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<br />I <br />I. <br /> <br />.._ A- ,..... ,"'. <br />,-"w ;'I-~) <br /> <br />CH,\PT~:R 3 <br /> <br />ENGINEERING <br /> <br />CONTINUED increase in the demand for Colorado River <br />water in the constituent areas of the District, together <br />with mounting indication< of the prospect of ear1y annexa- <br />tion of important sectors of the coastal basin. made evident an <br />approaching need for expanding the District softening and filtra- <br />tion plant, The plant i< designed for an ultimate capacity of 400 <br />million gallons per day, The administration building, head house. <br />main influent and effluent conduits, and several minor features <br />were constructed initially to accommodate the ultimate require- <br />ments. while the mixing and settling basins, filters, zeolite soften- <br />ers. and salt storage basins were built initially for a capacity of <br />100 m.g,d, The genel'al arrangement of the plant provides for <br />expansion by the addition of units of 100 m,g,d. capacity. <br />Experience in operation of the plant since June 1941 disclosed <br />several particulars in which advantages could be p:ained by changes <br />in design. principally in the mixing and settling basins and the <br />zeolite softeners, The settling basins in the initial 100 m,g,d. unit <br />are of the radial flow type with rotating sludge removal mechan- <br />isms, whereas it is proposed to use longitudinal flow type basins <br />with straight line sludge removal mechanisms in the first 100 m.g,d, <br />expansion of the plant. Design changes in the zeolite softeners <br />include provision for increased volume of ~eoli~e,_ porous. \l!.ate_ <br />underdrailK iflstead- or graver in- the softener beds, general re- <br />arrangement of the main conduit and the brining and rinsing <br />piping and controls, and addition of a lime receiving bin. conveyor, <br />slakers, and feeders to facilitate chemical control of the finished <br />water, Studies were made preparatory to design of the new <br />features. the investigations including an examination of existing <br />water treatment plants in a number of American cities, <br /> <br />Lime -recla /U(Ltion <br /> <br />I <br /> <br />I <br /> <br />Preliminary layouts were prepared for facilities at the softening <br />plant for reclamation of lime from the calcium carbonate sludge <br />precipitated in the lime softening process. After expiration in <br /> <br />I 49 I <br />