Water Treatment / Water Treatment / Waste Water Waste Water

Water Treatment / Water Treatment / Waste Water Waste Water

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Water Treatment and Water Treatment and DistributionDistribution

Water Treatment and Water Treatment and DistributionDistribution

Water Treatment

Distribution of Waste Water

Treatment is Essential

▪ 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

▪ 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 • Water available

• EPA standards for the water

• Quantity of water needed

• Treatment technologies

EVALUATINGRAW 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• 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

– 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

• 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?Questions?

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