Removal of micropollutants in municipal wastewater treatment plants by powder-activated carbon.

Micropollutants (MP) are only partly removed from municipal wastewater by nutrient removal plants and are seen increasingly as a threat to aquatic ecosystems and to the safety of drinking water resources. The addition of powder activated carbon (PAC) is a promising technology to complement municipal nutrient removal plants in order to achieve a significant reduction of MPs and ecotoxicity in receiving waters. This paper presents the salient outcomes of pilot- and full-scale applications of PAC addition in different flow schemes for micropollutant removal in municipal wastewater treatment plants (WWTPs). The sorption efficiency of PAC is reduced with increasing dissolved organic carbon (DOC). Adequate treatment of secondary effluent with 5-10 g DOC m(-3) requires 10-20 g PAC m(-3) of effluent. Counter-current use of PAC by recycling waste PAC from post-treatment in a contact tank with an additional clarifier to the biology tank improved the overall MP removal by 10 to 50% compared with effluent PAC application alone. A dosage of 15 g PAC m(-3) to a full-scale flocculation sand filtration system and recycling the backwash water to the biology tank showed similar MP elimination. Due to an adequate mixing regime and the addition of adapted flocculants, a good retention of the fine fraction of the PAC in the deep-bed filter were observed (1-3 g TSS m(-3); TSS: total suspended solids). With double use of PAC, only half of the PAC was required to reach MP removal efficiencies similar to the direct single dosage of PAC to the biology tank. Overall, the application of PAC in WWTPs seems to be an adequate and feasible technology for efficient MP elimination (>80%) from wastewater comparable with post ozonation.

Chronic network stimulation enhances evoked action potentials.

Neurons cultured on multielectrode arrays almost always lack external stimulation except during the acute experimental phase. We have investigated the effects of chronic stimulation during the course of development in cultured hippocampal neural networks by applying paired pulses at half of the electrodes for 0, 1 or 3 r/day for 8 days. Spike latencies increased from 4 to 16 ms as the distance from the stimulus increased from 200 to 1700 microm, suggesting an average of four synapses over this distance. Compared to no chronic stimulation, our results indicate that chronic stimulation increased evoked spike counts per stimulus by 50% at recording sites near the stimulating electrode and increased the instantaneous firing rate. On trials where both pulses elicited responses, spike count was 40-80% higher than when only one of the pulses elicited a response. In attempts to identify spike amplitude plasticity, we found mainly amplitude variation with different latencies suggesting recordings from neurons with different identities. These data suggest plastic network changes induced by chronic stimulation that enhance the reliability of information transmission and the efficiency of multisynaptic network communication.

Neuron network activity scales exponentially with synapse density.

Neuronal network output in the cortex as a function of synapse density during development has not been explicitly determined. Synaptic scaling in cortical brain networks seems to alter excitatory and inhibitory synaptic inputs to produce a representative rate of synaptic output. Here, we cultured rat hippocampal neurons over a three-week period to correlate synapse density with the increase in spontaneous spiking activity. We followed the network development as synapse formation and spike rate in two serum-free media optimized for either (a) neuron survival (Neurobasal/B27) or (b) spike rate (NbActiv4). We found that while synaptophysin synapse density increased linearly with development, spike rates increased exponentially in developing neuronal networks. Synaptic receptor components NR1, GluR1 and GABA-A also increase linearly but with more excitatory receptors than inhibitory. These results suggest that the brain's information processing capability gains more from increasing connectivity of the processing units than increasing processing units, much as Internet information flow increases much faster than the linear number of nodes and connections.

Treatment of toilet wastewater for reuse in a membrane bioreactor.

Toilet wastewater is treated and reused on site at Europe's highest membrane bioreactor (MBR), located in a cable car mountain station in the ski resort of Zermatt. Negative impacts on the sensitive mountain environment are minimised by reusing close to 100% of the treated wastewater for toilet flushing. Besides 100% nitrogen removal, 80% of phosphorus was also eliminated. This paper presents operational results, optimisations of sludge management, decoloration and long-term maintenance of biomass in the very low-loaded summer season. From a global view the experiences and results of the project are of great importance, proposing a solution to a problem existing 100-fold in the Alps as well as in arid regions all over the world: reducing water consumption for sanitation by reuse.

