PU580 Unit 7 Water Contamination Analysis Example

Course	PU580 Environmental Epidemiology
Unit	Unit 7
Paper type	Water contamination analysis
Length	About 850 words, 6 pages double-spaced
Format	APA 7 student paper
School	Purdue University Global
Program	Master of Public Health (MPH)
Updated	October 2026

Free sample paper for PU580 Unit 7

Compliant at the Plant and Over the Limit at the Dead Ends: A Unit 7 Water Contamination Analysis Following Disinfection By-Products Through a Composite Town's Distribution System, Where Water Age Is the Exposure Variable

[Student Name]

Purdue University Global

PU580: Environmental Epidemiology

Unit 7 Water Contamination Analysis

[Instructor Name]

[Date]

The town, its sampling sites and its figures are composite; the chemistry, the regulatory structure and the research cited are real.

What this part is doingThe analysis treats the distribution system as the exposure pathway rather than the treatment plant, which is where the regulatory conversation usually stops.

The Numbers

Total trihalomethanes in micrograms per liter, running annual averages by site, against a limit of 80.

1. Plant effluent: 31.

2. Downtown loop, 1.5 kilometers from the plant: 46.

3. North branch midpoint: 63.

4. North branch dead end, serving 310 homes: 94.

5. Industrial park spur dead end, serving 40 homes and a school: 101.

Four consecutive quarters above the limit at sites four and five. The system-wide average of all five sites is 67, which is compliant and is the figure that appeared in the annual report to customers.

The Chemistry, in the Order It Happens

1. The source is a reservoir with high dissolved organic carbon, highest after spring runoff and late summer algal growth.

2. Chlorine added at the plant reacts with that organic material to form trihalomethanes and other by-products.

3. The reaction continues in the pipe. Formation is not complete at the plant; it keeps going as long as free chlorine and organic precursors are both present.

4. Therefore concentration rises with water age, which is the time between leaving the plant and reaching a tap, and water age is longest at dead ends and in oversized mains with low demand.

5. Warm water accelerates the reaction, so the summer quarter is the worst everywhere and the dead ends exceed the limit in every quarter.

The plant is not making the violation. The pipe is, in the hours after the water leaves, and the pipe is where nobody was sampling.

Why the System Average Is the Wrong Statistic

The running annual average across sites is how compliance is calculated under the older rule, and it allows a system to comply while a defined group of customers receives water well above the limit for years. The households at site four are not exposed to 67 micrograms per liter; they are exposed to 94. An analysis for public health purposes should report the distribution of concentrations by population served, not one average, which is the reasoning behind the later rule's shift toward locational running averages.

Exposure Is Not Only Ingestion

Trihalomethanes are volatile, so showering and bathing contribute through inhalation and dermal absorption, and in some studies those routes contribute as much as drinking water does. The bladder cancer case-control work that examined routes separately found associations with showering, bathing and swimming as well as with ingestion, which means an exposure estimate built from liters drunk per day understates it (Villanueva et al., 2007). For the 40 homes and the school on the industrial spur, the relevant exposure includes a morning shower in 101 micrograms per liter water.

What this part is doingIncluding inhalation and dermal routes changes the exposure estimate by a factor that matters, and it changes what advice makes sense.

What the Health Evidence Supports and Does Not

The by-product mixture is genotoxic in laboratory systems and the epidemiology is strongest for bladder cancer, with consistent modest associations across studies; the evidence for reproductive outcomes is weaker and less consistent. The regulated four trihalomethanes are a small fraction of the hundreds of by-products formed, and the unregulated ones include compounds more genotoxic than those measured, which is the central honest point about this exposure (Richardson et al., 2007). The analysis therefore avoids both overstatement and the conclusion that a compliant system is a safe one.

What this part is doingThe actions are ordered by effect per dollar rather than by permanence, so the flushing schedule that costs nothing appears above the pipe replacement that would end the problem.

What the Town Should Do, in Order of Effect

1. Flush the two dead ends on a written schedule, weekly in summer, which lowers water age immediately and costs only water and staff time. Spatial and seasonal variation of this kind across distribution systems is well documented and is the first thing an operator can act on (Rodriguez & Serodes, 2001).

2. Reduce organic precursors at the plant through enhanced coagulation, which attacks formation rather than managing it downstream, at moderate capital cost.

3. Consider changing the secondary disinfectant to chloramine, which forms fewer trihalomethanes, while recognizing that it shifts the by-product mixture rather than removing it and carries nitrification risks in a system with low demand.

4. Re-engineer the industrial spur, either by looping it or by reducing main diameter, which is the permanent fix and the most expensive.

5. Sample at the dead ends every month rather than quarterly, and report results by site, since the current sampling plan was designed for compliance arithmetic and not for exposure assessment.

