Experimental Study on Wastewater Treatment of Expressway Service Area in BAF
The removal effect of main pollutant which was in the wastewater of expressway service area was investigated in the up-flow biological aerated filter (UBAF) with different hydraulic loadings. The result showed that with the increase of hydraulic loading, the removal rates of the chemical oxygen demand (COD) and turbidity decreased. At hydraulic loading of 0.5 m3/(m2&#x2022;h), removal rates of COD and turbidity were 79.6% and 80.2% respectively, which were better than that of 56.5% and 48.7% at hydraulic loading of 1.25 m3/(m2&#x2022;h).
The effect of bed material heights on the performance of biological aerated filter
when the oxidation of organic content and the nitrification of ammonia are in the same bioreactor, the competition for space, oxygen and organic carbon between the heterotrophic and nitrifying populations in different media heights affect mass transfer reactions and performance of biofilm reactor. The results showed that as a down flow biological aerated filter(BAF) with granular media, the active layer of nitrifiers is deeper than heterotrophs in BAF. And the optimum media height for the removal of SS,COD and NH 3-N is 40 cm,60 cm and 80 cm respectively. The removal efficiency of SS,COD and NH 3-N is 79.1%,63.9% and 96.4% respectively under the influent COD and NH 3-N of 122.1 mgCOD·L -1and 14.84 mgNH 3-N·L -1, influent flowing velocity of 15.8 L·h -1, and air:liquid ratio of 3:1.
Collagen dynamics in articular cartilage under osmotic pressure
Cartilage is a complex biological tissue consisting of collagen, proteoglycans and water. The structure and molecular mobility of the collagen component of cartilage were studied by 13C solid‐state NMR spectroscopy as a function of hydration. The hydration level of cartilage was adjusted between fully hydrated (∼80 wt% H2O) and highly dehydrated (∼30 wt% H2O) using the osmotic stress technique. Thus, the conditions of mechanical load could be simulated and the response of the tissue macromolecules to mechanical stress is reported. From the NMR measurements, the following results were obtained. (i) Measurements of motionally averaged dipolar 1H–13C couplings were carried out to study the segmental mobility in cartilage collagen at full hydration. Backbone segments undergo fast motions with amplitudes of ∼35° whereas the collagen side‐chains are somewhat more mobile with amplitudes between 40 and 50°. In spite of the high water content of cartilage, collagen remains essentially rigid. (ii) No chemical shift changes were observed in 13C cross‐polarization magic angle spinning spectra of cartilage tissue at varying hydration indicating that the collagen structure was not altered by application of high osmotic stress. (iii) The 1H–13C dipolar coupling values detected for collagen signals respond to dehydration. The dipolar coupling values gradually increase upon cartilage dehydration, reaching rigid limit values at ∼30 wt% H2O. This indicates that collagen is essentially dehydrated in cartilage tissue under very high mechanical load, which provides insights into the elastic properties of cartilage collagen, although the mechanical pressures applied here exceed the physiological limit. Copyright © 2006 John Wiley & Sons, Ltd.