Comparison of batch sorption tests, pilot studies, and modeling for estimating GAC bed life

Saint Paul Regional Water Services (SPRWS) in Saint Paul, MN experiences annual taste and odor episodes during the warm summer months. These episodes are attributed primarily to geosmin that is produced by cyanobacteria growing in the chain of lakes used to convey and store the source water pumped from the Mississippi River. Batch experiments, pilot-scale experiments, and model simulations were performed to determine the geosmin removal performance and bed life of a granular activated carbon (GAC) filter-sorber. Using batch adsorption isotherm parameters, the estimated bed life for the GAC filter-sorber ranged from 920 to 1241 days when challenged with a constant concentration of 100 ng/L of geosmin. The estimated bed life obtained using the AdDesignS model and the actual pilot-plant loading history was 594 days. Based on the pilot-scale GAC column data, the actual bed life (>714 days) was much longer than the simulated values because bed life was extended by biological degradation of geosmin. The continuous feeding of high concentrations of geosmin (100-400 ng/L) in the pilot-scale experiments enriched for a robust geosmin-degrading culture that was sustained when the geosmin feed was turned off for 40 days. It is unclear, however, whether a geosmin-degrading culture can be established in a full-scale filter that experiences taste and odor episodes for only 1 or 2 months per year. The results of this research indicate that care must be exercised in the design and interpretation of pilot-scale experiments and model simulations for predicting taste and odor removal in full-scale GAC filter-sorbers. Adsorption and the potential for biological degradation must be considered to estimate GAC bed life for the conditions of intermittent geosmin loading typically experienced by full-scale systems.     

Endocrine disrupters in the aquatic environment: the Austrian approach--ARCEM.

A consortium of Austrian scientists (ARCEM) carried out a multidisciplinary environmental study on Austrian surface and ground waters including chemical monitoring, bioindication, risk assessment and risk management for selected endocrine disrupters: 17beta-estradiol, estriol, estrone, 17alpha-ethinylestradiol, 4-nonylphenol, 4-nonylphenol ethoxylates (4-NP1EO, 4-NP2EO) and their degradation products, ocytlphenol, ocytlphenol ethoxylates (OP1EO, OP2EO) as well as bisphenol A. To obtain data representative for Austria, a material flow analysis served to select relevant compounds and water samples were collected monthly over one year at those sites routinely used in Austrian water quality control. The following results were obtained and conclusions drawn: 1. Chemical monitoring: As compared to other countries, relatively low levels of pollution with endocrine disrupters were detected. 2. Bioindication: In the surface waters under study, male fish showed significant signs of feminization and demasculinization (increased production of the egg-yolk protein and histological changes of the gonads. 3. Risk assessment: For humans, exposure via either drinking water abstraction (ground water) or fish consumption was considered. The exposure levels of the compounds under study were below those considered to result in human health risks. Likewise, for bisphenol A and octylphenols, there was no indication for risk posed upon the aquatic environment (fish). However, nonylphenol or 17alpha-ethinylestradiol exposure along with results of bioindication (2) suggest a borderline estrogenic activity in a considerable number of surface waters. Consequently the emissions of these substances into the surface waters affected have to be reduced. 4. Risk management: Waste water treatment experiments revealed a positive correlation between the removal rate of endocrine disrupters from the waste water and the sludge retention time in the treatment plants. These substances are removed to a higher extend at low loaded plants designed for nutrient removal than at plants that remove carbon and/or employ nitrification only. As to drinking water treatment, chlorine dioxide and ozone were found to eliminate all investigated substances, except nonylphenol ethoxylates. (For the complete study see: www.arcem.at)     

Determination of heart time volume using the Fick principle in the early postoperative phase after correction of congenital heart defects. Comparison of the calculation of arterio-mixed venous oxygen differences and pulmonary oxygen uptake with the calculation of arterial-central venous oxygen differences and pulmonary oxygen uptake

