retention time and pH.   The copper removal was less than theoretical in one test, but approached the theoretical values as the initial copper concentration decreased and retention
time increased.  When the effect of pH was investigated, copper removal was greater than
theoretical at pH values greater than 10.5 and less than theoretical at pH values less than
10.5.   The percent copper removal by precipitation ranged between about 94 and 99%.
Adsorption of copper on fly ash also occurs.   The theoretical curves for copper removal
do not consider the effect of copper adsorption on fly ash.   The experimental work showed
that adsorption can significnatly increase copper removal.   For the types of fly ash tested,
the adsorption capacities of copper on fly ash average 4.7 ug Cu/g fly ash.   The adsorbed
copper on the fly ash and the precipitated copper hydroxides will settle to the bottom of
the ash pond and be permanently sealed over by subsequent deposition of ash, thus preventing resolubUizing of the copper.
Experimental work by TVA indicates that removal of copper from chemical cleaning
wastes to 1.0 mg/1 can be obtained in alkaline ash ponds having pH equal to or greater
than 8.5. Factors necessary for equivalent copper removals to 1.0 mg/1 are: (a) a dUution factor of greater than or equal to 99 parts ash sluice water to 1 part of waste depending on the initial copper concentration in the waste, (b) an ash concentration in the ash
sluice water of greater than or equal to 1.67% by weight and (c) a retention time of up
to 10 hr depending on the amount of mixing of the waste with the ash sluice water.
Based on the theoretical considerations and the results of this study, the following process is proposed for the treatment in ash ponds of ammoniated-bromate chemical cleaning
wastes containing high concentrations of copper:
1. An ash pond is required in which the pH of the pond should be greater than 8.5 to
provide the necessary chemical precipitation.
2. Because dUution of the waste is required to break the complex copper-ammonia bonds,
the waste should be discharged into the ash pond at a controUed rate proportionate
to the ash sluice flow to provide the required dUution.   Required dUution wiU depend
on the copper and ammonia concentrations in the waste.  Appropriate dUution could
be accompUshed by discharging the ammoniated-bromate waste drains and flushes to
a holding pond and then by discharging the wastes into the ash pond using pumps,bypass valves and flow rate-measuring weirs.  A flow schematic for the treatment process
is shown on Figure 17.   At large multiple-unit plants having high ash pond flow rates,
an alternative to providing the holding pond is to drain the cleaning waste directly
from the boUer to the ash pond at a controUed rate proportionate to the ash pond flow.
aaaBBBBB.  Aah Sluice Water
   Chemical Cleaning Waete
*---*  Aah Pood Discharge
Diversion    Flow     weir
Box     Control   Box
Valee
Figure 17.  Schematic of system for treatment of copper metal cleaning wastes in ash pond.
3. A fly ash concentration equal to or greater than about 1.7% in the raw fly ash sluice
water is required to provide adsorption of copper.   If a holding pond for the waste is
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