Optimizing Coagulation with the Streaming Current Meter. Chuck Veal Micrometrix Corp

Transcription

1 Optimizing Coagulation with the Streaming Current Meter Chuck Veal Micrometrix Corp

2 Charged Particles Repel

3 Neutral Particles Flocculate

4 Coagulant Particles Al 3+ Monomeric hydrolysis products e.g. Al(OH) 2+ Various polymeric species Colloidal hydroxide precipitate Precipitated Al(OH) 3 Stable Destabilized Coagulated Restabilized Flocculated Sweep Flocculation

5 Floc Particle Growth 1 min 5 min 10 min 20 min 30 min

6 Double Layer Model Positive Counter-Ion Negative Co-Ion Highly Negative Colloid Stern Layer Diffuse Layer Ions in Equilbrium with Solution

7 SCM Charge Measurement ( + ) Positive ( 0 ) Neutral Ionic and Colloidal ( - ) Negative

8 Stabilized Colloids Repulsive Energy Attractive Energy Electric Repulsion Energy Barrier Net Interaction Energy Distance Between Colloids Attraction Van der Waals

9 Destabilized System Repulsive Energy Electric Repulsion Net Interaction Energy Energy Barrier Attractive Energy Distance Between Colloids Attraction Van der Waals

10 Common Techniques For Dose Control SCM Streaming Current Monitor PCA Particle Charge Analyzer Zeter Potential Meter Jar Tester

11 Zeta vs. Streaming Current Zeta Potential Induce electric field, measure particle motion Only discrete (visible) particles are measured. Off-line or batch mode only Single particles are selected visually from a charge distribution. Streaming Current Induce particle motion, measure electric field. Particles, colloids, molecular/ soluble (ionic) are measured. Real Time measurement Online or Offline modes Charge distributions are averaged and displayed electronically.

12 SCD AND ZETA POTENTIAL READING WITH COAGULANT DOSAGE RATIO OF COAGULANT DOSAGE(OPTIMUM=1) ZETA METER(mv) SCD

13 Jar Tests vs. Streaming Current Jar Test Time consuming technique (30min to 1 hour) Predicts plant settling for discrete Coagulant Doses Off-line or batch mode only No Alarm Functions or Process Feedback Streaming Current Continuous Real time SCM Quick Results ie. PCA (2min) Measures actual Charge Neutralization Process. Real Time measurement Online or Offline modes Early Warning system to avoid Process Upsets

14 Particle Charge Analyzer

15 Coagulant Demand by Titration

16 Piston Sample Cell + Sample Electrodes PCA Measurement Cell

17 PCA Technique Prepare a stock solution of chemical and mimic the current plant dosage into 100ml of Raw water to determine a target endpoint This endpoint is used during changing plant conditions to quickly determine dosage

18 Optimum Endpoint The theoretical optimum endpoint is zero mv, but most plants run slightly above or below zero because of the unique process dynamics for a given plant.

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20 Streaming Current Meter

21 Remote Sensor

22 SC Sensor Motor Stainless Steel Electrodes Replaceable Sleeve Teflon and Delrin Material Spare Sleeve / Piston Inlet Piston Sample Outlet Electrodes Probe Housing Sleeve

23 Stationary Liquid / Piston Stationary

24 Piston Upstroke Liquid / Piston

25 Te flon Piston To p Ele c tro d e Thum b sc re w Pro be Housing Elec tro de Lead Wire Te flo n Sle e v e O- Ring Bottom Elec trode/ Plug Assembly

26 Probe Service

27 Remove Boot

28 Remove Bottom Electrode

29 Remove O-Ring

30 Remove & Replace Teflon Sleeve

31 Probe Signal

32 SCM with Self Cleaning

33 Plant Diagram Coagulation Flocculation Sedimentation Filtration Pump SCM Controller Feedback Control Sample Point * Well Mixed * Quick Response Set Point * Emperical * Based on Process Performance Storage

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35 Sample point Sample near the center of a pipe or channel Avoid sample locations prone to collecting silt, sand or grit. Shorten sample lines when possible to minimize clogging and reduce response time.

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39 Determination of Proper Set Point First optimize plant process - flocculation, particle and TOC removal Minimize filter effluent turbidity/particle count Minimize coagulant dose and maintain water quality Maximizing plant / process efficiency Zero streaming current reading

40 Floc Particles Optimum Floc Vs. Light Fragile

41 SCM vs. NTU SCM NTU Streaming Current Response Chemical Dosage mg/l Chemical Savings

42 Streaming Current Controller

43 SCM Control Feedback signal produced by the SCM Controller changes the output to the pump proportionally. Process controller has programmable tuning constants that allow the operator to compensate for lag times Built-in alarm functions that alert the operator immediately if an overfeed or underfeed of chemicals is encountered

44 Flow & SCM Control Flow meter Mixing Unit Flocculator Pump SCM Flow Proportional * No Lag * Feedforward SCC Controller SCM Control * Feedback Control * Reverse Acting

45 Recommendations for Successful Operation Replace piston and probe components as preventative maintenance Periodically check optimization of the process and verify the SC setpoint

46 Contact info Chuck Veal Ph