water / wastewater treatment

Water / Wastewater Water / Wastewater TreatmentTreatment

Water / Wastewater Water / Wastewater TreatmentTreatment

American Bar AssociationAmerican Bar Association

Forum on the Construction IndustryForum on the Construction Industry

American Bar AssociationAmerican Bar Association

Forum on the Construction IndustryForum on the Construction Industry

Presented By:Presented By:Wayne Lorenz, PEWayne Lorenz, PE

Wright Water Engineers, Inc.Wright Water Engineers, Inc.

William McConnell, PEWilliam McConnell, PEVertex EngineeringVertex Engineering

Stephen A. HessStephen A. HessSherman and Howard LLCSherman and Howard LLC

InfrastructureCivil Works Projects for Lawyers

Part 1: Part 1: Water Water

TreatmentTreatment

Part 1: Part 1: Water Water

TreatmentTreatment

Greeley, Greeley, ColoradoColoradoGreeley, Greeley, ColoradoColorado

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 – Permeable Membranes

Water is a Universal Solvent

▪ Carry Nutrients and Chemicals

▪ Support Chemical Reactions

▪ Suspend Materials

▪ Supports Life

▪ Carry Disease

Purification for Drinking Water Must Be Measured

▪ Measurements must be taken at the plant and during transmission (grab samples)

▪ Identify Bacteria, Viruses, Organics and other constituents.

Environmental Protection Agency (EPA)

▪ Leading Federal Agency Establishing and Enforcing Water Quality Standards – Clean Water Act

• Standards for Discharge

– Safe Drinking Water Act & Amendments• Standards for impurities in drinking water

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 raw water quality 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

• Groundwater

• Seawater

TESTING

▪ Microbial Testing – Testing performed on sample and if

microorganisms are present assume others of the same are present and they spring from the same source

▪ Evaluating Water Chemistry – Easier: Possible indicator of microbial presence

Treatment Plant Size (MGD)

▪ 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

▪ Triple Bottom Line

▪ People

▪ Planet

▪ Profit

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

Plant Instrumentation and Construction (Scada)

Source of Water to Plant

▪ GROUNDWATER – Springs and Wells

• Higher in dissolved solids and hardness

• Pumped & Artesian Wells

▪ OCEAN• High Cost to Remove Salt – but margin is narrowing

▪ SURFACE WATER • Affected by the environment

Desalination Plants

Water Purification Processes

▪ Primary Components – Gathering Raw Water – Series of Purification Steps – Storage, pending distribution

Denver, ColoradoDenver, ColoradoDenver, ColoradoDenver, Colorado

Effluent Structures

▪ Choice of Structure Depending on Source• Water Availability

• Bathymetry

• Sediment Transport

• Environmental Regulations

• Climatic Conditions

• Constructability

• Operations and Maintenance

Pumping Considerations

Pumping Considerations

• 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

City of Denver 5 Step Treatment Process

1. Coagulation/flocculation- Raw water from reservoirs is drawn into mixing basins at our treatment plants where we add alum, polymer and sometimes lime and carbon dioxide. This process causes small particles to stick to one another, forming larger particles.

2. Sedimentation- Over time, the now-larger particles become heavy enough to settle to the bottom of a basin from which sediment is removed.

3. Filtration- The water is then filtered through layers of fine, granulated materials (sand, sand/coal, etc.). As smaller, suspended particles are removed, turbidity diminishes and clear water emerges.

4. Disinfection- To protect against any bacteria, viruses and other microbes that might remain, disinfectant is added before the water flows into underground reservoirs throughout the distribution system and into your home or business. (example – chlorine).

5. Corrosion control- pH is maintained by adding alkaline substances to reduce corrosion in the distribution system and the plumbing in your home or business.

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

– 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

– Ozone Disinfection • Control of carbon based materials in water

– Ultraviolet Germicidal Irradiation • Use of light to destroy microbes in water

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 Adsorption• Uses adsorption 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

Membrane Type of Filters Ultrafiltration

Nanofiltration

Reverse Osmosis (desal)

Aeration

Final Treatment

Final Treatment

▪ Chemical treatment of water to disinfect

▪ Final treatment of waster as regulated by the Environmental Protection Agency and state Departments of Health

Part 2: Wastewater Treatment

How it works

▪ A combination of civil engineering, biology and chemistry – Weirs, Clarifiers– Aerobic, Anaerobic– Dissolved Oxygen, Eutrophication

Wastewater Treatment and Wastewater Treatment and DistributionDistribution

Wastewater Treatment and Wastewater Treatment and DistributionDistribution

Brighton, COProject Completion: 2015

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

• Controls the discharge of all pollutants into above ground waters

• Ensure that surface waters would meet standards necessary for human sports and recreation

Preliminary Wastewater 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.

