Modelling waste stabilisation ponds with an extended version of ASM3

In this paper an extended version of IWA's Activated Sludge Model No 3 (ASM3) was developed to simulate processes in waste stabilisation ponds (WSP). The model modifications included the integration of algae biomass and gas transfer processes for oxygen, carbon dioxide and ammonia depending on wind velocity and a simple ionic equilibrium. The model was applied to a pilot-scale WSP system operated in the city of Florianópolis (Brazil). The system was used to treat leachate from a municipal waste landfill. Mean influent concentrations to the facultative pond of 1,456 g(COD)/m(3) and 505 g(NH4-N)/m(3) were measured. Experimental results indicated an ammonia nitrogen removal of 89.5% with negligible rates of nitrification but intensive ammonia stripping to the atmosphere. Measured data was used in the simulations to consider the impact of wind velocity on oxygen input of 11.1 to 14.4 g(O2)/(m(2) d) and sun radiation on photosynthesis. Good results for pH and ammonia removal were achieved with mean stripping rates of 18.2 and 4.5 g(N)/(m(2) d) for the facultative and maturation pond respectively. Based on measured chlorophyll a concentrations and depending on light intensity and TSS concentration it was possible to model algae concentrations.

Thermophilic anaerobic digestion in compact systems: investigations by modern microbiological techniques and mathematical simulation

Thermophilic anaerobic digestion in compact systems can be an economical and ecological reasonable decentralised process technique, especially for rural areas. Thermophilic process conditions are important for a sufficient removal of pathogens. The high energy demand, however, can make such systems unfavourable in terms of energy costs. This is the case when low concentrated wastewater is treated or the system is operated at low ambient temperatures. In this paper we present experimental results of a compact thermophilic anaerobic system obtained with fluorescent in situ hybridisation (FISH) analysis and mathematical simulation. The system was operated with faecal sludge for a period of 135 days and with a model substrate consisting of forage and cellulose for a period of 60 days. The change in the microbial community due to the two different substrates treated could be well observed by the FISH analysis. The Anaerobic Digestion Model no. 1 (ADM1) was used to evaluate system performance at different temperature conditions. The model was extended to contribute to decreased methanogenic activity at lower temperatures and was used to calculate energy production. A model was developed to calculate the major parts of energy consumed by the digester itself at different temperature conditions. It was demonstrated by the simulation study that a reduction of the process temperature can lead to higher net energy yield. The simulation study additionally showed that the effect of temperature on the energy yield is higher when a substrate is treated with high protein content.

Modelling COD and N removal in the water and in the benthic biofilm for the River Wupper in Germany

The River Wupper, a tributary of the River Rhine, is at several locations influenced by anthropogenous nitrogen input, hydraulic structures, and influents from other tributaries. These influences have an impact both on the water quality and on the hydrodynamic conditions. The model approaches used for this article are based on work of Rauch et al. and the River Water Quality Model No. 1; they allow the simulation of the nitrogen conversion in the River Wupper. They are compatible with the activated sludge models and can thus be used also for integrated approaches. The calibration and validation of the model was realized using actual data of the River Wupper over a length of 60 km with one dam, 10 weirs, three wastewater treatment plants and 11 tributaries. The model considers the nitrogen conversion and COD removal and has a strong focus on biofilm processes in the benthic zone. Additional information is given about the sedimentation processes, the physical oxygen input processes, biofilm detachment processes, molecular diffusion, the influence of the laminar border layer and the changing of COD fractions and biofilm densities.

[Febrile state, bloody diarrhea and megacolon]

We report about a forty year old female patient with severe bloody diarrhoea and fever over a period of 14 days due to an infection with Salmonella enteritidis. X-ray of the abdomen showed a toxic megacolon. With the diagnosis of an infectious colitis we started therapy with ciprofloxacin i/v. The toxic megacolon progressed despite intensive care and parenteral nutrition. Additionally the patient received metronidazole i/v and in combination with a roll technique in bed in the knee-elbow-position the leucocytosis and the megacolon decreased. A toxic megacolon is in about 3% associated with an infection with Salmonella enteritidis. It is essentially diagnosed by X-ray. Patients should receive intensive care, and because of the high mortality rate an interdisciplinary management is required. The article discusses the major differential diagnosis of the toxic megacolon, as well as the pathogenesis and therapy of Salmonella ent, infection. In case of an infection with Salmonella ent. physicians should acknowledge the possibility of development of a toxic megacolon.

Acute ischaemic colitis in a female long distance runner

A 34 year old female long distance runner is reported with bloody diarrhoea. Colonoscopy revealed patchy haemorrhagic mucosal lesions throughout the colon. The most extensive lesions were found in the sigmoid colon. Histologic examination disclosed mucosal haemorrhage, dilated capillaries, patchy fibrosis and superficial erosions. Additional findings in this patient were haemorrhagic gastritis, microscopic haematuria and rhabdomyolysis. The only medication taken by the patient was oral contraceptives. We conclude that ischaemic colitis is one of the possible mechanisms leading to gastrointestinal blood loss in competitive runners.

