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Waipawa's Dissolved Air Flotation System

This project aims to the improve the ability to meet consent compliance, by providing customized and optimized tertiary treatment. These systems would take the place of the non performing lamella clarifiers.

A DAF unit is a dissolved air flotation system for removing algal solids from discharges. 


The installation of DAF units at the Waipawa and Waipukurau WWTPs aims to improve the ability to meet consent compliance by providing customised and optimised tertiary treatment. These systems would effectively take the place of the non-performing lamella clarifiers. With the improved treatment quality post DAF units, it is expected that the sand filters and the UV treatment process will also see an improvement in their efficiency.

These improvements will see the discharge quality greatly improved and subsequently, compliance with discharge consents become routinely achievable prior to the construction of the centralised WWTP planned as part of the overall Wastewater Strategy.


The new DAF has been in operation for more than a year now and has been meeting expectations and performance requirements during that time. After the year of performance testing under the design/build contract, the contract is now signed off as complete, seeing the fulfilment of this project.

Ongoing optimisation of the DAF will be carried out as part of normal operations at Waipawa WWTP, as the Operations team continue to seek more efficient ways of running the WWTP as a whole.

DAF Aug 23 update

All data gathered during the performance testing and ongoing operation of the DAF will inform any potential future projects where pond-based treatment requires improved treatment performance and reduced environmental impact.


The operations team have had the first of a series of training sessions on the new DAF plant - an initial walk over and some general principles of operation. The new DAF is expected to be filled in mid March. Now, they will test all equipment before optimising performance through fine tuning several parameters/pieces of equipment.

DAF training


DAF installation is almost complete with just a few items to be tidied up. We have experienced some small delays due to material availability issues and slow shipping times. The new transformer for the site is now live and we are working with the operations team on a changeover of all equipment to the new power supply this week. Once all this installation work is complete, the DAF contractor will start fine tuning its performance for the make-up of our wastewater. It will then then have a proving period where it will operate for 28 days as we closely monitor its performance.

20220221 DAF

With the DAF being installed in December 2021, work continued on the DAF installation at the Waipawa WWTP over the Christmas/New Year break.

Good news - 90% of the pipework has been installed. Electrical installation is now underway with live meter boards, distribution boards and main cables now installed. A changeover of the existing equipment is due late January.

Pre-commissioning work should be completed in the next two weeks before moving into full commissioning, optimisation and operator training during February.

 DAF 20220113


Update | 13 December 2021

The DAF unit is planned to arrive onsite today after a slight delay. Meanwhile, the feed pumps have been installed, slabs completed, pipework installation has progressed swiftly with approximately 80% expected to be completed pre-Christmas and the polymer make up unit has been installed.

DAF Feed pumps

Update | 6 December 2021

The container ship transporting the DAF unit has been delayed and is now expected in Napier on the 9th Dec. Meanwhile the slab has been completed and this week we should see arrival onsite of all the pipework spooling and the main feed pumps Update 15 November, 2021

Update | 15 November 2021

Enviroden have commenced on-site with initial installation of DAF feed piping supports and feed pump foundations. The DAF foundation slab construction has progressed with the first of two concrete pours completed, more reinforcing steel will be placed this week and then a final pour of the support plinth, bund and drainage channel will happen early next week.

DAF Slab 1

DAF Slab under construction

Update | 6 October 2021

The DAF unit has undergone its final testing overseas. Painting and other work to prepare for transport are being completed. Meanwhile work onsite is progressing with work on the DAF unit support slab commencing this week.

New DAF Unit - Able to pump 80m3 of Effluent an hour


New DAF Unit - Progressive Cavity Pump and Pressure Chamber pushes the material through the treatment process

New DAF HMI Control Panel

Update | September 2021

Work has commenced excavating for the DAF support slab. Meanwhile work on the DAF unit itself continues overseas with the unit recently undergoing leak/pressure testing. We are still targeting a November delivery date and are aiming to have much of the work completed in preparation for that date.

DAF pic 1

Update |25 August 2021 | Lockdown Update

The Detailed design by contractor Enviroden continues to be progressed. Lockdown should not cause any significant delay with the overseas manufactured unit scheduled for arrival in early November.

Example DAF

Update | 2 August 2021

We have been working behind the scenes to award a contract for the supply and installation of a Dissolved Air Flotation (DAF) unit at the Waipawa WWTP to Enviroden Ltd, they are a reasonable local company based out of Dannevirke. The DAF unit will improve the tertiary treatment ability of the plant and works by floating the solids content from the effluent using compressed air and “scraping” the sludge of the top of the unit to then be pumped to geobag storage for de-watering.

DAF process


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