preventing and reducing water pollution

1. Preventing and ReducingPreventing and Reducing
Water PollutionWater Pollution

3. PREVENTING AND REDUCINGPREVENTING AND REDUCING
NONPOINT SOURCE POLLUTIONNONPOINT SOURCE POLLUTION
 Key to reducing nonpoint pollution – mostKey to reducing nonpoint pollution – most
from agriculture – is to prevent it fromfrom agriculture – is to prevent it from
reaching surface water bodies – reducereaching surface water bodies – reduce
runoff:runoff:

Plant vegetative buffersPlant vegetative buffers

Cattle off steep slopes and flood zonesCattle off steep slopes and flood zones

4. PREVENTING AND REDUCINGPREVENTING AND REDUCING
NONPOINT SOURCE POLLUTIONNONPOINT SOURCE POLLUTION

Cover cropland with vegetation – and other soilCover cropland with vegetation – and other soil
conservation practicesconservation practices

Slow release fertilizersSlow release fertilizers

No fertilizers on steep slopesNo fertilizers on steep slopes

Apply pesticides only when neededApply pesticides only when needed

Keep cattle from surface water and flood zonesKeep cattle from surface water and flood zones

Use more organic farmingUse more organic farming

Set discharge standards for nitrates from WTPsSet discharge standards for nitrates from WTPs
and industrial plantsand industrial plants

5. LAWS FOR PREVENTING ANDLAWS FOR PREVENTING AND
REDUCING WATER POLLUTIONREDUCING WATER POLLUTION
 Developed countries – laws set waterDeveloped countries – laws set water
pollution standardspollution standards

U.S.U.S. Clean Water ActClean Water Act (originally Water Pollution(originally Water Pollution
Control Act) – sets standards for allowable levelsControl Act) – sets standards for allowable levels
of key water pollutants, requires polluters to getof key water pollutants, requires polluters to get
permits – many improvements, not everywherepermits – many improvements, not everywhere

EPA is experimenting with aEPA is experimenting with a discharge tradingdischarge trading
policypolicy similar to that for air pollution control.similar to that for air pollution control.
 Developing countries – rarely have lawsDeveloping countries – rarely have laws

6. Reducing Water Pollution throughReducing Water Pollution through
Sewage TreatmentSewage Treatment
 Septic tankSeptic tank – on site disposal system – can– on site disposal system – can
reduce point-source but increase non-pointreduce point-source but increase non-point
source water pollutionsource water pollution

7. Reducing Water Pollution throughReducing Water Pollution through
Sewage TreatmentSewage Treatment
 Septic tankSeptic tank::

Wastewater percolate through gravel and soil –Wastewater percolate through gravel and soil –
somewhat cleansedsomewhat cleansed

Can backupCan backup

Can pollute groundwater and surface waterCan pollute groundwater and surface water

Cannot use bleach, etc.Cannot use bleach, etc.

Must pumpMust pump

¼ of U.S. homes¼ of U.S. homes

8. Where Does It Go When
It’s Imperative –
Mastic Beach

9. Reducing Water Pollution throughReducing Water Pollution through
Sewage TreatmentSewage Treatment
 Urban areas – wastewater treatment plantUrban areas – wastewater treatment plant
 Stages of sewage treatment:Stages of sewage treatment:

Bar screen – removes large objectsBar screen – removes large objects

Primary sewage treatmentPrimary sewage treatment – a– a physicalphysical processprocess
– uses screens and grit tank to remove large– uses screens and grit tank to remove large
floating objects and allows settlingfloating objects and allows settling
• Removes 60% of suspended solids, 30 – 40% of BODRemoves 60% of suspended solids, 30 – 40% of BOD
• Does not remove pathogens, phosphates, nitrates,Does not remove pathogens, phosphates, nitrates,
toxinstoxins

10. Reducing Water Pollution throughReducing Water Pollution through
Sewage TreatmentSewage Treatment

Secondary sewage treatmentSecondary sewage treatment – a– a biologicalbiological
process - aerobic bacteria remove as much asprocess - aerobic bacteria remove as much as
90% of dissolved and biodegradable, oxygen90% of dissolved and biodegradable, oxygen
demanding organic wastesdemanding organic wastes

Tertiary (advanced) sewage treatmentTertiary (advanced) sewage treatment – uses– uses
specialized chemical and physical processes tospecialized chemical and physical processes to
remove additional pollutants – especiallyremove additional pollutants – especially
nutrientsnutrients

