Shatin Sewage Treatment Works

Summary

This video explains the multi-stage process of sewage treatment, designed to serve a population of 600,000. The process includes screening, primary and secondary sedimentation, biological treatment with activated sludge, and final effluent disinfection. Surplus sludge is thickened, digested anaerobically to produce renewable biogas, and dewatered for disposal. The treatment works focus on improving sustainability and environmental protection while ensuring the safe discharge of treated sewage into the river.

Takeaways

• 😀 The sewage treatment works serve a population of 600,000 and process 250,000 cubic meters of sewage daily.
• 😀 The treatment process includes primary screening, sedimentation, secondary biological treatment, final sedimentation, and sludge digestion.
• 😀 Mechanical ball screens are used for initial sewage treatment to remove solids larger than 6mm.
• 😀 Primary sedimentation removes about 50% of suspended solids from the sewage.
• 😀 Secondary biological treatment uses compressed air in aeration tanks to support microorganisms (activated sludge) that break down pollutants.
• 😀 The retention time for secondary biological treatment is around 9 hours.
• 😀 Final sedimentation separates treated sewage and activated sludge, with a portion of the sludge returned to the aeration tank to maintain microbial populations.
• 😀 The surplus activated sludge is thickened and then treated in sludge digesters through anaerobic digestion, which produces methane (a renewable energy source).
• 😀 Sludge is dewatered to a minimum of 30% water content using centrifuges before disposal.
• 😀 The treated effluent is disinfected and discharged into a river via export piping after final sedimentation.
• 😀 The responsible department (STL) continuously works to improve sewage treatment methods for sustainable development and environmental protection.

Q & A

What is the capacity of the sewage treatment works described in the script?

The sewage treatment works serves a population of 600,000 people and processes up to 250,000 cubic meters of sewage daily.

What are the main stages in the sewage treatment process?

The main stages in the sewage treatment process are preliminary treatment, primary sedimentation, secondary biological treatment, final sedimentation, sludge digestion, and sludge dewatering.

How are larger solids removed in the treatment process?

Larger solids are removed in the preliminary treatment stage by mechanical screens, which filter out solids exceeding 6 mm in size.

What happens during the primary sedimentation stage?

During primary sedimentation, suspended solids in the sewage settle out by gravity in the primary sedimentation tanks, removing about 50% of the solids.

How does the secondary biological treatment work?

In secondary biological treatment, sewage is aerated in biological treatment tanks, where compressed air supports the growth of microorganisms known as activated sludge. These microorganisms break down organic pollutants in the water.

What is the retention time in the secondary biological treatment stage?

The retention time in the secondary biological treatment stage is approximately 9 hours.

What is the purpose of the final sedimentation tanks?

The final sedimentation tanks are used to separate the treated water (effluent) from the activated sludge after biological treatment. A portion of the activated sludge is returned to the aeration tank to maintain the microorganism population.

What is surplus activated sludge, and how is it treated?

Surplus activated sludge is the remaining sludge after biological treatment. It is thickened to reduce water content before being sent to anaerobic digesters for further processing.

How is biogas produced in the sewage treatment process?

Biogas, containing methane, is produced during the anaerobic digestion of sludge. This biogas can be used as a renewable energy source.

What is the purpose of sludge dewatering, and how is it done?

Sludge dewatering is done to reduce the water content and volume of the sludge, making it easier to handle and dispose of. This is achieved using centrifuges to dewater the sludge to a minimum of 30% water content.

How is the final effluent disinfected before being released into the environment?

After final sedimentation, the effluent is disinfected to ensure it meets environmental and health standards before being discharged into a local river through export piping.

What role does the sewage treatment works play in environmental protection?

The sewage treatment works contributes to environmental protection by continuously improving its operations to minimize pollution, promote sustainability, and ensure the safe discharge of treated water.