Cleaner water in NE Victoria with help from SEW

Recent major upgrades to water treatment plants in North East Victoria mean residents can now enjoy cleaner, better tasting drinking water flowing from their taps.

The recent opening of the $5.2 million Corryong water treatment plant - near the upper reaches of the Murray River in the Australian Alps - provides a major improvement to the quality of water for Corryong and Cudgewa residents, while the opening of Whitfield’s $2.2 million water treatment plant in October 2012 marked a new beginning for a town which previously endured regular water restrictions, water carting and boil water notices.

Jack Timmins, process engineer with Laurie Curran Water, explained that his company is a process engineering firm specialising in the design and construction of water and wastewater treatment facilities, and is well known throughout Australia for its expertise in the dissolved air flotation and filtration (DAFF) process.

“For the Corryong water treatment plant project we were contracted by the local water authority, North East Water, to design and construct a 3.2 ML/d DAFF water treatment plant for potable water for the towns of Corryong and Cudgewa.

“We used SEW-Eurodrive geared motors on our vertical inline flocculators. The system required two sets of heavy-duty filters, with four flocculators, with each one driven by an SEW geared motor. We also used an SEW-Eurodrive geared motor on a thickening mechanism for the washwater treatment,” said Timmins.

Laurie Curran Water worked closely with SEW-Eurodrive to ensure the geared motors had the right torque levels and configuration.

Timmins explained that flocculation is widely employed in the purification of drinking water as well as sewage treatment, stormwater treatment and treatment of other industrial wastewater streams.

“During flocculation, gentle mixing accelerates the rate of particle collision, and the destabilised particles are further aggregated and enmeshed into larger precipitates.”

He said flocculation is affected by several parameters, including mixing speeds, mixing intensity and mixing time.

He explained that they used SEW’s geared motors with MOVIMOT integrated frequency inverters on all five projects.

“We like to use a decentralised motor control system as opposed to having it in the central computer. This allows us to walk up and adjust the speed of the flocculators while looking down into the system. By using a decentralised system, we can physically see the rotation of the flocculators instead of walking down, looking at the computer, then walking up again, adjusting the flocculator and back to the computer until we got it right.”

Timmins explained that each filter is about 5 m high, and would normally need two people to set the flocculators up; one telling the other what is going on.

“And it was the same for the sludge thickening system, with its 3.3 m high thickener vessel. By using a decentralised system, we are able to fine-tune the system so that the speed of the flocculators and thickeners matches the speed that we use in our jar testing. As well as accuracy of the settings, using a decentralised system eliminates the need for a control house mounting of the VSD and the associated wiring and set-up,” he said.

“We have been very pleased with the products, the service and the advice we get from SEW; making sure the most applicable equipment/model is used.

“We worked closely with them regarding torque levels and to ensure the geared motors were not over- or undersized, and that we had the right configuration; the right output shaft to suit our standard paddle design.

“We use a computer-based Citect system to basically start and stop the systems, but the speed control is done integrally using the MOVIMOT drives.

“This allows us to optimise the system through our process, to allow for the ever-changing quality of the water. The MOVIMOT drives give us the flexibility to adjust the system.”

Timmins said the Corryong water treatment plant project also included a dual water treatment module for the treatment of raw water drawn from the Hamilton Hill reservoir, chemical dosing systems for aluminium, caustic soda, polyelectrolyte and gaseous chlorine, a 300 kL washwater tank to accept filtered washwater and DAF float, and a 2.5 kL sludge storage tank.

However, he said the Whitfield water treatment plant, in Victoria’s King Valley wine region, was a little different.

“As well as being smaller at just 150 kL/d with two flocculators, this plant used a mechanical float-off removal mechanism instead of a sludge thickener.

“We only needed three MOVIMOT drives on the Whitfield water treatment plant. But while it’s a much smaller site, we went through the same design issues with SEW, especially on the mechanical float-off removal mechanism,” Timmins said.

Major components of the Whitfield water treatment plant included a 300 kL raw water tank, which accepts water from the King River pump station, chemical dosing systems for caustic soda, aluminium chlorohydrate and sodium hypochlorite, a 235 kL clear water tank, and 25 kL washwater tank and a 15 kL sludge storage tank.

He went on to say that both water treatment plant projects had been very successful, and the residents in the areas are now enjoying cleaner, better tasting drinking water flowing from their taps.