Transcript Document 7134945

Infrastructure
Civil Works Projects for Lawyers
American Bar Association
Forum on the Construction Industry
Water Treatment /
Waste Water
Presented By:
Your Name Here
Prepared By:
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Water Treatment and
Distribution
Water Treatment
Distribution of Waste Water
Treatment is Essential
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Manufacturing
Power Generation
Chemical Production
Pharmaceutical
Health Care
▪ ¾ of earth surface is covered in water, but
only one-half of one % is fresh and even a
smaller portion of that is usable
Treatment Methods
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Chemical Process
Environmental Process
Mechanical Process
Plant Design features (Civil Engineering)
Filtration Systems
Skimmers
Ultraviolet
Light
Ozone Generators
Water is a Universal
Solvent
Carry Nutrients and Chemicals
Support Chemical Reactions
Suspend Materials
Supports Life
Carry Disease
Environmental Protection
Agency (EPA)
▪ Leading Government Agency Establishing
and Enforcing Water Quality Standards
– Clean Water Act
• Standards for Discharge
– Safe Drinking Water Act
• Standards for impurities in drinking water
Purification Must Be
measured
▪ Measurements must be taken at the plant and
during transmission
▪ Identify Bacteria Viruses or Organics
Water Treatment Plants
▪ Design Considerations:
• What quality and quantity of water is required?
• What raw water supply is available?
• What type of plant process is necessary?
– Engineering determined by
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Water available
EPA standards for the water
Quantity of water needed
Treatment technologies
EVALUATING
RAW WATER SUPPLY
– Variation in Availability
• Does water supply vary a lot by season
– Control Supply of Water and Quality
– Inability to Control Water and Quality
• Large or small body of water as supply
• River water supply and consistency of flow
TESTING
▪ Microbial Testing
– Testing performed on sample and if present
assume others of the same are present and they
spring from the same source
▪ Evaluating Water Chemistry
– Easier: often instantaneous and possible indicator
of microbial presence
Treatment Plant Size
▪ Cost Considerations
– Size of Population to be served (75 to 150 gallons
per day per person)
▪ Contact Time
– How Long does disinfectant need to be in the
water to be effective
CIVIL & STRUCTURAL
DESIGN
Physical Structure Design
Transportation of Water
Tanks and Pumping
SUSTAINABLE DESIGN
▪ Minimize Waste From Plant
▪ Minimize Power Use
Plant Instrumentation and
Construction
▪ Instrumentation necessary to monitor raw
water coming in and effluent going out and
distribution system
▪ Construction decision between private and
public management
– Cost Considerations
– Long Term Maintenance Considerations
Source of Water to Plant
▪ GROUNDWATER
– Springs and Wells
• Higher in dissolved solids and hardness
• Pumped & Artesian Wells
▪ OCEAN
• High Cost to Remove Salt
▪ SURFACE WATER
• Affected by the environment
▪ OTHER SOURCES
• EXAMPLE – recycled water for non-potable uses
Water Purification Processes
▪ Primary Components
– Gathering Raw Water
– Series of Purification Steps
– Storage, pending distribution
Intake Structures
▪ Choice of Structure Depending on Source
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Water Availability
Bathymetry
Sediment Transport
Environmental Regulations
Climatic Conditions
Constructability
Operations and Maintenance
Pumping Considerations
• Choice of pump varies for pressure needs
• Pump needs continuous flow across the blades
• Pump choice determined by pressure needed in
processing water.
• Pump considerations moving water to higher
elevations
• Pump considerations dependant on size of pipe and
allowable pressure
• Energy Use – efficiencies derived from variable speed
drives
Treatment Process
– Chemical Injection
• Carefully monitored uring the treatment process to
maintain maximum efficiency
– Chlorine
• Effective disinfectant best used on warmer water
– Ammonia
• Used to limit disinfection by-product caused by
chlorine
– Potassium Permanganate
• Controls color, taste and odors
– Acids and Caustics
• Used to control PH level of water
Treatment Process
– Ozone Disinfection
• Control of carbon based materials in water
– Ultraviolet Germicidal Irradiation
• Use of light to destroy microbes in water
– Flocculation
• Add chemicals to water to cause suspended solids to
coagulate and become larger to be removed by filters
– Sedimentation
• Low flow velocity basins allowing solids to drop out
Filtration
– Rapid Sand Filters
• Passing water through sand beds to remove solids
– Slow Sand Filters
• Graded layers of sand filters water as it passes
– Activated Carbon Absorption
• Uses absorption to capture organics
– Membrane Filtration
• Operate at the molecular level
Membrane Type of Filters
• Ultrafiltration
– Separate large organic molecules and colloidal silica
• Nanofilters
– Capable of removing hardness, heavy medals, color, taste and
large organics
• Reverse Osmosis
– Predominately used for desalinazation
• Distillation
– Separate water from impurities by phase change
• Aeration
– Increase oxygen content, reduce carbon dioxide and remove
hydrogen suphide, methane and other volatile compounds
Final Treatment
▪ Chemical treatment of water to disinfect
– Chemical baths to disinfect water as final process
▪ Final treatment of waster as regulated by the
Environmental Protection Agency
WASTE WATER
How it works
▪ A combination of civil engineering, biology
and chemistry
– Weirs, Clarifiers
– Aerobic, Anaerobic
– Dissolved Oxygen, Eutrophication
Regulatory Scheme
– Prior to 1947 – no regulation of waste water
– 1948 to 1970 – Federal Water Pollution Control
Act (FWPCA)
– 1970 to Present – EPA Clean Water Act
• Eliminates the discharge of all pollutants into above
ground waters
• Ensure that surface waters would meet standards
necessary for human sports and recreation
Preliminary Waste Water
Treatment
– Screening
• Coarse Screens and Bar Screens
– Removes Large Items
• Fine Screens – Static, Rotary Drum or Step
– Removal of Fines
• Grit Removal
– Removal of coarse suspended material (silt, sand and gravel)
– Gravity / Velocity grit removal
– Aerated Grit Chamber
• Shredding or Grinding
– Shred or grind material in the flow to reduce the size of the
inert material so it does not interrupt the process
Preliminary Treatment
– Flow Equalization
• Plant is most efficient if constant flow is maintained
• Peak flows mid-morning and evening
• Construct equalization basin to release constant flow to
plant
• Must aerate and mix liquids in basin to prevent oder
and settling solids.
