subgroup on the lowermoor water pollution meeting
TRANSCRIPT
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Consultation Meeting
Subgroup on the Lowermoor Water Pollution Meeting
INTRODUCTION
Frank Woods
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PROGRAMME (I) - Presentations
• Introduction• Water quality modelling • Health effects reported• Population studies • Information on contaminants• Final comments
We want to hear from YOU
PROGRAMME (II)
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WATER QUALITY MODELLING
Malcolm BrandtJames Powell
Black & Veatch Ltd
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System OverviewCrowdy Reservoir
Aluminium Sulphate(normally added in small quantity prior to settlement tank)
Settlement tank
LowermoorTreatment Works
Sand Filter
Contact Tank(Disinfection)
Storage Reservoir
Distribution Network
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Modelling Objectives
1. Investigate the extent of mixing (dilution) of the alum within the treatment works
2. Predict the peak concentration of alum in the water leaving the works
3. Simulate the spread of the alum through the network (trunk mains only)
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Approach
CFD model of contact tank
CFD = Computational fluid dynamics
• Models 3 dimensional fluid flow
• Widely used in engineeringe.g. design of aeroplanes, yachts, Formula one…..
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Approach
CFD model of contact tank
CFD model of storage reservoir
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Approach
CFD model of contact tank
CFD model of storage reservoir
Trunk main network model
• Tracks the slug of contaminated water through the pipes
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Contact tankLayout
Out
In62L/s
Alum 56,000mg/L6.8L/s
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Contact tankLayout
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Contact tankLayout
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Contact tankSimulation of Alum discharge
4300
3200
2100
1000
Concentration(mg/L Al)
0
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Contact tankPoints of Note
• Sinks to bottom and spreads
• Holes in wall cause most mixing
• Concentration at outlet falls rapidly after discharge ends
Outlet
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Approach
CFD model of contact tank
CFD model of storage reservoir
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Storage reservoirLayout
In
Out
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Storage reservoirSimulation of Alum
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Storage reservoirPredicted Outlet Concentration
• Peak entering network = 325 mg/L Al
• Corresponding acidity
0
75
150
225
300
375
0 6 12 18 24Time (hr)
Con
cent
ratio
n (m
g/L
Al)
0%
20%
40%
60%
80%
100%
% R
emai
ning
in ta
nkConcentration % Remaining in tank
6 July 8:40pm
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Storage reservoirPredicted Outlet Concentration
• 60% still in tanks after 6hr (6 July 11:00pm)
• 25% still in tanks after 12hr (7 July 5:00am)
0
75
150
225
300
375
0 6 12 18 24Time (hr)
Con
cent
ratio
n (m
g/L
Al)
0%
20%
40%
60%
80%
100%
% R
emai
ning
in ta
nk
Concentration % Remaining in tank
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Approach
CFD model of contact tank
CFD model of storage reservoir
Trunk main network model
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CAMELFORD
Tintagel
Boscastle
Delabole
LowermoorWater Treatment
works
Port IsaacSouth West
Water Network
Network modelMap
• Trunk (spine) mains only
• Model ‘drags’ the concentration profile from the clear water tank through the network
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Network modelSt Teath and Helston
0
50
100
150
200
250
300
350
Wed 06 Jul00:00
Thu 07 Jul00:00
Fri 08 Jul00:00
Sat 09 Jul00:00
Sun 10 Jul00:00
Mon 11 Jul00:00
Con
cent
ratio
n (m
g/L
Al)
Off 9" Delabole to St Endellion (1) SWW samples Private samples
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Conclusions
• Simulation of mixing in the tanks has been used to predict the peak concentrations
56,000 mg/L Al
1500 mg/L Al
325 mg/L Al
Lower after reservoirs
Peak
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Conclusions
• The time that the slug of contaminated water arrived at different locations has been estimated
56,000 mg/L Al
1500 mg/L Al
325 mg/L Al
Lower
6 July 5:00pm
Peak at
6 July 5:40pm
6 July 8:40pmDelabole Res In7 July 0:00am
St Endelion Res In8 July 6:00am
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Conclusions
• The slug of contaminated water will get delayed and maybe diluted in:– Reservoirs– Local mains– Consumer plumbing– Consumer tanks
56,000 mg/L Al
1500 mg/L Al
325 mg/L Al
Lower
6 July 5:00pm
Peak at
6 July 5:40pm
6 July 8:40pmDelabole Res In7 July 0:00am
St Endelion Res In8 July 6:00am
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POPULATION STUDIES
Lesley Rushton
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Population Studies
• Several studies have investigated the occurrence of various health problems including: – Symptoms immediately following the incident – Hospital treatment (hospital discharges)– Causes of death– Incidence of cancer/leukaemia
• Most of these studies have compared the population in the contaminated area with a population from another area
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Summary of Results
• Symptoms survey: More people in the contaminated area noticed changes in the water and reported symptoms.
