environmental assessment and sustainability civ913 chemical assessment of river water quality
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Environmental Assessment and Sustainability CIV913
CHEMICAL ASSESSMENT
of
RIVER WATER QUALITY
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CHEMICAL ASSESSMENT
Monitoring the State of the Freshwater Environment• Provides a sound scientific understanding of present.• Understanding of how conditions are changing.
Hence:• Facilitates environmental management through:
– Basis for assessing priorities for action.• Objectives and standards.
– Charts progress against plans and targets.
• Provides information for the public and interested groups.
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CHEMICAL ASSESSMENT
• Environment Agency (EA)– River Quality Objectives (RQO)– General Quality Assessment (GQA)
• Chemical
• Biological
– Statutory Water Quality Objectives (SWQO)– Local Environmental Agency Plan (LEAP)
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CHEMICAL ASSESSMENT
• Statutory Standards– Environmental Quality Standards (EQS)
• Non-Statutory Standards.– Environmental Quality Objectives (EQO)– River Classification Schemes
• eg GQA.
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CHEMICAL ASSESSMENT
Statutory Standards.• International and National
– Dangerous Substances Directive 76/464/EEC **• List I and List II substances • UK Interpretation of List II• UK National Network Sites
– Freshwater Fish Directive 78/659/EEC *• Rivers and canals• Salmonid Waters (salmon and trout)• Cyprinid Waters (roach, bream, chub)
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CHEMICAL ASSESSMENT
Statutory Standards.
• Directive on the Quality of Surface water Abstracted for Potable Supply 75/440/EEC– Applies to designated sites.– Mandatory limits for 21 substances
• eg 95 percentile NO3 limit of 50 mg/l *
– Guideline values for 31 substances.
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CHEMICAL ASSESSMENT
River Classification:• Non-statutory. Used for planning and trend analysis.• Chemical, biological, nutrients and aesthetics• UK currently has chemical and biological.
– Chemical parameters expressed as percentiles:• Dissolved Oxygen (DO). 10 percentile.• BOD (Inhibited). 90 percentile.• Total ammonia. 90 percentile.
– 6 Grades of chemical quality *
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CHEMICAL ASSESSMENT
Sampling.• Time based. Concentration versus time.
– Exposure of fish to pollutant• Volume based. Load versus flow.
– Impact of a discharge on the river quality.• Approaches identical when flow is constant.• UK Water Industry almost exclusively TIME BASED.
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CHEMICAL ASSESSMENT
Sampling• Grab Sampling (Snap or Spot).
– Instantaneous behaviour– Used for judging compliance with percentile or
maximum type standards.– Suffers when there are extremes of quality– Most common form for routine monitoring and
classification in UK.
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CHEMICAL ASSESSMENT
Sampling• Composite Sampling (Flow related)
– Representative measure of a continuous process.– Low resource requirements– Gives average concentrations or loads.– Used increasingly for factory compliance
monitoring.
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CHEMICAL ASSESSMENT
Statistical Approach
(Avoid data-rich/Information poor)• Sampling error (Uncertainty)• Confidence Levels and Intervals
– Important in compliance monitoring.– Higher confidence levels have wider intervals– More samples reduce the interval at a given level
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CHEMICAL ASSESSMENT
Statistical Approach
(Avoid data-rich/Information poor)• Parametric and non-parametric methods.
– Parametric allows fewer samples eg 12 pa
– UK River Classification assumes: *• Normal distribution for DO
• Log-normal distribution for BOD and NH4
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CHEMICAL ASSESSMENT
Sampling Programmes.
• Restricted sampling windows eg 09.00 to 16.00 hrs• Relative and absolute objectives.
– eg trend detection (relative)– eg what is mean nitrate level for water intake in a
given river (absolute)
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CHEMICAL ASSESSMENT
Sampling Location.• Divide river into stretches with defined beginnings
and endings eg– major outfalls, major tributaries.– each stretch approximately 10Km (UK)
• One sampling point per stretch– accessible– not too close to local effects eg weirs, plumes,
outfalls.
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CHEMICAL ASSESSMENT
Sampling Locations.
• Measure DO on-site.
• Store sample at< 5’C and send for analysis
• Transport time.
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CHEMICAL ASSESSMENT
Monitoring for Dangerous Chemicals in the UK
List I : Surface waters downstream of Point Sources.
• All plants liable to handle and discharge
• All sewage treatment works with these substances
• Mainly cadmium, mercury and HCH (hexachlorocyclohexane, known as lindane)
• HCH from imported wool, treatment of seeds and domestic wood preservative.
• Cd failures mainly from minewaters.
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CHEMICAL ASSESSMENT
Monitoring for Dangerous Substances in the UK
List II Substances• Failures mainly copper, zinc and pH.
– Main sources, industrial, domestic, mine drainage, contaminated land leachate.
• Zinc and pH.– China clay, contaminated land, point sources.
• Most pesticide discharges are diffuse.
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CHEMICAL ASSESSMENT
Monitoring Chemicals for Freshwater Fish
• DO, BOD, pH, ammonia, zinc, copper, and temperature.
• Domestic and industrial discharges, and drought main causes of failure
• River Ecosystem classification– RE1 - RE5
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CHEMICAL ASSESSMENT
Monitoring for Water Abstraction.• Dissolved hydrocarbons, colour, copper, dissolved
iron, nitrate and polycyclic aromatic hydrocarbons (PAH) main causes of failure.
• Hydrocarbon, colour and iron mainly from natural sources.
• Nitrate limit 50mg/l. – 68 Nitrate Vulnerable Zones. (Arable farming)– Control agricultural practice– Nitrogen limits on STWs >10,000pe.
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Advantages and Disadvantages of Chemical Methods
Advantages
• Quantitative
• Easy to sample
• Analysis easy
(getting easier)
Disadvantages
• Indirect– interpretation required
• Usually discontinuous
• you only find what you are looking for