and Kd (equilibrium rate constant). As proof-of-concept, we functionalized an elastin-like recombinamer (ELR) hydrogel with a synthetic glycosaminoglycan and immobilized fibroblast growth factor 2 (FGF2), demonstrating that human umbilical vein endothelial cells cultured on top of ELR hydrogel differentiated into tube-like structures. Taking this concept further, we developed a tunable macroporous ELR cryogel material, containing a synthetic glycosaminoglycan and FGF2 that showed increased blood vessel formation and reduced immune response compared to control when implanted in a subcutaneous mouse model. These results demonstrated the possibility for specific release of desired growth factors in/from a modular 3D scaffold in vitro and in vivo.

Oxygen uptake rate measurements for evaluation of ozonation of municipal wastewater.

Ozonation has become more frequently used as oxidant to reduce chemical oxygen demand (COD) and toxic substances in wastewater originating from different industrial processes. An ozonation pilot plant followed by two parallel biological filters are used to investigate the possibility to reduce the high concentration of refractory COD in the effluent from a municipal wastewater treatment plant, partly loaded with biologically treated wastewater from a large pharmaceutical industry. COD measurements are used to evaluate the overall reduction of organic matter, oxygen uptake rate (OUR) and volatile fatty acids measurements are used for evaluation of the biodegradability of the remaining COD after ozonation. The impact of the ozone dose on the overall COD degradation and degradability of the remaining COD has been estimated. Biochemical oxygen demand (BOD) measurements confirm that parts of the COD are converted into biodegradable organic matter by ozonation. Biofilters following the ozonation plant secure that any degradable organic matter produced by ozonation is removed, which is confirmed from OUR-measurements.

Applicability of experience from laboratory reactors with biological phosphorus removal in full-scale plants.

Enhanced biological phosphorus removal (EBPR) has been used at many wastewater treatment plants all over the world for many years. In this study a full-scale sludge with good EBPR was tested with P-release batch tests and combined FISH/MAR (fluorescence in situ hybridisation and microautoradiography). Proposed models of PAOs and GAOs (polyphosphate- and glycogen-accumulating organisms) and microbial methods suggested from studies of laboratory reactors were found to be applicable also on sludge from full-scale plants. Dependency of pH and the uptake of both acetate and propionate were studied and used for calculations for verifying the models and results from microbial methods. All rates found from the batch tests with acetate were higher than in the batch tests with propionate, which was explained by the finding that only those parts of the bacterial community that were able to take up acetate anaerobically were able to take up propionate anaerobically.

Experience from 10 years of full-scale operation with enhanced biological phosphorus removal at Oresundsverket.

Ten years of full-scale experience with enhanced biological phosphorus removal (EBPR) has been evaluated. During the start-up period lack of carbon source was the main operational problem and a higher level of volatile fatty acids was secured by introducing a primary sludge hydrolysis. Acidic thermal sludge hydrolysis was used as the sludge treatment method at the plant during about three years. One effluent stream, rich in carbon and precipitant, was brought back to the process leading to an improvement of the phosphorus removal both by an improved biological process and chemical precipitation. A quite stable process of EBPR was developed with low levels of effluent phosphorus concentration. Stringent effluent discharge limits during short evaluation periods necessitated a continued work for improvement of the short-term stability. During periods with lack of carbon, such as industrial holiday or rainy periods, both simultaneous precipitation and reduced aeration have been successfully tested as strategies for securing low levels of effluent phosphorus.

Use of phosphorus release batch tests for modelling an EBPR pilot plant.

The aim of this study was to evaluate how routinely performed phosphorus release tests could be used when modelling enhanced biological phosphorus removal (EBPR) using activated sludge models such as ASM2d. A pilot plant with an extensive analysis programme was used as basis for the simulations. Without any calibration the prediction of phosphorus removal was poor and the initial release rates from the simulations were not similar to those found from the laboratory tests. A period with low organic loading was chosen as a calibration period. In this period averages of daily influent measurements were used as influent parameters. First, calibration was performed in order to fit effluent COD and MLVSS in the sludge. Next, the phosphorus content in the sludge was decreased to the measured level by decreasing the fermentation rate. Finally, the initial phosphorus release rate was calculated from a simulated batch test and the PHA uptake rate was increased to fit this release rate with the average initial rates from laboratory batch tests performed during the period. The calibrated model was verified with data from the subsequent period where acetate was dosed.