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The purpose of this study was to establish an acid-etching procedure for altering the Ca/P ratio of the nanostructured surface of hydroxyapatite (HAP) by using surface chemical and morphological analyses (XPS, XRD, SEM, surface roughness, and wettability) and to evaluate the in vitro response of osteoblast-like cells (MC3T3-E1 cells) to the modified surfaces. This study utilized HAP and HAP treated with 10%, 20%, 30%, 40%, 50%, or 60% phosphoric acid solution for 10 minutes at 25°C, followed by rinsing 3 times with ultrapure water. The 30% phosphoric acid etching process that provided a Ca/P ratio of 1.50, without destruction of the grain boundary of HAP, was selected as a surface-modification procedure. Additionally, HAP treated by the 30% phosphoric acid etching process was stored under dry conditions at 25°C for 12 hours, and the Ca/P ratio approximated to 1.00 accidentally. The initial adhesion, proliferation, and differentiation (alkaline phosphatase (ALP) activity and relative mRNA level for ALP) of MC3T3-E1 cells on the modified surfaces were significantly promoted (P < 0.05 and 0.01). These findings show that the 30% phosphoric acid etching process for the nanostructured HAP surface can alter the Ca/P ratio effectively and may accelerate the initial adhesion, proliferation, and differentiation of MC3T3-E1 cells.

Catalytic combustion of volatile organic compounds (VOCs) such as ethylene, toluene, and acetaldehyde over novel Pt/CeO2–ZrO2–SnO2/γ-Al2O3 catalysts prepared by a coprecipitation method was investigated. The introduction of a small amount of SnO2 within the CeO2–ZrO2 lattice as a promoter was considerably effective to enhance the oxygen release and storage abilities of the catalysts, so that complete oxidation of VOCs was markedly activated. This improvement of the reducibility of the catalyst can be ascribed to the simultaneous reduction of Ce4+ and Sn4+ in the CeO2–ZrO2–SnO2 solid solutions. By the optimization of the composition and the Pt amount, complete oxidation of ethylene, toluene, and acetaldehyde was realized at temperatures as low as 55, 110, and 140 °C over a Pt(10 wt %)/Ce0.68Zr0.17Sn0.15O2.0(16 wt %)/γ-Al2O3 catalyst, respectively.

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Yearly discharge of antibiotic-resistant bacteria (ARB) from combined sewer overflow (CSO) was estimated. The volume of CSO was estimated from operating data of the pumping station. In the target sewer catchment, 23% of the total of the volume of combined sewage was discharged untreated as CSO. Combined sewage contained 3-log larger E. coli than secondary treatment effluent although the abundance of antibiotic-resistant E. coli was not significantly different. In the target-combined sewer catchment, a yearly total of 4.8 × 10 16 CFU of E. coli was discharged from 6.1 × 10 6 m 3 of CSO, while 1.3 × 10 12 CFU of E. coli from 2.1 × 10 7 m 3 of effluent from the wastewater treatment plant (WWTP). This E. coli discharge was equivalent to 7.9 × 10 9 CFU/m 3 from CSO, and 6.2 × 10 4 CFU/m 3 from WWTP effluent. Consequently, a yearly total discharge of antibiotic-resistant E. coli from CSO was 3.7-log larger than the WWTP effluent. The small-flow CSO events, which had hourly flow rate smaller than five times of the average dryweather flow, accounted for 43% of the total CSO volume, but 79% of the total discharge of antibiotic-resistant E. coli due to a small dilution factor with stormwater and frequent discharge. Reduction of small-flow CSO events would be important for effective reduction of ARB discharge from CSO.