With a water source prone to highly variable raw water quality during weather events and a growing population, the Canungra Water Treatment Plant needed to be upgraded to improve water security for the region in the future. In 2016, Seqwater begun construction on the new $4 million plant, able to produce 1.5 million litres of treated drinking water each day.
Located in South East Queensland’s Scenic Rim Region, Canungra’s population is expected to triple over the next 20 years, and the standalone water supply system providing water to the township and residential surrounds was nearing the end of its service life.
Originally commissioned in 1975, the Canungra Water Treatment Plant hadn’t had any major upgrades or additional works carried out in over 35 years outside of the addition of a fluoride dosing system in 2009.
An upgrade was essential and was built in line with Seqwater’s Water Security Program, a 30-year plan to secure water across the region.
Increasing treatment capabilities
The original treatment plant was capable of treating 400,000 litres of water per day, which it drew from Canungra Creek.
However, the creek has a high potential for increased turbidity in the raw water, with NTU levels peaking in excess of 100 (the maximum treatment capability of the original plant) during rain events. In these cases, the plant would be forced to temporarily switch off until the creek settled.
This susceptibility to rapid changes in raw water quality meant it was necessary to upgrade the facility with membrane filtration technology, which is able to remove particles from water over a wider range of raw water turbidites. This allows the water treatment plant to continue to treat water during rainfall events.
The water is now screened and pumped at the raw water inlet structure, with two submersible pumps that are run in a duty/standby arrangement. The water is then dosed with aluminum chlorohydrate (ACH), which is a change from the type of coagulant used in the old plant.
“The use of ACH is recommended with the use of the membrane filtration, and provides other benefits such as giving us a broader dose range which is of a great benefit when treating ever changing creek water,” Seqwater Supply Operations Coordinator, Craig Bolin, said.
The dosed water is then pumped into the inlet structure and continues through the flocculation and clarification processes, where a large percentage of the solids, heavy metals and organics are removed prior to filtration — with the addition of pre-chlorination after clarification.
At this stage, the water is then filtered through the ultra-membrane filtration process. There are two membrane filtration trains — again operated in a duty/standby arrangement — which filter the clarified water. Ancillary systems include backwashing, chemical cleaning and neutralisation, and membrane testing to verify the integrity of the membranes. After filtration, sodium hydroxide is dosed for pH adjustment, sodium hypochlorite for disinfection and sodium fluoride.
With the new plant now capable of treating nearly four times the amount of water as the original plant, and able to treat raw water with turbidity up to 1000NTU, water quality issues are a thing of the past.
Expanding storage capacity
With the treated water pumped from on-site storage to the Appel Street reservoir on a demand basis determined by the reservoir level, increasing the water storage was also a high priority. The limited storage capacity of the original plant — 40,000 litres — compounded the risk of water shortages for the community whenever the plant was closed for maintenance, or because of dirty water due to rain events.
The new plant has increased its site storage capacity to 310,000 litres. With more water able to be stored on site, it puts Seqwater in a better position to supplement the nearby reservoirs when required.
Building the new around the old
The new Canungra plant was developed as a brownfield project, built on the same site as the existing plant.
Mr Bolin said maintaining the water supply to the Canungra network during the upgrade was imperative, and proved to be a significant challenge as the original plant remained in operation while the new plant was being constructed around it. The construction involved progressively decommissioning and removing existing structural components of the old plant while also installing the new facility.
“As the facility was upgraded, new infrastructure had to be integrated into system, all while continuing to treat water and meet supply demands,” Mr Bolin said.
“It required Seqwater working together with contractor Monadelphous and retailer Queensland Urban Utilities to manage the various transitions from the old plant to the new.”
Pump procurement and selection
Mr Bolin said there were a number of factors that were considered when selecting the pumps.
“Matching the pump’s capability to deliver the right pressure and energy to suit the flow requirements for treatment is the most important factor when selecting a pump,” Mr Bolin said.
“The other major consideration is the actual fit — making sure the pump curve fits into the system curve properly. The pumps have to be matched to exact specifications otherwise they are at risk of becoming damaged, overheating or impacting the flow rate.”
Seqwater Senior Project Manager, Allan Cupitt, said finding pumps that met the specifications for the project proved to be a challenge.
“A challenge arose when we couldn’t locate the brand of pump that fit in with our systems, so we had to find a replacement with the right specifications that would allow the pump curve to properly intersect with the system curve.”
Once the pumps had been selected, installed and the required testing had taken place, including pressure testing for leaks, the pumps were operated through their required flow ranges. During this process, flow and pressure are monitored along with power factors such as temperature and vibration.
Mr Bolin said the treatment plant is maintained via scheduled tasks established by the manufacturer’s recommendation.
“The Seqwater maintenance section carries out this schedule, along with external providers for any specialised maintenance service,” Mr Bolin said.
“Seqwater also undertakes its own internal maintenance, which is over and above the manufacturer’s specifications.
“Water treatment plant operators continuously monitor instrumentation with inspections carried out on a daily basis. Inspections include sampling, instrument verification and calibration. Repairs or adjustments are then made if needed.”
A secure future
Construction started in 2016 and is now complete, and the new water treatment plant is operational.
Queensland Minister, Mark Furner, was pleased with the results, explaining that the $4 million plant would be able to cater to the growing Canungra community and its increased water demand in the future.
“The new plant will be able to produce 1.5 million litres of treated drinking water each day…ensuring we can meet the community’s future water needs,” Mr Furner said.
Scenic Rim Regional Council Mayor, Greg Christensen, said the new plant is important in supporting the community into the future.
“A secure and reliable water supply is critical to Canungra’s continued prosperity and the health of its residents and the environment,” Mr Christensen said.
“This project complements Seqwaters plans to connect Beaudesert and Wyaralong Dam to the SEQ Water Grid for the first time, to ensure the future water supply security for the Scenic Rim.”
The Canungra Water Treatment Plant is a standalone water supply system providing water to the township of Canungra and Maurita Crescent. The network also includes several Queensland Urban Utilities-owned reservoirs located at Appel Street and Maurita Crescent.