Water system
Aqua Ohio - Marion
EPA ID OH5100414 · Marion County · 47,102 people served
Aqua Ohio - Marion treats its own water from Scioto River and Little Scioto River intakes, blended with local groundwater wells.
The system's record
- Aquifer
- local wells
- Water bodies
- Scioto River, Little Scioto River
- Raw intakes
- Little Scioto River
Scioto River - Active wells
- 18
- Serves
- 47,102 people · Marion County
- EPA ID
- OH5100414
About this area's water
Did you know
- Marion's 1924 sewage treatment plant, designed by engineer George Gascoigne, was noted at the time as one of the few plants in Ohio achieving complete treatment year-round.
- Aqua Ohio's Marion system traces its corporate lineage to the Consumers Ohio Water Company, which was later renamed Aqua Ohio, Inc.
- In December 2025 a citywide complaint about earthy-tasting tap water led Aqua to shut off its primary river intake entirely and run Marion on primarily well water; the utility never identified the specific compound…
- About 3 million of the 8.5 million gallons Marion's wastewater plant treats each day is stormwater, so on a typical day roughly a third of what the plant handles is rain rather than sewage.
History4
- 1903-1905Marion's first sewage treatment plant opened in 1903 and was operational by 1905; the State Department of Health soon judged it inadequate because it was polluting local waterways.
- 1924A modern replacement sewage plant designed by consulting engineer George Gascoigne went into service, one of the few plants in Ohio achieving complete treatment year-round.
- 2025-12Organic compounds in the water feeding the Marion Water Treatment Plant caused a citywide taste-and-odor complaint; Aqua adjusted intakes and treatment, shifted to primarily well water, and increased…
- 2026-07PUCO approved an Aqua Ohio rate increase of about $9.5 million in additional annual water revenue (down from the $13.4 million requested) plus $1.04 million for wastewater, affecting Marion customers.
Treatment & pressure
How it is treated
Aqua Ohio's Marion plant treats surface water drawn from a river intake on the Scioto/Little Scioto system, supplemented by local groundwater wells. Operators can take the primary river intake out of service and run on primarily well water while adjusting treatment, as they did during the December…
Water pressure
Not published.
What it costs
PUCO case 25-0594-WW-AIR: Aqua Ohio requested $13.4M in additional annual water revenue for its roughly 47,000 Ohio customers; PUCO approved about $9.5M (plus $1.04M wastewater)…
Water quality & impurities
EPA compliance record
Lead at the tap: 90th-percentile result 3.7 ppb in 2023 (action level 15 ppb).
EPA record: no health-based violations since 2015.
Projects & plans2
Recent and current work
- Emergency source switch and enhanced treatment · 2025 · completed
After the December 2025 odor event, Aqua ceased using the primary river intake, ran on primarily well water, adjusted treatment and increased testing.
Planned or needed
- Aqua Ohio system-wide infrastructure investment tied to PUCO case 25-0594-WW-AIR · 2026 · planned
The July 2026 rate increase funds infrastructure spending across Aqua Ohio's territories; we found no Marion-specific project.
Supply stress
The Marion plant's river intake is exposed to upstream agricultural runoff and treated wastewater effluent, which surfaced in December 2025 when organic compounds forced Aqua off the primary river intake and onto primarily well water for several days. Local reporting also describes historical difficulty controlling disinfection…
Sewers
Sanitary
The City of Marion, not Aqua, runs the sanitary sewers and wastewater treatment plant, discharging to the Little Scioto River. The plant dates to 1903-1905, was rebuilt in 1924, modified in 1953, and by 1956 ran methane digesters for heating at 5.4 MGD. A 1978 activated sludge project cost $12.5 million and raised capacity to 10.5 MGD; a…
Storm
No separate stormwater utility was identified, but roughly 3 million gallons of stormwater per day reaches the wastewater plant — about a third of its 8.5 MGD average flow — indicating substantial inflow and infiltration into the sanitary system.
Sourcesverified
Compiled from the utility's own reports and public records, then independently re-checked against primary sources.
Main supplier in 1 ZIP code
Serves
Main water supplier in 2 ZIP codes
- 43302 · Marion65% of residents
- 43342 · Prospect29% of residents
Also present in 1 more ZIP code
- 43314 · Claridon Township and Caledonia25% of residents
Population-weighted resident shares; a ZIP code can have more than one system on record. Recomputed from each ZIP's own system list, not from the map's cached footprint.
Buys from · Sells to
Aqua Ohio - Marion does not buy water from another system on record; it treats its own source water.
No other system is on record buying water from Aqua Ohio - Marion.
What the records show about Aqua Ohio - Marion
Who runs it
EPA's record says Aqua Ohio - Marion has 18,841 service connections and serves 47,102 people.
EPA classes it as a community water system, one that serves the same residents all year.
EPA's record says it has substantially implemented source water protection under Ohio's program, dating the program from 2023. Its office telephone on EPA's record is 740-383-0933.
Source: EPA Safe Drinking Water Information System (SDWIS), water system record.
How the water is treated
EPA's treatment table registers these steps for Aqua Ohio - Marion: aeration, chloramine disinfection, corrosion control, coagulation and settling, chlorine disinfection, fluoridation, lime softening, powdered activated carbon, and sand or media filtration.
The list is what each system registered with EPA for treatment plants EPA still shows as active, and it can lag a plant upgrade.
Source: EPA Safe Drinking Water Information System (SDWIS) treatment table (EPA Envirofacts, pulled September 2026).
Violations
EPA's record shows no health-based violations for Aqua Ohio - Marion since 2015.
EPA logs no violations of any kind for Aqua Ohio - Marion since 2020.
