Water Infrastructure & Treatment

EVEN 2909: Introduction to Sustainability Engineering — Week 8

Evan A. Thomas, PhD, PE, MPH — University of Colorado Boulder

1 — Title

Section 1

How Water Systems Work

From source to tap: the engineered water cycle

2 — Section 1

The Water Cycle: Natural & Engineered

Natural Cycle

Evaporation from oceans, lakes, rivers
Condensation into clouds
Precipitation as rain, snow, hail
Infiltration into soils and aquifers
Runoff back to surface water bodies

Earth holds ~1.4 billion km³ of water — only 0.3% is accessible freshwater

Engineered Cycle

Withdrawal from rivers, reservoirs, wells
Treatment to drinking water standards
Distribution through pipe networks
Use by residential, commercial, industrial consumers
Collection via sewers
Wastewater treatment before discharge

3 — Water Cycle

Source Water: Surface vs. Groundwater

Surface Water (~60% of US supply)

Rivers, lakes, reservoirs
More vulnerable to contamination (runoff, discharges)
Subject to seasonal variability and drought
Requires more extensive treatment
Easier to monitor and manage at scale

Groundwater (~40% of US supply)

Aquifers — underground layers of rock and sediment
Naturally filtered through soil and rock
Generally higher quality, fewer pathogens
Vulnerable to over-pumping (e.g., Ogallala Aquifer)
Contamination is slow to develop but very hard to remediate

Key concept: The Safe Drinking Water Act (1974) sets standards for both source types. The EPA regulates over 90 contaminants under the National Primary Drinking Water Regulations.

4 — Source Water

US Water Infrastructure: A Massive System

Community water systems serve ~320 million Americans year-round
Most major infrastructure was built in the post-WWII era (1950s–1970s)
Design life of water mains: 75–100 years — many are at or past end-of-life
An estimated 6 billion gallons lost daily from leaks in aging pipes
Over 800,000 miles of pipe are in poor or very poor condition

Source: EPA, ASCE 2025 Infrastructure Report Card (Grade: C-)

5 — US Infrastructure

Conventional Treatment Process

Raw Water
Intake

→

Coagulation

→

Flocculation

→

Sedimentation

→

Filtration

→

Disinfection

→

Distribution

Physical Processes

Coagulation: Chemicals (alum, ferric chloride) destabilize particles
Flocculation: Gentle mixing forms larger clumps (flocs)
Sedimentation: Gravity settles flocs to the bottom
Filtration: Water passes through sand, gravel, or activated carbon

Chemical Processes

Chlorination: Most common disinfectant; maintains residual in pipes
Chloramines: Longer-lasting disinfectant (chlorine + ammonia)
pH adjustment: Controls corrosion and taste
Fluoridation: Added for dental health (~0.7 mg/L)

6 — Treatment Process

Distribution Systems & Boulder's Water

Distribution Infrastructure

Transmission mains: Large pipes (24–96″) from treatment to storage
Distribution mains: Smaller pipes (4–16″) serving neighborhoods
Service lines: Connections from mains to individual buildings
Storage tanks & reservoirs: Buffer supply and maintain pressure
Booster pumps: Maintain pressure in elevated areas
System must maintain 20 psi minimum at all times

Boulder's Water System

Source: Boulder Creek watershed, Barker Reservoir, Silver Lake, and the Colorado-Big Thompson project
Treatment: Betasso Water Treatment Facility (capacity: 36 MGD)
Distribution: ~470 miles of water mains
Storage: 16 treated water storage tanks
Boulder treats ~7 billion gallons/year
Snowmelt-dominated supply — vulnerable to climate change

7 — Distribution & Boulder

Section 2

Water Quality Challenges

What makes water unsafe, and why failures happen

8 — Section 2

Microbial Contamination

Waterborne pathogens are the leading cause of water-related illness worldwide — responsible for ~500,000 diarrheal deaths per year.

E. coli (Bacteria)

Indicator organism for fecal contamination. Most strains harmless, but O157:H7 causes severe illness. Easily killed by chlorine. EPA MCL: zero in treated water.

Cryptosporidium (Protozoa)

Chlorine-resistant parasite. Caused 1993 Milwaukee outbreak (403,000 ill, 69 deaths). Removed by filtration or UV treatment.

Giardia (Protozoa)

Cyst-forming parasite found in streams and lakes. Common in backcountry water. Causes “beaver fever” — weeks of GI distress.

Legionella (Bacteria)

Grows in warm water systems (cooling towers, hot tubs, building plumbing). Causes Legionnaires’ disease, a severe pneumonia.

Engineering takeaway: Multiple barriers (source protection, treatment, disinfection residual, monitoring) protect against microbial risk. No single step is sufficient alone.

