Monitoring and mitigating pesticides in water: a collaborative approach
Why, what and how
Dr Jo Clint Catchment Projects Manager Outline
• Introduction
• Monitoring
• Mitigating
• Conclusion
2 Thames Water Supply drinking water Provide sewerage services - 2.6 billion litres per day - 4.4 billion litres per day - 9 million drinking water - 15 million sewerage customers customers
3 Thames Water
Drinking Water Quality - Ensuring tap water is wholesome and compliant
Catchment Control Team - Understanding risks to water quality - Where risks come from - How they can be mitigated
Working with our neighbours - Overlapping areas of interest and work - Thames Catchment Management Steering Group (TCMSG)
4 Monitoring Why we monitor Health Wholesomeness • Drinking water standards Regulatory • Every treated water sample 0.1µg/l • Understanding the risks we need to mitigate • What’s typically in raw water that cannot be in treated water
• Drinking Water Safety Plans • From source to tap • Identifies and assesses risks to drinking water quality • Mitigation if required.
5 What we monitor Monitoring
• Pesticide risk assessment
6 What we monitor Monitoring
• Pesticide risk assessment
• Monitor for pesticides • Used in catchment • Likely to reach water sources • Likely to reach abstraction points • Difficult to remove
7 What we monitor Monitoring
• Pesticide risk assessment
• Monitor for pesticides • Used in catchment • Likely to reach water sources • Likely to reach abstraction points • Difficult to remove
8 What we monitor Monitoring
• Pesticide risk assessment
• Monitor for pesticides • Used in catchment • Likely to reach water sources Reservoir concentration • Likely to reach abstraction points • Difficult to remove
9 What we monitor Monitoring
• Pesticide risk assessment
• Monitor for pesticides • Used in catchment • Likely to reach water sources • Likely to reach abstraction points • Difficult to remove
10 Stages of water treatment and pesticide removal Example WTW (not at WTW have all/same stages of treatment)
Breaks down Removes Adsorbs Oxidises most some most a few pesticides pesticides pesticides pesticides
11 Pesticides: ease of removal Not all pesticides are equal (and neither are all WTW!)
Metaldehyde UV or RO • e.g. metaldehyde –
Hard a happy, stable molecule Quinmerac Metazachlor Fresh GAC Clopyralid Carbetamide Propyzamide Ozone / Mecoprop GAC / MCPA Slow sand filters Flufenacet Ease removal of Glyphosate Chlorination Bentazone Easy
12 What we monitor Monitoring
• Pesticide risk assessment
• Monitor for pesticides • Used in catchment • Likely to reach water sources • Likely to reach abstraction points • Difficult to remove Catchment: 11,000km 2 • Risk based approach River length: 4,000km
13 How we monitor Monitoring
• Grab samples • Pros and cons
• Frequency • Statutory • Enhanced – time of use
• Locations • Abstraction points • Water treatment stages • Upstream catchment
14 How we monitor Monitoring
• Grab samples • Pros and cons
• Frequency • Statutory • Enhanced – time of use
• Locations • Abstraction points • Water treatment stages • Upstream catchment
15 Collaboration in monitoring Monitoring
• Thames Catchment Management Steering Group
• Collective research Comparison • Common interests 0.14 TWGrab samples sample Enborne at 0.12 Shalford Bridge • Cooperative sampling ChemcatcherPassive Shalford sampler 0.10 Bridge • Combined datasets 0.08
0.06
0.04
Metaldehyde (µg/l) Metaldehyde 0.02
0.00 Jul-2016 Oct-2016 Feb-2017 Jun-2017
16 Collaboration in monitoring Monitoring
• Thames Catchment Management Steering Group • Collective research • Common interests • Cooperative sampling • Combined datasets
17 Collaboration in monitoring Monitoring
• Thames Catchment Management Steering Group • Collective research • Common interests • Cooperative sampling • Combined datasets
18 Collaboration in monitoring Monitoring
• Thames Catchment Management Steering Group • Collective research • Common interests • Cooperative sampling • Combined datasets
19 Why we mitigate Mitigation
• We have to meet the drinking water standard • Historically, engineering solutions were the obvious answer • Expectations have changed
• Prevention vs cure • Mitigate at source • Sustainable • Holistic • “Because it’s the right thing to do”
20 What we mitigate Mitigation
• Pesticides most at risk of failure • Frequently found in raw water at abstraction points at concentrations that could challenge treatment • Deteriorating trends • Hard to remove
21 What we mitigate Mitigation
• Pesticides most at risk of failure • Frequently found in raw water at abstraction points at concentrations that could challenge treatment • Deteriorating trends • Hard to remove
22 How we mitigate Mitigation • Catchment management • Working with farmers to reduce the amount of metaldehyde reaching watercourses • Information about the issue • Encouraging Integrated Pest Management, including cultural controls • Education about alternative options • Incentivisation • Product substitution • Payment for ecosystem services
Voluntary approach
23 Collaborative mitigation Mitigation
• Thames Catchment Management Steering Group • Agreed areas of responsibility • Sharing lessons learned
24 Collaborative mitigation
25 Conclusion
• Monitoring: • essential, but we have to take a risk-based approach.
• Collaboration: • efficiencies for all companies involved.
• Mitigation: • work in progress, • catchment management remains the preferred approach
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