Inorganic & Organic Pollution

Organic Pollution

Inorganic Pollution

What is Organic Pollution?

The main types of organic waste are:• Sewage• Silage• Animal slurry: urine and faeces

washed off farmyards and fields• Food processing waste• Chippings from paper mills• Effluent from leather tanneries

Organic pollution is when human activity allows organic compounds to enter a water body which causes harm to the ecosystem

The leather tanneries in Morocco

Urine is used to treat the skins

slurry

These wastes are rich in organic compounds such as proteins, lipids and carbohydrates

These wastes are rich in organic compounds such as proteins, lipids and carbohydrates

Pollution SourcesThese organic wastes can be released from either point or diffuse sourcesThe two photos below show these different sources. Which is which?

• With the exception of plastics (e.g. in sewage) and some man-made chemicals, these wastes are largely biodegradable

• If this waste enters a water body, anaerobic decomposers such as bacteria and fungi will begin to break down the waste…..

Diffuse source Point source

Pollution across a large area

Pollution from a specific point

Manure and Silage

Manure and silage are two important organic pollutants

Manure is egested faeces and contains organic matter (e.g. indigested grass), as well as hormones, antibodies and heavy metals

Silage is grass which has been anaerobically digested by bacteria and which then can be used to feed livestock – it is stored in bags

Silage is rich in proteins, lipids and carbohydrates as well as phosphates

Why has the volume of silage increased?

intensive livestock farming has become more common

Why has the volume of silage increased?

intensive livestock farming has become more common

Manure and Silage

If either manure or silage enter water bodies then bacteria will rapidly feed on the wastes, reducing the O2 content.

What is producedIn this process?Ammonia

What is producedIn this process?Ammonia

Bacteria multiply

Oxygen removed

Organisms, e.g. fish, die

Organic matter decays

Manure or silage

sedimentation

Waste needs to be treated as for earlier sewage pollutionOr this can be avoided by collecting the flushings in ponds; both the water and the nutrients can then be recycled via irrigation water. Click HereClick Here

flash animation

Sewage Pollution

Sewage is a “mix of domestic and industrial waste in liquid form”But what is sewage comprised of?

SEWAGE

DEBRISe.g. plastics

DISSOLVED ORGANIC MATERIAL

e.g. bacteria, urine, soap

WATER (up to 99.9%!

DISSOLVED INORGANICMATERIAL e.g. N, P

PARTICULATE ORGANIC WASTE e.g. food, goldfish

Sewage Pollution

• In the developed world, the quantity of raw sewage output is approximate 150-200 gallons per person per day (600-800 litres).

• Raw sewage may also contain variable amounts of pesticides, heavy metals and other toxic compounds because people pour unused portions of products down sinks

Problems of Sewage

DISEASES

CHOLERA

SALMONELLA

E. Coli

POLIOHEPATITIS A

• These diseases are common in LDCs due to lack of water treatment

TYPHOID FEVER

Contains pathogens-organisms (e.g.microbes) capable of causing disease

Can you name some of the diseases that might be carried by sewage?

Sewage Treatment

1. ScreeningScreen removes large materials e.g. paper/ vegetable cuttings

2. Initial sedimentationCoarse solids e.g. grit settle out

Some OM may flocculate (clump together) and also settle

The sediment - primary sludge - may be allowed to accumulate in thesedimentation tank for weeks to allow some microbial breakdown of the OM

The supernatant – unpleasant smelling turbid liquid is passed on at intervals into either a trickling filter bed or an activated sludge treatment tank

Sewage Treatment

3a. Trickling filter bed is made of graded stones, grit and clinker covered with bacteria, fungi and protozoa

As the effluent trickles slowly over the bed the fauna digest the OM and in turn other organisms e.g. predatory protozoa, nematodes and insect larvae eat these microorganisms

By the time the effluent drains from the bottom of the bed, most OM has been degraded to mineral salts

3b Activated sludge treatment An additional starter culture of microorganisms are added, speeding up and increasing the effectiveness of the processStirring/aeration increase O2 levels to stimulate respirationAfter several hours the biochemical oxygen demand (BOD) by 90%

Sewage Treatment

3.Secondary sedimentationThe solids and microorganisms are allowed to settle

4. Tertiary treatmentInvolve adding iron sulfate to remove phosphates microstraining to remove any remaining bacteria before being returned to a river

5. Anaerobic digestion The sludge from the first and second sedimentation tanks is passed into an anaerobic digestion tank for treatment before disposal

Anaerobic microorganisms break down the sediment, eventually producing methane which can be used as a power source

Remaining sediment is dried and can be used for landfill or fertilisers

Sewage Treatment

There are a number of stages to the treatment process:

screeningFlocculation and settling

Grit trap

Clean water to

rivers

Trickle beds(aeration)

sewage

landfill

O2 added

debris heavy sediment

to sludge digestion

Inorganic Pollution

Title Page

Nitrate & Phosphate Pollution

Low availability of N&P limits plant growth, so farmers add nitrate and phosphate fertilisers

Nitrates are highly-soluble, phosphates erode

Such pollution has increased as farmers increasingly grow winter (e.g. sugar beet) as well as summer crops. Only 40% of nutrients are used by crops in the winter (72% in the summer)

Effects of Nitrate Pollution

Blue-baby syndrome (methaemoglobinaemia)

• If large amounts of nitrates in water are ingested by an infant they are converted to nitrite

• The nitrite reacts with oxyhaemoglobin (O2 carrying blood pigment) to form methaemoglobin, which cannot carry oxygen

• Body tissues may be deprived of O2, blue coloration of mucous membranes & digestive/respiratory problems

• Concentrations > 100 mg l-1 of NO3- potentially form nitrosamines (carcinogens) in the stomach stomach cancer

Eutrophication

Click HereClick Hereflash animation

Control of Nitrates

1. Agricultural techniques• avoid fallow periods esp. autumn and winter by sowing cover crops.• nitrate fertiliser should be applied (e.g. spring) to ensure maximum

uptake by plants• animal manure should not be used in autumn and winter • grasslands should be ploughed on a small-scale or not at all

2. Slow release fertilisers - excess fertilisers can be leached

3. Nitrate treatment plants• Water is passed through an ion - exchange resin which removes

nitrate ions and replaces them with chloride ions• expensive and complex process

4 main controls

4. Nitrate Sensitive Areas (NSAs) introduced from 1990 in 32 areas across the UK

KEYNSA SCHEME

Distribution of the NSAs

Control of Nitrates

How do they work?Farmers receive payments to reduce fertiliser and manure applications, avoid autumn application of fertilisers and autumn ploughing

How do they work?Farmers receive payments to reduce fertiliser and manure applications, avoid autumn application of fertilisers and autumn ploughing

Aims: • reduce/stabilise high NO3

- levels in public water supplies via changes to farming activity

• ensure that the abstracted water meets the EU 50 mg/l-1 limit for NO3

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Control of Phosphates

Phosphate StrippingPrimary sewage treatment removes 5 – 15% of nutrients.

Secondary sewage treatment removes 30 – 50% of nutrients.

Phosphates are precipitated using coagulants of lime or compounds of

Fe/Al. 90-95% efficient.

Or Phosphate-containing waters are passed into a lagoon or pond. If the water is retained for 3+ days, nutrients will be taken up by algal blooms these will transfer phosphate to the sediment.

Or Duckweed or water ferns can be used to absorb phosphates from ponds.