Construction of a domestic wastewater disinfection filter from biosynthesized and commercial nanosilver: a comparative study

Biosynthesis of nanoparticles is an eco-friendly process and considered one of the most significant aspects of nanotechnology. Silver nanoparticles (Ag NPs) have a better bactericidal activity due to its high surface area to volume ratio. In this paper, Streptomyces sp. U13 (KP109813) was used to biosynthesize silver nanoparticles (Ag NPs) to construct wastewater disinfection filter. The biosynthesized nanosilver and a commercially available ink nanosilver were characterized, and their wastewater disinfection efficiency was compared. The nanometrological characteristics of both nanosilver such as structure, shape, and size were investigated using the X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FTIR), high-resolution transmission electron microscope (HR-TEM), and UV-visible spectroscopy. The results revealed that the biosynthesized and ink Ag NPs were well dispersed and had a spherical shape, with sizes ranged from 5 to 37 nm and from 2 to 26 nm, respectively. To examine the disinfection capabilities, Ag NPs were loaded on two substrates, foam and limestone gravel, and packed into a glass column receiving domestic wastewater. Results showed that Ag NPs attached to limestone gravel eliminate 100% of the coliform bacteria better than foam. Comparing to control columns (without silver), only 50 and 10% reduction of the total coliform in gravel and foam column were achieved, respectively. This work concluded that the type of substrate controls the amount of Ag NPs loaded on it and thus controls the disinfection process. No significant difference between biosynthesized and ink nanosilver in wastewater disinfection was observed. Using limestone gravel filter loaded with 200 mg/l Ag NPs with contact time of 150 min achieves a complete eradication of coliform bacteria.