Worlds Largest Membrane Treatment Facility Wins Top Industry Award
Black & Veatch announced the full commissioning and operation of its Chestnut Avenue Water Works (CAWW) extension project for the Public Utilities Board (PUB) of Singapore. Black & Veatch provided study, pilot testing, design and supervision of construction, testing and start-up for the CAWW extension, which was completed on a fast-track schedule in just two years. The 72-million- gallon-per-day (273-million-liter-per-day) treatment works is now the largest potable water treatment facility in the world incorporating membrane filtration. The project recently earned the top prize of the Association of Consulting Engineers Singapores (ACES) Design Excellence Awards for 2003.
The panel of judges noted the CAWWs exceptional quality, originality and innovation, which includes
"A typical immersed membrane plant requires filtrate pumps to provide the necessary pressure across the membranes," said Tse Yau Shing, Black & Veatch CAWW project director. "Instead, Black & Veatch employed the use of efficient siphonic action to draw flow through the membranes to significantly simplify the ultrafiltration membrane plant design, replacing variable-speed filtrate pumps with simple control valves. The CAWW installation is the worlds first large-scale plant in this respect."
The siphon system offers savings in pumping costs compared to the normal variable-speed pumping system and in lower maintenance costs by requiring fewer pumps and associated electrical controls.
The CAWW control system is a hybrid design with a programmable logic control/supervisory control and data acquisition (PLC/SCADA) system in a hierarchical structure, integrated with a distributed control system (DCS) architecture. The CAWW is Singapores first water works to incorporate a large fieldbus network, called Profibus, to control individual process trains and equipment that contain complex instrumentation and algorithms. Profibus provides cost and time savings compared to traditional PLC/SCADA setups.
"Another first for the CAWW is the use of dual redundant self-healing rings on the main control network running at 100 million bits per second," said Tse Yau Shing. "The self-healing ring topology overcomes single-point failures by using Hirshman Ethernet switches. While other projects have employed a self-healing methodology, CAWW is the first to use dual redundant rings to cater to multiple breakages and scalability of network speed to gigabit levels."
Safety took top priority in the construction of the new works due to space constraints and the demanding schedule. Black & Veatch recommended that a provision be made in the contract documents for 1 percent of the contract sum to be retained for compliance with the specified safe working practices. With a SARS prevention program, the CAWW work site is also one of the earliest recipients of the National Environment Agencys award of the Singapores "OK" label recognizing exemplary hygiene standards at the site.
Because the project is near a nature reserve, Black & Veatch devoted planning resources to preserving trees and minimizing disturbances to the natural habitat of animals. The design minimized the number of trees affected by construction so as to maintain the habitat of a resident colony of banded leaf monkeys.