West Taieri Membrane Filtration Upgrade

Background
The Dunedin City Council wanted to upgrade the ageing West Taieri Water Treatment Plant so that the water supply could receive a higher grading. They decided to tender a design/build treatment contract for a membrane plant. The contract was let to Filtec as based on the quality of the design and technical capability.

Challenge
In order to continue producing potable water for supply whilst the upgrade was underway, the client wanted to keep the existing building whilst building a new one for the upgrade. Once the footprint parameters were established, a contract was let for the construction of a new building that encompassed the old building allowing the existing system to continue its operation. A new timber tank reservoir was also constructed allowing the old redundant reservoir tanks to be reused into the new process.

Process
The water is supplied from the river pumps to a large raw water reservoir, from here the water is gravity fed through a 1 mm strainer to a flocculation tank.
The water flows from the flocculation tank and into the membrane tanks where a light vacuum is applied to the submerged membrane fibres in order to produce permeate. This water is then pH corrected and disinfected with Cl2 before sending to reticulation.
Cleaning of the membranes takes place approximately every 6 months. Due to constraints on discharge consents, all spent chemicals are neutralised in a buried tank before being discharged to the ponds.

Specification