Alterations in the baroreceptor-heart rate reflex in conscious inbred polydipsic (STR/N) mice.

STR/N is an inbred strain of mice which is known to exhibit extreme polydipsia and polyuria. We previously found central administration of angiotensin II enhanced cardiovascular responses in STR/N mice than normal mice, suggesting that STR/N mice might exhibit different cardiovascular responses. Therefore, in this study, we investigated daily mean arterial blood pressure and heart rate, and changes in the baroreceptor-heart rate reflex in conscious STR/N mice and control (ICR) mice. We found that variability in daily mean arterial blood pressure and heart rate was significantly larger in STR/N mice than in ICR mice (p<0.05). There was a stronger response to phenylephrine (PE) in STR/N mice than in ICR mice. For baroreceptor reflex sensitivity, in the rapid response period, the slopes of PE and sodium nitroprusside (SNP) were more negative in STR/N mice than in ICR mice. In the later period, the slopes of PE and SNP were negatively correlated between heart rate and blood pressure in ICR mice, but their slopes were positively correlated in STR/N mice. These results indicated that STR/N mice exhibited the different cardiovascular responses than ICR mice, suggesting that the dysfunction of baroreceptor reflex happened in conscious STR/N mice.

A health risk assessment of reclaimed municipal wastewater for industrial and miscellaneous use.

The study evaluated the safety of reclaimed water using health risk assessment and biotoxicity tests. The reclaimed water was produced from reverse osmosis and used in industrial and miscellaneous purposes. The health risk assessment was conducted based on the concentrations of detectable pollutants in reclaimed water in a hypothetical scenario. The estimated carcinogenic and non-carcinogenic risks are lower than the generally accepted level. Biotoxicity evaluation included three genotoxicity tests, a chronic toxicity test using medaka fishes, and a subchronic toxicity test using mice. The reclaimed water is not genetically toxic, and does not cause significant chronic effects on these model organisms. These results confirm the safety of using reclaimed water from municipal wastewater treatment plants.

Recycling of spent filter backwash water using coagulation-assisted membrane filtration: effects of submicrometre particles on membrane flux.

Membrane separation technology has been widely used for recycling of spent filter backwash water (SFBW) in water treatment plant. Membrane filtration performance is subject to characteristics of the particles in the SFBW. A bench-scale microfiltration (MF) coupled with pre-coagulation was set up to evaluate the recovery efficiency of SFBW. Effect of particle size distribution and zeta potential of the coagulated SFBW on the membrane filtration as well as the coagulation strategies were investigated. Pore clogging was more severe on the membrane with 1.0 mum pore size than on the membrane with 0.5 mum pore size due to the fact that submicrometre particles are dominant and their diameters are exactly closed to the pore size of the MF membrane. Pre-settling induced more severe irreversible fouling because only the submicrometre particles in the water become predominant after settling, resulting in the occurrence of more acute pore blocking of membrane. By contrast, pre-coagulation mitigates membrane fouling and improves membrane flux via enlarging particle size on membrane surface. The variations of zeta potential in response to coagulant dosing as well as fractal dimension were also compared with the performance of the subsequent filtration. The result showed that pre-coagulation induced by charge neutralization at the optimum dosage where the zeta potential is around zero leads to the optimal performance of the subsequent membrane filtration for SFBW recycling. At such condition, the fractal dimension of coagulated flocs reached minimum.

Reclamation of the wastewater from an industrial park using hollow-fibre and spiral-wound membranes: 50 m3 d(-1) pilot testing and cost evaluation.

