Wastewater New York State Practice Exam

The appearance of duckweed in a final clarifier is an indication of what phenomenon?

1. De-nitrification

2. Filtration

3. Nitrification

4. Coagulation

The correct answer is: Nitrification

The presence of duckweed in a final clarifier is indicative of nitrification occurring in the wastewater treatment process. Duckweed is a type of aquatic plant that thrives in nutrient-rich environments, particularly where there is an abundance of nitrogen compounds, such as ammonia, which is a byproduct of nitrification. Nitrification is the biological process in which ammonia is converted into nitrate by nitrifying bacteria. This process typically takes place in the presence of adequate oxygen and is essential for reducing the toxicity of ammonia in wastewater. When nitrification effectively takes place, increased nutrient levels can lead to the rapid growth of duckweed, as it utilizes the available nitrogen for its growth. In contrast, the other options refer to different processes. De-nitrification is the conversion of nitrates back to nitrogen gas, which typically occurs in anoxic conditions, thus not conducive to duckweed growth. Filtration is a physical process that does not relate specifically to nutrient uptake by plants. Coagulation involves the agglomeration of particles to form flocs, and while it is essential in the treatment process, it does not directly influence the conditions that promote duckweed growth. Therefore, the presence of duckweed points towards a situation where nitrification is actively taking place,