Youn-Kyoo Choung

Performance of membrane bioreactor system with sludge ozonation process for minimization of excess sludge production

This study investigated the effects of sludge ozonation on excess sludge minimization and enhancement of nutrient removal in membrane bioreactor (MBR). Two modified Ludzack-Ettinger (MLE) type MBR system were operated in parallel with or without a batch-type sludge ozonation process. A -flat type microfiltration membrane (pore size 0.4 μm) was used. The specific ozone dosage was set at 0.1 gO3lgSS. In the control run (without sludge ozonation), the daily sludge production was about 1.04 gld. However, in the ozone run (with sludge ozonation), the daily sludge production was negligible. In addition, the MLSS concentrations and the volatile fraction of MLSS in the reactor maintained constant around 8,000 mg/L and 0.75, respectively, without excess sludge. The concentration of effluent was maintained at a satisfactory level in both runs. Furthermore, the MBR system with sludge ozonation process showed relatively better nutrient removal than without sludge ozonation. It revealed that ozonated sludge might be completely degraded in the reactor and effectively used as a carbon source. During the operation, the transmembrane pressure was maintained lower than 10 kPa under 0.36 mld of flux regardless of presence of sludge ozonation. Application of sludge ozonation to the MBR system was significantly effective for minimization of excess sludge production as well as for enhancement of nutrient removal.

Degradation of Antibiotics (Tetracycline, Sulfathiazole, Ampicillin) Using Enzymes of Glutathion S-Transferase

ABSTRACT Swine wastewater is not easily treated in biological wastewater treatment plants. One reason is that some antibiotics are not easily degradable in a normal treatment system and inhibit the biological organisms in the treatment system. Specifically, tetracycline, sulfathiazole, and ampicillin are representative antibiotics found in poultry wastewater. To degrade these refractory and impediment antibiotics more easily, a special method is needed, such as an enzyme method. This research used a special enzyme in an experiment that tested feasibility with an enzyme assay of biological treatment in vitro. The Glutathion S-Transferases (GSTs) are a family of proteins that catalyze the conjugation of reduced glutathione with a variety of hydrophobic chemicals containing electrophilic centers. Using GSTs, these major antibiotics were transformed into components that were non-toxic to the microorganisms that treat manure wastewater. The initial concentration of tetracycline, sulfathiazole, and ampicillin were 100 mg/L, 100 mg/L, and 50 mg/L, respectively, and the concentration of pig feed was the same as usual. The GSTs have made the effect of biotransformation of antibiotics as their mode. They were 60–70% transformed by GSTs at the end of the degradation reaction. This lowered their inhibitory strength against microorganisms.

A novel laboratory cultivation method to examine antibiotic-resistance-related microbial risks in urban water environments

Although microbial risk due to antibiotic-resistant microbes in water has been a serious public health concern, the current culture-dependent detecting methods using nutrient-rich conditions may not be suitable for evaluating microbial risk. In the present study, a novel cultivation method was developed to detect antibiotic-resistant microbes at various nutrient levels. A nutrient-rich medium Luria-Bertani broth (LB) was diluted at a wide range of dilution factors (10(0)-10(4)) and amended with either tetracycline or vancomycin. A standard environmental cultivation medium, R2A, was also used by amending with antibiotics. The diluted LB with antibiotics was able to detect previously known oligotrophic and antibiotic-resistant bacteria in drinking water and swine manure samples, respectively. These results validate the capability of the new method to detect antibiotic-resistant microbes in various environmental water samples. Using the developed method in assessing microbial risk due to antibiotic-resistant microbes in river and municipal wastewater plants, we found that the viable counts and antibiotic resistance fraction were significantly influenced by the type and concentration level of antibiotic exposure and the cultivation medium conditions. This suggests a further need to standardize cultivation method procedures, to assess microbial risk in water samples.

The study of electron equivalent fluxes about decomposition of sulfamethazine and sulfathiazole using oxygen-based membrane biofilm reactor

Abstract The subject of this research was electron equivalent fluxes about the decomposition of pharmaceuticals (sulfamethazine and sulfathiazole) using an oxygen-based membrane biofilm reactor (MBfR). The influent concentrations in pharmaceuticals feed-medium were (in ppb): sulfamethazine (40) and sulfathiazole (85). The oxygen-based MBfR system consisted of two membrane modules connected to a recirculation loop. The main membrane module contained a bundle of 32 hydrophobic hollow-fiber membranes inside a polyvinyl-chloride pipe shell and the other module contained a single fiber used to take biofilm samples. Pure O2 was supplied to the inside of the hollow fibers through the manifold at the base, and the O2 pressure for both reactors was 13 kPa. (1 kPa = 0.0099 atm = 0.145 psi). HRT was 3 h. The decomposition ratio of pharmaceuticals (sulfamethazine and sulfathiazole) using oxygen-based MBfR was (%): sulfamethazine (77 ± 2) and sulfathiazole (87 ± 2). In all cases, nitrification was the largest provider...