The feasibility of reclaiming effluent from industrial park wastewater treatment plants through a membrane process was evaluated in three phases. In phase 1 we selected nine wastewater treatment plants (WWTPs), each with a design capacity exceeding 10,000 m3 d(-1), and analyzed the corresponding effluent composition. 'Potential recycling percentage', R, ranged from 50% to 80% for the industrial park WWTPs, indicating a high feasibility for the reuse of effluent. In phase 2, a 50 m3 d(-1) pilot plant was installed in one of the selected WWTPs and underwent testing for one year. The quality of the reclaimed water was suitable for general-purpose industrial use. In the two ultrafiltration (UF) modules tested, the hydrophilic polyethersulfone hollow-fibre module was more tolerant to variable properties, and had higher recycling percentages than those of backwashable hydrophobic polyvinylidene difluoride spiral-wound module. Using the spiral-wound UF module helped reduce the cost for producing 1 m3 of reclaimed water (US$0.80) compared with a hollow-fibre module (US$0.88). In phase 3, we evaluated the negative effects of refluxing the reverse osmosis retentate, containing high total dissolved solids and non-biodegradable organics, with the biological treatment unit of the upstream WWTP. Biological compactibility tests showed that the refluxed retentate ratio should be reduced to maintain the conductivity of mixed liquor in the aeration tank at less than 110% of the original value.

Reuse potential analysis on WWTP effluent of industrial parks in Taiwan.

This study examined the reuse potential of the effluents discharged from several unified wastewater treatment plants (WWTPs) of industrial parks in Taiwan, with designed capacity exceeding 10,000 CMD. Parameters were selected based on the relevant reuse purposes. The "potential recycling percentage", R of the WWTP effluent was defined as the maximal percentage of pure water extractable by the "ideal reverse osmosis module" while the RO retentate still met local effluent standards and required no treatment. The analytical results demonstrated that the WWTP effluents had potential for recycling. A pilot plant was installed in one of the WWTPs. The treatment process included a sand filter, an ultrafiltration unit (UF) and a reverse osmosis module (RO). Results of this study demonstrated that the production quantity and quality are stable and appropriate for various purposes, including both industrial and domestic applications.

Postoperative outcome in Chinese patients having primary total knee arthroplasty under general anaesthesia/intravenous patient-controlled analgesia compared to spinal-epidural anaesthesia/analgesia.

OBJECTIVE: To compare postoperative outcomes in patients having primary total knee arthroplasty receiving general or regional anaesthesia. DESIGN: Randomised prospective study. SETTING: Regional hospital, Hong Kong. PATIENTS: Patients having primary total knee replacement were randomised to either general anaesthesia followed by postoperative intravenous patient-controlled analgesia with morphine, or combined spinal-epidural anaesthesia followed by postoperative epidural infusion of bupivacaine 0.1% with fentanyl 2 microg/mL. MAIN OUTCOME MEASURES: Visual analogue scale pain scores, perioperative blood loss, time to first meal and ambulation, and prevalence of postoperative complications. RESULTS: Sixty consecutive patients were enrolled in this study. Postoperative median pain scores were consistently lower at 1 (P<0.0001), 6 (P=0.08), 12 (P=0.003), 24 (P=0.14), and 48 hours (P=0.007) in those given regional anaesthesia. Although there was a trend towards fewer complications in the latter group, there were no statistically significant differences between the two groups with respect to the incidence of postoperative blood loss, haemodynamic instability, pruritus, nausea, vomiting, urinary retention, or other surgical/medical complications. Postoperatively, patients given regional anaesthesia also resumed meals earlier (P<0.0001), and showed a trend towards earlier ambulation and hospital discharge. CONCLUSION: Chinese patients undergoing total knee arthroplasty with regional anaesthesia/regionally delivered analgesia enjoyed better postoperative pain relief and resumed meals earlier than those receiving general anaesthesia/intravenous patient-controlled analgesia. The former also showed trends towards less adverse effects, postoperative complications, earlier ambulation, and earlier hospital discharge.

Size-dependent anaerobic digestion rates of flocculated activated sludge: role of intrafloc mass transfer resistance.

The anaerobic digestion rate for flocculated sludge has been considered to be lower than that of original sludge, particularly in the later stages of digestion; attributed this relatively slower rate to the increased mass transfer resistance for reactants through the large flocs after flocculation. This study confirmed that methane production was retarded by flocculation. The structure of the floc was identified with fluorescence in situ hybridization (FISH) and a confocal laser scanning microscope (CLSM) technique. To verify the mass transfer resistance induced by flocculation, microsensors were applied to assess the response of oxygen concentration distribution inside the flocs that are subjected to sudden changes in ambient oxygen levels. Response time for the electrode at a floc's center was five times greater than the response time in original sludge flocs. Although the effective diffusivity of oxygen in the floc increased by 2.3 times after flocculation, the increased size of the flocculated floc was the major contributor to the total mass transfer resistance to oxygen.

