Evaluation of a novel oxidation ditch system for biological nitrogen and phosphorus removal from domestic sewage.

A novel oxidation ditch system using anaerobic tanks and innovative dual dissolved oxygen (DO) control technology is proposed for biological nitrogen and phosphorus removal from domestic sewage. A continuous bench-scale experiment running for more than 300 days was performed to evaluate the system. Monitoring and controlling the airflow and recirculation flow rate independently using DO values at two points along the ditch permitted maintenance of aerobic and anoxic zone ratios of around 0.30 and 0.50, respectively. The ability to optimize aerobic and anoxic zone ratios using the dual DO control technology meant that a total nitrogen removal efficiency of 83.2-92.9% could be maintained. This remarkable nitrogen removal performance minimized the nitrate recycle to anaerobic tanks inhibiting the phosphorus release. Hence, the total phosphorus removal efficiency was also improved and ranged within 72.6-88.0%. These results demonstrated that stabilization of the aerobic and anoxic zone ratio by dual DO control technology not only resulted in a marked improvement of nitrogen removal, but it also enhanced phosphorus removal.

Operation of a new sewage treatment process with technologies of excess sludge reduction and phosphorus recovery.

This paper shows the potential application of a new sewage treatment process with technologies of excess sludge reduction and phosphorus recovery. The process incorporated ozonation for excess sludge reduction and crystallisation process for phosphorus recovery to a conventional anaerobic/oxic (A/O) phosphorus removal process. A lab-scale continuous operation experiment was conducted with the ratio of sludge flow rate to ozonation tank of 1.1% of sewage inflow under 30 to 40 mgO3/gSS of ozone consumption and with sludge wasting ratio of 0.34% (one-fifth of a conventional A/O process). Throughout the operational experiment, a 60% reduction of excess sludge production was achieved in the new process. A biomass concentration of 2300 mg/L was maintained, and the accumulation of inactive biomass was not observed. The new process was estimated to give a phosphorus recovery degree of more than 70% as an advantage of excess sludge reduction. The slight increase in effluent COD was observed, but the process performance was maintained at a satisfactory level. These facts demonstrate an effectiveness of the new process for excess sludge reduction as well as for phosphorus recovery.

Advanced sewage treatment process with excess sludge reduction and phosphorus recovery.

An advanced sewage treatment process has been developed, in which excess sludge reduction by ozonation and phosphorus recovery by crystallization process are incorporated to a conventional anaerobic/oxic (A/O) phosphorus removal process. The mathematical model was developed to describe the mass balance principal at a steady state of this process. Sludge ozonation experiments were carried out to investigate solubilization characteristics of sludge and change in microbial activity by using sludge cultured with feed of synthetic sewage under A/O process. Phosphorus was solubilized by ozonation as well as organics, and acid-hydrolyzable phosphorus (AHP) was the most part of solubilized phosphorus for phosphorus accumulating organisms (PAOs) containing sludge. At solubilization of 30%, around 70% of sludge was inactivated by ozonation. The results based on these studies indicated that the proposed process configuration has potential to reduce the excess sludge production as well as to recover phosphorus in usable forms. The system performance results show that this system is practical, in which 30% of solubilization degree was achieved by ozonation. In this study, 30% of solubilization was achieved at 30 mgO(3)/gSS of ozone consumption.

Removal and recovery of phosphate and ammonium as struvite from supernatant in anaerobic digestion.

Removal of phosphorus and nitrogen is required to prevent eutrophication problems in lakes and enclosed coastal seas. And recovery of phosphorus from wastewater has been attracting attention because of lack in phosphorus resources in the near future. In this study, reaction kinetics and design parameters of struvite production are experimentally investigated by using basic reaction type and a draft-tube type reactors. Struvite production rate, which is a very important parameter in reactor design and efficiency estimation, is formulated in an equation consisting of a rate constant (k2), and magnesium, phosphate and ammonium concentrations. The value of k2 is shown to be increased with struvite concentration and mixing intensity in the reactor. The developed equation is applied to the results obtained from the draft-tube type reactor experiments and verified for its applicability. High struvite concentration of 10-25% is maintained in the draft-tube reactor experiments. 92% removal and recovery efficiency with effluent phosphorus concentration of 17 mg/L is achieved under the conditions of 4 minutes reaction time, pH of 8.5 and Mg/P molar ratio of 1.1.