ChlorinationChlorination – to kill pathogens – may be health– to kill pathogens – may be health
and environmental problemsand environmental problems
• Alternatives use ozone and UV lightAlternatives use ozone and UV light

11. Reducing Water Pollution throughReducing Water Pollution through
Sewage TreatmentSewage Treatment

12. The Sewage Treatment Process

13. Reducing Water Pollution throughReducing Water Pollution through
Sewage TreatmentSewage Treatment
 Clean Water Act requires primary andClean Water Act requires primary and
secondary treatment (with some exceptions)secondary treatment (with some exceptions)
 Many violations and malfunctionsMany violations and malfunctions
 CSOs during heavy rainfall eventsCSOs during heavy rainfall events
 Major health risksMajor health risks

14. Reducing Water Pollution throughReducing Water Pollution through
Sewage TreatmentSewage Treatment
 Sewage sludgeSewage sludge – leftover solids– leftover solids

Can be used as fertilizer – health risks if bacteriaCan be used as fertilizer – health risks if bacteria
and toxic chemicalsand toxic chemicals

Landfills or incinerated – adds to water and airLandfills or incinerated – adds to water and air
pollutionpollution
 Preventing toxic chemicals from reachingPreventing toxic chemicals from reaching
WTPs would eliminate chemicals from sludgeWTPs would eliminate chemicals from sludge
and water dischargedand water discharged

15. Fig. 21-17, p. 513
Sludge
Groundwater
Contamination
Harmful chemicals
and pathogens
may leach into
groundwater
and shallow wells.
Odors
Odors may cause illness or
indicate presence of harmful gases.
Livestock Poisoning
Cows may die after grazing
on sludge-treated fields.
Dust Particles
Particles of dried sludge
carry viruses and harmful
bacteria that can be
inhaled, infect cuts or enter
homes.
Surface Runoff
Harmful chemicals
and pathogens may
pollute nearby
streams,lakes, ponds,
and wetlands.
Exposure
Children may walk or
play in fertilized fields.
BUFFER
ZONE

16. Alternatives to WTPsAlternatives to WTPs
 CompostingComposting
toiletstoilets – waterless,– waterless,
odorless – convertodorless – convert
human waste intohuman waste into
fertilizerfertilizer
supplementsupplement

17. Alternatives to WTPsAlternatives to WTPs
 Natural and artificial wetlands can help treatNatural and artificial wetlands can help treat
sewage – ex:sewage – ex:

California near Humboldt Bay – 65 hectareCalifornia near Humboldt Bay – 65 hectare
wetland – acts as a natural WTP for the town ofwetland – acts as a natural WTP for the town of
16,000 people - < ½ the price of conventional16,000 people - < ½ the price of conventional
WTPWTP

18. Core Case Study: Using Nature toCore Case Study: Using Nature to
Purify SewagePurify Sewage
 Ecological wastewaterEcological wastewater
purification by apurification by a livingliving
machinemachine

Uses the sun and a seriesUses the sun and a series
of tanks containing plants,of tanks containing plants,
snails, zooplankton,snails, zooplankton,
crayfish, and fish (thatcrayfish, and fish (that
can be eaten or sold forcan be eaten or sold for
bait)bait)

19. Reducing Water Pollution throughReducing Water Pollution through
Sewage TreatmentSewage Treatment
 Clean Water Act (CWA) – has significantlyClean Water Act (CWA) – has significantly
improved water quality in many U.S. streamsimproved water quality in many U.S. streams
and lakes – but a long way to go:and lakes – but a long way to go:

Many areas too polluted for swimming and fishingMany areas too polluted for swimming and fishing

Many seafood advisories against eating fish dueMany seafood advisories against eating fish due
to toxinsto toxins

Major agricultural runoff – esp. animal wastes –Major agricultural runoff – esp. animal wastes –
stored in lagoons – leak, overflow, rupturestored in lagoons – leak, overflow, rupture

Many chemical plants, leaking gas storage tanksMany chemical plants, leaking gas storage tanks

Does CWA apply? – Supreme Court caseDoes CWA apply? – Supreme Court case

20. Reducing Water Pollution throughReducing Water Pollution through
Sewage TreatmentSewage Treatment
 Some want to strengthen CWA to preventSome want to strengthen CWA to prevent
pollution rather than focusing on end-of-the-pollution rather than focusing on end-of-the-
pipe removalpipe removal
 Many farmers and developers see the CWAMany farmers and developers see the CWA
as limiting their rights as property owners toas limiting their rights as property owners to
fill in wetlandsfill in wetlands