Potential of activated sludge ozonation.

The disposal of sewage sludge and the agricultural use of stabilised sludge are decreasing due to more stringent regulations in Europe. An increasing fraction of sewage sludge must therefore be dewatered, dried, incinerated and the ashes disposed of in landfills. These processes are cost-intensive and also lead to the loss of the valuable phosphate resources incorporated in the sludge ash. The implementation of processes that could reduce excess sludge production and recycle phosphate is therefore recommended. Partial ozonation of the return sludge of an activated sludge system significantly reduces excess sludge production, improves the settling properties of the sludge and reduces bulking and scumming. The solubilised COD will also improve denitrification if the treated sludge is recycled to the anoxic zone. However, ozonation partly kills nitrifiers and could therefore lead to a decrease of the effective solid retention time of the nitrifier, thus reducing the safety of the nitrification. This paper discusses the effect of ozonation on sludge reduction, the operating stability of nitrification, the improvement of denitrification and also presents an energy and cost evaluation.

Potential of activated sludge disintegration.

The disposal of sewage sludge and the agricultural use of stabilised sludge are decreasing due to more stringent regulations in Europe. An increasing fraction of sewage sludge must therefore be dewatered, dried, incinerated and the ashes disposed of in landfills. These processes are cost-intensive and also lead to the loss of valuable phosphate resources incorporated in the sludge ash. The implementation of processes that could reduce excess sludge production and recycle phosphate is therefore recommended. Disintegration of biological sludge by mechanical, thermal and physical methods could significantly reduce excess sludge production, improve the settling properties of the sludge and reduce bulking and scumming. The solubilised COD could also improve denitrification if the treated sludge is recycled to the anoxic zone. However, disintegration partly inhibits and kills nitrifiers and could therefore shorten their effective solid retention time, thus reducing the safety of the nitrification. This paper discusses the potential of disintegration on sludge reduction, the operating stability of nitrification, the improvement of denitrification and also presents an energy and cost evaluation.

A new approach to improve sludge dewatering using a semi-continuous hydraulic press system.

In future, it will be necessary to incinerate an increasing proportion of the sludge produced by public wastewater treatment. In this context, equipment for more effective dewatering of sewage sludge is required. A hydraulic press system (Bucher HP) which has been used to date in the food industry could represent an alternative to the sludge dewatering systems currently used. The basic suitability of this press system was demonstrated in comprehensive industrial-scale trials at the Glarnerland STP (Switzerland). Dry solids contents of up to 43% were measured in the pressed sludge. Currently, the optimization of individual process parameters is being investigated in a pilot plant at the Schwelm STP operated by Wupperverband (Germany).

Clinical and simulator wear study of alumina ceramic THR to 17 years and beyond.

Three THAs with cementless monolithic alumina ceramic sockets and cementless Co-alloy stems were retrieved because of aseptic loosening after 17 and 24 years. At revision heads and cups were marked for orientation. Maps were drawn of wear patterns with the use of light microscopy and surveyed by SEM. In a simulator experiment 28-mm-diameter alumina heads and liners were used. The cups were mounted inverted in a hip simulator and run with calf serum as the lubricant. The hip loads were 2 kN maximum and a 1-Hz frequency for 20 million cycles. Wear severity was classified into five grades. In retrieved implants, SEM analysis showed that the main wear zones (MWZ) had Grade 4 wear. The peripheral wear zones (PWZ) showed grain pull-out regions (Grade 5 wear). These corresponded to neck-socket impingement and head-acetabular cup separation. Gray was due to transferred CoCr particles from the stem. In the simulator study, the MWZ had only localized areas of grain pull out surrounded by polished surface regions (Grade 4 wear) at 20 million cycles; stripe wear was not seen. The alumina ceramic bearings proved excellent up to 22 years in simulator studies and clinical studies. However, microseparation kinematics would be necessary in the simulator to duplicate the more peripheral wear zones.

Progress in sensor technology--progress in process control? Part 1: sensor property investigation and classification.

