1

Process Analytical

Instrumentation in Water

Treatment

Plants – the Basics

Kevin Menning

Hach Company

HI AWWA

Honolulu, HI

Feb 3, 2014

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Develop Baseline Data

Characterize your process

Use The Data to Develop a Strategy

The Road to Process

Improvement

Gordon

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Why go through so much

effort?You want to make your plant as efficient as possible

The baseline data will eventually make your work easier

The database becomes a reference tool that can identify

opportunities for improvement

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Outline

The Sample

Lab & Process – Pros & Cons

WTP Process Instruments

Calibration and Verification

Data Analysis

5

The Sample

Hach is not the expert with this – you have to be.

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The Important Role of the

Sampler!

The accuracy of your

analysis is only as

good as the care that

was taken in obtaining

a the sample.

7

Why was

the

Chlorine

Analyzer

reading .8

mg/L

lower

than the

sink

sample?

8

Types of Sampling Points

�Source Water

� Rivers & Streams

� Reservoirs & Lakes

� Groundwater

�In-plant

� Sampling taps

� Basins

�Distribution

� Residential taps

� Sampling stations

� Each one is unique

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Sample Taps

10 pipe diameters

Poor, may

draw

sediment

X

Poor, avoid ells,

valves, T’s and other

areas of turbulence

Best

Better

Poor, may

draw air

XX X

X

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Planning

•#1 = Identify your sampling sites

•#2 = Install the analytical instrumentation

•#3 = Gather and analyze the data

•#4 = Maintain that instrumentation

•#5 = Continually evaluate sampling site and

what information it is providing to you.

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Why is laboratory

monitoring necessary?– Test parameters for which automated

analyzers are not available

– Frequency of test does not justify analyzer

purchase

– Verify function of on-line instrumentation

– Parameter does not require constant control

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Accuracy and Precision

• Two words that sound a lot alike,

but very important differences

• Precision is how well you can

repeat the answer over and over• HTTC 10 table iron test

• Accuracy is how close to the true

value your answer is.• How do determine if your answer is accurate?

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Calibration and Verification

• Two words that sound a lot alike,

but very important differences

• Calibration is using standards

and following the procedure in the

manual for calibration.

• Verification is comparing to a

standard or another instrument

and making sure it is with-in a

certain % usually 10%.

• Will cover more in depth later

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Laboratory Disadvantages– Time and labor intensive

– Sampling and technique variations may lead to

inconsistent results.

• Example – 2100N vs 1720E unkown

– Grab sample may not detect a problem (such as

underfeed or overfeed of treatment chemicals)

soon enough to prevent process problems or

failure.

El Dorado Filter Break through

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Laboratory vs.

On-line Monitoring

Problem detected at 7pm!

What if you were only testing 4 times a day?

Lab Test1pm 3pm 5pm 7pm 9pm 11pm

Problem

Occurs

5:30pm

Measurement every 2 hours – 1:00pm, 3:00pm, 5:00pm, …..

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Laboratory vs.

On-line Monitoring

Problem detected at 5:32pm!

Process

Monitor 1pm 3pm 5pm 7pm 9pm 11pm

Problem

Occurs

5:30pm

Measurement every 2 minutes – 1:02pm, 1:04pm, 1:06pm, …..

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Advantages of automated

analysis

– Fast detection and correction of abnormalities

– Saves operator time

– Reduces operator error

– May reduce reagent costs

– Instrumentation can be used to control chemical

addition using 4-20 mA outputs, relays and

SCADA

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Advantages of automated

analysis - continued

� Initiate backwash, start/stop pumps, adjust

chemical feed while human “masters” perform

functions machines can’t!

� Less downtime – predicts equipment failure, alerts

operators to problems

� Alerts operators to trends in water quality

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Dis-advantages of

automated analysis

• Electronic equipment can fail, redundancy is a really

good idea

• It has to be maintained, someone has to be able to fix it

• Initial costs can be somewhat high

• Can lead to deteriorating skills - you still need to run

the system without it!

• Contracting for regular outside service may be

necessary

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Common Process Parameters

pH

Turbidity

Particle Counters

Streaming Current Monitor

Free Chlorine

Total Chlorine / Monochloramine / Free Ammonia

----------------------------------------------------------------------

Ozone

Chloride Dioxide

Alkalinity

Fluoride

Conductivity

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Applications in the System

LEGENDTurbidity

Ozone

Chlorine

StreamingPotential

pH

Particle Counting

PlantIntake

Ozone Contactors (Pre-Chlorination)

Filter Wastewater Backwash

FlocculationBasin

Flash Mixers

Filter Beds

Settling Basin

House

WaterTower

ClearWell

Chlorine Addition

BoosterStation

To Distribution System

(Ammonia Addition)

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pH monitoring

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Difference between

conventional and differential

pH electrodes

Differential probes on top

Combination probes on bottom

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METER

Ion Sensing

Half-Cell

Reference

Half-Cell

Ag/AgCl

Wire

Internal Filling

SolutionReference

Electrolyte

Salt Bridge

JunctionWhen the junction clogs the probe won’t function

Differential pH Measurement

Better grounding and replaceable junction and solution

Protects the internal junction

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“Inside” Differential pH

Sensor

Salt Bridge

Ground Rod

Reference ElectrodeReference Solution Chamber

Measuring Electrode

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Types of Mountings

Union Mount

Flow-thru Mount

Insertion Mount

Immersion Mount

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What is wrong with this install?