9 — Microbial Contamination

Chemical Contamination

Lead

No safe level of exposure. Leaches from lead service lines, solder, and fixtures. EPA action level: 15 ppb. Estimated 9.2 million lead service lines remain in the US.

Nitrates

From agricultural runoff and septic systems. Causes “blue baby syndrome” (methemoglobinemia) in infants. EPA MCL: 10 mg/L.

Arsenic

Naturally occurring in groundwater, especially in the western US and South Asia. EPA MCL: 10 ppb. Long-term exposure linked to cancer.

PFAS (“Forever Chemicals”)

Synthetic chemicals used since the 1950s. Do not break down in the environment. Found in drinking water of an estimated 110+ million Americans.

Disinfection Byproducts (DBPs)

Formed when chlorine reacts with organic matter. Trihalomethanes (THMs) and haloacetic acids (HAAs) are regulated. Trade-off: disinfection vs. DBP formation.

Microplastics

Found in >80% of tap water samples globally. Health effects still being studied. No current EPA regulation. Particles range from 1μm to 5mm.

10 — Chemical Contamination

The Flint Water Crisis: A Case Study in Failure

April 2014

Switch to Flint River

To save ~$5M over 2 years, the city switches from treated Detroit water (Lake Huron) to the Flint River. No corrosion control treatment is applied.

Summer 2014

Residents Complain

Discolored, foul-smelling water. E. coli detected. Boil-water advisories issued. Officials dismiss concerns.

October 2014

GM Stops Using Flint Water

General Motors switches its engine plant back to Lake Huron water — the Flint River water was corroding engine parts.

February 2015

Lead Detected

EPA employee Miguel Del Toral finds high lead levels in a resident’s home. His memo is suppressed for months.

September 2015

Dr. Mona Hanna-Attisha

Pediatrician publishes data showing blood lead levels in Flint children doubled or tripled after the switch. State finally acknowledges the crisis.

January 2016

Federal Emergency

State of emergency declared. 12 deaths from Legionnaires’ disease linked to the water. Criminal charges filed against officials.

11 — Flint Crisis

Flint: Engineering Lessons

What Went Wrong

No corrosion control: Flint River water was 19x more corrosive than Detroit water. Orthophosphate dosing ($100/day) would have prevented lead leaching.
Regulatory failure: Michigan DEQ misinterpreted the Lead and Copper Rule, exempting Flint from corrosion control requirements
Ignored residents: Complaints from a predominantly Black, low-income community were dismissed for over a year
Cost-cutting: An emergency manager (appointed, not elected) made the switch to save money

Environmental Justice

Flint is 54% Black with a 40% poverty rate. The crisis raised national awareness of how race and income intersect with environmental risk.

Key question: Would this have happened in a wealthy, white suburb? Multiple investigations concluded that race and poverty were contributing factors in the government’s failure to act.

Outcome

$626 million settlement for residents
Ongoing service line replacement (>10,000 pipes)
Criminal convictions of state officials
Revised Lead and Copper Rule (2021)

12 — Flint Lessons

PFAS: “Forever Chemicals”

PFOA: C₈HF₁₅O₂

F F F F F F F O

| | | | | | | ||

F—C—C—C—C—C—C—C—C—OH

| | | | | | |

F F F F F F F

Carbon-fluorine bonds are among the strongest in organic chemistry — essentially unbreakable by natural processes

What Are PFAS?

Per- and polyfluoroalkyl substances — over 14,000 compounds
Water-repellent, grease-repellent, heat-resistant
C-F bond energy: ~485 kJ/mol (extremely stable)

Where They Come From

Firefighting foam (AFFF) — military bases, airports
Non-stick cookware (Teflon)
Waterproof clothing (Gore-Tex)
Food packaging, cosmetics, carpets

Health Effects

Cancer (kidney, testicular)
Thyroid disease
Immune system suppression
Reproductive and developmental harm

Regulatory Status (2024–2025)

EPA final MCLs: 4 ppt for PFOA and PFOS
Compliance deadline: 2029
Estimated cost: $1.5 billion/year for utilities

13 — PFAS

Emerging Contaminants

Contaminants for which health effects are suspected but regulation is limited or absent.

Microplastics

Fragments <5mm found in 94% of US tap water samples. Sources: synthetic clothing, tire wear, plastic waste breakdown. Conventional treatment removes ~70%; advanced filtration removes >95%.

Pharmaceuticals & Personal Care Products

Hormones, antibiotics, antidepressants detected in water supplies. Enter through wastewater discharge and agricultural runoff. Concentrations typically ng/L to μg/L.

