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<br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />The town Utility Department estimates that non-metered taps consume nearly three times as <br />much water as metered taps, Over the three year period, observed usage varied from about <br />112 to 763 gal/cap/day, Also of interest is the current peak day usage (production) of about <br />1.03 million gallons per day, which equals about 763 gal/cap/day and includes outdoor uses <br />and commercial uses, <br /> <br />4.3 Major Unit Process Evaluation <br /> <br />Influent Measurement and Chemical Addition <br /> <br />As water enters the plant, it passes through an automated butterfly valve and orifice <br />flow meter. Operators have reported that this meter is unreliable due to air sensor lines <br />becoming plugged periodically, The rate of flow into the WTP is controlled by the butterfly <br />valve, which receives a signal from the water level sensor at the clarifier. <br /> <br />Dry alum (100# bags) is mixed with house water and added as a coagulant. Dosage varies <br />from 9 to 30 mg/!. Soda ash (100# bags) is mixed with house water and added at the clear <br />well for pH contro!. Dry polymer, NALCO 8102, is added during April-June as a coagulant <br />aid, According to the operator's estimate, dosage rate varies from ,05 to 0,5 mg/!. The dry <br />feed system has been temperamental, but adequate for operations, as modified over the years, <br />However, improvements could be made in storage and handling of dry chemicals, The <br />gaseous chlorine systems is described in Disinfection, <br /> <br />Flocculation and Sedimentation <br /> <br />Discrete particles in the raw water, called "turbidity", should be removed through the <br />processes of flocculation and sedimentation, Except for the disinfection process, flocculation <br />is the most significant treatment step in a conventional water treatment plant. Flocculation is <br />the formation of visible, fibrous particles through chemical addition and mixing, so as to <br />entrap turbidity and remove it from the water. Since turbidity can include microscopic <br />particles, such as Giardia cysts and viruses, controlled flocculation is essential to modern <br />treatment of surface waters, Proper contact and mixing conditions are required to optimize the <br />flocculation process, The Lyons WTP can remove solids (flocculation particles and turbidity) <br />in two ways, by sedimentation or by filtration, or both. <br /> <br />15 <br />