°pH Control°

pH Control

1.) The purpose of pH control in the treatment process is twofold..

  1. maintain proper coagulation.
  2. control plant effluent pH for corrosion control
    At two of our plants the target is 7.4.
    At the other plant the target is 7.6

  3. In the future, enhanced coagulation will change the way we currently operate.

2.) pH control can be accomplished by the addition of a base to raise the pH or an acid to lower the pH.

  1. two of our plants use Quick lime (CaO) -slakers
  2. the other plant uses hydrated lime (Ca (OH)2) - slurry
  3. Other chemicals can also be used to raise the pH, such as caustic (NAOH) which is very expensive or soda ash, which is also called sodium carbonate Na2(CO3).
  4. Queen Lane had sulfuric acid tanks on site which could have been used for pH control in algae bloom conditions but it was never used.
  5. With enhanced coagulation in the future, pH control will become critical and acid and base chemical addition will be required.

3. Lime addition is not continuous...When Belmont and Queen Lane use alum as coagulant, the lime can be shut off due to the sufficient alkalinity already present in the River. During storm events, lime is needed to keep the coagulation process working satisfactorily. When using ferric chloride, lime addition is greater than when using alum.

4. Application Points

  1. One WTP doses lime at the "E" Shaft, which is the point of coagulation prior to the floc/sed basins.
  2. One WTP doses slaked lime at the rapid mix-
  3. One WTP doses slaked lime before the floc/sed basins also.

5. Importance Of pH control
pH control is a critical unit process. Failure of the lime feed can result in the loss of proper coagulation and result in a turbidity excursion..

  1. One WTP has a pH alarm on "F" Shaft (pre-floc/sed) which notifies the chemist if the coagulation process is being upset...pH too high indicates coagulant feed problems (could also indicate the growth of Algae on the river)...pH too low indicates lime feed problem.
  2. The chemist monitors pH every three hours with a digital pH meter that has been calibrated using a 3 point calibration (4, 7, & 10).

It is also important to maintain steady pH in the plant effluent for corrosion control to be effective in the distribution system.

6. Maintenance Of Lime System

  1. Lime slakers are difficult to maintain and generate lime grit which must be removed and disposed.
  2. Hydrated lime system has mixers to maintain a slurry. Feed lines must be flushed regularly to prevent clogging...They must also be chlorinated from time to time to prevent bacteria growth.

Navigate Belmont WTA's Site:


Main Page The River Pri Seds $Chem Treatment$



Floc Filtration Post Chem Distribution

YOUR LOCAL WATER TREATMENT PLANT....Bringing the people of Your City, and It's Suburbs, the FINEST quality Drinking Water available anywhere in the World!

Go to the CapeCanaveral Top Menu

1