Water Corporation fulfils automation vision

The new AU$28 million Water Corporation-owned Kwinana water reclamation plant (KWRP) is not only Australia's largest municipal wastewater reuse plant, but also the site of the country's most comprehensive application of the Profibus philosophy to date. Profibus DP and PA communications are integral to the plant's success in improving both water efficiency in the Perth basin and environmental management in the Kwinana industrial area.

Water Corporation has been implementing Profibus DP and PA networks for over four years in its water and wastewater treatment plants. It will become an integral part of its planned networking of all the metropolitan water treatment plants over the next five years.

John Holland Engineering was contracted to deliver the project and it engaged Veolia, a water and wastewater specialist engineering company, to undertake the process design and commissioning of the plant. Electrical services and instrumentation were contracted to PCT and maintenance is handled by KBR Water Services, the corporation's maintenance provider.

[image] The Water Corporation's Kwinana reclamation plant.

"We chose Profibus because we wanted a fieldbus technology that would enable us to optimise our management decisions and support our long-term aim of networking our major plants, initially in the Perth area and ultimately, across the whole state," comments Dennis Yovich, principal engineer, electrical, in the corporation's mechanical and electrical services branch.

The application of fieldbus technology within plants is key to Water Corporation's 'big picture'. The plan is to intelligently connect the five largest water treatment plants within a 50 km radius of Perth and control after-hours operation from a centralised operations room at Leederville. To be successful it is critical that an operator in Leederville can perform detailed diagnostics of any instrumentation or control problem and then decide what action is required. Profibus on the plants makes much of this possible.

Western Australia's many water treatment plants (plus over 980 pumping stations) are spread across 2.5 million km2. "We need to maximise the information we obtain from these remote sites," comments Yovich. "Measurement and control equipment is becoming more sophisticated, there are fewer and fewer people available in the remote sites and the time and distances to reach some of the plants are excessive. In the event of a problem, we firstly need to know that a problem exists and then we need to access the problem area to analyse what has to be done, who has the necessary skills and what spares and equipment are required should our tradesmen need to travel to site." Profibus enables centralised maintenance staff to remotely re-range a flow meter, to understand the precise nature of the service required by a distant analyser unit used for measurement of disinfection properties of water, or to be alerted to a faulty gas leak detector anywhere on the network.

Why would instruments need to be re-ranged regularly? In an industry where there is wide variation in seasonal demand and output rates can swing between say 0-500 ML/day to 0-50 ML/day, seasonal re-ranging of flow meters is crucial for better resolution to improve accuracy of chlorine dosing and thus ADWG (Australian drinking water guidelines) compliance.

"The integration of digital I/O, utilising ASi bus, in the Profibus world, such as alarms, chlorine gas leaks, chlorine residual, low level alarms, empty pipe detection, is exceptional. We use ASi bus combined with Profibus PA, making all analog measurement, such as flow, temperature, pressure and level and digital switching, completely homogeneous. This homogeneity is a unique advantage of the Profibus system and makes so much more data available," says Yovich. "The more information we have, the better management decisions we can make - enabling us to boost our management and maintenance efficiencies in unprecedented ways, optimise our processes and, ultimately, to pass on big savings to end users."

Kwinana Water Reclamation Plant

The Kwinana Water Reclamation Plant (KWRP) commissioned in late 2004 is located in WA's main heavy industrial belt south of Perth.

It treats about 24 million litres per day of secondary treated wastewater from the nearby Woodman Point wastewater treatment plant. Its daily output of about 17 million litres of high-quality (350 mg/L TDS average) industry-grade water is sold to a number of large industrial customers on the Kwinana strip. Since these industrial users represent some of the largest users of Perth's public water supply, the KWRP is playing an important role in helping the WA government achieve its goal of 20% state-wide reuse of wastewater by 2012. At the same time, the KWRP is helping to reduce industry demand for scheme water by approximately 6 GL/year - about 2% of Perth's total unrestricted scheme water use.

[image] Blower flow and temperature measurement.

In line with the Water Corporation 'big picture', Profibus technology was specified at the outset for this greenfield project. Over 150 devices, including Promag electromagnetic flow meters, t-mass gas mass flow meters, Prowirl vortex flow meters, Cerabar pressure transmitters, conductivity, pH and turbidity systems, as well as level switches and ultrasonic level monitors, were linked up on Profibus PA segments in the micro-filtration feed system, CMF-S trains (continuous micro filtration-submerged), RO feed systems, RO clean-in-place systems etc.

Endress+Hauser was involved in the system design of the Profibus topology to accommodate the Profibus PA segments that connect the instrumentation to the plant automation system. Related activities included system integration planning and realisation in the pre-commissioning phase and complete application commissioning for all plant instrumentation.

The plant asset management system couples the installed instrumentation fieldbus to a single workstation PC-based tool that performs the functions of:

• Plant inventory;
• Device configuration;
• Device documentation;
• Storage of device parameters.

The operators are able to perform detailed troubleshooting of each measuring instrument from any internet-linked site in WA. Already, during the commissioning phase, FieldCare has provided useful information to KBR to assist with optimising the processes.

"The future-proofing of the Kwinana Water Reclamation Plant using Profibus technology, in conjunction with FieldCare and FDT/DTP tools, will bring us close to our centralised ops room vision," said Dennis Yovich.