By Kody Cook, Journalist, Pump Industry Magazine

The $5.5 million upgrades to the Wauchope Water Treatment Plant (WTP) in New South Wales have been completed, with the final stage of the project – a new $1.7 million chlorine dosing facility – helping to secure the region’s water supply and increase drought resilience.

A spokesperson for Port Macquarie Hastings Council said the upgrades to the Wauchope WTP were implemented in part due to the prolonged 2018 and 2019 drought.

“At the time, Council had estimated that without above average rainfall, our water supply would be exhausted before the end of 2020,” the spokesperson said.

The Port Macquarie Hastings Bulk water supply scheme – which supplies Port Macquarie, Bonny Hills, Camden Haven, Kew and Kendall – is an unfiltered water supply, which significantly restricts Council on the water quality that can be extracted from both the Hastings River and two bulk storage dams. This is especially the case during drought when dams and river water quality is impacted.

Upgrading the Wauchope WTP from a 7ML/d treatment plant to a 21ML/d plant was pinpointed as the best option to mitigate water supply challenges.

The Wauchope WTP is a membrane filtration plant and expanding the plant would allow Council to extract higher turbidity water and treat it through microfiltration to meet the Australian Drinking Water Guidelines (ADWG). Although the WTP would usually only provide water to Wauchope, in emergency situations the filtered water can also be supplied through the bulk supply mains to the Port Macquarie bulk water supply scheme.

The total upgrades have been jointly funded with $1.4 million from the New South Wales Government’s Critical Drought Initiative and $4.1 million from Port Macquarie Hastings Council.

The upgrade breakdown

The upgrade works to the Wauchope WTP were split into two major deliverables:

  • The installation of two additional membrane filtration plants
  • The construction of a new chlorine dosing facility and baffle curtains in the Clearwater tank

Membrane filtration plants

Two additional membrane trains were installed within the existing WTP.

The original design of the WTP was built to accommodate an ultimate capacity of 21ML/d, made up of three DuPont Memcor filters which have a capacity of 7ML/d each. While only one filter was installed at the time, all the ancillary works had already been installed, so the expansion required Council to simply install two additional filtration skids into the existing building.

This project contract was awarded to DuPont Memcor and included design of the stainless steel cell to hold the membranes, procurement and installation of two additional filtration skids and the pumps, instrumentation and ancillary equipment to run the filters.

The additional membranes installed were Memcor S10N PVDF membranes, the same as the existing membranes. Each filtration train also included the installation of a filtration pump and backwash pump. The pumps installed were KSB pumps MCPK 250-200-315 with a 30kW TEFC motor mounted on a galvanised MS – Steel Bend Type – baseplate.

As part of the upgrade, Council also upgraded the two pumps on the existing skid to larger pumps which improved the ultrafiltration performance as the existing pumps were assessed as undersized for the backwash flow.

The Council spokesperson said that when the works commenced Council was in ‘crisis’ mode, as it was responding to the drought conditions.

“Initial planning and contract procurement was undertaken on the membrane filters with the inclusion of these already catered for within the original WTP build. It was a fairly straightforward engagement of DuPont Memcor who supplied the original membrane filter unit.”

Chlorine dosing facility

A new gas chlorine facility, including a new building, was built to provide sufficient disinfection up to 21ML/d, to match the upgraded capacity of the WTP.

This was completed as a design and construction (D&C) project which was awarded to Building Heights Construction with chlorination specialist West Water as subcontractors to do the chlorine design and construction.

The chlorine facility has been designed to store three 750kg chlorine drums and the auxiliary equipment to manage chlorine gas pressure dosing. In particular the facility was built as a chlorination rail system for managing the chlorine drum delivery and disposal of empty drums.

The project also involved installation of baffle curtains within the Clearwater Tank to improve mixing of chlorine downstream of the point of dosing.

The spokesperson explained that, unlike the membrane filters, the existing plant facility wasn’t initially designed to accommodate the upsizing of the chlorine dosing facility.

“We were considering options for gas chlorine or other forms of dosing and how we would house the dosing facility and meet the hazardous chemical storage requirements. This complicated this upgrade, so Council chose to separate this work from the membrane upgrade, and tender the chlorination upgrade project works as a Design and Construct project.”

Building heights teamed up with a Western Australian treatment plant process specialist called West Water and Stowe Electrical to deliver the project.

Testing and ongoing maintenance

The spokesperson said that proof of performance testing was undertaken to confirm the performance of the membranes and that pumps met the specifications.

“The gas chlorine dosing system was provided with a low load chlorinator (4kg/h) for normal operation and a high load chlorinator (8kg/h) for times of high demand. Each chlorinator is fully adjustable within the range of operation.

“Operators are continually monitoring chlorine levels in downstream reservoirs and making adjustments to optimise the dosing rate. It is planned to do some die tests to confirm the effectiveness of the baffles in the Clearwater Tank for mixing.”

Ongoing servicing and maintenance for the membrane plant includes:

  • Regular backflushing of membranes
  • Routine maintenance of pumps, valves, pipework and fittings
  • Routine maintenance of control systems and instrumentation
  • Routine maintenance of electrical systems
  • Regular cleans, routine clean in place and pressure decay monitoring

Ongoing servicing and maintenance for the chlorine dosing facility includes:

  • Calibration of load cells
  • Calibration of chlorine sensors
  • Adjustment and fine tuning of chlorinators
  • Routine maintenance and calibration of water sampling and analysis equipment
  • Routine maintenance of pumps, valves, pipework and fittings, fans and louvres, drum rails and carriage
  • Routine maintenance of control systems and instrumentation
  • Routine maintenance of electrical systems
  • Delivery of chlorine gas drums

Overcoming COVID and contamination

“The company that did the pipework fabrication was based in Albury-Wodonga and they were originally engaged to do the installation as well,” the spokesperson said.

“However, coming from Victoria, under the COVID-19 border crossing restrictions, they were required to isolate in Sydney for two weeks. This would have caused additional delays but in the end they found a Sydney-based company to do the installation on their behalf, and the delays were minimal.

“With only a small operational team in Council, managing our water supply, we also had to ensure there was isolation from our team and the contractors to minimise COVID-19 contamination risks while they were onsite.”

The spokesperson explained that the installation of the baffle curtains in the clearwater tanks also presented a complicated challenge, as it needed to be completed by divers whilst maintaining the quality of the drinking water.

“The work by the divers was quite taxing, both with having to manage the amount of time they were underwater and also making sure they worked in decontaminated dry suits so there was no risk of contaminating the water supply.

“The diving company had staff working with CCTV outside of the tank, providing instructions to the divers on how to complete the work. The divers had to make two trips to Port Macquarie to complete the work, due to the restrictions on how long they could work underwater.”

Although it has not yet been required, the plant’s new full capacity of 21ML/d means that the Port-Macquarie Hastings area is well prepared for future drought conditions and will be able to ensure that residents and businesses have access to high-quality water even during long dry spells.

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