Phosphorus removal under anoxic conditions in a continuous-flow A2N two-sludge process.

The Anaerobic-Anoxic/Nitrification (A2N) system is a continuous-flow, two-sludge process in which Poly-P bacteria are capable of taking up phosphate under anoxic conditions using nitrate as an electron acceptor. The process is very efficient because it maximizes the utilization of organic substrate for phosphorus and nitrogen removal. An experimental lab-scale A2N system fed with domestic sewage was tested over a period of 260 days. The purpose of the experiment was to examine phosphorus removal capacity of a modified A2N two-sludge system. Factors affecting phosphorus and nitrogen removal by the A2N system were investigated. These factors were the influent COD/TN ratio, Sludge Retention Time (SRT), Bypass Sludge Flow rate (BSF) and Return Sludge Flow rate (RSF). Results indicated that optimum conditions for phosphorus and nitrogen removal were the influent COD/TN ratio around 6.49, the SRT of 14 days, and the BSF and RSF were fixed at about 26-33% of influent flow rate.

Non-filamentous sludge bulking caused by a deficiency of nitrogen in industrial wastewater treatment.

Deficiency in the nutrient supply such as nitrogen usually results in activated sludge bulking and this phenomenon often takes place in the industrial wastewater treatment plants with activated sludge process. The effects of nitrogen deficiency on activated sludge bulking were studied specially in some experiments carried out in a sequencing batch reactor fed with brewing process wastewater in this paper. The experimental results showed that the sludge settled properly at an influent BOD/N value of 100/4. When the value of BOD/N was 100/3, filaments had an excessive growth at one time during the reaction process. Afterwards, the number of filamentous bacteria began to reduce and simultaneously an excessive growth of viscous Zoogloea with high percentage of moisture was observed and non-filamentous activated sludge bulking occurred. When the influent BOD/N value was 100/2, the excessive growth of filamentous microorganisms could not be observed at all times and the sludge characterization was similar to the case in which BOD/N value was 100/3. When the value of influent BOD/N was 100/0.94, more serious non-filamentous bulking occurred. Furthermore, the effects of nitrogen deficiency on the nitrogen sources and phosphorus sources utilization rate and the COD removal rate were investigated in the experiments.

Relation between radiographic mottle for double and single emulsions.

The radiographic density fluctuations produced by using dual screen-film systems are designated as the radiographic mottle. The density fluctuation of the radiographic mottle for the double emulsions at a density of the double emulsions consists of those for the front and back emulsions on a radiograph. However, the relation between the Wiener spectra of the radiographic mottle for the double and single emulsions had not been studied. Hence we compared the Wiener spectra of the radiographic mottle for the double emulsions with the sum of those for the front and back emulsions on the same radiographs and with the sum of those for the emulsions at the same densities. At all densities of more than 0.62 for lower spatial frequencies (< or = 1 mm-1), the Wiener spectral values of the radiographic mottle for the double emulsions were greater than the sum of those for the front and back emulsions for both comparisons on the same radiographs and at the same densities. In order to investigate the reason of the above phenomena, we separated the Wiener spectral values of the radiographic mottle for various densities into those of the three factors, i.e., quantum mottle, structure mottle, and film granularity, and performed the same comparisons as the radiographic mottle. Also, to explain the results for the three factors, we obtained the Wiener spectral values of the spatial fluctuations of the light exposure or the fluorescence intensity and the gradients of the characteristic curves of the film for the double and single emulsions of the x-ray film. As a result of the investigation, we found that the phenomena on the radiographic mottle were caused by that (1) on the same radiographs the squares of the gradients of the characteristic curves for the double emulsions were about 5.3 times as great as those for the single emulsion at densities of more than 0.62 of the double emulsions, and (2) at the same density of more than 0.62 those were more than about 2.2 times as great as those for the single emulsion.

[Intraoperative plasmapheresis in patients undergoing CABG surgery; effect on intraoperative and postoperative homologous blood transfusion requirements].

To evaluate the effect of intraoperative plasmapheresis on intraoperative and postoperative homologous blood transfusion requirements, we assigned 89 patients undergoing primary CABG procedure to either the experimental group (plasmapheresis, n = 31, A group) or the control group (traditional method, n = 58, B group). All patients underwent hemodilution by withdrawal of autologous blood before cardiopulmonary bypass. In A group, the average volume withdrawn during plasmapheresis was approximately 948 ml (platelet rich plasma (PRP) and red blood cells). We removed an average of 751 ml of whole blood in B group. The percentage of patients without homologous blood transfusion in A group was 40% versus 32% in B group. The difference was not statistically significant. It was concluded that our method of plasmapheresis was effective in reducing homologous blood transfusion, but it was not more effective than the traditional hemodilution method.

[Reduction of the amount of perioperative blood transfusion by autotransfusion techniques in valvular heart surgery].

We used autotransfusion in valvular heart surgery and evaluated its effect on perioperative homologous blood requirements. Methods of autotransfusion we used were intraoperative blood salvage using Cell Saver 4 and retransfusion (IAT), postoperative autotransfusion of shed mediastinal blood (PAT), and hemodilutional autotransfusion (HAT). The patients undergoing valvular heart operations were divided into three groups; group 1 (control group), group 2 (using IAT and PAT group), and group 3 (using IAT, PAT, and HAT group). Perioperative homologous blood requirements significantly decreased in group 3 compared to group 1 and group 2. Operations without homologous blood transfusion significantly increased in number in group 3 compared with group 1. In conclusion, autotransfusions described above were useful blood conservation techniques in valvular heart surgery.

[The efficacy of blood conservation technique for coronary artery bypass graft surgery].

To evaluate the efficacy of blood conservation technique at our center, 144 patients undergoing primary coronary artery bypass grafting were studied between Jan. 1988, and Dec. 1990. Combined intraoperative and postoperative autotransfusion technique reduced the requirement of homologous blood to a half and 24% of the patients were without homologous transfusion. With more use of dilutional autotransfusion, 41% of the patients were without homologous transfusion. Intraoperative and postoperative autotransfusion technique is effective and dilutional autotransfusion is also a relatively effective method to reduce homologous transfusion.

[Congenital stomatocytosis associated with aplastic anemia].

A seven year-old boy with hereditary stomatocytosis complicated with aplastic anemia was reported. He was admitted to our hospital because of pale and general fatigue. On physical examination, he had severe anemia, petechiae, but no hepatosplenomegaly. Peripheral blood cell count revealed pancytopenia; RBC 103 X 10(4)/microliters, Hb 3.5 g/dl, Ret 21%, WBC 1,200/microliters, Pl 1.3 X 10(4)/microliters, and bone marrow revealed markedly hypocellular marrow. Red cell morphology demonstrated stomatocytosis. Red cell life span (51Cr T1/2) was 12 days, Coombs' test and Ham's test were negative. Indirect bilirubin was 1.1 mg/dl and marked decrease of haptoglobin was found. Family studies showed that his father and sister had stomatocytosis on peripheral blood examination, but no anemia. The patient had severe anemia because of complicated aplastic anemia. Congenital stomatocytosis with aplastic anemia is extremely rare. The authors are interested in a possible relationship between hereditary stomatocytosis and aplastic anemia although the precise mechanism remains to be elucidated.