Two Peoples Bay WTP Stage 3 Upgrade

Construction of new chlorination and fluoridation facilities and other works at a water treatment plant 30km east of Albany WA

Stage 3 involved the upgrade of the chlorination of Two Peoples Bay WTP Stage 3 Upgrade,  fluoride dosing and PLC and SCADA systems at the Two Peoples Bay WTP.

The existing gas chlorination facilities were beyond their economic life, and the storage facilities did not meet the current standards. A new storage system based around 4x 68kg cylinders replaced the 2 x 1t drum installation, with new vacuum regulators, chlorinator, pipework, instrumentation and local OIP.

The fluosilicic acid (FSA) storage and dosing system was replaced with a sodium fluoride system (NaF) using a new batching and dosing plant using dissolvable bags made from food grade PVA, which had been trialled by the Water Corporation. This eliminated the risk of NaF dust exposure to the operators.

Decommissioning of the FSA tank and dosing equipment required special attention due to the very high hazards presented by FSA.

Following a lengthy and detailed risk assessment and planning stage, the bulk acid was transferred to another treatment facility. The unrecoverable acid was diluted and tankered for disposal. The pipework was carefully flushed with lime water to neutralize and precipitate the fluorides. The sludge was then removed for disposal. This work was completed smoothly in accordance with the detailed safe working procedure (SWP) without incident. The area was then prepared for the new equipment.

New electrical controls were provided for the clearwater pumps, new level transmitters were supplied for the two weirs and new data radios for the weirs and summit tanks, and the site main PLC was upgraded to handle the additional I/O.