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S K Toh

Publications and source records attributed to S K Toh.

9 recordsLinked to original sources
PubMed2002

Size-effect on the physical characteristics of the aerobic granule in a SBR.

Owing to a fast growth rate, aerobic granules display a wide range of sizes, approximately 0.3-5.0 mm in diameter. As the diameter increases, the aerobic granule undergoes serial morphological and physical changes that could cause problems to the reactor operation, a phenomenon which, however, has not been fully studied hitherto. In this study, aerobic granules from a sequencing batch reactor were mechanically separated into various size-categories in order to investigate their physical properties, including sludge volumetric index (SVI), settling velocity (sv), specific surface hydrophobicity, granule strength, total solids, percentage volatile solids and other structural properties. Also, the live and dead biomass distribution was examined under a confocal laser scanning microscope after treatment with nucleic acid viability stains. Regardless of size, the biomass (both live and dead) was densest in the outer layer of the granule, which was about 600+/-50 microm thick. The live cells appeared only in the peripheral zone, while dead biomass spread into the inner zone. The biomass distribution pattern justified the changing physical properties of the granules as they grew bigger. As size increased, the sv, granule total density and biomass density increased but not in parallel with the size increment, while the granule strength, specific surface hydrophobicity and SVI decreased. Nonetheless, beyond a threshold size (4.0 mm diameter), the granules presented peculiar values in those properties, deviating from the initial trends. This was due to both inner and outer structural changes. The physical properties associated significantly with the size factor, for which the correlation coefficients were above 0.67. In view of biological viability and physical properties, the operational size-range suggested for optimal performance and economically effective aerobic SBR granular sludge is a diameter of 1.0-3.0 mm.

Aerobiosis↗
PubMed2002

Adaptation of anaerobic ammonium-oxidising consortium to synthetic coke-ovens wastewater.

A consortium with autotrophic anaerobic ammonium oxidising (AAAO) activity was developed from municipal sludge, and its ability to remove high ammonium concentrations in a toxic wastewater such as coke ovens wastewater is presented here. The enriched AAAO consortium was acclimatised to a synthetic coke ovens wastewater to establish anaerobic ammonium oxidation (AAO) activity. Phenol was the main carbon component of the synthetic wastewater whereby it was added stepwise from 50+/-10 to 550+/-10 mg l(-1) into an anammox enrichment medium. Ammonium-N removal was initially impaired; however, it gradually recovered. After 15 months of further selection and enrichment, the ammonium removal rate reached 62+/-2 mg NH(4)(+)-N l(-1) day(-1), i.e. 1.5 times the rate in the original AAAO reactor. The new consortium demonstrated higher ammonium and nitrite removal rates, even under phenol perturbation (up to 330+/-10 mg l(-1)). It is therefore concluded that the AAO activity in the consortium was resistant to high phenol and has potential for treating coke-ovens wastewater.

Anaerobiosis↗
PubMed2001

Enrichment of autotrophic anaerobic ammonium-oxidizing consortia from various wastewaters.

The option for biological nitrogen removal has recently been broadened with the description of simultaneous nitrification/denitrification, anaerobic ammonium oxidation (ANAMMOX) and the concept of CANON (completely autotrophic nitrogen removal over nitrite). An autotrophic anaerobic ammonium oxidation (AAAO) consortium was successfully selected and enriched from municipal treatment plant sludges in Sydney, Australia, but not from industrial coke-oven wastewater sludges. Chemolithoautotrophic basic salt (CLABS) medium was used in the selection of AAAO organisms and chloramphenicol was added to the initial stage of selection to eliminate denitrifiers. Two different temperatures, 37 degrees C and 55 degrees C, were used in the selection of mesophilic and thermophilic consortia, respectively. Thermophilic AAAO organisms were not selected at 55 degrees C. Mesophilic AAAO activities, however, were evident in both batch and continuous cultures, whereby ammonium was consumed concurrently with a decrease of nitrite, giving a ratio of 1:1-1:1.3 in ammonium removal rate over nitrite consumption rate. A continuous-mode mesophilic fixed-bed reactor was established to enrich the AAAO consortium. After 1 year, biofilms, pinkish in color, had developed on the support media and side wall of the feed-line tubing. Ammonium and nitrite consumption increased from approximately 15 mg to 60 mg d(-1) L(-1) over a period of 243 days. Later, transmission electron microscopy (TEM) and fluorescence in situ hybridization (FISH) techniques revealed that the dominant cell type in the AAAO consortium had a similar morphology and 16S rDNA sequence homology to that of the recently described ANAMMOX organism, "Brocadia anammoxidans".

Bacteria, Anaerobic↗
PubMed2001

Double blind, randomised, placebo controlled study of a platelet activating factor antagonist, lexipafant, in the treatment and prevention of organ failure in predicted severe acute pancreatitis.

