Water Disinfection Using Silver and Zinc Oxide Nanoparticles

Waterborne disease has changed a basic challenge in human population. recently, the use of nanotechnology and application of nanomaterials for the control of pathogens in water is widely increased in research. Common indicator for microbial quality of water are determine presence of total and fecal coliforms. The purpose of this study was to evaluate the effect of Silver (Ag) and zinc oxide (ZnO) nanoparticles (NPs) and combination of them in removing total and fecal coliform bacteria from contaminated water. In this experimental study a synthetic solution was made by adding effluent to distilled water. In each run, the nano silver (20-100 μg /L) and ZnO NPs (0.25-2 mg/L) were added to contaminated water. The samples were tested by 15-tube series method based on the instruction 9221-B of 21th edition of standard method book on water and wastewater experiments. Bacteria removal efficiency were examined in contact times (15, 30,60, 90 and 120) minutes. Our data indicate a decrease in the number of bacteria (MPN) in the presence of the nanoparticles. Results revealed that the removal percentage of coliform bacteria removal increased with increasing the contact time and concentrations of nanoparticles. Ag NPs at a concentration of 100 μg /L and ZnO NPs at a concentration of 2 mg/L showed the highest percentage of removal bacteria and the combination of ZnO and Ag NPs have been high synergistic behavior against coliform bacteria in contaminated water. therefore, using a combination of ZnO and Ag NPs can become a new and efficient method for the removal of indicator bacteria from contaminated water.

Suspended solids and bacteria removal mechanisms in ceramic filter and pervious concrete filter: a review

The need for drinking water with affordable access is increasing nowadays. The poor water quality problems can be solved by several water treatment methods, i.e. ceramic filter (CF) and pervious concrete filter (PCF). Those two mentioned technologies work based on the pores that exist within the filter. This study aimed to review (1) the influence of the material composition of the CF and PCF on hydraulic characteristics (porosity, permeability, pore size, pore structure, pore connectivity/ distribution) and its removal effectiveness, and (2) the removal mechanisms of suspended solids and bacteria based on its hydraulic characteristics. The study reviewed 45 literature, including books, reports, and published articles. The type, mineral, and sources of clay and the type, shape, proportion, and size of combustible materials on CF will affect its hydraulic characteristic. The shape, size, and type of aggregate, the ratio of water to cement, and the ratio of aggregate to cement on PCF will affect its hydraulic characteristics. The removal mechanisms of suspended solids are straining on the surface and trapping on the deadlocked pores. On the other hand, the bacteria removal mechanisms strain the bacteria in the dirt layer and trap the bacteria in the pores.

Disinfection Treatments of Disposable Respirators Influencing the Bactericidal/Bacteria Removal Efficiency, Filtration Performance, and Structural Integrity

In the outbreak of COVID-19, the extended wear of single-use, disposable respirators was inevitable due to limited supplies. As a respirator is front-line protection against particulate matter, including bioaerosol and droplets, a comprehensive understanding for the reuse strategy is needed. In this study, eight different disinfection methods commonly applied for the reuse of respirators were compared for their influence on the filtration and bactericidal/bacteria removal performance, with in-depth discussion on the cause of effects. Treatments including oven-dry, ultraviolet irradiation (UV), microwaving, laundering with and without detergent, and immersion in hypochlorite, isopropanol, and ethanol were performed to respirators. Immersion in ethanol or isopropanol was effective for inactivation and removal of bacteria, yet such a treatment significantly deteriorated the filtration efficiency in about 20–28%, dissipating the surface charges. Laundering, while effective in removing the attached bacteria, triggered physical damage, leading to a possible reduction of filtration performance. A short-term oven-dry, UV irradiation, and microwaving mostly preserved the filtration performance, yet the drawback lied in the incomplete bactericidal efficiency. This study would contribute to the public health and safety by providing scientific background on the effect of disinfection treatment methods for respirators.