CHEMICAL TREATMENTS 403 



For ponds, volumes usually are known in acre-feet (surface area in acres 

 X average depth in feet). Relatively large amounts of chemicals are 

 needed for treatment, and these usually can be weighed in pounds. The 

 correction factor is 2.7 (pounds/acre- foot per part per million). 



Example: How much of chemical A (60"() active ingredient) is needed 

 for a 2-ppm treatment of a 2.0-acre pond that averages 2.5 feet deep? 



Volume = 2.0 acres x 2.5 feet = 5.0 acre-feet; 



5.0X2.0X2.7 ^, , r .  , A 



= 45 pounds oi chemical A 



0.60 



Calculations for Constant-Flow Treatments 



The weight of chemical needed for constant-flow treatments is computed 

 just as for prolonged-bath treatments. However, in this case the volume 

 (capacity) of water to be treated is equal to the flow rate times the treat- 

 ment time (for example, 10 gallons per minute x 30 minutes). Correc- 

 tion factors are the same. The formula is: 



flow treatment final correction 



rate x time x concentration x factor weight of 



= chemical 



chemical strength (decimal fraction) needed 



Example: A trough receiving a water flow of six gallons per minute is to 

 receive a 1-hour (60-minute) constant-flow treatment of chemical B (lOO% 

 active strength) at a concentration of 5 ppm. How many grams of chemical 

 B must be dispensed to maintain the treatment concentration? 



6.0x60x5.0x0.0038 ^ „, r  • , t> 



= 6.84 grams oi chemical B. 



1.00 ^ 



Constant-Flow Delivery of Chemicals 



Of the variety of constant-flow devices that have been adapted to 

 hatchery use, commercial chicken waterers are the most reliable (Figure 

 G-1). 



All such devices deliver only liquids. Dry chemicals first must be put 

 into solution before they can be dispensed. If the amount of dry chemi- 

 cal needed already has been computed by the formula given in the previ- 

 ous section, it only is necessary to determine the amount of liquid that 

 will be dispensed from the chicken waterer over the period of treatment. 

 This is done by simple proportion. For example, if the constant-flow de- 

 vice delivers 20 milliliters per minute and the treatment is to be 60 

 minutes long, 1,200 milliliters will be delivered in all. This is the water 