What the Analysis Cannot Say

It cannot estimate anybody's risk, because the exposure duration for individual households is unknown and the published risk estimates come from populations with different by-product mixtures. It cannot tell the school whether its pupils were harmed. And it cannot rule out that switching disinfectant creates a new problem the current sampling would not detect, which is the argument for measuring the unregulated by-products before changing anything.

References

Richardson, S. D., Plewa, M. J., Wagner, E. D., Schoeny, R., & DeMarini, D. M. (2007). Occurrence, genotoxicity, and carcinogenicity of regulated and emerging disinfection by-products in drinking water: A review and roadmap for research. Mutation Research, 636(1), 178-242. https://doi.org/10.1016/j.mrrev.2007.09.001

Rodriguez, M. J., & Serodes, J. B. (2001). Spatial and temporal evolution of trihalomethanes in three water distribution systems. Water Research, 35(6), 1572-1586. https://doi.org/10.1016/S0043-1354(00)00403-6

Villanueva, C. M., Cantor, K. P., Grimalt, J. O., Malats, N., Silverman, D., Tardon, A., Garcia-Closas, R., Serra, C., Carrato, A., Castano-Vinyals, G., Marcos, R., Rothman, N., Real, F. X., Dosemeci, M., & Kogevinas, M. (2007). Bladder cancer and exposure to water disinfection by-products through ingestion, bathing, showering, and swimming in pools. American Journal of Epidemiology, 165(2), 148-156. https://doi.org/10.1093/aje/kwj364

The Purdue Global PU580 Unit 7 instructions

Unit 7 usually gives distribution system monitoring data and asks what it means. Report the results by site rather than as a system average, and say how many people each site serves. Explain the chemistry in the order it happens, so that formation continuing inside the pipe is clear. Identify water age as the variable, and name what lengthens it. Explain why a compliance average can hide a population receiving water above the limit for years. Include inhalation and dermal routes, since these compounds are volatile and ingestion-only estimates understate exposure. State what the health evidence supports and what the unregulated by-products leave open. Then rank actions by effect per dollar, not by permanence.

Inside the PU580 Unit 7 example

The analysis on this page lists five sites with their running averages and the populations behind them, then gives the chemistry in five steps ending at water age. A highlighted line states that the plant is not producing the violation and the pipe is. A margin note explains why the distribution system is treated as the pathway. The section on compliance arithmetic shows how a 67 average conceals households at 94. Routes beyond ingestion follow, with another note on how much that changes the estimate. Five actions are ranked from a flushing schedule that costs water and staff time to re-engineering a spur, flagged by a further note, and three honest limits close it.

PU580 Unit 7 rubric: what earns full points

Marking rewards a site-by-site reading. Reporting a system average as the finding costs marks, because the exposure question concerns the households at the dead ends. Credit goes to a chemistry account that makes in-pipe formation explicit, and to naming water age with its causes. Points follow for explaining the difference between compliance arithmetic and exposure assessment. Including inhalation and dermal routes is rewarded, since many submissions estimate from liters drunk. The health section is scored on restraint: strongest evidence for bladder cancer, weaker for reproductive outcomes, and the regulated four as a fraction of hundreds of by-products. Ranking actions by effect per dollar completes the score.

PU580 Unit 7 help from the desk

The commonest error is accepting the compliance average, which describes nobody's exposure. The second is treating the treatment plant as the problem, when formation continues in the pipe and the dead ends are where the violation lives. Third, do not estimate exposure from drinking water alone, because showering and bathing contribute through volatilization and skin. Avoid recommending a disinfectant change as the first step, since it shifts the by-product mixture and brings nitrification risk in a low-demand system. And do not describe a compliant system as safe, given how little of the mixture is measured. An analysis of your own system data comes back inside two days. One more thing graders look for: say how many people each sampling site serves, since a violation at a site serving forty homes and one serving three hundred call for different urgency.

Get a PU580 Unit 7 example written to your instructions

For PU580 Unit 7 the contaminant might be a disinfection byproduct, a metal, a pathogen or an industrial solvent. Send the case materials or data your section provides, along with the questions and rubric. Every exposure route and the people on the receiving end are traced in the free first custom sample, returned within 24-48 hours. The paper above is an original model document written by our desk, not a submitted student paper and not an official Purdue University Global document.

More PU580 papers and MPH samples

PU580 Unit 7 questions, answered

Where can I find a free PU580 Unit 7 sample paper?

The whole water contamination analysis, all five sites and the ranked actions, is published here.

Why are dead ends worse?

Because water age is longest there. Formation continues as long as free chlorine and organic precursors are both present, so concentration rises in the pipe.

What is wrong with a system average?

It can be compliant while a defined group of customers receives water above the limit for years. Those households are exposed to their own number, not the average.

Do showers matter for this exposure?

Yes. These compounds are volatile, so inhalation and skin contact add substantially, and an ingestion-only estimate understates the dose.

What is the cheapest effective action?

A written flushing schedule at the dead ends, weekly in summer, which lowers water age immediately and costs only water and staff time.