To ensure correctly operating control systems, the measurement and control equipment in WWTPs must be mutually consistent. The dynamic simulation of activated sludge systems could offer a suitable tool for designing and optimising control strategies. Ideal or simplified sensor models represent a limiting factor for comparability with field applications. More realistic sensor models are therefore required. Two groups of sensor models are proposed on the basis of field and laboratory tests: one for specific sensors and another for a classification of sensor types to be used with the COST simulation benchmark environment. This should lead to a more realistic test environment and allow control engineers to define the requirements of the measuring equipment as a function of the selected strategy.

Positive pressure ventilation with the ProSeal versus classic laryngeal mask airway: a randomized, crossover study of healthy female patients.

IMPLICATIONS: The ProSeal and classic laryngeal mask airways are equally effective ventilatory devices in healthy female patients at tidal volumes of 8 and 12 mL/kg with the cuff semi- or fully inflated, but leakage of small volumes of air from the mouth occurs more frequently with the laryngeal mask airway.

Debris from failed ceramic-on-ceramic and ceramic-on-polyethylene hip prostheses.

To compare the properties of wear debris between ceramic-on-ceramic and ceramic-on-polyethylene total hip prostheses, particles were isolated and characterized from tissue biopsies obtained at revision arthroplasty or autopsy from two similar uncemented modular hip systems. Group A hips (11 patients; mean, 31 months in vivo) had titanium shells with alumina inserts, alumina femoral heads, and titanium alloy stems. Group B hips (seven patients; mean, 42 months) were the same as Group A but with polyethylene acetabular inserts. Particles were characterized using an electrical resistance particle analyzer, scanning electron microscope, and energy dispersive xray spectroscope. Most of the particles in Group A were ceramic, whereas most of the particles in Group B were polyethylene. Metal particles from the femoral stem and the acetabular shell also were present. If one Group A hip with impingement is excluded, the rate of particle production is significantly lower in the ceramic-on-ceramic group than in the ceramic-on-polyethylene group. With the number of samples available, no significant difference in average size could be detected among the different types of particles or among the groups.

Development of physical examination skills in a third-year surgical clerkship.

BACKGROUND: Previous studies have revealed deficiencies in physical examination (PE) skills of third-year medical students. The purpose of this study was to determine if formal teaching of PE skills and more supervised experiences with clinical faculty would increase the competency of these skills. METHODS: Forty-nine third-year medical students were assigned to one of two groups: group A was given formal instruction on PE skills at the beginning of the clerkship, and group B received the same instruction at the midpoint of the clerkship. The two groups received an assessment of the PE skills before, in the middle, and at the end of clerkship, utilizing a physician-developed checklist. RESULTS: Group A had a pretest score of 57.7%. Group B scored 59.8% on the pretest. Independent groups t tests were used to compare the two groups. At the midterm examination, group A increased their score to 71.0%, while group B decreased their score to 55.6%. From beginning to final, both groups had significant improvements in all areas, with group A scoring an overall mean of 75.1% (P = 0.0001), and group B scoring 75.5% (P = 0.0001). CONCLUSION: These findings show the effectiveness of structured learning situations for improving third-year surgery students' PE skills. There is also an indication that usual clerkship activities may not enhance learning of PE skills.

An evaluation of study habits of third-year medical students in a surgical clerkship.

BACKGROUND: This study was developed to assess study habits of medical students in a third-year surgical clerkship and to determine the relationship of these study habits to performance outcomes. METHODS: A questionnaire designed to assess medical student study habits was administered at the end of five consecutive 10-week multidisciplinary surgical clerkships. The results of questionnaires from 81 students were analyzed in respect to results on the National Board of Medical Education (NBME) surgical subtest and the multiple stations clinical examination (MSCE) given at the end of each clerkship. RESULTS: Although only 18 of the total 81 students reported studying in formal but self-directed groups, students who reported studying in a group on average scored 4 points higher on the MSCE than those who did not study in a group (P = 0.001). However, no significant differences or correlations were discovered between any of the study habits and the individual results on the NBME. CONCLUSION: Students may benefit from collaborative studying when it comes to clinical experience as demonstrated by improved performance on the MSCE.

Reversing sevoflurane-associated Q-Tc prolongation by changing to propofol.

