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a F washed pea gravel to 3/4" to 21/2" washed stone. Two four inch diameter perforated pipe manifolds,and the four-inch diameter perforated inlet pipe from the pretreatment tank, are located in the filter. The lower manifold, located at the bottom of the tank, provides for recirculation of a portion of the wastewater that has been treated through,the aerobic media through the gravel filter. The discharge from the pretreatment tank enters the filter just above the lower manifold and mixes with the recirculated water in the filter. The combined wastewater flows up through the gravel to the second manifold at the surface of the gravel filter. The filter is designed to provide for denitrification of the wastewater treated in the.attached growth section of the tank_ The upper manifold discharges into the sludge pump well, where solids sloughed from the attached growth media are washed up.from the gravel filter settle and are pumped on a timed basis to the pretreatment tank. The treated water overflows from the sludge pump well to the recirculation well through a four-inch cross-over pipe. The water is recirculated over the attached growth media or up through the gravel filter. The proportioned distribution to the lower manifold in the anaerobic section is concurrent with the application to the attached growth media. The water recirculated to the media is applied through three sprinkler heads located above the media. The sprinkling action provides for aeration of the water;to assure aerobic conditions in the attached growth media as well as distribution of the water over the surface of the media. The pump in the recirculation well provides for discharge of the treated water from the plant as well as for recirculation. Discharge from the plant is controlled by a solenoid-activated valve that is activated by the programmable controller. The valve is normally closed except at the completion of the recirculation/treatment cycle, when it is activated to provide for discharge from the plant. A particulate filter is provided ahead of the valve to protect it from clogging by solids in the water. The treatment cycle provides for circulation of water over the media for a three hour period, followed by a 60 minute rest period. A minimum of two.three-hour cycles occur during each 24-hour period. Three float switches are provided in the recirculation well for non-cycled control of the plant. The bottom float is provided to assure that the recirculation pump does not run dry, the middle float initiates a treatment cycle if the wastewater level in the plant rises, and the upper float activates the audible/visual alarm indicating the need for service. 2.2 Test Protocol The NSF Standard 40 Performance Evaluation method and requirements are included in Appendix B. Start up of the plant is accomplished by filling one-third of the volume with raw wastewater and the remainder of the volume with fresh water. The plant is then dosed at the design loading rate(450`gpd) three weeks. Doses were made during three dosing periods: �_J 6 a.m. to 9 a.m. - 35 percent of daily rated capacity 11 a.m. to 2 p.m. - 25 percent of daily rated capacity 5 p.m. to 8 p.m. - 40 percent of daily rated capacity 2 Draft Report