polymer dosage, and supernatant suspended solids following flocculation and 



settling. 



Polymer screening 



33. The polymers that were screened included 27 cationic, 8 anionic, 

 and 1 nonionic polymer. Seven cat ionics and two anionics were evaluated in 

 combination. Table 19 lists the polymers that were evaluated during this 

 study. Polymer dosages ranged from 0.5 to 75 ppm for polymers used alone and 

 from 5.5 to 58 ppm combined for polymers used in combination. Based on 

 results of the initial screening process, most of the polymers were not effec- 

 tive for the upper estuary composite sediment. The polymers used in combina- 

 tion slightly improved performance, but the improvement was insufficient to 

 justify the additional cost and the feeding and mixing requirement for 



two polymers . 

 Polymer optimi z ation 



34 . Ten cationic and five anionic polymers were selected for optimiza- 

 tion. Figure 13 illustrates the typical curve of suspended solids versus 

 dosage for each polymer. The optimum dosage was determined as that resulting 

 in the minimum value for supernatant suspended solids. For example, the opti- 

 mum dosage for Magnifloc 1586C, illustrated in Figure 13, is 15 ppm, resulting 

 in a supernatant suspended solids concentration of 37 mg/£. 



Polymer selection 



35. Based on the results of the optimization testing, an appropriate 

 polymer and chemical dosage concentration can be selected. The primary selec- 

 tion factors are suspended solids removal effectiveness and cost. The liquid 

 polymers were found to be ineffective when applied to the New Bedford Harbor 

 supernatant and were eliminated from further consideration. 



36. Following the initial screening for suspended solids removal effec- 

 tiveness, the remaining polymers were subjected to a preliminary cost compari- 

 son. This was accomplished by calculating the estimated cost per ton of 

 solids removed for each polymer. The results of this analysis are summarized 

 in Table 20. 



37. The emulsion polymers and a dry polymer had the lowest optimum dos- 

 age and cost. However, because of the complexity of using dry polymers in the 

 field, the emulsion polymers may be preferred. Magnifloc 1586C was selected 

 as having the greatest potential for application to the New Bedford project in 

 the EFS evaluation of dredging and dredged material disposal alternatives. 



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