Energy demand in sludge dewatering.

This work investigates the energy required to dewater a suspension, i.e., activated sludge dewatered by centrifugation or consolidation. Total energy input to the suspension from the dewatering device, bond strength between adjacent water and solid surface, and intra-cake friction loss were evaluated for original and flocculated sludges. In centrifugal dewatering, most energy input during the initial stage was consumed by overcoming process irreversibility other than intra-cake friction, and, thereby, had a low energy efficiency. To increase centrifuge speed or to flocculate the sludge at optimal flocculant dosage would yield a high-energy input. In the consolidation test, most energy input at the initial stage was consumed in breaking down the bond strength until the moisture content reduced to less than the critical content. During subsequent dewatering stages, friction loss became the dominant source of energy loss. Dewatering sludge with high-energy efficiency is beneficial to optimally operate a dewatering process.

Comparison of dewaterability and floc structure of synthetic sludge with activated sludge.

This work compared the appearance, dewaterability, floc size, fractal dimensions derived from free-settling test and light-scattering test, and detailed structural information of floc interior including porosity, Sierpinski carpet fractal dimension, and the fractal dimension of the pore boundaries of a synthetic sludge and an activated sludge. The present synthetic sludge could probe the change in filterability and in fractal dimensions extracted from small angle light scattering test and from free-settling test after conditioning, however, failed to reproduce the detailed structural information of sludge flocs. The use of specific synthetic sludge depends on the field of interest. For instance, the present synthetic sludge is not appropriate to simulate the intrafloc transport of solute owing to its incapability to reproduce the detailed floc structure or to its change after conditioning.

Advective flow in a sludge floc.

The interior of sludge floc is highly heterogeneous, while the large pores in the floc control the advective flow. This work for the first time numerically details fluid flow and mass transfer processes in pores of activated sludge floc. The dimensionless permeabilities and mass dispersion coefficients were contoured against pore size ratio and the floc Reynolds number. With a pore size less than 20% of the floc size, the commonly adopted homogeneous model overestimates the floc permeability, and pore velocity is less than 2% of the bulk velocity. This is particularly true for flocs with low porosity. Although the convective flux is low, the dispersive mass transfer rate can be much higher than the diffusional rate, attributable to the strong Taylor dispersion effect. The three-dimensional pore structures in waste activated-sludge floc were identified using confocal laser scanning microscope (CLSM) images. Large pores were used to numerically estimate the permeability and dispersion coefficient for these pores. The permeability and the dispersion coefficient of the tortuous pores can be one order of magnitude lower than those for the equivalent straight pores. Besides the dispersion effect, the pore tortuosity appeared as the most important geometrical factor retarding the advective flow in the sludge pores. In addition, the small side pores connected to the large pore had only a mild effect on the flow process, and can be neglected in analysis.

Effect of pre-hydrolysis on floc structure.

Morphological changes in flocs were elucidated by small-angle light scattering, free settling tests and microscopic observation to determine the effects of pre-hydrolysis (alkaline treatment and ultrasonication) on two sludges--primary raw sludge from the Malabar Sewage Treatment Plant, Sydney (sludge M) and biological sludge collected at the nitrogen removal unit of St Marys Sewage Treatment Plant in Sydney (sludge S). Ultrasonication or alkaline treatment released a marked amount of insoluble organic matter in a soluble form. The latter treatment was more efficient than the former. Meanwhile, the pre-hydrolyzed flocs had more compact structures than the original ones, as shown by their higher free-settling fractal dimension, lower areal porosity and smaller internal pores. In particular, alkaline treatment yielded flocs with more compact interiors than did ultrasonication. Such detailed structural information could not be elicited by monitoring the change in floc size. The greater resistance to mass transfer of the hydrolyzed flocs thus produced does not reduce the efficiency of subsequent digestion, indicating that the surface reaction rate on the solid surface might have dominated since the pre-hydrolysis steps modified the local chemical environment to promote digestion.