• Hospital treatment rates increased slightly compared with other areas.
• Death and cancer rates are both lower than those of the whole of Cornwall.
• A study of Leukaemia cases in children showed a possible association with high rates of infection.
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Comments
• None of these studies are easy to carry out.
• None have good exposure data • Holiday makers were not included.• Information on other causes of the
diseases was often not available or not collected.
• In spite of these problems the results are generally reassuring.
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INFORMATION FROM INTERVIEWS
Anita Thomas
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Thank you
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General observations
Water quality and usage
Reported health effects in adults and children – acute and chronic
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Concerns about chronic effects
• Joints
• Memory, coordination and concentration
• Cancer
• Thyroid disease
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Nerves and brain
• Neuropsychological tests
• Study design
INFORMATION ON CONTAMINANTS
Kevin Chipman
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Hazard • What adverse effects may a chemical cause?
• How potent is it ?
Exposure • What was the dose ?
• For how long was exposure ?
Establish the likelihood of harm
Assessment of Risk
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• Information from human exposures
e.g. aluminium exposure from the use of antacid medication & kidney dialysis.
Look for evidence of harmful effects
Is there a dose that is SAFE (NO ADVERSE EFFECT) ?
• Effects in animals
What organs are affected by the chemicals ?
What is the dose that is SAFE ?
A. Short term exposure
B. Long term exposure
How Have We AssessedPotential for Harm ?
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Potential for Adverse Reactions to the Chemical Exposures at Lowermoor
What about the immediate effects of the short-term relatively high exposure?
• The chemicals probably caused some of the immediate effects.
• In particular, exposure to increased copper, zinc and sulphate (and the combinations) probably contributed to symptoms such as stomach ache and ulcers.
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What about the Possibility of Delayed or Persistent Harm to Health?
A focus on aluminium:
• Aluminium is hazardous• In particular in animals it can damage the brain, the liver,
kidney, bone and can affect the developing embryoBut!• If taken in drink, only small amounts reach the organs and
we clear it from the body quickly• The maximum SAFE dose for long term intake is close to
that in antacids. • The long term exposure was much lower than this safe dose • Delayed or persistent harm would not be expected
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Bottle-fed Children
• In babies, the dose may have been higher compared to adults
• Therefore the Subgroup considered that the risk (albeit unlikely) from aluminium and other metal exposures such as lead was greatest for bottle-fed infants.
• This explains why bottle–fed children have been highlighted as a group for which further studies have been recommended.
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Contaminants otherthan Aluminium
• Similar assessments were made for other metals (lead, copper, zinc, manganese, and iron as well as sulphate and acidity).
• We also considered possible combined effects of these contaminants
• These may have contributed to immediate effects on the intestine.
• Delayed or persistent effects from the exposures are unlikely.
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Particular areas given close attention
CANCER….. It is encouraging that the toxicology evidence on the contaminants generally did not give reason for concern about ability to cause cancers
ALZHEIMER’S disease……Although it has been considered in the past that aluminium may cause this disease, evidence now suggests that it is NOT a cause.
THYROID disease……There is no evidence to suggest that any of the contaminants concerned could have affected the thyroid
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Particular Gaps in Knowledge and the Need for Further Studies
• Neuropsychological studies (e.g. effects on
memory)
• Child development
• Joint problems
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FINAL COMMENTS
Frank Woods