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That certainly was a whistlestop tour of the wastewater treatment process! Here’s a reminder of how our wastewater is treated and released as effluent discharge...

1. Pre-Treatment

2. Primary Treatment

3. Secondary Treatment

4. Aeration

5. Final Sedimentation

6. Sludge Treatment and Disposal

7. Disinfection

8. Effluent Discharge or Reuse

Effluent Discharge or Reuse The final treated water, now meeting regulatory standards, can be discharged into receiving water bodies or, in some cases, reused for non-potable purposes like irrigation or industrial processes.

Secondary Treatment Secondary treatment aims to remove dissolved and suspended biological matter that remains after primary treatment. This is often achieved through biological processes, such as activated sludge treatment or trickling filters, where microorganisms break down organic pollutants.

Final Sedimentation The mixture from the secondary treatment is allowed to settle again, allowing the remaining suspended particles to settle as sludge. The clarified water, now called secondary effluent, is ready for further treatment.

Aeration In some secondary treatment processes, aeration basins are used. Oxygen is introduced to promote the growth of aerobic bacteria, which further digest organic matter. This helps in reducing the biochemical oxygen demand (BOD).

Pre-Treatment The wastewater undergoes a preliminary screening process to remove large objects such as sticks, leaves, and debris. This step prevents damage to equipment in subsequent stages.

Disinfection The treated water undergoes a disinfection step to kill or deactivate harmful bacteria, viruses, and parasites. Common disinfectants include chlorine, chloramine, or ultraviolet (UV) light.

Primary Treatment In the primary treatment stage, the wastewater is settled in large tanks, allowing heavier solids (sludge) to settle at the bottom. The clarified liquid, known as primary effluent, is then moved to the next stage.

Sludge Treatment and Disposal The sludge collected during the treatment processes (primary and secondary) undergoes further treatment, which may include digestion, dewatering, and drying. The treated sludge can be used as a fertiliser or disposed of in an environmentally safe manner.