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<br />- -'~ "- <br />.... '''1 <br />1.,0.1 <br /> <br />40 <br /> <br />METROPOI.ITAN WATEH DISTRICT <br /> <br />dium silicate was fed without interruption to the softener influent <br />water in order to raise the silica content to such a le\'el that disso- <br />lution of this element from the zeolite would be reduced to a mini- <br />mum_ At the end of the tiscal year more than 1.]00.000 gallons of <br />water had been softened per cubic foot of the newer zeolite, in serv- <br />ice for slightly more than two years. and its operation continued <br />to be satisfactory. Due to the high pel'centage of tines in the fOil I' <br />softener units containing the revivitied original zeolite, the attrition <br />losses in these were sufficiently high to require the consolidation <br />of this material into three units_ Enough new commercial zeolite <br />was purchased to till the fourth unit with the new mineral and to <br />bring the remaining eight units up to proper volume. <br />During the fiscal year 888 cubic feet of synthetic siliceous zeolite <br />were manufactured by the District at the softening plant to make <br />up the normal attritioll losses during softener operation. This pro- <br />ductioll was discontinued and the zeolite manufacturing equipment <br />was dismantled in January ]948 to make room for the contractor's <br />operations during the construction of the softening plant extensioll. <br /> <br />Re_,carch H.ork <br />The deta.iled investigation into the characteristics of other cation <br />exchangers,_ particlllarly the synthetic resins, was continued. Al- <br />though more time will be needed to determine the life expectancy <br />of some of the exchangers. much valuable information has been <br />obtained relative to salt requirements for regeneration and resist- <br />ance to breakdown under the condition of low chlorine residual <br />usually present in District softeller influent water_ <br />The designs for the larger experimental electrolytic water softell- <br />ing unit were completed and several items of equipment necessary <br />for its construction were procllred. Actual construction of the IInit <br />will be delayed until operatiolls of the general contractor 011 plant <br />expansion are completed. <br />Tests were continued to determine whether certain controlled <br />changes in the softened water. particularly with reference to the I <br />pH and total alkalinity. would give an improved product from the <br />corrosion standpoint. <br />Additional laboratory tests were run to determine the efficacy <br />of Rct.ivflted ~ili('.a a~ a coagulation aid during the lime softening <br />phase of plant operation_ A relativel)' new sol, produced with chlor- <br />ine as the activating agent, was used in these investigations and <br />appears promising on the basis of these studies_ <br />