Applicability assessment of ceramic microbeads coated with hydroxyapatite-binding silver/titanium dioxide ceramic composite earthplus™ to the eradication of Legionella in rainwater storage tanks for household use

Abstract

Water environments appear to be the habitats of Legionella species. Legionellosis is considered as a preventable illness because bacterial reservoirs can be controlled and removed. Roof-harvested rainwater has attracted significant attention not only as a groundwater recharge but also as a potential alternative source of nonpotable water. We successfully developed ceramic microbeads coated with hydroxyapatite-binding silver/titanium dioxide ceramic composite earthplus™ using the thermal spraying method. The ceramic microbeads were demonstrated to have bactericidal activities against not only Legionella but also coliform and heterotrophic bacteria. Immersing the ceramic microbeads in household rainwater storage tanks was demonstrated to yield the favorable eradication of Legionella organisms. Not only rapid-acting but also long-lasting bactericidal activities of the ceramic microbead were exhibited against Legionella pneumophila . However, time-dependent attenuation of the bactericidal activities against Legionella were also noted in the sustainability appraisal experiment. Therefore, the problems to be overcome surely remain in constantly managing the Legionella -pollution by means of immersing the ceramic microbeads. The results of our investigation apparently indicate that the earthplus™-coated ceramic microbeads would become the favorable tool for Legionella measures in household rainwater storage tanks, which may become the natural reservoir for Legionella species. Our investigation would justify further research and data collection to obtain more reliable procedures to microbiologically regulate the Legionella in rainwater storage tanks.

Progress in Hydroxyapatite–Starch Based Sustainable Biomaterials for Biomedical Bone Substitution Applications

“…Seeing the current biomedical issues and the huge potential of biomaterials, in this study, we aim to present the possibilities of using hydroxyapatite and starch mixtures for developing sustainable materials intended for medical applications. Both materials have proved their biocompatibility and may be extracted from natural sources by simple, safe, and economical procedures leading to materials with sustainable features. − The comparative sustainability of starch based materials especially nanocrystals has been recently summarized . This study reviews the methods for preparing hydroxyapatite–starch composites and the use of starch as porogen agent in sintering of hydroxyapatite.…”

Purification of living environments using photocatalysts: Inactivation of microorganisms and decomposition of allergens

“…). To summarize, most studies have shown that photocatalysts eliminate more than 90% of bacteria in one hour regardless of whether they are gram-positive [ 4 , 10 , 12 , 13 , 36 , 89 ] or gram-negative [ 1 , 9 , 10 , 12 , 21 , 30 , 31 , 33 , 36 , 38 , 55 , 56 , 80 , 91 , 95 ]. Thus, photocatalysis can be used to eliminate various bacterial species.…”

“…Several studies have focused on water sterilization using photocatalysts. In addition, there have been studies on the elimination of bacteria under experimental conditions in accordance with the ISO and various other conditions, such as the elimination of bacteria in running water [ 56 ], seawater [ 25 ], and rainwater [ 55 ]. Furthermore, the application of photocatalysts to oral implants [ 12 ] and disinfection of aerosols by photocatalysts [ 33 ] have been studied.…”