[Changes in the serum pancreas enzyme following i.v. stimulation with secretin in subjects with a normal pancreas]

The diagnostic value of serum enzyme provocative tests (SEP) is disputed. In particular, the specificity of the test has not been adequately investigated. New interest in the test has arisen with the introduction of pancreas-specific serum enzyme tests. It has been shown that a poststimulatory increase of serum enzymes is found in chronic pancreatitis with well preserved exocrine function, but also in healthy individuals and particularly cigarette smokers. Recently it has been postulated that the lack of a poststimulatory enzyme response is typical of advanced chronic pancreatitis. We investigated the effect of secretin (1 CU/kg i.v.) on serum levels of amylase, pancreasisoamylase, lipase and trypsin for 30 minutes in 48 volunteers without pancreatic disease (19 non-smokers, 19 smokers and 10 patients with hypoxemia). Mean values of all enzymes were significantly higher after stimulation. Enzyme response of trypsin and lipase was more pronounced than that of amylase or pancreasisoamylase. However, depending on the enzyme studied, no significant increase of serum values was found in 47.4% to 89.5% of smokers, 26.3 to 68.4% of non-smokers and 10 to 50% of patients with hypoxemia. The marked variability of enzyme response in controls demonstrates the low specificity of this test. Therefore, SEP are of no diagnostic value in pancreatic disease.

Lipasuria in acute pancreatitis: result of tubular dysfunction?

Lipase, in contrast to amylase, is completely reabsorbed by the proximal tubules after glomerular filtration. Therefore, no lipase is detectable in the unconcentrated urine according to the current opinion. The handling of lipase (detected with an enzyme-immunoassay) by the kidney was investigated in comparison with creatinine, amylase, and beta-2-microglobulin by clearance studies in acute pancreatitis (n = 10), burn injury (n = 4), glomerular proteinuria (n = 8), and controls without evidence of pancreatic or renal diseases (n = 5). In initial stages of acute pancreatitis a measurable clearance of lipase (mean: 49.6 microliters/min, range: 0.5-234) was found in association with corresponding increased clearances of beta-2-microglobulin (mean: 10.5 ml/min, range: 0.02-58.9) and of amylase (mean: 8.9 ml/min, range: 2.4-22.6) in nine of ten patients. This finding is consistent with a defect of tubular function. However, regression analysis failed to show a significant correlation between lipase and beta-2-microglobulin clearance. Repeated measurements during the course of pancreatitis in seven patients showed reversibility of tubular dysfunction. In patients with burn injury a similar elevation of clearances of beta-2-microglobulin and of amylase was found, but tubular dysfunction in this condition was not associated with lipasuria. In glomerular proteinuria a lipase clearance was found in two of five cases with moderate, and in the other three cases with severe impairment of creatinine clearance. beta-2-microglobulin clearance was normal in the former and only slightly elevated in the latter group. In conclusion lipase is measurable in the urine of most patients with acute pancreatitis as a result of a reversible tubular dysfunction.(ABSTRACT TRUNCATED AT 250 WORDS)

Diagnosis of achlorhydria by plasma secretin determination--a tubeless approach

To investigate the value of plasma secretin determination in the diagnosis of impaired gastric secretion, blood samples were drawn for secretin assay (radioimmunoassay) at specified intervals before and after pentagastrin stimulation in 10 healthy volunteers and 11 subjects with suspected hypo- or achlorhydria (less than 10 mEq HCl/2 h). The tests were performed twice, once with and once without aspiration of gastric juice for estimation of acid output. In six other patients with proven achlorhydria, the test was performed once without gastric aspiration. The best discrimination of a single plasma secretion level between controls and patients with hypo- and achlorhydria was obtained 60 min after pentagastrin stimulation. All controls and four subjects with an acid output more than 10 mEq/2 h had secretin levels within normal limits. In contrast, 12 of the 13 subjects with hypochlorhydria had abnormally low basal corrected secretin levels at 60 min, including nine achlorhydria patients. It is concluded that secretin determinations after pentagastrin stimulation may be a valuable diagnostic and epidemiological tool to identify patients with impaired gastric secretion.

[Mesenterial anemia as a cause of jogging anemia?]

