A comparative assessment of biofiltration and activated sludge diffusion for odour abatement

The deodorization performance of a biofilter and an activated sludge diffusion (AS) system was comparatively evaluated in terms of removal efficiency (RE) and process stability at empty bed residence times (EBRT) ranging from 94 to 32s. Both bioreactors were fed with a synthetic odorous emission containing H(2)S, butanone and toluene at 23.6-43.3, 4.3-6.3 and 0.4-0.6 mg m(-3), respectively. While the outlet H(2)S concentration was always lower than 1.4 mg m(-3), the REs for butanone and toluene remained higher than 95% in both bioreactors regardless of the EBRT. The continuous supply of wastewater in the AS unit did not affect removal and appeared to be a requirement for efficient pollutant abatement. Despite the narrow carbon source spectrum treated, the AS system maintained a large bacterial diversity over time. Therefore, the results obtained confirmed the potential of AS systems as a robust and efficient biotechnology for odour treatment in WWTPs.     

Recovery of struvite from animal wastewater and its nutrient leaching loss in soil

Contaminants in swine wastewater were recovered in the form of struvite, a crystal of magnesium ammonium phosphate (MAP), using a newly designed process, and the leaching loss of MAP in soil was examined. The continuous flow process was operated under optimal conditions: 1.0 molar ratio of magnesium (Mg) addition with respect to orthophosphate (OP) and an aeration rate of 0.73 L/L min. Five treatments were performed with three replications for soil pH and nutrient leaching loss tests. It was found that 93% of the OP in the swine wastewater was crystallized, and the MAP crystal formation was verified by X-ray diffraction (XRD) and scanning electron microscope (SEM) analyses. The analyses revealed that the pattern of pH change and N leaching losses for MAP-treated soil were remarkably different from those for fused super phosphate (FSP)-urea-treated soils. The pH levels for the control and FSP-urea-treated soils after a five-week experiment were unchanged or slightly decreased, whereas an increase in pH was observed in the MAP-treated soils. Leaching loss of N was higher in FSP-urea treatments, with MAP treatments showing N losses of only 1.93 and 2.05%, respectively, while FSP-urea treatments showed N losses of 7.82 and 6.47%, respectively, during the same period. Phosphate (P) leaching was very slow in both MAP- and FSP-treated groups.     

Fluctuation analysis and faradaic impedance at micro liquid/liquid interface—II

Tetramethylammonium, tetraethylammonium and cesium ion transfer reactions across the water/nitrobenzene micro-interface were studied by fluctuation analysis and ac impedance technique to elucidate the origin of micro-convections at the interface. It is shown that the effect of micro-convections on ion transfer process is enhanced by non-equilibrium conditions at the interface, ie by the existence of a mixed potential difference.     

Ion-induced desorption of surface contaminants

We report measurements of mean desorption areas per incident ion for hydrocarbon contaminated surfaces of different solids bombarded with 30 keV H₂⁺, O⁺₂, and Ar⁺ and 15 keV O⁺ ions. The results for heavy ions are consistent with a momentum transfer mechanism for desorption. A molecular effect is observed for O₂⁺ ions which desorb significantly more than two separate O⁺ of the same velocity. Our results for hydrogen ions; together with results of other workers for low-energy light ions, lead us to the conclusion that desorption occurs efficiently in inelastic collisions.     

Prior assessments for bands of probability measures: Empirical bayes analysis

Summary A useful non-parametric class of priors is formed as those probability measures which lie between an upper and a lower measure and it is called a Wand of probability measures Lavine (1991), Moreno and Pericchi (1991), Wasserman and Kadane (1992). This class allows considerable freedom in tail behaviour as long as the upper and lower measures have different tails. This property is inherited from the class of Interval of measures DeRobertis and Hartigan (1981), from which the Band of probability measures class is obtained by restricting attention to those measures that integrate to one, Although the analysis of this restricted class is somewhat more involved, the restriction is quite natural and may lead to robustness in situations in which the larger class is not robust. In fact, it is a generalization of the class implicitly considered by Edwards, Lindman and Savage (1963) in “Precise Measurement Theory”. An empirical analysis is performed with the two classes above. That is, we choose within a class of priors that measure which maximizes the probability of the actual data Good (1983). This “optimal” measure is used in this robust Bayesian context to assess the band of probability measures.     

Practical adaptive notch filter for missile bending mode rejection

A practical adaptive notch filter based on the /spl Hscr//sub /spl infin// bending frequency estimator is proposed to remove the time-varying structural mode of a missile from the rate sensor measurements. Simulation results using flight test data show the reliable bending frequency estimation performance with this new technique.     

Diffraction by an arbitrary-angled dielectric wedge. II. Correctionto physical optics solution

For pt.I see ibid., vol.39, no.9, p.1272-81 (1991). The error of the physical optics solution for the E-polarized plane wave incidence in connection with diffraction by an arbitrary-angled dielectric wedge is corrected by calculating the nonuniform current distributed along the dielectric interfaces. Two kinds of series expansions to the nonuniform current are employed. One is an asymptotic expansion as the multipole line source located at the edge of the dielectric wedge, since the correction field seems to be a cylindrical wave emanating from the edge in the far-field region. The other is arbitrary electric and magnetic surface currents expanded by infinite series of the Bessel functions, i.e. the Neumann expansion, of which fractional order is chosen to satisfy the edge condition near the edge of the dielectric wedge in the static limit. Both of the two different expansion coefficients for a wedge angle of 45°, relative dielectric constants 2, 10, and 100, and the E-polarized incident angle of 150° are evaluated by solving the dual series equation numerically after finite truncation