EquilizationEquilization Basin – Pendleton, SCBasin – Pendleton, SC

Primary Treatment

▪ Remove settled organics and floatable solids– Primary Clarifiers

• Flow Velocity Decrease

• Solids settled out –

sludge pumped off

http://techalive.mtu.edu/meec/module21/WastewaterPrimaryTreatment.html

Michigan Environmental Education Curriculum



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

Coagulation Process

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 microorganisms in the treatment system

Secondary Treatment Cont.– Fixed Film System

• http://www.youtube.com/watch?v=Hdn6zqSHK6Y

• Trickling Filters – waste water distributed over a media, air added to media and bio-film grows and sloughs off

– Rotating Biological Contractor • Rotating disks equally apply oxygen to

microorganisms attached to disks. The build up is removed

– Suspended Growth System – Treatment Ponds – Secondary Sedimentation

http://www.youtube.com/watch?v=Hdn6zqSHK6Y

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.

– 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.

– 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

Membrane Bioreactor

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

Aerated Lagoon ConstructionBurlington, CO

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

Nitrogen & Phosphorous Removal

▪ 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 (sodium hypochlorite) less hazardous, but dissipates quickly

– Calcium Hypochlorite

» Wet or Dry – less hazardous but complicated to store

• Dechlorination» Used to remove the chlorine from the effluent so as not

to to kill aquatic life down stream

Contact Basin

Chemical Treatment

Disinfection Cont.

– Ultraviolet Radiation • Kills virus and bacteria in wastewater

• Leaves no residue to kill aquatic life

Disinfection Cont.

– Ozonation• Effective but expensive to produce

High Cost

Solids Handling

▪ All solids from preliminary treatment, primary treatment and secondary treatment, are blended together for final treatment

• Thickening

• Stabilization

• Conditioning

• Dewatering

• Reduction

Solids Cont.– Floatation

» 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. 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 and produces energy.

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 moved

to open area to be worked into the ground

Belt Filter Press

Drying Beds

Final Solids Disposal

▪ Divided into two categories – Class A

• Can be used by general public

– Class B • Disposed in landfill OR

• Certain agricultural applications

Legal Issues Presented by Legal Issues Presented by Water ProjectsWater Projects

Differing Site Conditions Differing Site Conditions ClausesClauses

▪ Water and wastewater projects often involve horizontal pipeline Water and wastewater projects often involve horizontal pipeline construction over great distancesconstruction over great distances

▪ Such projects also involve substantial excavation over relatively large Such projects also involve substantial excavation over relatively large areasareas

▪ The nature of such construction and the economic limitations on how The nature of such construction and the economic limitations on how much pre-construction geotechnical work can be performed results in much pre-construction geotechnical work can be performed results in many claims for “differing site conditions” many claims for “differing site conditions”


▪Common law rule – Contractor bears the risk (as the party that promised to Common law rule – Contractor bears the risk (as the party that promised to get the job done)get the job done)▪When a Contractor promises to construct a project for a stipulated sum, the When a Contractor promises to construct a project for a stipulated sum, the Contractor is not entitled to an increase in the contract price as a Contractor is not entitled to an increase in the contract price as a consequence of subsurface conditions that are harsher than those anticipated. consequence of subsurface conditions that are harsher than those anticipated. A Contractor who promises to build twelve miles of water lines thinking the A Contractor who promises to build twelve miles of water lines thinking the ground is easy to excavate bears all the additional cost when it turns out the ground is easy to excavate bears all the additional cost when it turns out the pipeline goes through substantial rockpipeline goes through substantial rock▪Consequences: When a Contractor bears all the risk of unfavorable site Consequences: When a Contractor bears all the risk of unfavorable site conditions, the Contractor will generally charge substantially more money to conditions, the Contractor will generally charge substantially more money to accommodate that risk. accommodate that risk.

Differing Site ConditionsDiffering Site Conditions

▪ Major form contract documents (AIA, Major form contract documents (AIA, ConsensusDOCS, EJCDC, FAR) are less ConsensusDOCS, EJCDC, FAR) are less harsh and allow DSC claimsharsh and allow DSC claims

▪ Why would an owner want to provide Why would an owner want to provide otherwise?otherwise?– Enlightened self interest – eliminate contingencyEnlightened self interest – eliminate contingency

Why Include a DSC Clause?Why Include a DSC Clause?

▪ Effect of the “contractor bears all the risk” approachEffect of the “contractor bears all the risk” approach– Contractors spend money on site investigationContractors spend money on site investigation

– Price goes upPrice goes up

– Contractors bid, assuming there will be no problemsContractors bid, assuming there will be no problems

– Claims or failure of performance more likely as contractor Claims or failure of performance more likely as contractor may not have a sufficient budgetmay not have a sufficient budget

– Contractors increase bid to cover unknownContractors increase bid to cover unknown

– Owner gets fixed price - but it is higherOwner gets fixed price - but it is higher

▪ DSC clauses may mitigate these effectsDSC clauses may mitigate these effects


▪There is no general rule allowing a Contractor the right to recover based on There is no general rule allowing a Contractor the right to recover based on differing site conditions, which means very careful attention must be paid to differing site conditions, which means very careful attention must be paid to the precise language of the clause at issue.the precise language of the clause at issue.

