Potable Water Treatment Upgrade


Hendl & Murray Engineering (HME) was recently involved in a water treatment plant upgrade. The upgrade involved installing ultra violet light dosing into one of the process streams, making it the largest drinking water UV installation in New Zealand.

A large storm event in 2017 called the Tasman Tempest highlighted the need for a much wider operating envelope for the Water Treatment Plant. This UV upgrade has improved the plant’s operability and allows it to cope better with extreme weather events such as this.

All fabricated stainless steel plate items were modelled by HME’s Design Team using Autodesk Inventor. 3D models were used to generate flat patterns which were laser cut from 10mm 316 stainless steel plate then formed/welded in HME’s Hamilton workshop.

1200NB PN10 flanges were manufactured to order in an offshore factory and the 1900mm and 1200NB x 10mm thick pipe was also procured offshore.

Stainless steel pipework all prefabricated in HME’s Hamilton workshop was trucked to site for final assembly and installation.

The UV reactors were installed, with stainless steel pipework in a confined below ground room, with the help of Head Contractor Brian Perry Civil. One tricky aspect of the job was manoeuvring the larger sections within the tight available space – some weighed up to 8.5 tonnes. We achieved the installation by careful placement of hooks, slings and rigging equipment, not to mention the pinpoint accuracy of the trucks and hiabs working their way down a steep temporary access ramp.

Each flange that connects the plant and pipework were fastened using 32 x M36 stainless steel bolts, 768 bolts in total, all torqued and checked to prevent any leaks.

The water flows from concrete tanks on site through three 1200mm diameter 10mm thick 316 grade stainless steel pipes to the three UV reactors. The cleansed water then flows on through the pipes and out to a 1900mm diameter 10mm thick 316 grade stainless steel manifold, and back into concrete holding tanks ready for distribution to New Zealand households.

The water flow through the treatment plant is powered by gravity. Using both UV rays and the power of gravity, the system has a very sustainable accent.