We designed water intake screens for a really cool project in New York City a few years ago. Sadly, as with a lot of public art projects, it's no longer in place. Waterfalls in the middle of the Hudson River were pretty. Click here to learn more.
Debris handling at raw water intakes is a common, expensive process. Side intakes at low head dams are a common application for raw water intakes at municipal water treatment facilities. Debris handling at these facilities is typically performed by mechanically driven equipment. Operation and maintenance of this equipment is expensive.
Coanda screens are an inexpensive alternative to traditional solutions. Coanda screens utilize the natural flow of water to clean the screen and maintain reliable flow. The screens use water’s natural tendency to adhere to whatever surface it is traveling on (the Coanda effect). This effect enhances efficiency and cleans the screens as clean water falls through and debris and aquatic life pass over.
Cook Legacy extended the U.S. Bureau of Reclamation’s advances in capacity approximation by integrating mechanical, fluid dynamics, and 3D modeling capabilities into design software. These advances are useful in evaluation of green field projects and essential in evaluating a retrofit.
We recently designed and implemented a Coanda screen for a low head dam in the southeastern United States. A water treatment plant retrofitted an existing low head dam by installing a Coanda screen on half the structure. The system had an 18 MGD capacity. The screen panels had a footprint of approximately 100 square feet. Cook Legacy used its sizing model to design an accurate screen by analyzing the flow elevations above the crest, velocities inside the collection chamber, and elevations in the pump station at different flow patterns. These details allowed a smooth implementation of the Coanda screen with the entire system. The Coanda screens are not completely self-cleaning. The site will have debris lines at flows less than 18 MGD, but debris will pass over the screen at higher flow volumes. Coanda screens have less moving parts than traditional designs, making it a viable alternative in the raw water intake market.