in the water column. The solids that are suspended will flow over the weir 

 structure. The concentration of the suspended solids is needed to determine 

 the effectiveness of the containment area and to determine if any effluent 

 regulations will be violated. 



42. The effluent (supernatant) suspended solids concentration is deter- 

 mined as follows: 



Total settling volume = 100,000 cu yd * 2 ft/ 10 ft 



= 20,000 cu yd (ponding depth repre- 

 sents only 20 percent of total depth) 



Theoretical detention time = 20,000 cu yd/3,200 cu yd/day 



= 6.3 days 



Hydraulic efficiency = 0.9 [1 - exp (-0.3L/W)] 



= 0.23 (assuming length-to-width ratio 

 is 1) 



The hydraulic efficiency factor is applied due to containment area inefficien- 

 cies (Shields, Schroeder, and Thackston 1987). 



Retention time =6.3 days x 0.23 

 = 1.45 days 



43. The effluent suspended solids curve (Figure 7), a retention time of 

 1.45 days, and a 2-ft ponding depth yield a suspended solids concentration of 

 108 mg/£ in the column. A resuspension factor of 1.5 is recommended for a 

 ponding depth of 2 ft or greater and a surface area less than 100 acres. The 

 effluent suspended solids concentration estimated for the field conditions is 

 162 mg/£. For the 300,000-cu yd site, a retention time of 18.8 days produces 

 an effluent suspended solids concentration of 126 mg/£ including resuspension. 



Design of Typical Chemical Clarification Components 



44. Polymer-assisted clarification of a CDF effluent requires equipment 

 to dilute and feed the polymer, to rapidly mix the polymer solution with the 

 supernatant, to slowly mix the flocculent solids to encourage particle-to- 

 particle contact and agglomeration, and to settle the flocculated suspension. 



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