Massachusetts Wastewater Practice Exam

In what scenario would biological treatment be preferred over chemical treatment?

1. High concentration of heavy metals.

2. Nutrient removal required.

3. Low organic load.

4. High toxicity to microorganisms.

The correct answer is: Nutrient removal required.

Biological treatment is preferred over chemical treatment in scenarios where nutrient removal is required. This is primarily because biological processes, particularly those involving microorganisms, are effective at metabolizing and removing nutrients such as nitrogen and phosphorus from wastewater. These organisms break down organic matter and assimilate nutrients, making the biological treatment method particularly suitable for wastewater that has a high nutrient load. Chemical treatments, while effective in certain situations, often do not specifically target nutrient removal and can sometimes lead to the creation of residuals that may require further treatment. In cases where wastewater contains elevated levels of nutrients, biological treatment methods such as activated sludge systems, trickling filters, or constructed wetlands are typically utilized for their efficiency and effectiveness. In contrast, scenarios involving high concentrations of heavy metals, low organic loads, or high toxicity to microorganisms are less suited for biological methods. Heavy metals can inhibit biological processes, low organic loads may not support the growth of microorganisms, and high toxicity levels can harm the very organisms needed for biological treatment. Thus, when nutrient removal is a priority, biological treatment is the most advantageous approach.