Union

Mount

One of my favorite mounts

Spin lock ring

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Why should you not use this

mount?

Threaded flow

through mount

Is the most

common

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Flow cell mount for pH

Why is this a good way?

What is the 30 second rule?

pH

probe

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What is

wrong with

this pH

mount?

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Insertion

pH

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Immersion Mount

Handrail Mounting

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Unique immersion mount

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Questions on pH??

Turbidity is next

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What is Turbidity?

• Turbidity is:

1) The measure of light scattered by suspended particles

2) A qualitative physical property measured photometrically

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What is Turbidity?

A measure of suspended solids

A measure of relative water clarity

An indicator of water quality

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What is Turbidity?

Turbidity is made up of particles not in true solution

& could include:

1) Silt

2) Clay

3) Algae & Other Microorganisms

4) Organic Matter (pulp in fruit juices)

5) Other Minute Particles

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What is NOT Turbidity?

• Turbidity is NOT:

1) Able to identify the type of particles

2) A chemical property

3) A spectrophotometric type of analysis

4) A direct measure of total suspended

solids (TSS)

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Why Turbidity is Important

Turbidity measurements are one of the

most critical tools we have in recognizing

changes in raw water quality, detecting

problems in coagulation and

sedimentation, and troubleshooting

filtration problems.

The instruments work really well

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Applications

• >10 NTU Applications

Raw Water

Settled Water??

Filter Backwash Water

• <10NTU Applications

Settled Water

Filtered Water

Combined Filter Effluent

Finished Water

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Choose the Right Turbidimeter for

the Application - examples

• >10 NTU Applications

Surface Scatter High Range Turbidimeter

Probe type Turbidimeter

• <10NTU Applications

1720E Low Range Turbidimeter

Ultra Turb sc

• <0.1 NTU

FilterTrak 660 Laser Nephelometer

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Surface Scatter High Range

Turbidimeter0-9,999 NTU Range

Non-fouling optical design-low maintenance – optics never touch the sample

Tungsten Light Source

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Here is a photo of the next type of turbidimeter

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Range:

0.001 - 4000 NTU;

Color-independent measurements

Self-cleaning sensor prevents erroneous values

Why would pick this type instead of a surface

scatter type?

Probe type Turbidity Sensors

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Insertion type turbidity probe

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1720E Low Range

TurbidimeterRange 0.001 – 100 NTU

EPA Method 180.1 for regulatory reporting

Bubble removal system

What is wrong

with the drains?

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Laser Nephelometer

FilterTrak 660

0.000 to 5,000 mNTU = 0 to 5.0 NTU

note = 1,000 mNTU = 1.000 NTU

660 nm Laser Light Source

sub-micron sensitivity

0.005 NTU detection

Detects a 0.3 mNTU or 0.0003 NTU change

Tracks nicely with particle counters

The output reading is in mNTU

EPA approved Method 10133

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Particle Counters

It sizes and counts

particles 2 to 750

microns

Filter removal %

Plant removal %

Predicts early filter breakthroughTulsa alum feed Turbs flat line PC got jumpy

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Streaming Current Monitor

Measures the charge that exists

on small, suspended particles in

liquid.

A streaming current meter is the

only online instrument that can be

used to measure coagulated

particle stability for the feedback

control of coagulant dosage.

Batesville and Russell Key is where you sample

Chlorine Residual

�Two Types of Chlorine Residual:� Free Residual Chlorine

� Molecular Chlorine (Cl2), Hypochlorous Acid (HOCl), and Hypochlorite ion (OCl-).

� Combined Residual Chlorine

� Chlorine-Ammonia containing compounds; such as Monochloramine, Dichloramine, and Trichloramine.

�Total Chlorine:� Free Residual + Combined Residual

�Both types of residuals act as disinfectants, but differ in their ability to produce a germ-free water

supply during the same contact time

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Online Chlorine Monitoring –

Major Technologies

Colorimetric:

measuring intensity of color developed

by reaction of chlorine with indicator

DPD . The deeper color, the higher

chlorine concentration. Beers Law

chemistry.

Main Differentiators:

• Independent of major sample

parameters (pH, flow, temperature,

hardness),

• Established calibration curve

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Online Chlorine Monitoring –

Major Technologies

Amperometric:

measuring electrical current

generated in a circuitry by reaction of

chlorine with electrodes The larger

current value, the higher chlorine

concentration.

Main Differentiators:

• No chemical reagents required

• Fast response to analyte

concentration changes

Online Chlorine Monitoring –

Technologies Comparison

Colorimetric Amperometric

Pros

• Accuracy (no calibration required)

• Unattended operation (up to 30 days)

• Predictable and simple maintenance

• Results independent of changes in

sample pH, temperature, Cl2concentration, etc.

