228 



BIRGE 



8.0 



• ,pH 



A , Total dissolved solids 

  , Conductivity 



3.0 



1.0 



200 300 400 



FLY ASH LEACHING TIME, hr 



500 



E ^ 



<J 0) 



E Q 



2.0 ^,9 



> -I 

 HO 



QO 



U-< 



U 



CO 



0.0 



Fig. 1 Changes in fly-ash effluent with leaching time. 



for the first elution interval. As seen in Fig. 1, changes in these 

 effluent parameters were most pronounced during the initial 4 days 

 of ash-leaching time, presumably correlating with the period during 

 which leachable components were most rapidly removed from the fly 

 ash. Mean values for the first 500 hr are given in Table 4. 



Midway in the second elution interval, at 770 hr, the influent 

 source was changed to carbon-filtered tap water. This action was 

 taken to determine whether influent water of higher pH and greater 

 buffering capacity would alter the leaching process. Initially, 

 conductivity and total dissolved solids of the effluent rose propor- 

 tionately with increases observed for the new influent water, but 

 values for these parameters declined steadily over the third and 

 fourth elution intervals, closely approaching those obtained for 

 influent water by 2000 hr (see Materials and Methods section). After 

 the change to influent tap water, effluent pH for the second elution 

 interval increased steadily from 4.5 to 7.1. A gradual increase 

 continued thereafter, and, during the last two elution intervals, pH 

 ranges of 7.1 to 7.9 and 7.0 to 7.7 were recorded for influent and 

 effluent water, respectively. Although total alkalinity was not 

 determined during the first 1000 hr, ranges for the third and fourth 

 elution intervals were 32 to 55 and 46 to 62 ppm CaCOj, compared 

 with 54 to 69 ppm for influent tap water. After 2000 hr of 

 continuous washing of the original fly-ash sample, influent and 



