What percentage of bacteria, viruses, and cholera vibrio can trickling filters remove?

Trickling filters are a type of wastewater treatment technology that primarily utilize a bed of media (such as stones, gravel, or plastic) to support the growth of biofilm containing microorganisms. These microorganisms break down organic matter and can also play a significant role in removing pathogens, including bacteria, viruses, and cholera vibrio.

The correct choice reflects the efficacy of trickling filters in removing a substantial portion of these pathogens. Research and operational data indicate that trickling filters can successfully remove approximately 90 to 95 percent of bacteria, viruses, and cholera vibrio from wastewater. This high removal rate is largely due to the biofilm's ability to metabolize and assimilate pollutants as well as the physical filtration properties of the media.

It's important to note that while trickling filters are quite effective, they typically do not achieve complete (100 percent) removal of all pathogens. Various factors, such as the design of the filter, operational conditions, and the specific characteristics of the influent, can influence the actual removal rates in practice. Thus, while some treatment processes can achieve very high levels of pathogen removal, it is more realistic to expect the level of removal indicated by the correct answer.