Tennessee Wastewater Operator Practice Exam

What condition may occur if some voids in trickling filter media are blocked?

1. Ponding

2. Enhanced filtration

3. Improved aeration

4. Increased velocity of flow

The correct answer is: Ponding

Ponding is a condition that can occur in trickling filter systems when some voids in the filter media become blocked. In a trickling filter, wastewater is distributed over a bed of media which provides surfaces for the biofilm to grow, and that biofilm helps in the treatment process by breaking down pollutants. If certain spaces within this media become clogged with debris, biomass, or other materials, the efficiency of the flow through the media can be compromised. When the voids are blocked, wastewater cannot freely pass through the media as intended. This leads to an accumulation of water on the surface of the filter, creating areas of standing water, known as ponding. Ponding can adversely affect the treatment process as it can reduce effective aeration and hinder the growth and health of the biofilm. The reduction in hydraulic flow can also create anaerobic conditions, which are undesirable for biological treatment processes. The other choices do not accurately describe the impact of blocked voids in trickling filter media. Enhanced filtration, improved aeration, and increased flow velocity typically indicate a well-functioning system rather than a system experiencing blockages. When voids are blocked, the treatment efficiency decreases rather than improving, highlighting the importance of maintaining clear and unobstructed filter