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The original filters at this facility were Clay Tile Underdrains, Gravel, Sand, Anthracite, and Surface Wash. During the design phase, Roberts performed many site visits to evaluate the existing equipment and make recommendations as to the replacement thereof. In addition, Roberts supplied a pilot unit that would evaluate and record the benefits of eliminating the Sand and Anthracite, replacing it with deep bed mono media. The goal of the plant was to increase filter runtime and decrease backwash frequency and volume. In addition, the existing filters showed signs of being upset to the point that media was being found downstream of the filters, as far as the UV channels, therefore clogging the UV system.
It was recommended to the engineering firm involved, to replace the existing filters with new Trilateral type underdrains, eliminate the surface wash system, and incorporate air scour and deep bed mono media sand. In addition, alterations to the PLC system currently installed, to change specific parameters of the sequence, to allow the automatic operation of the new filter configuration.
By changing from the conventional filter configuration and media loading and the addition of air scour, the runtimes, capacity, and backwash frequency were dramatically enhanced allowing the plant to treat incoming waters without the need to bypass the same. During the construction phase of the project, a test was run to evaluate the ability for one (1) refurbished filter to accept the entire plant flow. This goal was achieved without incident. This new process, in plants maintaining a log, have achieved benefits that show the ability to increase their production rates 2.5 times that of the previous configuration, without the need to add more filters, thereby decreasing the cost of construction, decreasing the cost to the customer, and maintaining the permit level assessed to the plant. Backwash requirements were decreased from 24 hour intervals to 72 hour intervals while backwash volume was decreased by approximately 60%. Thus an overall cost savings and maximum Return on Investment. (ROI)