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7.8.2 <br />7.8.3 <br />7.8.3.1 <br />7.8.3.2 <br />The advantages to gravity filtration systems are: <br />1. Gravity filters provide for more treatment options including aeration and detention without <br />requiring another pumping step. If regulations change or the water becomes contaminated, <br />additional treatment steps can be added to gravity filters. <br />2. Water from the gravity filters does not go immediately into the distribution system. If <br />problems with the filters occur or if sodium permanganate is overfed (causing pink water), <br />operators have time to react and correct the problem. <br />3. Gravity filters are open to view and access. This is advantageous in that it enhances the <br />observation, operation and maintenance of the filter functions and components. <br />4. Gravity filtration systems have a greater amount of flexibility with less disruption during <br />normal maintenance procedures. <br />The disadvantages to gravity filtration systems are: <br />1. The facilities tend to have more capital cost than pressure type facilities. <br />2. Typically requires the facility to be constructed on two floor levels. <br />3. Provides for less available headloss than pressure facilities which can result in shorter filter <br />run times. Shorter filter run times result in more backwashing which takes a filter out of <br />service. <br />Building Layout/General Sequence <br />Gravity filter building layouts are included in Appendix F. The chemical rooms are located on the <br />east side of the building, with exterior doors accessible for deliveries. The electrical, mechanical, <br />high service pump room, and generator rooms are located in close proximity to each other to <br />allow for short conduit runs to motor controls. <br />The gravity filter layout occurs on two levels to allow for filter height to provide head for the <br />filtering process. The raw water enters the building through the high service pump room where <br />chlorine and potassium permanganate are added. The water travels through the filters by gravity <br />to the clearwell. The water travels from the clearwell to the high service pump chamber where it <br />is pumped into the distribution system. Fluoride, chlorine, and phosphate will be added to the <br />finished water. <br />Main Level <br />Chemical Rooms <br />Chemical rooms are clustered on the east side of the building with exterior doors to allow easy <br />access for chemical deliveries. It is expected that chemical rooms will be required for chlorine <br />gas, sodium permanganate, fluoride, phosphate, and possibly polymer to aid in backwash <br />settling. <br />High Service Pump Room <br />The high service pump room contains the pumps that pump treated water from the clearwell into <br />the distribution system. Because most of the electrical load is located in the high service pump <br />room, it is in close proximity to the electrical room and generator room. <br />FEASIBILITY STUDY RAMSY 154354 <br />Page 30 <br />