dosages. It is believed that the onset of silica fouling could have been materially retarded, if not prevented, by the w e of proper caustic regenerant dosages and temperatures from the start. A major problem was the fouling of anion resins by organic contamination-large organic molecules that are retained by the resin and adversely influence quality through leakage during operation. The efficiency of hypochlorite cleaning procedures for organic-contaminated resins remains to be proved; such operations may damage resins through accelerated oxidation of active groups. Since normal chlorination of the city supply is not sufficient to oxidize and remove existing organic matter or to prevent biological fouling, additional chlorination has been provided. Standard strong base resins have been replaced by new porous anion exchangers, Xvhich display greater capacity for the large ions. However, t o avoid contamination, organic matter should be removed by chlorination, coagulation, retention, and filtration, prior t o deionization. At the time the mixed bed plant n a s installed, space limitations precluded installation of hydrogen cycle cation exchange and decarbonation tanks, which were indicated bv raw n ater characteristics. Substantial reductions in regenerant and labor costs now have been accomplished by installation of thwe units which reduce ionizable Eolids in the mixed bcd influent by approximately 80%.
apacity
ACKIVOWLEDGMEST
The authors wish to thank L. E. Miller and Lee Whj te OF the Department of Chemistry, University of Illinois, for their c o o p erntion in arranging for the installation and operation of the mixed bed unit. Acknowledgment is also made of the assistance received from R. D. Tilson, Wilson &- Anderson, Consulting Engineers, R. E. Brown, Department of Chemistry, University of Illinois, and E 5 ) , calculations based on their equations show that Q 9 = Qm within what is considered experimental error. However, for linear equilibrium (K = l), QS for any regeneration less than complete will be greater than Qm. I t s value varies linearly from Qm a t complete regeneration to y&t as regeneration approaches zero
Qs
=
yQt -
Q
(