Congenital or acquired forms of the long Q-T syndrome may result in ventricular tachycardia known as torsade de pointes. Many drugs including volatile anaesthetics modify the Q-T interval. Sevoflurane is known to prolong of the rate-corrected Q-T interval (Q-Tc). The objective of this study was to determine whether the sevoflurane-associated Q-Tc prolongation is rapidly reversible when propofol is substituted for sevoflurane. Thirty-two female patients were allocated to two groups. All patients received sevoflurane induction and anaesthesia for 15 min. In one group, sevoflurane was then discontinued and anaesthesia maintained on propofol for another 15 min. The second group received sevoflurane anaesthesia for 30 min. Measurements were taken before, and 15, 20, 25 and 30 min after induction. Q-Tc prolongation was significantly reduced 5, 10 and 15 min after propofol had been substituted for sevoflurane. We conclude that the sevoflurane-associated Q-Tc prolongation is fully reversible within 15 min when propofol is substituted for sevoflurane.

Online monitoring of air quality at the postanesthetic care unit by proton-transfer-reaction mass spectrometry.

The subthreshold exposure to trace anesthetic gases is not associated with considerable risk of adverse health effects. Online control of ambient air exchange at the postoperative workplace may help in supervising air quality and lead to cost reduction. A proton-transfer-reaction mass spectrometer system was used for online monitoring of volatile organic compounds, especially anesthetic gases. The mean exposure to sevoflurane and isoflurane at the urological postanesthesia care unit (PACU) was 15.9 and 9.5 parts per billion, respectively. Sevoflurane and isoflurane concentrations at the urological PACU showed a patient turnover-dependent burden during our investigation period. Because modern PACUs have a high ventilation capacity, the 24-h occupational burden by anesthetic gases at the PACU is relatively low. Monitoring and controlling of ambient air by automatic built-in alarm systems would be useful for quality control of the postoperative workplace. Moreover, energy costs of ventilation systems could be reduced by coupling ventilation capacity to the effective exposure.

Cervical spine motion during airway management: a cinefluoroscopic study of the posteriorly destabilized third cervical vertebrae in human cadavers.

UNLABELLED: We conducted a randomized, controlled, crossover study to determine cervical spine motion for six airway management techniques in human cadavers with a posteriorly destabilized third cervical (C-3) vertebra. A destabilized C-3 segment was created in 10 cadavers (6-24 h postmortem). Cervical motion was recorded by continuous lateral fluoroscopy. The following airway management techniques were performed in random order on each cadaver with manual in-line stabilization applied: face mask ventilation (FM), laryngoscope-guided orotracheal intubation (OETT), fiberscope-guided nasal intubation (FOS-NETT), esophageal tracheal Combitube((R)) (Kendall-Sheridan, Neustadt, Germany) insertion (ETC), intubating laryngeal mask insertion with fiberscope-guided tracheal intubation (ILM-OETT), and laryngeal mask airway insertion (LMA). Afterward, maximum head-neck flexion (FLEX-MAX) and maximum head-neck extension (EXT-MAX) without manual in-line stabilization was performed to determine maximum motion. The maximum posterior displacement of C-3 and the maximum segmental sagittal motion of C2-3 were determined. There was a significant increase in posterior displacement for the FM (1.9 +/- 1.2 mm, P: < 0.01), OETT (2.6 +/- 1.6 mm, P: < 0.0001), ETC (3.2 +/- 1.6 mm, P: < 0.0001), ILM-OETT (1.7 +/- 1.3 mm, P: < 0. 01), LMA (1.7 +/- 1.3 mm, P: < 0.01), FLEX-MAX (3.7 +/- 1.9 mm, P: < 0.0001), EXT-MAX (1.8 +/- 1.7, P: < 0.01), however, not for FOS-NETT (0.1 +/- 0.7 mm). Posterior displacement was less for the ILM-OETT and LMA than for the ETC (both P: < 0.04). There were no significant increases in segmental sagittal motion with any airway manipulation other than with FLEX-MAX (-4.5 +/- 4.0 degrees, P: < 0.01). Posterior displacement was similar to FLEX-MAX for the OETT and ETC; however, it was less for the FM, FOS-NETT, ILM-OETT, and LMA (all P: < 0.01). Posterior displacement was similar to EXT-MAX for all airway manipulations other than for FOS-NETT (P: < 0.001). For cervical motion and the techniques tested, the safest method of airway management in a patient with a posteriorly destabilized C-3 segment is FOS-NETT. LMA devices may be preferable to the ETC. IMPLICATIONS: In the cadaver model of a destabilized third cervical vertebrae, significant displacement of the injured segment occurs during airway management with the face mask, laryngoscope-guided oral intubation, the esophageal tracheal Combitube (Kendall-Sheridan, Neustadt, Germany), the intubating and standard laryngeal mask airway; but not with fiberscope-guided nasal intubation. For cervical motion and the techniques tested, the safest airway technique with this injury is fiberscope-guided nasotracheal intubation. Laryngeal mask devices are preferable to the esophageal tracheal Combitube.