Comparison of the calculation by means of the arterio-mixed venous oxygen difference and the oxygen uptake with the calculation by means of the arterio-central venous oxygen difference and the oxygen uptake. OBJECTIVE: How reliable is the measurement of cardiac output on Fick's principle without a pulmonary artery catheter? SETTING: PICU in an University hospital. DESIGN: In the postoperative period following complete repair of congenital heart disease we carried out 91 simultaneous measurements of blood gases in 45 infants and children (mean age 18.6 months, mean body weight 8.9 kg) from a systemic artery, the A. pulmonalis, and the V. cava superior. We also determined the pulmonary oxygen uptake in 24 patients (48 measurements). Cardiac output was calculated on Fick's principle using the arterio-mixed venous oxygen difference and the pulmonary oxygen uptake (HZV a-pa) and compared to the cardiac output derived from the central venous values (HZV a-zv). We differentiated between patients with a left to right shunt of 10% or more postoperatively (group A, n = 18) and all others (group B, n = 27). RESULTS: In both groups the correlation coefficient between HZV a-zv and HZV a-pa was high (group A: r = 0.97, group B: r = 0.94). In group A HZV a-pa (mean: 1958 ml/min) was higher than HZV a-zv (mean: 1340 ml/min), group B showed the opposite situation (mean HZV a-pa: 1136 ml/min, mean HZV a-zv: 1373 ml/min). With the Wilcoxon signet-rank test we found significant differences between the partial pressure of oxygen and the saturation of central venous and mixed venous blood samples in both groups, but HZV a-zv and HZV a-pa were different significantly on a level of p < or = 0.01 only in group A. CONCLUSIONS: In both groups HZV a-pa and HZV a-zv correlated well. Therefore, if a pulmonary artery catheter is not inserted; the course of the cardiac output can be calculated with acceptable reliability from the central venous blood gases. By means of Fick's principle the pulmonary blood flow is determined, which is higher than the systemic blood flow in cases of left to right shunting, because of the recirculation in the pulmonary blood circuit. Interpreting the results this has to be taken into account.     

Environmental risk assessment for quaternary ammonium compounds: a case study from Austria.

Quaternary ammonium compounds (QAC) are widely used as disinfectants, biocides, and detergents, among a variety of other applications. The cationic surface-activity of QAC determines their potential to act as a biocide on both target and non-target organisms. This study aims to provide a broad-based environmental risk characterization and evaluation for selected QAC with particular focus on the situation in Austrian rivers. A modular study design was employed involving environmental exposure characterization, QAC fate and effect analysis in wastewater, ecotoxicological effect characterization, and environmental risk evaluation. A wide array of Austrian surface waters and wastewater effluents were screened for the selected key compounds, benzalkonium chlorides and dialkyldimethylammonium chlorides with different C-chain lengths. Ecotoxicological effect characterization was based on both microbiotests for a set of representative aquatic organisms and a literature review. For risk evaluation, the PEC/PNEC ratio was above 1 for some rivers. Notably, small rivers with a high particulate matter were contaminated with QAC in the case of high water incidents. Hence, for the Austrian sites studied, a QAC-derived risk to sensitive aquatic non-target organisms could not be excluded.     

Determinants of young children's search strategies in a large-scale environment.

26 3–6 yr olds searched for an object after traveling a route along which the object was used and later discovered missing (critical events). Ss then recalled the order of locations along the traveled route (sequence recall) and the locations for critical events (event recall); they also drew a map of the search environment. The correlation between event recall and search scores was significant only for Ss with good sequence recall. Correlations between sequence recall and search scores were higher for Ss who placed locations on the route in drawing maps. It is concluded that the acquisition of route knowledge in the development of spatial representation determined the likelihood that inferences would be made. When inferences were made, the accuracy of memories for sequences and events further determined the accuracy of the inferred critical search area. (8 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Magnesium secondary alloys: Alloy design for magnesium alloys with improved tolerance limits against impurities