Primary Treatment
▪ Remove settled organics
and floatable solids
– Primary Clarifiers
• Flow Velocity Decrease
• Sediment settled out –
sludge pumped off
Enhancing Primary
Treatment
▪ Pre-aeration
– Introduction of air in the grit chamber
• Promotes flocculation, scum floatation and removal
• Benefits odor control
▪ Coagulation
– Chemical introduction to promote the settling of
finely dispersed solids to promote forming large
solids out of finely dispersed solids
Secondary Treatment
– Process to convert organic wastes to move more
stable solids that can either be removed by
settling or discharged to the environment, without
causing harm.
– Biological process involve the use of bacteria in
the treatment system
Secondary Treatment
– Fixed Film System
• Trickling Filters – waste water distributed over a
media, air added to media and bio-film grows and
sloughs off
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Suspended Growth System
Treatment Ponds
Secondary Sedimentation
Rotating Biological Contractor
• Rotating disks equally apply oxygen to
microorganisms attached to disks. The build up is
removed
Suspended Growth System
– Activated Sludge System
• Primary effluent is mixed with activated sludge and air
added, microorganisms grow and pumped to settling
tank to be removed or used as activated sludge
• Complete mix activated sludge – Uniformly introduced
– Plug Flow
• Waste Water flows as a plug winds its way through a
series of channels as air is introduced in a decreasing
progression. Large clumps of microorganisms removed
at end.
Suspended Growth System
– Extended Aeration
• Long detention time and high sludge age
• One direction flow through channel in tank
• Resilient to shock load
– Sequencing Batch Reactor
• Batches of flow cycled to multiple basins, eliminate
need for clarifier and sludge removal system.
Suspended Growth System
– Membrane Bioreactor
• Effluent pumped across membrane as air is introduced
in the bottom of the membrane promoting aerobic
condition treating effluent.
• Greatly reduces the amount of space needed to treat
wastewater.
Treatment Ponds
– Facultative Lagoon / Pond
– Aerated Lagoon
• Different methods to set up an aerobic and anaerobic
condition for water treatment
– Secondary Sedimentation
• Separate solids from treated water
• Concentrate and thickens sludge to optimize handling
TERTIARY TREATMENT
– Enhanced treatment of effluent for the removal of
heavy metals and toxic compounds, not filtered in
the secondary treatment.
• Usually used to remove nitrogen and phosphorus
• Very expensive and labor intensive
– Nitrogen removal
– Nitrification / Denitrification
» Convert ammonia nitrogen to nitrate
– Ammonia Stripping
» Adding Quick Lime
TERTIARY TREATMENT
▪ Phosphorus Removal
– Add Feric Chloride, Lime or Alum
▪ Land Application
– Spray secondary disinfected wastewater or large
landmass and use soil filtration
Disinfection
– Chlorination
– Gas or Liquid
» Effective, but hazardous Sodium Hypochlorite.
» Liquid bleach less hazardous, but dissipates quickly
– Calcium Hypochlorite
» Wet or Dry – less hazardous but complicated to store
• Dechlorination
» Used to remove the chlorine form the effluent so as not
to to kill aquatic life down stream
Disinfection
– Ultraviolet Radiation
• Kills virus and bacteria in wastewater
• Leaves no residue to kill aquatic life
– Bromide Chloride
• Mix of bromine and chlorine no downstream residue
– Ozonation
• More effective than chlorine, but expensive to produce
Solids Handeling
▪ All solids from preliminary treatment,
primary treatment and secondary treatment,
are blended together for final treatment
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Thickening
Stabilization
Conditioning
Dewatering
Reduction
Solids
– Flotation
» Adding water in a pressurized environment. When
depressurized, bubbles cause dense material to rise to
surface for skimming.
– Gravity Settling
» Sludge settles and compacts in a circular tank like
sedimentation, constantly stirred to create channels for
water to exit. Dried sludge is removed from bottom of
tank.
– Stabilization
» Lime stabilization – lime added to kill microorganisms
and stop odor. Sludge applied to land. Very Expensive
and sludge with lime is very heavy.
» Anaerobic Digestion – Decomposition of sludge in the
absence of oxygen. Traditional method but very
dependent on perfect conditions.
Dewatering
– Centrifugation
• Spun to remove water and dry solids
– Belt Filter Press
• Sludge formed into a cake by adding polymers and
then pressed dry.
– Drying Beds
• Layers of sludge exposed to air until dry then ,oved to
open area to be worked into the ground
Final Solids Disposal
▪ Divided into two categories
– Class A
• Can be used by general public
– Class B
• Disposed in landfill OR
• Certain agricultural applications
Questions?
Thank You