Alumina ceramic bearings for hip endoprostheses: the Austrian experiences.

The current authors review clinical and retrieval experiences with hemispheric monolithic alumina ceramic sockets (Group 1), implanted between 1976 and 1979, and similar modular titanium sockets with alumina ceramic inlays (Group 2), implanted between 1990 and 1995. Both cementless sockets articulated with alumina ceramic femoral ball heads for total hip joint replacements. Clinical followup of patients with hemispheric monolithic alumina ceramic sockets (Group 1, 138 sockets) resulted in a total failure rate of 19.6% after 5 to 20 years. Radiologic analysis of eight stable sockets showed migration of 0.2 mm to 2.89 mm, but in four sockets at risk for late aseptic failure after an average followup of 12.5 years as much as 13.4 mm of migration was seen. Histologic evaluation revealed pseudosynovial membranes as thick as 1 mm with fine birefringent wear particles within mononuclear macrophages around two stable retrieved sockets. The membranes around four loose sockets were 6 to 10 mm thick and also heavily loaded with larger alumina wear particles. After 7 years followup clinical analysis of patients with modular titanium sockets with alumina ceramic inlays (Group 2, 30 sockets) resulted in four revisions, compared with one revision of 50 identical sockets (control group) with polyethylene instead of alumina ceramic inlays. Wear particle analyses in scanning electron microscopy showed significantly more particles (x 10(9) +/- standard deviation/g dry tissue) from the control group (4.26+/-6.38), compared with alumina ceramic bearings of Group 1 (0.70+/-0.79), and of Group 2 (1.62+/-2.13). The alumina particle sizes ranged between 0.13 and 78.38 microm. The mean annual linear wear of 38.8 microm was calculated for the bearings in Group 1, and of 26.94 microm for bearings in Group 2. These results support the good tribologic and biologic performance of alumina ceramic bearings for total hip arthroplasty.

Korean hand acupressure reduces postoperative vomiting in children after strabismus surgery.

A double-blind, randomized, placebo-controlled study was conducted to investigate the effectiveness of Korean hand acupuncture in preventing postoperative vomiting in children scheduled for strabismus surgery. In one group, acupressure was performed 30 min before induction of anaesthesia by applying an acupressure disc onto the Korean hand acupuncture point K-K9; the disc remained in situ for at least 24 h. The second group functioned as placebo group. The treatment groups did not differ with regard to patient characteristics, surgical procedure and anaesthetic administered. In the acupressure group, the incidence of vomiting was significantly lower (20%) than in the placebo group (68%). We conclude that Korean hand acupressure of the acupuncture point K-K9 is an effective method for reducing postoperative vomiting in children after strabismus repair.

Antibiotic-associated colitis in orthopaedic patients.

Antibiotic-associated colitis was diagnosed in 23 orthopaedic patients: 17 had abdominal symptoms, 3 had a fever and the remaining 3 had no symptoms but increasing C-reactive protein values or white blood count. The antibiotic was clindamycin in 19, cephalosporins in 3 and a combination of vancomycin and fusidic acid intravenously in one. The antibiotics were stopped in 12, changed in 5 and continued in the remaining 5. Oral treatment for colitis was given in 21 patients, and in one patient the only treatment was stopping the antibiotics. One patient died after a myocardial infarct; the remaining 22 were discharged after successful treatment of their primary condition and the colitis.