The development of secondary magnesium alloys requires a completely different concept compared with standard alloys which obtain their corrosion resistance by reducing the levels of impurities below certain alloy and process depending limits. The present approach suitable for Mg-Al based cast and wrought alloys uses a new concept replacing the β-phase by τ-phase, which is able to incorporate more impurities while being electro-chemically less detrimental to the matrix. The overall experimental effort correlating composition, microstructure and corrosion resistance was reduced by using thermodynamic calculations to optimise the alloy composition. The outcome is a new, more impurity tolerant alloy class with a composition between the standard AZ and ZC systems having sufficient ductility and corrosion properties comparable to the high purity standard alloys.     

Matched direction detectors and estimators for array processing with subspace steering vector uncertainties

In this paper, we consider the problem of estimating and detecting a signal whose associated spatial signature is known to lie in a given linear subspace but whose coordinates in this subspace are otherwise unknown, in the presence of subspace interference and broad-band noise. This situation arises when, on one hand, there exist uncertainties about the steering vector but, on the other hand, some knowledge about the steering vector errors is available. First, we derive the maximum-likelihood estimator (MLE) for the problem and compute the corresponding Crame/spl acute/r-Rao bound. Next, the maximum-likelihood estimates are used to derive a generalized likelihood ratio test (GLRT). The GLRT is compared and contrasted with the standard matched subspace detectors. The performances of the estimators and detectors are illustrated by means of numerical simulations.     

Treatment of superficial basal cell carcinoma and squamous cell carcinoma in situ with a high-energy pulsed carbon dioxide laser

BACKGROUND: High-energy pulsed carbon dioxide (CO2) lasers have been used extensively to resurface wrinkled and photodamaged skin with a low risk of scarring. Results of histological studies demonstrate precise ablation depths in treated skin with minimal thermal damage to underlying tissue. Our objective was to determine if a pulsed CO2 laser could effectively ablate superficial malignant cutaneous neoplasms (superficial multifocal basal cell carcinoma [BCC] and squamous cell carcinoma [SCC] in situ). OBSERVATIONS: Thirty superficial neoplasms (17 BCCs and 13 SCCs) and their surrounding 3-mm margins were treated with either 2 or 3 passes of a pulsed CO2 laser (500 mJ, 2-4 W) using a 3-mm collimated handpiece. The treated areas were subsequently excised and evaluated histologically by serial sectioning at 5-micron intervals for residual tumor at the deep and lateral margins. Average patient age was greater for those with SCCs than for those with BCCs (76.5 vs 56.7 years; P = .001). The average tumor thickness of SCC in situ was significantly greater than that of superficial BCC (0.57 vs 0.34 mm; P = .01). All (9 of 9 patients) BCCs were completely ablated with 3 passes, and residual tumor in the deep margins was seen in 5 of 8 patients treated with 2 passes of the pulsed CO2 laser (P = .005). Incomplete vaporization of the SCC depth was seen in 3 of 7 patients treated with 3 passes and in 2 of 6 patients treated with 2 passes. Those SCCs incompletely treated were significantly thicker than those completely ablated (0.65 vs 0.41 mm; P = .01). Positive lateral margins were seen in 1 BCC and 3 SCC specimens. CONCLUSIONS: Pulsed CO2 laser treatment can be effective in ablating superficial BCC. Treatment of the neoplasm and a minimum of 4-mm margins with 3 passes (500 mJ, 2-4 W) is recommended for complete vaporization using this laser system. Because 3 passes did not completely ablate all SCC in situ, use of this modality alone is not recommended for treatment of thick or keratotic lesions. No direct comparison of efficacy can be made with other destructive modalities that have not been evaluated with comparably sensitive histological techniques. Further study is needed to establish any cosmetic advantage of pulsed CO2 lasers over other destructive modalities for treatment of superficial malignant neoplasms and long-term cure rates.