Antibiotic Resistance Genes (ARGs)

Wastewater treatment plants are “hotspots” for antibiotic resistance gene transfer between bacteria. ARGs can persist through treatment and enter the environment.

Cyanotoxins

Produced by harmful algal blooms (HABs) in warming lakes and reservoirs. Microcystins damage the liver. HABs are increasing with climate change and nutrient pollution.

The challenge: We can detect contaminants at parts-per-trillion — far beyond what we can regulate or treat economically. How do we set standards for thousands of new compounds?

14 — Emerging Contaminants

Section 3

Treatment Technologies

From conventional to cutting-edge approaches

15 — Section 3

Advanced Treatment Technologies

Membrane Filtration

Microfiltration (MF): 0.1–10 μm pore size. Removes bacteria, protozoa, sediment. Low pressure.
Ultrafiltration (UF): 0.01–0.1 μm. Removes viruses plus everything MF removes.
Nanofiltration (NF): 0.001–0.01 μm. Removes hardness, some organic contaminants.
Reverse Osmosis (RO): <0.001 μm. Removes virtually everything including dissolved salts, PFAS. High energy cost.

Each step down in pore size increases energy and cost but improves removal.

Other Advanced Methods

UV Disinfection

254 nm light damages DNA/RNA of pathogens. Effective against Cryptosporidium (chlorine-resistant). No chemical residual — often paired with chlorine.

Ozonation

Strong oxidant (O₃). Destroys taste/odor compounds, inactivates pathogens, breaks down organics. More expensive than chlorine but fewer DBPs.

Granular Activated Carbon (GAC)

Adsorbs organic contaminants, PFAS, taste/odor compounds. Used in PFAS treatment trains. Requires periodic replacement or regeneration.

16 — Advanced Treatment

Point-of-Use Treatment

When centralized treatment is unavailable — critical for the 2 billion people without safe water access.

LifeStraw / Hollow Fiber Filters

UF membranes (0.02 μm) remove 99.999% of bacteria and 99.99% of protozoa. No power needed. ~$20 per unit, treats 1,000–4,000 liters.

Ceramic Filters

Porous clay pots impregnated with colloidal silver. Flow rate: 1–3 L/hr. Low cost ($8–15), locally manufactured. Effective against bacteria and protozoa.

Solar Disinfection (SODIS)

Fill clear PET bottles, place in sun for 6+ hours. UV-A + heat inactivate pathogens. Free but slow. Requires clear water and sunny conditions.

Chlorine Dosing

Household chlorine (sodium hypochlorite) at 1–2 mg/L. Cheapest method per liter treated. Residual protection against recontamination. Used globally.

Design challenge: The best technology is one people will actually use consistently. Taste, convenience, cost, and cultural acceptance matter as much as removal efficiency.

17 — Point-of-Use

Nature-Based Solutions & The Lume Sensor

Nature-Based Treatment

Constructed Wetlands

Engineered ecosystems that use plants, soil, and microbes to treat wastewater. Low energy, low cost. Common for small communities and stormwater.

Bioretention / Rain Gardens

Engineered soil and plant systems that filter stormwater runoff. Remove nutrients, metals, sediment, and some pathogens.

Managed Aquifer Recharge (MAR)

Intentionally storing treated water underground. Natural filtration through soil provides additional treatment. Used for drought resilience and water banking.

The Lume Sensor

Real-time water quality monitoring using tryptophan-like fluorescence (TLF).

Principle: Microbial contamination produces tryptophan-like compounds that fluoresce at 280 nm excitation / 350 nm emission
Advantage: Near-instantaneous results vs. 18–24 hours for lab culture tests
Applications: Source water monitoring, treatment verification, distribution system surveillance
Correlation: TLF levels track E. coli concentrations in field studies

Week 8 Lab: You will use the Lume sensor to measure TLF in water samples from Boulder Creek and compare to E. coli culture results.

18 — Nature-Based & Lume

Section 4

Global Water Access

2 billion people without safe drinking water

19 — Section 4

The Global Water Challenge

The WASH Framework

Water, Sanitation, and Hygiene are deeply interconnected:

Safe water supply prevents waterborne disease
Sanitation prevents fecal contamination of water sources
Hygiene (handwashing) breaks transmission chains
All three must improve together for health gains

Who is Most Affected?

Sub-Saharan Africa: 400M+ without basic water
South Asia: High contamination of groundwater (arsenic, fluoride)
Rural communities: 80% of those lacking basic water live in rural areas
Women and girls: Spend an estimated 200 million hours daily collecting water globally

Source: WHO/UNICEF Joint Monitoring Programme, 2023

20 — Global Challenge

Safe Water & Carbon Credits

The Virridy Model

Safe water supply projects can generate verified carbon credits by displacing the need to boil water with firewood or charcoal.

