Method and apparatus for controlling the coagulant dosage for water treatment

• US 4,855,061 A
• Filed: 04/26/1988
• Issued: 08/08/1989
• Est. Priority Date: 04/26/1988
• Status: Expired due to Term

• Current Assignee: USFilter
• Original Assignee: C.P.C. Engineering Corporation
• Inventors: Martin, Arnold D.
• Primary Examiner(s): Hruskoci, Peter
• Application Number:
  US07/186,309
• Time in Patent Office: 469 Days
• Field of Search: 210/702, 210/709, 210/743, 210/745, 210/746, 210/96.1, 210/103, 210/105, 210/101, 210/143, 364/500, 364/558
• US Class Current: 210/709
• CPC Class Codes: C02F 1/5209 Regulation methods for flocculation or precipitation
• CPC Class Codes: G01N 33/18 Water
• CPC Class Codes: G05D 21/02 characterised by the use of electric means

Abstract

Apparatus for controlling the coagulant dosage rate includes a charge sensor located adjacent a coagulant pump for measuring the net electrical charge on coagulated water before water treatment and a turbidity meter for measuring the effluent turbidity after water treatment. A programmable controller responds to the output signal of the charge sensor to continuously adjust the dosage rate to maintain a set point of charge value in the coagulated water corresponding to a desired effluent turbidity. To maintain calibration of the charge sensor, the controller is also responsive to the output signal of the turbidity meter to adjust the charge value set point as required so that the it corresponds to a preselected effluent turbidity.

Claims

1. In a water treatment system including a means for feeding coagulant into water to be treated to form coagulated particles, apparatus for controlling the coagulant dosage comprising:

charge sensing means for measuring the net electrical charge of the water after addition of the coagulant;

turbidity sensing means for measuring effluent water turbidity after water treatment to remove said coagulated particles and form said effluent water; and

control means responsive to the charge sensing means and the turbidity sensing means for controlling the dosage rate of the coagulant feeding means, the control means responsive to the charge sensing means for adjusting the dosage rate of the coagulant feeding means to maintain a set point of charge value to be measured by the charge sensing means and responsive to the turbidity sensing means for adjusting the charge value set point to maintain a preselected turbidity to be measured by the turbidity sensing means.

2. The apparatus of claim 1 in which the charge sensing means is arranged to measure the net electrical charge of the water after coagulant additions and before water treatment.

3. The apparatus of claim 1 in which the charge sensing means comprises a streaming current detector.

4. The apparatus of claim 1 in which charge sensing means comprises a zeta meter.

5. The apparatus of claim 1 in which the control means comprises a programmable logic controller.

6. The apparatus of claim 1 comprises a microprocessor-based controller.

7. The apparatus of claim 1 including flow proportioning means for maintaining a constant proportion of coagulant dosage to water flow.

8. The apparatus of claim 1 including means for controlling the pH of the water to be treated to maintain a substantially constant pH.

9. Apparatus for controlling the coagulant dosage added to water flowing in a water treatment system comprising:

means for feeding coagulant into water to be treated to form coagulated particles;

charge sensing means for measuring the net electrical charge of the water after addition of the coagulant;

turbidity sensing means for measuring effluent water turbidity after water treatment to remove said coagulated particles and form said effluent water; and

control means responsive to the charge sensing means and the turbidity sensing means for controlling the dosage rate of the coagulant feeding means, the control means responsive to the charge sensing means for adjusting the feed rate of the coagulant feeding means to maintain a set point of charge value to be measured by the charge sensing means and responsive to the turbidity sensing means for adjusting the charge value set point to maintain a preselected turbidity to be measured by the turbidity sensing means.

10. Apparatus for controlling the coagulant dosage added to water flowing in a water treatment system, comprising:

a coagulant pump having an adjustable feed rate for feeding coagulant into water to be treated to form coagulated particles;

a streaming current detector for measuring the net electrical charge of the water after addition of the coagulant and before water treatment to remove coagulated particles and form effluent water;

turbidity sensing means for measuring the turbidity of said effluent water after said water treatment; and

a programmable controller responsive to the streaming current detector and the turbidity sensing means for controlling the dosage rate of the coagulant pump, the controller responsive to the detector for adjusting the feed rate of the coagulant pump to maintain a set point of charge value to be measured by the detector and responsive to the turbidity sensing means for adjusting the charge value set point to maintain a preselected turbidity to be measured by the turbidity sensing means.

11. A method of controlling the coagulant dosage added to water flowing in a water treatment system to form coagulated particles comprising:

measuring the net electrical charge of the water after addition of the coagulant and before water treatment to remove said coagulated particles and form effluent water;

measuring the turbidity of said effluent water after said water treatment; and

controlling the dosage rate of the coagulant added to the water in response to measurement of the net electrical charge to maintain a set point of charge value in said water and adjusting the charge value set point in response to measurement of the effluent water turbidity to maintain a preselected turbidity in said effluent water.