Anemia in runners is common but its origin is unknown. The present study reports on frequency and origin of gastrointestinal blood loss in cross-country skiers and runners. 41 participants in the Engadin Ski Marathon were checked by questionnaire and occult blood test. 8 (19%) had diarrhea or abdominal pain during or immediately after skiing and 3 (7%) had hemoccult-positive stools. In addition, the blood flow of the superior mesenteric artery was measured by duplex scanning in two trained runners after standardized exercise. While the mesenteric blood flow in the asymptomatic runner changed only insignificantly there was an impressive decrease in the second runner, who had been treated for anemia, down to 20% and 40% (30 and 90 min respectively) after exercise. It is concluded that the occurrence of gastrointestinal blood loss in cross-country skiing, and the significant decrease in mesenteric blood flow in a symptomatic runner, indicate a close and possible causal relationship between mesenteric ischemia and "jogging anemia".

[Gastrointestinal involvement in acquired immunologic deficiency syndrome (AIDS)]

The gastrointestinal tract is a major target organ of the acquired immunodeficiency syndrome. Opportunistic infections or Kaposi's sarcoma within the gastrointestinal tract are the two most frequent lesions. Diarrhoea, weight loss or odynophagy may be the presenting symptoms or signs for which a gastroenterological consultation is sought. In this report we present our own observations of patients with AIDS. Diagnostic and therapeutic aspects of this new syndrome are discussed.

[Postprandial hyperemia of the superior mesenteric artery]

With the use of ultrasonic duplex scanning it is now possible to assess the blood flow dynamics in the human mesenteric artery noninvasively. The changes associated with a standardized food load were measured and the results compared with the blood flow of the common carotid artery. 20 healthy subjects (age 30.1 +/- 5 years) were studied fasting and 6 times at 15 minutes interval after the test meal (1000 kCal). While the flow parameters of the carotid artery were virtually unaffected by food intake, a steep increase in mesenteric blood flow was observed. Maximal hyperemia (2.7-fold increase, range 1.4-5.7) was reached 45 minutes after food intake.

Endoscopic removal of a large, obstructing and bleeding duodenal Brunner's gland adenoma

About 10-30% of benign duodenal tumors are Brunner's gland tumors. These are almost always benign. Usually they present as incidental findings in the form of small polypoid lesions at barium examination or at panendoscopy. We present a case with a large obstructing and bleeding Brunner's gland adenoma located in the duodenal bulb which was removed by endoscopic polypectomy.

[Primary colon tuberculosis]

Two cases of primary gastrointestinal tuberculosis are reported. One patient showed radiologic, colonoscopic and histopathologic features of Crohn's disease. After a five-year follow-up, acid-fast bacilli were identified in colonic tissue cultures. In both patients fecal cultures were repeatedly negative for Mycobacterium tuberculosis. The two patients were successfully treated with antituberculous therapy. The authors emphasize the importance of considering tuberculosis in patients presenting with Crohn's disease. In this regard colonoscopy with tissue culture of targeted biopsy may be a valuable aid in establishing the diagnosis of tuberculous colitis.

[Prolonged coma caused by diazepam sedation in ventilated patients. Diagnostic and therapeutic use of the benzodiazepine antagonist Ro 15-1788]

Repeated administration of diazepam in two ventilated patients had caused drug cumulation and coma over several days. In both cases central nervous depression could be demonstrated by the benzodiazepin antagonist Ro 15-1788 which induced reversal of coma. Estimation of plasma concentrations in a 70-year-old female patient 150 hours after the last administration showed a diazepam concentration of 437 ng/ml and a desmethyl-diazepam concentration of 483 ng/ml. The calculated elimination half-life of these substances were 109 and 403 hours. In the second case benzodiazepin could be demonstrated in urine for 10 days after withdrawal of medication. These observations suggest that diazepam is not a suitable drug for prolonged sedation in artificially ventilated patients. The benzodiazepin antagonist Ro 15-1788 represents a valuable diagnostic aid in ascertained or suspect cases of benzodiazepin intoxications. It can also be used therapeutically for reversal of central nervous depression.

[DIDMOAD syndrome (diabetes insipidus, diabetes mellitus, optic atrophy, deafness) with cerebello-pontine atrophy]

The case is reported of a 32-year old women of Dutch origin who presented with diabetes insipidus, diabetes mellitus, atrophy of the optic nerve, and dilatation of the urinary tract, the combination known as "DIDMOAD syndrome". Unusual features of this case were regional atrophy of the cerebellum and the pons, and hydrocephalus internus which were associated with alterations of personality and mental function. The clinical symptoms of the syndrome simulated "essential" type 1 diabetes with advanced complications such as retinopathy and autonomous and peripheral neuropathy. The presence of diabetes insipidus with polyuria and polydipsia was not recognized for years because the symptoms were ascribed to diabetes mellitus. The neurologic and psychological symptoms in this patient suggest a more generalized defect of the central nervous system in this syndrome than has been observed previously. Recognition of the condition is of importance because it requires specific therapeutic measures (e.g. for diabetes insipidus), and because of the genetic and prognostic implications.