Data management using the personal digital assistant in an acute pain service.

Handheld personal digital assistants (PDA) are increasingly being used by physicians for a variety of information and data management purposes. We evaluated a PDA-based data management system for our acute pain service. A structured questionnaire survey was conducted to assess staff experience and attitude towards the paper system before the introduction of the PDA, and three months after introduction of the PDA system. We compared the time taken to conduct the acute pain round before and after the implementation of the PDA. The time saved in data management and the amount of paper saved were estimated. Data from 177 patients with a total of 635 acute pain follow-up visits were entered over a three-month period. User satisfaction, ease of access to drug reference and clinical guidelines were similar between the two systems. The respondents found that the PDA was easy to use but less so than the paper system (P = 0.007), in particular, when accessing a patient's cumulative data (P = 0.007). There was no missed follow-up or data entry with the use of PDA. The time taken to attend follow-up visits was similar for the two systems (Paper: 8.8 +/- 3.2 compared to PDA: 7.0 +/- 2.0 minutes, P = 0.151). The estimated annual amount of paper and time saved in data management was 650 sheets and 130 man-hours respectively. Our experience with the use of the PDA in APS was satisfactory. The PDA system can potentially reduce time and paper use and missed data entry and patient follow-up.

Bilevel thresholding of floc images.

Frequently encountered problems on bilevel thresholding of floc images include information loss during the image conversion stage, sampling bias owing to spatially inhomogeneous luminous flux over an optical microscope image or among a series of images, thresholding error adopting various algorithms, and resampling errors during three-dimensional reconstruction. Among these steps the choice of thresholding algorithm could yield most of the processing error. Ways to reduce the potential processing errors are discussed.

Structure of conditioned sludge flocs.

Free settling tests, small-angle light scattering, microtome-slicing techniques, and confocal laser scanning microscopy were performed to examine how the cationic flocculation or freezing and thawing affected the floc structure. The floc size, internal pore size, mass fractal dimensions determined from free-settling test or small angle light scattering test, aeral porosity, boundary fractal dimension and Sierpinski carpet fractal dimension of pore boundary from 2D slices, and the volume porosity, compactness, and the pores' box-counting fractal dimension from 3D reconstructed image, were estimated and compared. Cationic flocculation would produce large flocs with internal pores of shape resembling a long "tube" with rough surface. Freezing and thawing would produce flocs with internal pores with lower aspect ratio and a smoother boundary.

Bilevel thresholding of sliced image of sludge floc.

This work examined the feasibility of employing various thresholding algorithms to determining the optimal bilevel thresholding value for estimating the geometric parameters of sludge flocs from the microtome sliced images and from the confocal laser scanning microscope images. Morphological information extracted from images depends on the bilevel thresholding value. According to the evaluation on the luminescence-inverted images and fractal curves (quadric Koch curve and Sierpinski carpet), Otsu's method yields more stable performance than other histogram-based algorithms and is chosen to obtain the porosity. The maximum convex perimeter method, however, can probe the shapes and spatial distribution of the pores among the biomass granules in real sludge flocs. A combined algorithm is recommended for probing the sludge floc structure.

Anaerobic digestion of polyelectrolyte flocculated waste activated sludge.

This work examined how adding one of three polyelectrolyte flocculants (T3052: cationic, T2000: non-ionic, and T1052: anionic) affected the anaerobic digestion of wastewater sludge. Methane production, floc characteristics (morphology and zeta-potential) and process parameters (soluble chemical oxygen demands (SCODs) and reductive potentials) were monitored along the digestion tests. The digestion rates of T2000- and T1052-conditioned sludge resembled that for original sludge. The T3052-flocculated sludge generated methane at a higher rate during the first 6 days of digestion than did the original one. In the following stage, the digestion rate of sludge flocculated with T3052 at dosage exceeding 15 g/kg dried solids declined. For example, at 40 days of digestion the methane production amounts for original, 15 g/kg DS flocculated, and 40 g/kg flocculated sludge were of 136, 105, and 85 g/kg DS, respectively. The role of flocculants could change in different stages of digestion. The dosed polymers had no apparent toxicity to the inoculum used. The changes in SCOD, adenosintriphosphate concentrations, oxidative and reductive potential, and zeta-potentials did not correlate with the noted hindered digestion for T3052-conditioned sludge. Microphotographic observation revealed that the flocs of T3052-conditioned sludge were not only of a large size, but also were resistant to structural deterioration during digestion. Therefore, mass transfer resistance was proposed to account for the hindered digestion efficiency observed for T3052-conditioned sludge.

