Design and delivery of sampling programmes
Download
1 / 24

- PowerPoint PPT Presentation


  • 136 Views
  • Updated On :

DESIGN AND DELIVERY OF SAMPLING PROGRAMMES. Meteau 2008 Lisbon Malcolm Morgan Drinking Water Inspectorate. Key Issues.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about '' - philippa


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
Design and delivery of sampling programmes l.jpg
DESIGN AND DELIVERY OF SAMPLING PROGRAMMES

Meteau 2008

Lisbon

Malcolm Morgan

Drinking Water Inspectorate


Key issues l.jpg
Key Issues

  • The success of any survey, monitoring programme or investigation involving sampling and analysis is totally dependent on the quality of design and delivery of the sampling programme

    • What samples to take

    • When to take them

    • How to take them

    • Who will take them

    • How to measure success of delivery


Overall design l.jpg
Overall Design

  • Where and when should samples be taken

    • Points in system

    • Geographical and temporal distribution

    • Number of samples

    • Programme period


Factors affecting overall design l.jpg
Factors Affecting Overall Design

  • Accessibility of sampling points

  • Sampling methodology

  • Who will take the samples

  • Sample transport logistics

  • Sample preservation and storage

  • Analytical capability

  • Laboratory constraints

  • Uncertainty of analysis

  • Uncertainty of sampling

  • QA/QC for sampling


Sampling points l.jpg
Sampling points

  • Plumbing metals do not only arise from plumbing

    • Source water

    • Distribution

    • (Contamination during sampling and storage)

    • (Contamination during analysis)

  • Factors affecting metals pick up from plumbing

    • Water quality

    • Type of plumbing

    • Contact time (stagnation time)


Sampling points6 l.jpg
Sampling points

  • At the tap

    • Normal drinking water tap

    • Stagnation sample

      • How long?

    • Flushed sample

      • Metals from other sources



How to sample l.jpg
How to Sample

  • Fixed stagnation time

    • 30 minutes

    • 4 hours

    • 8 hours

    • 12 hours

    • 16 hours

  • Short stagnation

    • Exact time critical

    • Must use trained samplers

    • High precision needed at low concentrations

    • Relatively high distortion from sampling errors

  • Long stagnation

    • Exact time less critical

    • Disruption for householder

    • Possible to use householder to sample


How to sample9 l.jpg
How to sample

  • Randomstagnationtime

    • Easy to programme

    • Minimum disruption for householder

    • Can use trained samplers

    • Good for checking compliance with a standard

    • Difficult to assess changes in uptake due to treatment changes etc


When to sample l.jpg
When to Sample

  • Time of year

    • Seasonal variations

  • Time of day

    • Diurnal variations

    • Practical considerations


Who takes the sample l.jpg
Who Takes the Sample

  • Dedicated sampler

    • Trained

    • Experienced

    • Reliable

    • Work easily audited

  • Occasional sampler

    • Not main job, may not give high priority

    • May be trained

    • May not be experienced

    • May not be reliable

    • Work less easily audited


Who takes the sample12 l.jpg
Who Takes the Sample

  • Ad hoc sampler (eg householder)

    • Poorly trained

    • May not be reliable

    • Will not be experienced

    • Not easily audited

    • Extra H & S implications

    • Could influence choice of sampling points


How do we measure success l.jpg
How do we measure success?

  • What is success

  • Why measure success

  • What to measure

  • How do we measure

    • Qualitative

    • Quantitiative

  • What do we do with the results


What is success l.jpg
What is success

  • All samples:

    • Taken from the right place

    • At the right time

    • In the right way

    • Delivered to the laboratory

      • On time

      • In perfect condition


Or more realistically l.jpg
Or more realistically

  • Pre-defined percentage of samples

    • Taken according to schedule

    • By appropriately trained samplers

    • Acceptably small deviation from procedure

    • Delivered safely to laboratory

  • Quality control programme

    • Delivered in full

    • Satisfactory results


Qualitative measures l.jpg
Qualitative measures

  • Internal Audit:

    • Sampling procedures

    • Sampler training

    • Sampling practice

    • Sample preservation, handling and transport

    • Exception reports

      • actions


Quantitative measures l.jpg
Quantitative measures

  • Quality control samples

    • Trip blanks

    • Spiked samples/standards

    • Duplicate samples

    • Reagent blanks/Bottle blanks/Procedural blanks

  • Control charts

    • Statistical control

    • Action records


What do we do with the results l.jpg
What do we do with the results

  • Qualitative

    • Review to learn lessons for future work

    • Calculate confidence in quality of sampling

      • X% of sampling events subject to error

      • Can sub-divide into types of error


What do we do with the results19 l.jpg
What do we do with the results?

  • Quantitative

    • Estimate of uncertainty of sampling

    • Identify unsuspected sources of error

      • Training issues

      • Process issues

      • Contamination/deterioration

    • Initiate immediate corrective action


Standards for sampling l.jpg
Standards for sampling

  • ISO 5667 Series:

    • Design

    • Procedures for taking different types of sample

    • Sample preservation

    • QA & QC for sampling


Bs8550 a new draft standard for auditing water sampling l.jpg
BS8550 A new draft Standard for auditing water sampling

  • Concentrates on qualitative aspects

  • Should have wider applicability

  • Wide consultation on initial draft

    • Regulators

    • Accrediting body

    • Sampling organisations

  • Road tested


Bs 8550 next steps l.jpg
BS 8550 Next Steps

  • Public consultation

    • Includes workshop in March 2009

  • Revision and publication

  • Bring to ISO for consideration as basis of an International Standard


Summary l.jpg
Summary

  • The design and size of a sampling programme determines what use can be made of the data generated

  • The quality of delivery of the sampling programme is critical to the quality of the data generated


Final thoughts l.jpg
Final thoughts

  • The uncertainty of analysis is typically up to 20%

  • In a well controlled sampling programme the uncertainty of sampling is typically 20-50%

    • Can be several hundred percent in some programmes

    • All bets are off if sampling quality is not controlled


ad