Online Monitoring of Metaldehyde

Alice Elder, Affinity Water

Jeff Stubbs, Anatune Ltd.

Contents

• The challenge

• The solution

• The future implications

WTW Site Overview

• 36 Mld Treatment Works serving North London

• 4 groundwater sources• One on-site, 3 off-site (furthest being 7.5km away)

• Karstic geology• Heavily surface-influenced• Flashy

• Site is subject to a DWI Undertaking for metaldehyde• Treatment of individual and total pesticides• Online monitoring

Water Quality Challenges

On site

borehole

Remote

source 1

Remote

source 2

Remote

source 3Seasonal

Metaldehyde

(Max 4.55 ug/l)

Historic Aquifer

Pollution –

Metaldehyde

(Ave. 0.19 ug/l)

Historic Aquifer

Pollution –

Metaldehyde

(Ave. 0.07 ug/l)

Seasonal

Metaldehyde

(Max 0.29 ug/l)

Other pesticides Other pesticides

Turbidity

(>100 NTU)

Turbidity

(>10 NTU) (>30 NTU)

Turbidity

(>60 NTU)

Nitrate

(>70 mg/l)

Bromates

(~30 ug/l)

Source Metaldehyde Trends

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Existing Treatment

Membrane Ultra Filtration(Disinfection/Crypto removal)

Granular Activated Carbon Filters

Remote 2(8.73 Ml/d)

Remote 3(4.5 Ml/d)

Remote 1(9.09 Ml/d)

Onsite(9.09 Ml/d)

Clarifiers

Bromate Blending

Final Conditioning(Residual Disinfectant/Plumbsolvency)

Metaldehyde Blending

Abstraction management

Waste

Handling

Main Unresolved Issues:• Metaldehyde• Loss of output

More Challenges….

• Some current treatment methods struggle to remove some compounds

• Newer removal techniques more costly

• Treatment only needed when a trigger value exceeded

• Treatment being wasted if used when levels are low

• Need for a better ‘Control Philosophy’ for treatment management

• More measurements needed with quicker results turnaround

Importance of More Measurements

• 1 daily sample taken for lab (around 12pm in example above)

• Lab sample misses the spike in pesticide concentration overnight

• Monitoring every hour allows changes in levels to be observed

• Action can be taken on results immediately rather than wait for lab results

Potential Solution

• Increase sampling frequency (more per day?)

• Prioritise samples to get results quicker

Issues

• More transporting samples to lab

• Increased pressure on lab to turnaround

• Water has left WTW when results are obtained

• Hard to make decisions when issue has gone

• Not the most efficient use of time/money

Potential Solutions & Issues

✓ Allows monitoring at WTWs

✓ More data points to make better decisions

✓ Faster turnaround than taking samples to lab

Issues

× Sensitivity – some unable to detect below trigger levels

× Compound specific

× Comparison with lab results questionable

What About Current Online Instrumentation?

What Was Needed….

• Install instrumentation used in lab (proven, reliable, sensitive) at WTW• Automate sample preparation so whole workflow can be as unattended as

possible• Results as quickly as possible• Lab grade/UKAS accredited, comparable results• Similar sensitivity to lab performance• GC or LC platforms• Mass Spec/Diode Array/UV detection• Potential to link data to SCADA input and treatment control philosophy• Gives greatest degree of monitoring with best measurement performance• Saves wasting expensive treatment measures when not required

Online Monitor Solution -Instrumentation

Agilent 7890/7000C GC-QQQ (Analyser)

GERSTEL Dual Head Multipurpose Sampler (MPS) with SPE (Automated Sample Prep)

Flow Cell

Online Monitor Solution -The Cabin

System OverviewMonitoring KioskSite SCADA

Anatune

Instrument

Control SystemSampling & Filtration

waste

Source 1

Source 2

Source 3

Data

Results

Trending

Alarms / Events

Remote Control

Site

PLC

Validation Summary

15 footer

Aqua-Check 516 Result Aqua-Check 520 Result

516 A 0.1012 520 A 0.0795

516 B 0.1022 520 B 0.0823

516 C 0.1022 520 C 0.0737

516 D 0.1072 520 D 0.0795

516 E 0.1016 520 E 0.0759

516 F 0.1026 520 F 0.0791

Average Result (ppb) 0.1028 Average Result (ppb) 0.0781

Reported (ng/L) 102.8 Reported (ng/L) 78.1

Assigned Value (ng/L): 95.3 Assigned Value (ng/L): 77

Z_score (-2 to 2) 0.79 Z_score (-2 to 2) 0.17

Carried out = 21/11/2016 Carried out = 06/02/2017

Current Instrument Status

• Running since September 2016

• Real live data

• Running in low and high frequency modes

• Improvements on operator intervention frequency

• Data validation and transfer refinements to SCADA

• Results better than the lab!!

• Concept proven. Other compounds and different analysers being discussed for other problem sites

• ITT went out in January 2017

• Offer letter sent out in August 2017

• Contract still to be signed

• Design Specification to the tenderers• Metaldehyde• Turbidity• Aluminium

• Anatune online metaldehyde monitor was a critical component in developing designs

The Treatment Solution

Remote

Source 1

Remote

Source 2

Remote

Source 3

Onsite

Source

New pipe

route to site

Existing

pipe route

to site New

treatment

processes

The Solution - Sources

The Solution - Technologies

To GAC adsorbers

Four sources

Actiflo-

Turbo

Actiflo-

Carb

PAC

Dosing

New treatment

Remote

Source 1

Existing WTW

Anatune monitor

Feed forward control Feed back control

SCADA

Remote

Source 2

Remote

Source 3

Onsite

Source

The Solution – Control

• Implications for Affinity Water and PR19

• Implications for the industry

AMP6 AMP7 AMP8 Beyond…

The Future