Use of hospitalization and pharmaceutical prescribing data to compare the prevaccination burden of varicella and herpes zoster in Australia.

The aims of the study were to compare the burden of varicella and herpes zoster in Australia. No national surveillance exists for varicella or herpes zoster. We used hospital morbidity data from 1993-9 and pharmaceutical prescribing data from 1995-9. In the financial year 1998/99, there were 4718 hospitalizations for zoster compared to 1991 for varicella. For varicella the mean age of patients was 15 years compared to 69 years for zoster. The mean length of stay in hospital was 4.2 days for varicella and 12.7 days for zoster. Varicella accounted for 8396 (3726 with principal diagnosis varicella) bed days compared to 26 266 (5382 with principal diagnosis of zoster) for zoster. The in-hospital case-fatality rate was 0.4% for varicella and 1% for zoster. In 1999, 59 200 community-based cases of zoster were treated with antivirals. We estimate that 157 266 cases of zoster occurred in the community in 1999, a rate of 830 per 100 000 population. Herpes zoster has a higher burden of disease than varicella, and must be a component of disease surveillance in order to determine the full impact of vaccination on the epidemiology of varicella zoster virus (VZV).

Hydrogen production from wastewater sludge using a Clostridium strain.

Limited data in literature revealed a relatively low hydrogen yield from wastewater sludge, ca. 0.16 mg/g-dried solids, using anaerobic fermentation. We demonstrated in this work a much higher hydrogen yield, around 1.1 mg-H2/g-dried solids using a clostridium strain isolated from the sludge sample. The formed hydrogen would be consumed after passing the peak value at around 30-36 h of fermentation. We examined the effects of employing five different pre-treatments on substrate sludge, but noted no appreciable enhancement in hydrogen yield as commonly expected for methane production. Since a vast amount of organic matters had been released to water after hydrogen fermentation, we externally dosed methanogenic bacteria to the fermented liquor to produce methane. The fermented liquor could produce more methane than the non-fermented sample, indicating that the dosed methanogenic bacteria readily utilized the organic matters derived from the fermentation test.

Using filtrate of waste biosolids to effectively produce bio-hydrogen by anaerobic fermentation.

Waste biosolids collected from sewage works is a biomass containing a vast amount of polysaccharides and proteins, and thus is considered a potential substrate for producing hydrogen using anaerobic fermentation. This work demonstrated, contrary to the common assumption, that the solids phase in waste activated biosolids presents extra nutrients for anaerobes; it in fact prohibits effective bio-hydrogen production. Using filtrate after removal of solids from biosolids produces more hydrogen than using the whole biosolids, with the former reaching a level an order of magnitude higher than the literature results.

Producing hydrogen from wastewater sludge by Clostridium bifermentans.

Excess wastewater sludge collected from the recycling stream of an activated sludge process is biomass that contains large quantities of polysaccharides and proteins. However, relevant literature indicates that the bio-conversion of wastewater sludge to hydrogen is limited and therefore not economically feasible. This work examined the anaerobic digestion of wastewater sludge using a clostridium strain isolated from the sludge as inoculum. A much higher hydrogen yield than presented in the literature was obtained. Also, the effects of five pre-treatments-ultrasonication, acidification, sterilization, freezing/thawing and adding methanogenic inhibitor-on the production of hydrogen were examined. Freezing and thawing and sterilization increased the specific hydrogen yield by 1.5-2.5 times to that of untreated sludge, while adding an inhibitor and ultrasonication reduced the hydrogen yield.