Environmental Assessment and Sustainability CIV913

CHEMICAL ASSESSMENT

of

RIVER WATER QUALITY

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.

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)

CHEMICAL ASSESSMENT

• Statutory Standards– Environmental Quality Standards (EQS)

• Non-Statutory Standards.– Environmental Quality Objectives (EQO)– River Classification Schemes

• eg GQA.

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)

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.

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 *

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.

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.

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.

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

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

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)

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.

CHEMICAL ASSESSMENT

Sampling Locations.

• Measure DO on-site.

• Store sample at< 5’C and send for analysis

• Transport time.

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.

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.

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

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.

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