The Batu Kitang Treatment Plant is situated near the bank of Sungai Sarawak Kiri about 40 miles from the sea. Raw water is pumped from the river to the Treatment Plant where it undergoes the conventional treatment process of coagulation, flocculation, sedimentation, filtration, disinfection and pH adjustment.

Coagulation is by the alum-lime process and disinfection is by chloramination. Fluoridation has been practiced since 1966. The fully treated water is pumped to the various reservoirs in Kuching for distribution and storage.

Module No.1 of the Treatment Plant with its first raw water intake and a capacity of 3MgD was commissioned in 1957. In 1965 the capacity was increased to 4MgD by changing the pump impellers and the construction of a second stage pumping station and two underground reservoirs at Batu Lintang. Extension work to further increase the plant capacity to 6MgD commenced October 1968 and was completed in 1970. The extension of Module No.1 is designated as Module No.2.

In October 1994, a feasibility study on the upgrading of the old Batu Kitang Module 1 and 2 Plant commenced with a view to replace outdated systems and increase plant capacity.  The study was substantively completed in 1995 and confirmed the feasibility of upgrading the Plant to 68Mld.

Construction works on the upgrading to Module No. 1 and 2 commenced in November 1998 and was completed and commissioned in March 2000.

In November 1976, construction work on Module No.3, with a capacity of 9MgD comprising of a new treatment plant and raw water intake, was started, updated and commissioned in November 1978.

In order to cater for the increasing water demands and to ensure reliable supply of the water supply system, major staged improvement works to Raw Water Intake Nos. 1 and 2, including the laying of an 840mm steel raw water pumping main from Intake No.2 to Module Nos. 3 and 4 were commenced in 1990 and were substantively completed by the end of 1992. The improvement works included installation of new submersible pumpsets, booster pumpsets, back rack screens for debris removal and dislodging systems at both intakes and refurbishment of existing Kubota pumpsets at Intake No.2. Other notable improvement works carried out in 1994 included the upgrading of standby power generator sets for Module Nos. 3 and 4 and Intake No.2.

Around mid-1996, work commenced on the design and construction for the Batu Kitang Module 6 of 100MLD capacity to meet the rapidly increasing water demands of Kuching City and surrounding areas for another 10 years.

Construction works on the Module 6 Plant commenced on 24th March 1998 and was practically completed and commissioned in May 2000.

Earthwork for the Module 7 Plant commenced on 1st December 1997 and was completed in September 1998. Due to KWB’s tight financial position, however, the construction of the Module 7 Plant had to be deferred to commence early in the 8MP. Construction work for Module 7 Plant actually commenced in June 2002 and was completed and commissioned on 9th August 2006.

Today, Batu Kitang Treatment Plant accounts for more than 98% of the total water production for Kuching City.