▪ “ “Conditions”Conditions”– Subsurface StructuresSubsurface Structures

– Subsurface Soil ConditionsSubsurface Soil Conditions

▪Excavation more difficultExcavation more difficult

▪Construction impracticalConstruction impractical

▪Other Preexisting Physical ConditionsOther Preexisting Physical Conditions


▪ Common features of DSC clausesCommon features of DSC clauses– Type I and/or Type II claims recognizedType I and/or Type II claims recognized

– Contractor must give noticeContractor must give notice

– Contractor’s site investigation responsibilitiesContractor’s site investigation responsibilities

– Contractor’s ability to rely on information provided by Contractor’s ability to rely on information provided by ownerowner


▪ Different from what?Different from what?

▪ Different from:Different from:– What was represented (“Type I”)What was represented (“Type I”)– What was anticipated (“Type II”)What was anticipated (“Type II”)


Type IType I▪Based upon information provided by OwnerBased upon information provided by Owner▪Four elements of proofFour elements of proof

– 1 - subsurface or concealed1 - subsurface or concealed– 2 - physical in nature2 - physical in nature– 3 - differ from contract documents3 - differ from contract documents– 4 - reasonably relied4 - reasonably relied

Legal Issues Presented by Legal Issues Presented by Wastewater ProjectsWastewater Projects

Differing Site Conditions Clauses

Type II

▪Based upon what’s “normally expected”

▪Three elements of proof– 1 - unknown physical condition

– 2 - unusual nature

– 3 - different from ordinarily encountered

▪Heavier burden on contractor


▪ One approach is to have the contractor bear One approach is to have the contractor bear all the risk, by:all the risk, by:– Site inspection obligationsSite inspection obligations– Total disclaimer of information provided by Total disclaimer of information provided by

ownerowner


▪Typical battles over DSC claimsTypical battles over DSC claims

– DSC clauses usually require notice to the Owner within a short period DSC clauses usually require notice to the Owner within a short period after the DSC is uncovered so as to allow the Owner to consider what after the DSC is uncovered so as to allow the Owner to consider what course of action to take and to document the conditions lest a dispute course of action to take and to document the conditions lest a dispute later ariselater arise

– DSC claims very often include delay claims, for which a Contractor DSC claims very often include delay claims, for which a Contractor does well to maintain detailed documentationdoes well to maintain detailed documentation

– Most contracts require Contractors to undertake pre-bid Most contracts require Contractors to undertake pre-bid investigations, and very often an Owner defends against a DSC claim investigations, and very often an Owner defends against a DSC claim on the basis that the Contractor would have anticipated the conditions on the basis that the Contractor would have anticipated the conditions that were actually encountered if the Contractor had performed its that were actually encountered if the Contractor had performed its obligation to investigate.obligation to investigate.


▪General notes:General notes:

– Claims for Type II conditions are the predominant DSC claimsClaims for Type II conditions are the predominant DSC claims– A claim for a Type I DSC is more likely to give rise to a claim by the A claim for a Type I DSC is more likely to give rise to a claim by the

Owner against the geotechnical engineer than a Type II condition. Owner against the geotechnical engineer than a Type II condition. – A Type I condition often – but not always – implies that the actual A Type I condition often – but not always – implies that the actual

conditions were discoverable and/or known, but were negligently conditions were discoverable and/or known, but were negligently misrepresented. However, a Contractor only need show that the misrepresented. However, a Contractor only need show that the elements for a Type I claim exist, not that the Owner committed elements for a Type I claim exist, not that the Owner committed negligent misrepresentationnegligent misrepresentation

– Although subsurface conditions are by far the basis of most DSC Although subsurface conditions are by far the basis of most DSC claims, DSC claims can be made for other concealed conditions where claims, DSC claims can be made for other concealed conditions where appropriateappropriate


▪ EJCDC C-700EJCDC C-700– Key Clauses are §§ 4.02 and 4.03 of EJCDC C-700Key Clauses are §§ 4.02 and 4.03 of EJCDC C-700

– Parties recite the technical data upon which contractor entitled to relyParties recite the technical data upon which contractor entitled to rely

– Type I and Type II recognized, and “prompt” notice requiredType I and Type II recognized, and “prompt” notice required

– But, limits contractor’s reliance limited (see § 4.02.B - e.g., no claims But, limits contractor’s reliance limited (see § 4.02.B - e.g., no claims based on “the completeness of such reports for … means, methods”)based on “the completeness of such reports for … means, methods”)

– The contractor’s inspection of the site is part of the bidding The contractor’s inspection of the site is part of the bidding requirementsrequirements

– Contractor cannot make a claim based on what it knew or should Contractor cannot make a claim based on what it knew or should have known (see § 4.03.C.2)have known (see § 4.03.C.2)

Questions?Questions?

Thank YouThank You

water / wastewater treatment

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