Transcript ORGANIC AND INORGANIC POLLUTION

Inorganic &
Organic Pollution
Organic Pollution
Inorganic Pollution
What is Organic Pollution?
Organic pollution is when human activity allows organic
compounds to enter a water body which causes harm to the
ecosystem
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
These wastes are rich in organic
compounds such as proteins,
lipids and carbohydrates
Urine is used to treat the skins
slurry
The leather tanneries in Morocco
Pollution Sources
These organic wastes can be released from either point or
diffuse sources
The two photos below show these different sources. Which is
which?
Pollution
from a
specific
point
Pollution across
a large area
Diffuse source
Point source
• With the exception of plastics (e.g. in sewage) and some manmade 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…..
Manure and Silage
Manure and silage are two important organic pollutants
Silage is rich
in proteins,
lipids and
carbohydrates
as well as
phosphates
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
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.
Manure
or silage
What is produced
In this process?
Ammonia
Bacteria
multiply
Organic matter
decays
sedimentation
Organisms,
e.g. fish, die
Waste needs to be treated as for earlier sewage
pollution
Or this can be avoided by collecting the flushings in
ponds; both the water and the nutrients can then
be recycled via irrigation water.
Oxygen
removed
flash animation
Click Here
Sewage Pollution
Sewage is a “mix of domestic and industrial waste in liquid form”
But what is sewage comprised of?
PARTICULATE ORGANIC
WASTE e.g. food, goldfish
WATER
(up to 99.9%!
SEWAGE
DISSOLVED ORGANIC
MATERIAL
e.g. bacteria, urine, soap
DEBRIS
e.g. plastics
DISSOLVED INORGANIC
MATERIAL e.g. N, P
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
Contains pathogens-organisms (e.g.microbes) capable of
causing disease
Can you name some of the diseases that might be carried by sewage?
E. Coli
CHOLERA
TYPHOID FEVER
SALMONELLA
DISEASES
HEPATITIS A
POLIO
• These diseases are common in LDCs due to lack of water treatment
Sewage Treatment
1. Screening
Screen removes large materials e.g. paper/
vegetable cuttings
2. Initial sedimentation
Coarse 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 the
sedimentation 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 process
Stirring/aeration increase O2 levels to stimulate respiration
After several hours the biochemical oxygen demand (BOD) by 90%
Sewage Treatment
3.Secondary sedimentation
The solids and microorganisms are allowed to settle
4. Tertiary treatment
Involve 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:
landfill
debris
sewage
screening
heavy sediment
Grit trap
Clean
water to
rivers
Flocculation
and settling
Trickle beds
(aeration)
to sludge
digestion
O2
added
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 Here
flash animation
Control of Nitrates
4 main controls
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
Control of Nitrates
4. Nitrate Sensitive Areas (NSAs) introduced from 1990 in 32
areas across the UK
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-
KEY
NSA
SCHEME
How do they work?
Farmers receive payments to reduce
fertiliser and manure applications, avoid
autumn application of fertilisers and
autumn ploughing
Distribution of the NSAs
Control of Phosphates
Phosphate Stripping
Primary 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.