Households without safe water often boil water as their primary treatment
Boiling consumes biomass fuel → CO₂ and black carbon emissions
Providing a safe water source eliminates the need to boil
Avoided emissions are quantified and verified as carbon credits
Revenue from credit sales funds water system maintenance

This creates a sustainable financing mechanism for rural water infrastructure.

Suppressed Demand

What it means: In very poor communities, actual emissions are low because people cannot afford enough fuel to boil all their water. They drink unsafe water instead.

Traditional carbon accounting only credits actual displaced emissions
Suppressed demand recognizes what people would burn if they could afford to meet their basic needs
Without suppressed demand, the poorest communities generate the fewest credits — and receive the least investment

Gold Standard Methodology

Internationally recognized certification for water treatment projects
Requires monitoring that water is actually safe and being consumed
The Lume sensor enables real-time verification of water quality for credit issuance

21 — Carbon Credits

Section 5

Infrastructure & Sustainability

Aging systems, energy, climate, and the path forward

22 — Section 5

The Energy-Water Nexus

Aging US Infrastructure

ASCE grades drinking water infrastructure at C-
A water main breaks every 2 minutes in the US
Bipartisan Infrastructure Law (2021): $55B for water, but gap remains
Smaller utilities (<10,000 customers) face the greatest challenges — limited revenue, aging workforce

Where Energy Goes

Pumping: ~80% of water system energy
Treatment: ~15% (more for advanced treatment)
Distribution: ~5%
RO desalination: 3–6 kWh/m³ (10x conventional treatment)

Reducing water loss reduces energy use. Fixing leaks is a climate strategy.

23 — Energy-Water Nexus

Climate Impacts & Green Infrastructure

Climate Impacts on Water

Drought: Reduced snowpack, earlier runoff, lower reservoir levels. Colorado River at historically low levels.
Flooding: More intense precipitation events overwhelm combined sewers and treatment plants
Wildfire: Post-fire runoff carries ash, sediment, and contaminants into reservoirs (Marshall Fire, 2021)
Temperature: Warmer water holds less dissolved oxygen, promotes algal blooms and pathogen growth
Sea-level rise: Saltwater intrusion into coastal aquifers

Green Infrastructure Solutions

Permeable Pavement

Allows stormwater to infiltrate rather than run off. Reduces flooding, recharges groundwater, filters pollutants.

Rain Gardens & Bioswales

Planted depressions that capture and filter runoff. Reduce peak flows by 50–90%. Low maintenance.

Green Roofs

Vegetated rooftops that absorb rainfall, reduce urban heat island, and decrease stormwater volume by 50–90%.

Water Reuse

Direct and indirect potable reuse is growing. Colorado approved DPR in 2023. Advanced treatment trains make it safe and cost-effective.

24 — Climate & Green Infra

Career Paths in Water Engineering

Water/Wastewater Treatment Engineer

Design and optimize treatment plants. Work with municipalities, consulting firms, or equipment manufacturers. PE license required for stamping designs.

Water Resources Engineer

Manage water supply, stormwater, and flood control. Hydraulic modeling, dam safety, watershed management. Growing demand with climate change.

Environmental Consultant

Site remediation, compliance, environmental impact assessment. Firms include Stantec, Arcadis, Brown and Caldwell, Tetra Tech, CDM Smith.

Utility Operations & Management

Run water and wastewater systems. Aging workforce = strong job security. Operator certification (Class A–D). Median salary: $50–80K.

Global Development / WASH

Work with NGOs (WaterAid, IRC), UN agencies, social enterprises (Virridy). Field-based and policy roles. Engineering + public health background valued.

Research & Innovation

Sensor development, membrane technology, PFAS destruction, water reuse, AI for system optimization. PhD often preferred. National labs, universities, startups.

The water sector faces a workforce crisis: 1/3 of utility workers will retire in the next 10 years. Demand for water engineers is projected to grow 6–8% annually.

25 — Careers

Key Takeaways

US water infrastructure is aging and underfunded — $625B investment gap
The treatment process is a series of barriers: coagulation, flocculation, sedimentation, filtration, disinfection
Flint shows what happens when engineering decisions are driven by cost-cutting and institutional racism
PFAS are the next frontier of water contamination — new EPA limits at 4 parts per trillion
2 billion people worldwide still lack access to safe drinking water
Carbon credit financing can make rural water projects sustainable
Climate change is reshaping water availability, quality, and infrastructure needs

Up Next

Week 8 Lab: Water Quality Testing with the Lume Sensor

You will measure tryptophan-like fluorescence in Boulder Creek water samples and compare results to traditional E. coli culture methods. Come to lab with questions from today's lecture.

26 — Takeaways