Removal of airborne microorganisms emitted from a wastewater treatment oxidation ditch by adsorption on activated carbon

Abstract

Bioaerosol emissions from wastewater and wastewater treatment processes are a significant subgroup of atmospheric aerosols. Most previous work has focused on the evaluation of their biological risks. In this study, however, the adsorption method was applied to reduce airborne microorganisms generated from a pilot scale wastewater treatment facility with oxidation ditch. Results showed adsorption on granule activated carbon (GAC) was an efficient method for the purification of airborne microorganisms. The GAC itself had a maximum adsorption capacity of 2217 CFU/g for airborne bacteria and 225 CFU/g for fungi with a flow rate of 1.50 m 3 /hr. Over 85% of airborne bacteria and fungi emitted from the oxidation ditch were adsorbed within 80 hr of continuous operation mode. Most of them had a particle size of 0.65-4.7 μm. Those airborne microorganisms with small particle size were apt to be adsorbed. The SEM/EDAX, BET and Boehm's titration methods were applied to analyse the physicochemical characteristics of the GAC. Relationships between GAC surface characteristics and its adsorption performance demonstrated that porous structure, large surface area, and hydrophobicity rendered GAC an effective absorber of airborne microorganisms. Two regenerate methods, ultraviolet irradiation and high pressure vapor, were compared for the regeneration of used activated carbon. High pressure vapor was an effective technique as it totally destroyed the microorganisms adhered to the activated carbon. Microscopic observation was also carried out to investigate original and used adsorbents.

Concentration and size distribution of viable bioaerosols during non-haze and haze days in Beijing

“…Once the required volume of air had been drawn, the plates were removed from the sampler, covered, inverted, and incubated. The bacteria were incubated on 20 ml nutrient agar medium (LB, Aoboxing Biotech, Co., China) at 37°C for 48 h, and fungi were cultivated on 20 ml Rose Bengal medium (BR, Aoboxing Biotech, Co., China) at 25°C for 72 h (Li et al 2011a). The colonies were counted as colony-forming units (CFU m −3 ) using positive hole correction (Andersen 1958).…”

Novel integrated approach of adsorption and photo-oxidation using Ag–TiO2/PU for bioaerosol removal under visible light

“…reported that PU was a hydrophobic material [46]. Thus, a hydrophobic interaction between PU and bacteria could also contribute to the bacterial adsorption capacity of PU [47]. Several previous studies have reported that materials containing metal, TiO 2 , and SiO 2 on the surface could have numerous positive charges on their surface [44,46].…”

Advanced removal of C. famata in bioaerosols by simultaneous adsorption and photocatalytic oxidation of Cu-doped TiO 2 /PU under visible irradiation

“…Kara et al reported that removal of a microorganism is a complex process affected by many parameters such as the chemical and physical properties of the adsorbent, the microorganism's characteristics and the environmental conditions [40]. The porous structure and large surface area of the PU are favorable for the adsorption of airborne microorganisms [41]. Yeast can be adhered on the inner surface of the pores of PU by van der Waals force [42].…”

“…The yeast adsorption mechanism by PU is also due to its hydrophobicity and non-polarity. Most previous studies reported that microorganisms tend to attach to hydrophobic and non-polar materials [41,43]. Li et al reported that hydrophobic interaction between the yeast cell surface and the adsorbent surface can enable the cell to overcome the repulsive forces within a certain distance from the adsorbent and yeast [41].…”