BACKGROUND: Platelet activating factor (PAF) is believed to amplify the activity of key mediators of the systemic inflammatory response syndrome (SIRS) in acute pancreatitis, resulting in multiorgan dysfunction syndrome. We tested the hypothesis that a potent PAF antagonist, lexipafant, could dampen SIRS and reduce organ failure in severe acute pancreatitis. METHODS: We conducted a randomised, double blind, placebo controlled, multicentre trial of lexipafant (100 mg/24 hours intravenously for seven days commenced within 72 hours of the onset of symptoms) involving 290 patients with an APACHE II score >6. Power calculations assumed that complications would be reduced from 40% to 24%. Secondary end points studied included severity of organ failure, markers of the inflammatory response, and mortality rate. FINDINGS: Overall, 80/138 (58%) patients in the placebo group and 85/148 (57%) in the lexipafant group developed one or more organ failures. The primary hypothesis was invalidated by the unexpected finding that 44% of patients had organ failure on entry into the study; only 39 (14%) developed new organ failure. Organ failure scores were reduced in the lexipafant group only on day 3: median change -1 (range -4 to +8) versus 0 (-4 to +10) in the placebo group (p=0.04). Systemic sepsis affected fewer patients in the lexipafant group (13/138 v 4/148; p=0.023). Local complications occurred in 41/138 (30%) patients in the placebo group and in 30/148 (20%) in the lexipafant group (20%; p=0.065); pseudocysts developed in 19 (14%) and eight (5%) patients, respectively (p=0.025). Deaths attributable to acute pancreatitis were not significantly different. Interleukin 8, a marker of neutrophil activation, and E-selectin, a marker of endothelial damage, decreased more rapidly in the lexipafant group (both p<0.05); however, absolute values were not different between the two groups. INTERPRETATION: The high incidence of organ failure within 72 hours of the onset of symptoms undermined the primary hypothesis, and power calculations for future studies in severe acute pancreatitis will need to allow for this. Lexipafant had no effect on new organ failure during treatment. This adequately powered study has shown that antagonism of PAF activity on its own is not sufficient to ameliorate SIRS in severe acute pancreatitis

Acute Disease↗
PubMed2000

A prospective audit against national standards of the presentation and management of acute pancreatitis in the South of England.

BACKGROUND: The incidence of acute pancreatitis shows regional variations in the UK. AIMS: To document the incidence and presentation of acute pancreatitis in hospitals in Wessex, and to audit the process and outcome of management of patients against the UK guidelines. METHODS: A prospective survey was carried out of all patients with acute pancreatitis in a one year period, in eight geographically adjacent acute hospitals in the Wessex region. RESULTS: 186 patients with acute pancreatitis were identified, an incidence of 152 per million in the adult population. Aetiology was: gallstones 33%, alcohol 20%, idiopathic 32%, other 15%. There were 60 severe cases with 17 deaths. Age and APACHE-II score had significant relations to outcome, but delay to admission, serum amylase level, aetiology, and sex did not. The mortality rate (9.1%) was within the audit standard of 10%. Some management goals were not met: in mild cases, only one third of patients with gallstone pancreatitis had definitive treatment within four weeks. In severe cases, there was poor use of objective severity stratification (19%), low admission rates to a high dependency unit or intensive care unit (67%), and only 33% of patients had computed tomography. Only seven of 17 patients with severe gallstone pancreatitis had an urgent endoscopic retrograde cholangiopancreatography. CONCLUSIONS: The incidence of clinically diagnosed acute pancreatitis in England continues to rise. Current management of acute pancreatitis is suboptimal when compared with evidence based UK guidelines but the mortality rate was within the guideline standard.

Acute Disease↗
PubMed1999

Good outcome from surgery for ampullary tumour.

BACKGROUND: Ampulla of Vater tumours are rare but usually resectable. There is debate as to the better surgical approach between the standard radical procedure, which provides adequate resection margins, and local resection, which may carry a lower mortality. This study reports the 16-year experience of a specialist unit with these tumours, and compares our results with that of recently published series. METHOD: A retrospective review of patients admitted with an ampullary tumour to the Hepatobiliary and Pancreatic Surgery Unit, Royal Adelaide Hospital, Adelaide, Australia, between January 1981 and April 1997. RESULTS: Twenty-five patients (13 men, 12 women) of median age 65 years were admitted with an ampullary tumour to the unit during this period. The most common presentation was obstructive jaundice. Multiple endoscopic biopsy was found to be very reliable in distinguishing between benign and malignant tumours. Five patients, all male, had benign neoplasms: three adenomas, one carcinoid and one gangliocytic paraganglioma. Transduodenal local excision was performed in four patients. One patient had a Whipple procedure resulting in the only in-hospital death at 3 months. Twenty patients had adenocarcinoma, of which 13 patients had a pancreaticoduodenectomy, two local excisions, two palliative bypasses, two were unfit for surgery and one declined surgery. The resectability rate was 88%, with no operative mortalities. The 5-year actuarial survival of patients who underwent radical resection was 49%. CONCLUSIONS: Proximal pancreaticoduodenectomy, preferably a pylorus-preserving procedure, is safe and effective in the treatment of ampullary carcinoma, with low operative mortality and good long-term survival. Local resection is only recommended for small benign tumours and for patients who may be unfit for radical surgery.

Adult↗
PubMed1999

Early ERCP is an essential part of the management of all cases of acute pancreatitis.

The role of early endoscopic retrograde cholangiopancreatography (ERCP) and sphincterotomy in acute pancreatitis is controversial. Recent randomised controlled trials mostly support the value of this procedure, but concerns remain as to its safety, efficacy and practicability. This debate critically assesses the evidence for and against the use of early ERCP in acute pancreatitis.

Acute Disease↗