In the treatment of waste water before discharge which treatment stage inovolve biological treatment ?

Options

A. Primary stage
B. Secondary treatament stage
C. Reverse osmosis
D. Tertiary treatement stage

Answer

**Step-by-Step Solution:**

1. **Understanding Wastewater Treatment Stages**: Wastewater treatment involves several stages, each designed to remove different types of contaminants from the water. The main stages are primary, secondary, and tertiary treatment.

2. **Identifying the Primary Treatment Stage**: In the primary treatment stage, wastewater is collected in a tank where it is allowed to settle. This process helps heavy particles to settle down, but it does not involve biological treatment.

3. **Recognizing the Secondary Treatment Stage**: The secondary treatment stage is where biological treatment occurs. This stage utilizes microorganisms to break down organic matter and remove dissolved and colloidal waste through oxidation processes.

4. **Methods Used in Secondary Treatment**: The secondary treatment includes methods such as biofiltration, sludge processing, and oxidation ponds. These methods rely on the activity of microorganisms to effectively treat the wastewater.

5. **Understanding the Tertiary Treatment Stage**: The tertiary treatment stage aims to ensure that the treated water meets safety standards for domestic and industrial use. This stage focuses on removing pathogens and further purifying the water but does not primarily involve biological treatment.

6. **Conclusion**: Therefore, the stage of wastewater treatment that involves biological treatment is the **secondary treatment stage**.

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