Wataru Agui

Gram-negative bacteria viable in ultrapure water: identification of bacteria isolated from ultrapure water and effect of temperature on their behavior

Abstract This study describes the effect of temperature on the behavior of bacteria viable in ultrapure water and the contamination of ultrapure water by bacteria. Three species of bacteria were isolated from ultrapure water (total organic carbon, 60 ppb and 5 ppb; effluent resistivity > 18 MΩ cm at 25°C) and identified by morphological and physiological characteristics. The three isolates were incubated in water for injection and PYG broth to check the growth profile at various temperatures. In PYG broth, temperature influenced the behavior of bacteria directly; however, it did not in water for injection. By checking both viable and non-viable bacterial numbers and endotoxin concentration in pure water, the water was found to be contaminated with non-viable bacteria and newly generated endotoxins besides viable bacteria. A column treatment, a mixed bed of fully regenerated strong acid cation exchange resin (SACER) and strong base anion exchange resin (SBAER), was used to remove bacteria from pure water. Bacteria could not grow on the surfaces of ion exchange resins in the mixed bed. The removal of bacteria was more effective as pure water was circulated through the mixed bed more rapidly.

Removal of dissolved humic substances from water with a reverse osmosis membrane

Abstract This study describes the removal of dissolved humic substances (HS) from water at various pHs with a reverse osmosis membrane (RO). The RO used consists of cellulose acetate-spiral. The HS dissolved in water and in 0.1 N NaOH contained three and two different molecular weight (MW) components, respectively, in an apparent MW range from 100 to more than 100 000 according to gel filtration chromatography (GFC). The HS were dissolved to a total organic carbon (TOC) concentration of

Removal of humic substance dissolved in water I

Abstract This study is concerned with the absorption properties of a fractionated humic substance at varying pHs on surface-treated carbon adsorbents. Activated carbon fiber (PF) made from phenol resin, Pittsburgh activated carbon (AC), and electronic conductive carbon black (EC) are used. The adsorption properties of the carbon differ greatly depending on the characteristics of the humic substance fractions. The humic substance used is divided into two fractions of different molecular weights in the neutral solution. The lower- (mol wt 100 to 1000 as polyethylene glycol (PEG)) and higher- (mol wt 1000 to 5000 as PEG) molecular-weight components are adsorbed well on PF and AC, having a large volume of micropores, and EC, being rich in mesopores, respectively. After the removal of surface polar substances from the adsorbents, we correlate the adsorptive capacity and the pore-size distribution. These results suggest that pore-size distribution is an important factor in removing humic substances effectively.

Removal of humic substances dissolved in water with carbonaceous adsorbents

Abstract Adsorption properties of humic substances fractionated at varying pH on surface-improved carbonaceous adsorbents and the effect of inorganic salts on the adsorption removal of the humic fractions from aqueous solutions have been investigated. The adsorption properties of the adsorbents differ greatly depending on the characteristics of the humic substance fractions. The lower- and higher-molecular-weight fractions are adsorbed well onto micro- and mesopores of the adsorbents. When the valence and/or concentration of added inorganic compounds increase, lower-molecular weight components tend to aggregate to higher-molecular ones. After salting-out, the adsorbent being rich in micropores serves well as adsorbent for removing both fulvic and humic acids from aqueous solutions.

Disinfection of viable Pseudomonas stutzeri in ultrapure water with ion exchange resins

Abstract This study describes the disinfection of gram-negative bacteria, Pseudomonas stutzeri , isolated from ultrapure water (total organic carbon 5 ppb; effluent resistivity, > 18 MΩ cm at 25°C) with ion exchange resins using a batchwise procedure. A single bed of strong base anion exchange resin (SBAER) in OH − form shows disinfection ability; however, a bed of strong acid cation exchange resin (SACER) in H + form does not. Adsorption of bacteria on SBAERs occurs mainly due to the electrostatic attraction between positively charged SBAERs and negatively charged bacteria. In addition, hydrophilic interactions between SBAERs and bacteria are considered based on the results of adsorption isotherms. Since the positively charged SBAERs in Cl − form have no bactericidal effect, OH − ions are utilized for disinfection. Acrylic SBAERs in OH − form were more effective at disinfection than styrenic SBAERs. A mixed bed of SBAERs in OH − form and SACERs in H + form also disinfects bacteria more effectively.

Spontaneous breaking of microemulsion by surface-modified ion exchange resins

Abstract We find that a dehydrated ion exchange resin particle with quarternary ammonium groups has a sufficient effect and results in the destruction of a thermodynamically stable o/w-type microemulsion without any external cause.