MANY ENGINEERS believe that water, in all its various forms, is the most insidious force in nature.
Sure, it’s tasty and essential for life. Yes, we’re three-quarters water ourselves. Some, yawn, astronomers think liquid H2O might be the most precious substance in the universe because of the relatively tiny temperature window it needs to exist.
However, this is small comfort to anyone who’s ever had to mop up a flooded basement, keep moisture out of delicate instruments, or clean up an inundated neighborhood or city. Whether pulled down by gravity or condensing out of the air, water literally gets in everywhere.
Ironically, though they make their living cleaning up wastewater or supporting those that do, several engineers in upstate New York this summer had far more cause than they expected to sympathize with folks in New Orleans and along the Gulf Coast. That’s because these municipal, electrical, and construction professionals had to cope with and recover from a devastating, late-June flood at their wastewater plant. And, as if this wasn’t enough, these engineers had to deal with the extra tragic twist that they were within five weeks of finishing a major retrofit of their plant.
About two years ago, the Binghamton-Johnson City Joint Sewage Treatment Plant in Vestal, N.Y., started a $55-60 million retrofit project to improve its capability and capacity for treating wastewater. The plant also needed to comply with U.S. Environmental Protection Agency and New York State Department of Environmental Conservation regulations, according to Art Van Gelder, project manager for C&S Engineers, Syracuse, N.Y., which is the project’s design, build, and construction management firm.
The original plant had six primary settling tanks, four secondary settling tanks, three thickeners, three digesters, a belt filter press, a composting facility, and equipment for grit handling and other tasks.
However, because its 18.5-acre site is hemmed in by neighbors, a road, and two rivers, the plant’s construction and electrical engineers had to find a way to increase its capacity without increasing its footprint. The designers eventually settled on plans to implement an innovative biological aerated filter (BAF) system. Though this technology is gaining popularity in Europe, where riverfront space also is scarce, Van Gelder says there are less than a half dozen of these installations in the U.S. The Binghamton-Johnson City plant eventually bought its BAF system from Norway-based IDI Systems.
The initial reconfiguration involved converting the plant’s four secondary settling tanks into primary settling tanks, which typically have slower flow rates. New tanks added to the facility included eight carbonaceous filters, eight nitrification filters, and four de-nitrification filters, as well as backwash pumps, a second inflow pump station, and fine-screen rooms.
To monitor and manage all of the plant’s new equipment and systems, C&S and Matco Electric, Vestal, N.Y., networked pneumatic control valves on the plant’s 21 motors with Foundation fieldbus (FF) and DeviceNet protocols via Turck’s molded cables, connectors and cordsets. These motors average 200-300 hp, but include a few 450-hp units.
|FIGURE 1: MOSTLY EMPTY TRAY|
Installing twisted-pair Foundation fieldbus and DeviceNet terminated with molded cordsets reduced the amount of hardwiring used at the wastewater treatment plant. These waterproof cables and connectors survived a late-June flood without needing the deconstruction, drying, and rebuilding that a regular wire-in-conduit job would have required.
The new network also controls the plant’s level, flow, and pressure transmitters, as well as its analyzers and level switches. This twisted-pair networking topography, enabled by FF and DeviceNet, reduced the plant’s hardwiring by thousands of feet (See Figure 1). The plant previously relied on a point-to-point architecture that filled its existing cable trays. When it’s installed, FF’s cable usually contains one pair of wires for data, and one drain wire. DeviceNet cable usually has five total wires, including one pair for data, one pair for power, and one drain wire or shielded conductor.
Dan Dvorsky, Matco’s general foreman, says DeviceNet generally is used to control valves and pumps, while FF monitors the flow and level transmitters. The supplier provided custom-length cables and ends for a total of 200 valves on 20 tanks.
These improvements and the BAF system are designed to increase the plant’s capacity from 18.5 mgd average flow, with a peak of 23-25 mgd, up to 60 mgd. It was IDI’s developers that advised the plant to adopt FF and DeviceNet.
Flood and Recovery
Because water treatment plants are situated near channels that can accept their effluent, the Binghamton-Johnson City facility is located at the confluence of the Susquehanna and Chenango rivers, which both feed the greater Delaware watershed (See Figure 2 below). “All of the surrounding communities are higher than the plant,” says Van Gelder.
|FIGURE 2: DOWN BY THE RIVER|
The Binghamton-Johnson City Joint Sewage Treatment Plant is located next to (and occasionaly in) the confluence of the Susquehanna and Chenango rivers.