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