Pros

• Fast response to changes in Cl2concentration

• Reagentless technology

• No waste stream

Cons

• Reagents and waste stream

management

Cons

• Greater interference from sample pH,

temperature, flow, pressure, Cl2concentration, etc.

Colorimetric Chlorine

Analyzer -

it automates the lab method

Colorimeter

Pump

Module

KeypadWiring

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CL17 CHLORINE ANALYZERSAMPLE INLET SAMPLE VALVE

UNDER

PRESSURE

LIGHT SOURCE TO WASTE

DETECTORGLASS CELL

MAGNETIC STIRRERPINCHERS

INDICATOR

BUFFER SOLUTION

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CL17 Operation

Sample line

closed.

Reagents

dispensed

through

middle

tubes.

Process Chlorine -

Amperometric

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Online Chlorine Monitoring –

Case Study Setup

Controller

(sc200)

Grab sample

portChlorine

sensor

Optional

pH sensor

Sample

pressure

control kit

Digital controller – local data logging function

Optional pH sensor – additional information about the sample

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Calibration/Verification

Strategies - Chlorine

CL17 Chlorine Analyzer

– Calibration not recommended (by

Hach)

– Verification with lab DPD analysis

– What is an acceptable % variation?

Amperometric Chlorine

– Calibration and Verification vs grab

sample

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Which one costs more to operate?

Purchase cost

Reagent Cost vs Probe

Replacement Cost

Time to calibrate an maintain

Which one would I purchase?

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Calibration/Verification

Strategies - Turbidity

User-Prepared Standards

– Dilution water & 20 NTU Formazin

StablCal Standards

– 20 or 800 NTU Standard Solution

Comparison with Lab Reading

– not recommended (Hach)

Calibration

VerificationComparison with Lab Reading

ICE-PIC

How do you set the zero point for turbidity?

pH Calibration

Calibrate lab pH meters daily using two or

three buffer solutions.

How often should I calibrate my process pH

electrodes?

4.0 7.0 10.

0

Calibration

A calibration curve allows the meter to

convert a measured millivolt potential into a

pH reading.

pH

mV

pH Calibration

The optimal slope for pH is -

58±±±±3 mV/decade.

Calibration

mV

pH

0

+180

-180

4 7 10

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How often should I verify my

process pH electrodes?

What is an acceptable +/- %

10%??

Lets say my process pH probe says 7.25 and I verify

it with my lab unit and it reads 7.51. Is that ok?

One point process cal

When and why?

If you have a done a good 2 point cal in

the last month or so.

If you are not more than .5 pH units away

This is a quick way to bump up or down

the pH value to match your lab unit.

Leave the probe in the process

Troubleshooting

Offset:

mV reading in pH 7 buffer

– Should read 0 ± 30 mV in pH 7 buffer

Slope

– Optimal slope is -58 ± 3 mV/decade

– Can be lower and still work fine

Response time

– May require cleaning if slow in buffered solution

Cleaning / Reconditioning

Slow response may indicate need for cleaning

Warm water soap and tooth brush

Alternate soaking in dilute hydrochloric acid

and dilute sodium hydroxide 1 minute ea?

Phosphoric Acid, Acetone, Lime away

– Rinse with deionized water

– Condition in pH 7 buffer before use

– Store in pH storage solution

Helpful Hints

Use other buffers as a check – 8.3, 6.0 – phenol.

Triple sample +/- .01

Time to stability during cal and during sample

In and out of like solutions

Stir

More than one unit – pick the “Boss”

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Data Interpretation

One must learn to trust instruments

– Select the right instrument for the right job

– Install it correctly and at the proper location

– The instruments must be maintained and

calibrated regularly

– Periodically, proper function of the

instruments must be verified

– Always ask yourself – do the values seem

reasonable?

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Data Management &

Data Interpretation

Field Data

Plant Lab Data

Commercial Lab Data

SCADA Data

Etc.

You need to be able to easily do what is on the following slides

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Combine Data from

Field, Lab and Operations

Enable easy access to cross-functional data

Configure graphs for trend analysis, correlations, and control charting

Compare various sets of data to identify cost reduction opportunities

Example:

Raw Turbidity

Daily Avg,

Daily Min,

Daily Max

Gather and Organize Data for

Immediate Access and Analysis

Manual Data Entry:

• If manual data entry is necessary,

enter it directly into software

thereby eliminating multiple-

transcriptions Automated Data Entry:

• Download data directly

from instruments

• SCADA / HMI / Historians

• Dataloggers

• LIMS

• Commercial Lab Reports

• Other Third Party Software

Leverage Tools for Auto-

Report GenerationExample Discharge

Monitoring Report

Example Turbidity

Report

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Monitor On-Going Performance

Visual management provides easy sustained monitoring

– Customize dashboards for different levels of the organization

– Enable quick retrieval of reports, graphs, and entry forms

– Make review of data & information part of every day culture

Summary

Importance of Sampling

Accuracy & Precision

Calibration and Verification

Chose the right analyzer/mount for the job

Data Management systems

Develop Baseline data

.

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Thank You!

Kevin Menning

Technical Sales Specialist – HI, CA, OR, WA

kmenning@hach.com

970-227-2164