Harbour area treatment scheme
(HATS) stage 2A

  • A major sewerage infrastructure project in Hong Kong.
  • The HATS system will serve a population of five million on both sides of the Victoria Harbour with an average capacity of 2.4m cubic metres per day.

Arup has been appointed by the Hong Kong SAR Government’s Drainage Services Department as the Consultant for the Harbour Area Treatment Scheme (HATS) Stage 2A – Upgrading Works for Stonecutters Island Sewage Treatment Works (SCISTW) and eight Preliminary Treatment Works (PTWs) on the Hong Kong Island. 

HATS is one of the largest ever sewerage infrastructure projects in Hong Kong. HATS Stage 1, commissioned in 2001, provides treatment to about 75% of the sewage from urban areas around the Harbour. HATS Stage 2, a two-phase programme, will provide additional facilities to convey all remaining sewage from the Harbour area to SCISTW for chemically-enhanced primary treatment (CEPT) and disinfection, and subsequent biological treatment. The projected ultimate population served by HATS Stages 1 and 2 will be in order of five million, and the projected ultimate average dry weather flow (ADWF) will be 2.4m cubic metres per day. 

Arup is responsible for the design and construction supervision of the upgrading works of SCISTW and PTWs, responsible for civil, electrical and mechanical, process, environmental, control and automation engineering, as well as the overall project management and implementation of HATS Stage 2A. 

HATS Stage 2A has been completed in 2015, the remaining 25% of sewage generated on the northern and southwestern sides of Hong Kong Island will be collected for CEPT and disinfection before discharge, bringing further improvement to the water quality in Victoria Harbour.


  • Open gallery

    Upgrading works at Stonecutters Island Sewage Treatment works.

  • Open gallery

    An integrated control system combining HATS Stage 1 and Stage 2A operations. © Sun Fook Kong Bi-Water Joint Venture

  • HATS Stage 2 A - overall view of the harbourPlay video

    A short film introducing the Harbour area treatment scheme (HATS) stage 2A: the largest ever sewerage infrastructure projects in Hong Kong.