Water that is highly colored with organic material requires a _______ pH for coagulation; therefore, ________ before _________ may be necessary.

Water that is highly colored with organic material requires a _______ pH for coagulation; therefore, ________ before _________ may be necessary.

• A. lower, acid addition, flocculation
• B. higher, alkalinity addition, flocculation
• C. lower, acid addition, coagulation
• D. higher, alkalinity addition, coagulation

Answer: (C)

Coagulation efficiency for water with a lot of natural organic matter depends on pH. When the water is highly colored by organics, lowering the pH to a mildly acidic range improves how well the coagulant works. At lower pH, the coagulant forms positively charged species that better neutralize the negative charges on organic molecules, helping them come together into larger flocs. This enhances color removal and overall coagulation performance. Because the ideal pH for this scenario is acidic, acid addition before coagulation may be necessary to reach that optimum level.

Coagulation efficiency for water with a lot of natural organic matter depends on pH. When the water is highly colored by organics, lowering the pH to a mildly acidic range improves how well the coagulant works. At lower pH, the coagulant forms positively charged species that better neutralize the negative charges on organic molecules, helping them come together into larger flocs. This enhances color removal and overall coagulation performance. Because the ideal pH for this scenario is acidic, acid addition before coagulation may be necessary to reach that optimum level.