Pilot experiments with electrodialysis and ozonation for the production of a fertiliser from urine.

Pilot tests were performed with a process combination of electrodialysis and ozonation for the removal of micropollutants and the concentration of nutrients in urine. In continuous and batch experiments, maximum concentration factors up to 3.5 and 4.1 were obtained, respectively. The desalination capacity did not decrease significantly during continuous operation periods of several weeks. Membrane cleaning after 195 days resulted in approximately 35% increase in desalination rate. The Yeast Estrogen Screen (YES), a bioassay that selectively detects oestrogenic compounds, confirmed that about 90% of the oestrogenic activity was removed by electrodialysis. HPLC analysis showed that ibuprofen was removed to a high extent, while other micropollutants were below the detection limit. In view of the fact that ibuprofen is among the most rapidly transported micropollutants in electrodialysis processes, this result indicates that electrodialysis provides an effective barrier for micropollutants. Standardised plant growth tests were performed in the field with the salt solution resulting from the treatment by electrodialysis and subsequent ozonation. The results show that the plant height is comparable to synthetic fertilisers, but the crop yield is slightly lower. The latter is probably caused by volatilisation losses during field application, which can be prevented by improved application technologies.     

Imprcved Fast Neutron Tolerance of GaAs JFET's Operating in the Hot Electron Range

The fast neutron induced degradation of the electrical characteristics of n-channel GaAs junction field effect transistors (JFET's) operating in the Shockley mode (thermal equilibrium) was estimated previously. Advances in technology have led to the fabrication of devices with micron sized channel lengths which are capable of response at microwave frequencies. Short channel lengths, however, result in device operation under thermal nonequilibrium conditions and hot electron effects must be considered. The theory of Lehovec and Zuleeg, which provides the characteristics for JFET's operating in the hot electron range, is employed in this paper to estimate the neutron degradation of these devices. It is shown that JFET's operating in the hot electron range are more resistant to neutron exposure than are JFET's operating in the Shockley region. Devices with channel doping concentration of 1017 cm-3 are predicted to survive fluences of 1016 neutrons/cm2. Some preliminary test results are reported.     

D.C. leakage currents in ferroelectric memories

Abstract

Experimental data on d.c. leakage currents in lead zirconate titanate thin films (210 nm) are presented. The data show a flat, ohmic response up to a thresh-hold of approximately 2.0 V, above which they satisfy a modified Childl's Law, with a perfectly quadratic dependence: I = aV². This suggests that at 5 V operation the film behaves as a fully depleted device. The difficulty in distinguishing between Frenkel-Poole, Schottky emission, and true space-charge limited currents is briefly discussed.     

Radiation Effects in Gaas Junction Field-Effect Transistors

GaAs field-effect transistors for linear and digital circuits are finding applications in systems that have to function in a nuclear environment. This paper reviews and analyzes the radiation damage mechanisms in GaAs material and applies the material parameter changes to predict changes of electrical parameters of junction field-effect transistors due to exposure to fast neutrons and total dose ionizing radiation. The transient response to pulsed ionizing radiation is analyzed and experimental results are correlated with theoretical predictions. Annealing characteristics of radiation-generated defects are described. The prospects for hardening GaAs fieldeffect transistor integrated circuits against the effects of nuclear radiation are assessed.     

Transient Response of GaAs IC's to Ionizing Radiation

Transient responses of GaAs E-JFET planar integrated circuits caused by a 25 ns wide ionizing radiation pulse from a LINAC were measured. Present technology circuits with 2.5 ?m channel length devices have a measured logic upset level of about 1 × 1010 rad(GaAs)/s and a survival dose rate of approximately 1 × 1011 rad(GaAs)/s. A theoretical analysis for logic upset dose rate and a correlation of experimental results with theory is presented. For E-JFET devices with a channel length of 1 ?m, a logic upset dose rate of 1 × 1011 rad(GaAs)/s is predicted.     

Radiation effects in GaAs FET devices

The effects that space and nuclear radiation have on GaAs devices utilized for integrated circuit design are reviewed. The hardness capability of contemporary GaAs devices and logic circuits is presented in terms of four major nuclear and space radiation threat categories: total dose effects, dose rate effects, single particle phenomena, and neutron effects. The experimental test data and theoretical analyses presented demonstrate the tolerance of GaAs discrete JFETs and MESFETs and planar integrated circuits to fast neutron and ionizing radiation, under both transient and cumulative conditions.<>     

Leaching of biocides from façades under natural weather conditions

Biocides are included in organic building fa?ade coatings as protection against biological attack by algae and fungi but have the potential to enter the environment via leaching into runoff from wind driven rain. The following field study correlates wind driven rain to runoff and measured the release of several commonly used organic biocides (terbutryn, Irgarol 1051, diuron, isoproturon, OIT, DCOIT) in organic fa?ade coatings from four coating systems. During one year of exposure of a west oriented model house fa?ade in the Zurich, Switzerland area, an average of 62.7 L/m(2), or 6.3% of annual precipitation came off the four fa?ade panels installed as runoff. The ISO method for calculating wind driven rain loads is adapted to predict runoff and can be used in the calculation of emissions in the field. Biocide concentrations tend to be higher in the early lifetime of the coatings and then reach fairly consistent levels later, generally ranging on the order of mg/L or hundreds of μg/L. On the basis of the amount remaining in the film after exposure, the occurrence of transformation products, and the calculated amounts in the leachate, degradation plays a significant role in the overall mass balance.     

Behavior of metallic silver nanoparticles in a pilot wastewater treatment plant

We investigated the behavior of metallic silver nanoparticles (Ag-NP) in a pilot wastewater treatment plant (WWTP) fed with municipal wastewater. The treatment plant consisted of a nonaerated and an aerated tank and a secondary clarifier. The average hydraulic retention time including the secondary clarifier was 1 day and the sludge age was 14 days. Ag-NP were spiked into the nonaerated tank and samples were collected from the aerated tank and from the effluent. Ag concentrations determined by inductively coupled plasma-mass spectrometry (ICP-MS) were in good agreement with predictions based on mass balance considerations. Transmission electron microscopy (TEM) analyses confirmed that nanoscale Ag particles were sorbed to wastewater biosolids, both in the sludge and in the effluent. Freely dispersed nanoscale Ag particles were only observed in the effluent during the initial pulse spike. X-ray absorption spectroscopy (XAS) measurements indicated that most Ag in the sludge and in the effluent was present as Ag(2)S. Results from batch experiments suggested that Ag-NP transformation to Ag(2)S occured in the nonaerated tank within less than 2 h. Physical and chemical transformations of Ag-NP in WWTPs control the fate, the transport and also the toxicity and the bioavailability of Ag-NP and therefore must be considered in future risk assessments.