Applied Hydrobiology Sources and types of pollution
Water pollution:-Holdgate (1971) defined pollution as
something that is present in the wrong place, wrong time and wrong quantity.
The legal definition of water pollution-Pollution arises by the addition of something to water that changes its natural qualities (Wisdom 1956)
Complete definitionThe introduction by man into the
environment of substances or energy, liable to cause hazards to human health, harm to living sources and ecological systems, damage to structure and amenity or interference with the legitimate use of the environment Holdgate 1979).
What are pollutants?Acids and AlkalisAnions (e.g sulphides, sulphites, cyanide)DetergentsDomestic sewage and farm manuresFood processing wastes (including farm
processes)Gases (chlorine and ammonia)Heat
What are pollutants?MetalsNutrients (phosphates and nitrates)Oil and oil dispersants) Organic toxic wastes (phenols and
formaldehyde)PathogensPesticidesPolychlorinated biphenylsRadionuclides
Acute-large dose short durationChronic-small dose over long period
General effects
Diffuse source
Sources of pollutionPoint sourcesWaste water or effluent is discharged into
water sources at a particular point.e.g. sewage through a pipeMost effluents are point sources
Three types of sewerage systemFoul sewersSurface water or storm sewersCombined systems
Some industries treat their own waste but have to meet consent criteria, that depend on what the effluent is being discharged into
Standards30/20 sewage effluent should contain no
more than 30mg l-1 suspended solids and BOD should have a value not exceeding 20 mg l-1
In trout and salmon rivers this reduced to 15/10
Ammonia is set at 5 mg l-1 or 1 mg l-1 depending on the receiving water
Oxygen and WaterWhat else can affect the amount of O2 in
the water?TemperatureSpeed of water flowRoughness of surface over which water flows
More Examples: Oxygen and WaterBiochemical Oxygen Demand – What does
this mean?Anything in the water that bacteria can
break down. Bacteria will use up oxygen in the waterOther aerobic organisms will die
Sources of pollutionDiffuse sourcesThe hardest to combat. Water run off from
agricultural land, the hydrological cycle is contaminated in a diffuse way
PollutantsInert suspensionsMineral particulateSuspension of minerals in the waterComes usually from mining quarryingChanges the state of the river bed which in
turn changes aquatic habitats
Poisons and toxins
Acids and alkalis usual range pH 6-8Associated with industry and acid rainToxicity of ammonia, cyanide and some heavy
metals can increase at lower pH
When the pH drops below 6.0 species start to die off.When one species dies, others that depend on it may as well
Acid Rain Effects – Aquatic Systems
Heavy metals
Mining, quarrying, natural disturbanceZinc, copper, lead, cadmium, mercury,
chromium, nickel and aluminium
Organic chemical residues
Used in the manufacture of pesticidesInclude-organochlorides, organophosphates,
pyrethroids, phenols, herbicides, polychlorinated biphenyls (PCBs)
The Environment Agency has a red listMany endocrine disrupters
GasesAmmoniaMethaneReleased by anaerobic breakdownAmmonia very toxic to fish
Inorganic reducing agentsSulphides, sulphates, ferric compounds
Increase oxygen demand exerted on the water
Biodegradable organic matterPlant and animal originIncreases BOD
Inorganic materialsNitrates, phosphatesStimulate primary productivityAlgal blooms
Oils
Usually accidental spillageQuarter of incidents occur in fresh waterImpose high BOD
DetergentsSyntheticFoamingSome similar effects as oil
HeatPower stations use water for coolingStimulates biolgical processes
Biological agentsChemicals that affect biological systemsCarcinogens, radioactive chemicals
Tame surveySurvey of the chemical and biological effects
of pollution on a river