Summary of "Kuching Centralised Sewerage System (Zone 1, Package 1)"

Scientific Concepts, Discoveries, and Nature Phenomena

Wastewater Management Challenges in Kuching City
- Kuching, the capital of Sarawak with ~500,000 population, faces river and waterway pollution due to outdated wastewater treatment methods.
- Black water (toilet wastewater) is currently treated by individual septic tanks, which are inefficient, prone to leakage, and overflow.
- Grey water (from kitchens and bathrooms) is discharged untreated into waterways, further polluting the environment.
- Pollution affects the Sarawak River and other waterways, necessitating a modern, centralized wastewater management system.
Modern Centralized Sewerage System Design
- The project aims to replace septic tanks with a centralized sewer system covering densely populated areas.
- It includes a gravity flow sewer system, a centralized Wastewater Treatment Plant (WWTP), and property connections.
- The gravity flow sewer system eliminates the need for intermediate pump stations by using gravity to transport sewage to the WWTP.
- The WWTP is designed for 100,000 population equivalent, expandable to 400,000, and will treat wastewater to meet environmental standards before discharging effluent into the Sarawak River.
Sewer Network Components and Coverage
- Sewer system covers five key city zones (A to E), connecting commercial complexes, institutions, and residential properties.
- Network includes 64.5 km of sewer pipes: trunk, secondary, and tertiary sewers with pipe diameters from 225 mm to 1,500 mm.
- Trunk sewer runs under the Sarawak River and branches into secondary and tertiary sewers that connect to individual properties.
Construction Technologies and Methods
- Three main construction methods are used depending on soil conditions and sewer depth:
  - Slurry Method: Trenchless tunneling in hard rock at depths >6 m using tunnel boring machines (TBM), minimizing surface disruption.
  - Augering Method: Trenchless pipe laying in softer soil at depths 2.5–6 m, also using TBM with laser guidance and minimal traffic disruption.
  - Open Cut Method: Conventional trench excavation for shallow sewers (<2.5 m depth), involving surface excavation and reinstatement.
Wastewater Treatment Plant Components
- Facilities include guard house, operation building, generator house, substation, inlet pump station, activated sludge reactor, flow distribution chamber, secondary clarifiers, sludge dewatering and thickening building, and biofilter.
- The plant uses activated sludge process for biological treatment to meet environmental discharge standards.
Property Connection Methodology
- Residential wastewater is collected via pipes to inspection chambers near property boundaries, then connected to the public sewer.
- In cases where gravity flow is insufficient, small pumps are used to lift wastewater to the sewer.
- Existing septic tanks and private treatment plants will be decommissioned, disinfected, and backfilled.
- Commercial and institutional complexes have larger collection systems feeding into the public sewer.
Environmental and Social Impact
- The project aims to rehabilitate the Sarawak River and improve urban water quality.
- Public cooperation is essential for property connections and project success.
- The system is capital intensive and will be implemented in phases, starting with this pilot package.

Project Components Summary

Scope:
- First package covers 5 city zones with mixed commercial and residential areas.
- Sewer network: 64.5 km total (7.7 km trunk, 5.4 km secondary, 51.4 km tertiary).
- WWTP capacity: 100,000 population equivalent, expandable to 400,000.
Construction Methods:
- Slurry tunneling (deep rock)
- Augering tunneling (soft soil)
- Open cut (shallow trenches)
Treatment Process:
- Inlet pumping
- Activated sludge reactor
- Secondary clarifiers
- Sludge handling and biofiltration
Property Connections:
- Inspection chambers at property boundaries
- PVC pipe connections (100–225 mm diameter)
- Possible use of pumps for elevation changes
- Decommissioning of septic tanks and private treatment plants

Researchers and Sources Featured

Organizations and Companies:
- State Sewerage Services Department, Sarawak
- Consortium of contractors:
  - Come Foolin Mission Matsu Hoc Singley Consortium
  - Scenario Farad (ceramic-based construction, est. 1983)
  - Mission Matsu Construction Company Limited (Japan, est. 1874)
  - Hoaxing Liebherr Han (Malaysia, infrastructure experience over 30 years)
Authorities:
- World Health Organization (WHO) – declared Kuching a healthy city
- Malaysian Government – Ninth Malaysia Plan approval and funding