ENVIRONMENTAL
CHEMISTRY
COURSE CODE: CHEM 2111
BS CHEMISTRY SEM3
Lecture # 04
Lecturer
FARHAN BUTT
WATER POLLUTION
COURSE OUTLINE:
WATER POLLUTION
ENVIRONMENTAL CHEMISTRY
AGRICULTURAL WASTEWATER
Major agricultural contributors to water pollution
Nutrients
Pesticides
Salts
Sediments
Organic carbon
Pathogens
Metals
Drug residues.
AGRICULTURAL WASTEWATER
SOURCES
Nutrients
In crop production, water pollution from nutrients
occurs when fertilizers are applied at a greater rate
than they are fixed by soil particles
OR exported from the soil profile (e.g. by plant
uptake or when they are washed off the soil surface
before plants can take them up).
Excess nitrogen and phosphates can leach into
groundwater or move via surface runoff into waterways.
SOURCES
Nutrients
Phosphate is not as soluble as nitrate and ammonia
and tends to get adsorbed onto soil particles and enter
water bodies thorough soil erosion.
SOURCES
NUTRIENTS
In livestock production (nutrient-rich) animal waste
(e.g. urine) can be released directly into those
watercourses. Manure is usually collected for use as
organic fertilizer, which, if applied in excess, will lead to
diffuse water pollution.
EFFECTS
Nutrients
High nutrient loads can cause the eutrophication of
lakes, reservoirs, ponds and coastal waters, leading to
algae blooms that suppress other aquatic plants and
animals.
The excessive accumulation of nutrients may also
increase adverse health impacts, such as blue-baby
syndrome, due to high levels of nitrate
in drinking-water.
SOURCES
PESTICIDES
Insecticides, herbicides and fungicides are applied
intensively in agriculture in many countries. millions of
tones of active pesticide ingredients are used in
agriculture
EFFECTS
PESTICIDES
Pesticides may also affect biodiversity by killing
weeds and insects, with negative impacts up the food
chain.
Acute pesticide poisoning causes significant human
morbidity and mortality worldwide – especially in
developing countries, where poor farmers often use
highly hazardous pesticide formulations
SOURCES
SALTS
Irrigation can mobilize salts accumulated in soils
(leaching fractions), which are then transported by
drainage water to receiving water bodies and cause
salinization. Excessive irrigation can also raise water
tables from saline aquifers and increase the seepage
of saline groundwater into watercourses.
EFFECTS
SALTS
Highly saline waters alter the geochemical cycles of
major elements – such as carbon, iron, nitrogen,
phosphorus, silicon and sulphur
With overall impacts on ecosystems. Salinization can
affect freshwater biota by causing changes within
species and in community composition and can
ultimately lead to biodiversity loss and migration.
EFFECTS
SALTS
.
SOURCES
SEDIMENTS
Unsustainable land use and improper tillage and soil
management in agriculture are increasing erosion and
sediment runoff into rivers, lakes and reservoirs, with
massive quantities of soil lost and transported to water
bodies every year.
SOURCES
SOURCES
SEDIMENTS
High rates of erosion occur in areas where
precipitation is high, slopes are steep and vegetation
cover is poor. Erosion is aggravated by overgrazing in
pasturelands, by inappropriate ploughing on steep
slopes and, more broadly, by deforestation,
landclearing and the degradation of riverine
vegetation.
EFFECTS
SEDIMENTS
Sediments can cover and destroy fish spawning
beds, clog fish gills, and reduce useful storage volume
in reservoirs. Sedimentation can damage
watercourses, choke streams and make filtration
necessary for municipal and irrigation water supplies. It
can also affect delta formation and dynamics and limit
the navigability of water bodies.
SOURCES
ORGANIC MATTER
Organic matter from animal excreta, uneaten animal
feed, animal-processing industries and mismanaged
crop residues are all significant water pollutants.
Livestock-related wastes have among the highest
biological oxygen demand (BOD). For example, the
BOD of pig slurry is in the range of 30,000–80,000
milligrams per litre, compared with the typical BOD of
domestic sewage of 200–500 milligrams per litre
EFFECTS
ORGANIC MATTER
Organic matter consumes dissolved oxygen in water
as it degrades, contributing strongly to hypoxia in water
bodies. The discharge of organic matter also increases
the risk of eutrophication and algal blooms in lakes,
reservoirs and coastal areas.
SOURCES
PATHOGENS
Livestock excreta contain many zoonotic
microorganisms and multicellular parasites that can be
harmful to human health. Pathogenic microorganisms
can be waterborne or food-borne (the latter especially
if the food has been irrigated with contaminated
water).
SOURCES
EFFECTS
PATHOGENS
Pathogens from livestock that are detrimental to
public health include bacteria such as Escherichia coli ,
Salmonella spp. and parasitic protozoa all of which
cause hundreds of thousands of infections every year
Pollution prevention.
The storage and disposal of pesticide waste and
empty containers need to follow safety guidelines. Also,
efficient irrigation schemes will reduce water return
flows and therefore can greatly reduce the migration of
fertilizers and pesticides to water bodies
Manure management is one of the main concerns in
livestock production. Manure needs to be stored,
treated, handled and disposed of – or preferably reused
– safely. Manure treatments include composting and
anaerobic fermentation, which can produce valuable
organic fertilizers and soil conditioners.
Pollution prevention.
The right policies and incentives can encourage diets
that are more sustainable and healthy and thereby
moderate increases in food demand
.
Typical regulatory instruments include prohibitions on
the direct discharge of pollutants; limits on the
marketing and sale of dangerous products; and
restrictions on agricultural practices or the location of
farms.
Pollution prevention.
To reduce Sediment-borne pollutants
cooperative agreements can be developed between
landowners and relevant authorities to reduce erosion,
Efficient irrigation schemes will reduce water return
flows and therefore can greatly reduce the migration of
fertilizers and pesticides to water bodies
Pollution prevention.
Farmers may utilize erosion controls to reduce runoff
flows and retain soil on their fields.
Common techniques
It include
Contour ploughing,
Crop mulching,
Crop rotation,
Planting perennial crops
Installing riparian buffers.
Solutions What Can You Do?
Water Pollution Water Pollution
Improving Sewage Treatment
• Systems that exclude hazardous wastes
• Non-hazardous substitutes
• Composting toilet systems
• Working with nature to treat sewage
• Using wetlands to treat sewage
Improving Sewage Treatment
• Septic tank
• Treatment plant may
have an individual septic
tank, which treats the
wastewater on site and
discharges into the soil.
• Alternatively, domestic
wastewater may be sent
to a nearby privately
owned treatment system
(e.g. in a rural
community).
Solutions What Can You Do?
Water Pollution Water Pollution
• Prevent groundwater contamination • Fertilize your garden and yard plants
• Greatly reduce nonpoint runoff with manure or compost instead of
commercial inorganic fertilizer.
• Reuse treated wastewater for
• Minimize your use of pesticides.
irrigation
• Never apply fertilizer or pesticides near
• Find substitutes for toxic pollutants a body of water.
• Work with nature to treat sewage • Grow or buy organic foods.
• Practice four R's of resource use • Compost your food wastes.
(refuse, reduce, recycle, reuse) • Do not use water fresheners in toilets.
• Reduce resource waste • Do not flush unwanted medicines
down the toilet.
• Reduce air pollution
• Do not pour pesticides, paints,
• Reduce poverty solvents, oil, antifreeze, or other
• Reduce birth rates products containing harmful chemicals
down the drain or onto the ground.