Effects of recombinant human erythropoietin therapy on blood coagulation and fibrinolysis system.

This study was designed to examine the effects of recombinant human erythropoietin (rHuEPO) therapy on blood coagulation and fibrinolysis in patients scheduled for elective heart surgery and undergoing preoperative autologous blood donation. Twenty-seven patients were studied, of whom 16 patients received rHuEPO (group E) and 11 patients no rHuEPO therapy (group N). The patients in group E were given 6000 units of rHuEPO intravenously every other day, three times a week, beginning from two weeks prior to the operation. In both groups, 400 ml of blood was collected preoperatively for predeposit once a week for two weeks, and the self-donated blood was returned to the patient intra- and postoperatively. Blood samples were drawn at the beginning of the study, immediately before the operation and two weeks after the operation. They were analyzed to assess blood coagulation, fibrinolysis, platelet function and vascular endothelial cell function, in order to examine the effects of the administration of rHuEPO. No significant difference was observed between the two groups in the degree of changes in these parameters following the operation. As enhancement of blood coagulability and fibrinolytic activity was evident postoperatively in both groups, changes in these parameters during the preoperative autologous blood donation period were also assessed excluding the postoperative data. Again, there was no significant intergroup difference in any of the markers evaluated. It was concluded that the administration of rHuEPO during preoperative autologous blood donation is unlikely to affect coagulation and fibrinolysis.

Advanced treatment of sewage by pre-coagulation and biofilm process.

Treatment performance and operational parameters of a pre-coagulation and biofilm process were experimentally discussed with the pilot-scale plant treating actual municipal sewage. Perfect nitrification was accomplished within total hydraulic retention time (HRT) of 4 h at 20% volumetric added ratio of attached-growth media of biofilm in the aerobic tanks under temperature conditions as low as 17 degrees C. Treatment efficiencies in organic matter, T-N and T-P were high and stable with the total HRT of 8 h in the biological reactor. Concentrations of T-N and T-P in effluent were kept about 2 mgN/L and under 1 mgP/L, respectively. Attached growth bacterial mass and the potential activity of nitrification and denitrification in each tank in cold season were high enough to accomplish excellent treatment performance. Then the process was proved to be applicable to municipal sewage treatment for removal of nitrogen and phosphorus as well as organic matter.

Two distinct quinoprotein amine oxidases are induced by n-butylamine in the mycelia of Aspergillus niger AKU 3302. Purification, characterization, cDNA cloning and sequencing.

Two distinct quinoprotein amine oxidases were found in Aspergillus niger mycelia grown on n-butylamine medium and purified using chromatographic techniques. The respective enzymes were termed AO-I, which had already been isolated, and AO-II, a new enzyme found in this study. HPLC indicated that their molecular masses are 150 kDa and 80 kDa, respectively. On SDS/PAGE, the enzymes gave a similar but distinct mobility, which corresponds to 75 kDa for the subunit dimeric AO-I and 80 kDa for monomeric AO-II. The absorption spectra of both enzymes were different from each other; the absorption maxima in the visible region were at 490 nm for AO-I and 420 nm for AO-II. The enzymes showed positive quinone staining, comparable substrate specificity, and sensitivity to inhibitors typical for copper/topa quinone-containing amine oxidases, but they had different copper contents and also differed in their N-terminal sequences. Their peptide maps showed almost identical patterns, with the exception of two additional bands for AO-II. Among the peptides obtained from digestion of AO-II, peptides with sequences corresponding to the N-terminal part of AO-I were detected. Polyclonal antibodies raised against AO-I and AO-II recognized both enzymes, but with different specificities. Using precipitation with AO-I, the antibody prepared against AO-II was purified and was shown to be specific only for AO-II. The cDNA of AO-I was cloned and sequenced. A highly conserved tetrapeptide sequence, Asn-Tyr-Glu-Tyr, was identified in which the first tyrosine residue (Tyr404) that could be converted to topa quinone was present in the 670-residue deduced amino acid sequence. Northern blot analysis indicated that AO-I was highly expressed in A. niger grown on n-butylamine as a single nitrogen source. Genomic Southern blot analysis confirmed that both enzymes are likely to be encoded by the same gene.