Post on 26-Jul-2020
transcript
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