The biological nutrient removal process that does not produce much odor is the **Aerobic selectors**. Aerobic selectors are a part of the wastewater treatment process that operates in the presence of oxygen. In this process, microorganisms break down organic matter by using oxygen, which leads to the reduction of odor-producing compounds.
**Facultative selectors**, on the other hand, can produce some odors as they operate in both aerobic and anaerobic conditions. **Anaerobic selectors** and **Anoxic selectors** also have the potential to produce odors since they operate in the absence or limited presence of oxygen, allowing for the growth of anaerobic bacteria that can release odorous byproducts during the treatment process.
Therefore, among the options provided, the **Aerobic selectors** are the most likely to not produce much odor due to their oxygen-rich environment that promotes the degradation of organic matter without significant odor issues.