Source: EPA Safe Drinking Water Information System (SDWIS) violation records: health-based violations with compliance periods beginning in 2015 or later, all violations from 2020 or later (EPA Envirofacts, pulled September 2026).
Lead and copper at the tap
In the sampling period ending December 2023, the 90th-percentile lead result at Aqua Ohio - Marion was 3.7 ppb, under both the current 15 ppb action level and the 10 ppb level that applies from 2027.
The highest result on file is 4.4 ppb, in the period ending December 2017.
EPA has 4 sampling periods on file for Aqua Ohio - Marion since 2016, the first ending in 2016; no period was above 10 ppb.
Every water system has to inventory its service lines, the pipes from the main to each building. In the inventory Aqua Ohio - Marion sent EPA, 19,181 lines are counted.
| Material | Lines |
|---|---|
| Lead | 3,371 |
| Galvanized, needing replacement | 228 |
| Unknown material | 6,576 |
| Not lead | 9,006 |
| All lines | 19,181 |
Systems sample taps in the homes most likely to have lead pipes or solder. The 90th-percentile result is the level nine in ten of the sampled homes were at or below. Lead comes mostly from service lines and house plumbing, not the source water, so a low result for the system does not clear an old house.
EPA's dashboard status for this inventory: reported all required service line types.
Source: EPA Safe Drinking Water Information System (SDWIS) lead and copper 90th-percentile results (EPA Envirofacts), sampling periods ending 2016 or later; EPA's service line inventory dashboard, Ohio's 2026 Q2 submission.
PFAS
EPA's fifth national round of testing (UCMR 5) took 4 samples of the water entering the pipes of Aqua Ohio - Marion in 2023 to 2024 and measured 29 PFAS. No PFAS was detected, PFOA and PFOS (federal limit 4 ng/L each) among them.
Ohio EPA's own statewide sampling tested 1 plant of Aqua Ohio - Marion (latest sample October 2020). Not one of the six PFAS tested (PFOA, PFOS, PFHxS, PFNA, GenX and PFBS) was detected.
Ohio EPA's current sampling status map lists 1 plant of Aqua Ohio - Marion as sampled, most recently July 2025.
PFAS are the 'forever chemicals' from firefighting foam, plating shops and non-stick coatings. Results are for water leaving the plant, not your tap.
Source: EPA UCMR 5 occurrence data (final release, August 2026); Ohio EPA statewide PFAS sampling, 2019 to 2021, and its sampling status map.
Disinfection byproducts
Chlorine that disinfects water also reacts with organic matter to form byproducts. Two groups have federal limits: total trihalomethanes (TTHM, 80 µg/L) and five haloacetic acids (HAA5, 60 µg/L), judged on running yearly averages at each sampling site.
For TTHM, the average of Aqua Ohio - Marion's samples in 2019, the last year it was sampled, was 35.4 µg/L. The worst yearly average was 77.3 µg/L and the highest single sample was 146.6 µg/L, from 122 samples taken from 2012 to 2019.
For HAA5, the average in the last year sampled was 17.7 µg/L. The worst yearly average was 29.4 µg/L and the highest single sample was 57 µg/L, from 122 samples.
| Byproduct | Limit | Latest yearly average | Worst yearly average | Highest sample | Samples |
|---|---|---|---|---|---|
| TTHM | 80 µg/L | 35.4 µg/L (2019) | 77.3 µg/L | 146.6 µg/L | 122 |
| HAA5 | 60 µg/L | 17.7 µg/L | 29.4 µg/L | 57 µg/L | 122 |
A yearly average of 0 means nothing was detected in that year's samples. EPA's file stops at 2019; Ohio EPA's Drinking Water Watch has newer results.
Source: EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, distribution-system samples (non-detects counted as zero).
Nitrate, arsenic and radioactivity
Nitrate: the highest of 98 samples was 10.8 mg/L (as nitrogen), in 2019, the last year sampled. 1 of the samples went over the limit of 10 mg/L. Nitrate above 10 is unsafe for infants.
Arsenic was not detected in 8 samples (limit 10 µg/L).
| Contaminant | Samples | Highest result | Limit | Samples over limit |
|---|---|---|---|---|
| Nitrate (as nitrogen) | 98 | 10.8 mg/L | 10 mg/L | 1 |
| Arsenic | 8 | not detected | 10 µg/L | 0 |
| Combined radium | 1 | 0.9 pCi/L | 5 pCi/L | 0 |
Measured in finished water: at the plant's entry points and in the distribution system; raw well and intake samples are left out. Non-detects count as zero.
Source: EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, finished water.
Solvents and fuels
EPA's file holds results for all six solvent and fuel compounds it checked. Benzene, carbon tetrachloride, 1,2-dichloroethane, trichloroethylene, tetrachloroethylene, and vinyl chloride were not detected in 8 samples each.
| Compound | Limit | Samples | Detected in | Highest result | Samples over limit |
|---|---|---|---|---|---|
| Benzene | 5 µg/L | 8 | 0 of 8 | not detected | 0 |
| Carbon tetrachloride | 5 µg/L | 8 | 0 of 8 | not detected | 0 |
| 1,2-dichloroethane | 5 µg/L | 8 | 0 of 8 | not detected | 0 |
| Trichloroethylene (TCE) | 5 µg/L | 8 | 0 of 8 | not detected | 0 |
| Tetrachloroethylene (PCE) | 5 µg/L | 8 | 0 of 8 | not detected | 0 |
| Vinyl chloride | 2 µg/L | 8 | 0 of 8 | not detected | 0 |
"Not detected" means the lab's result was below what its method can measure, not that the compound is absent. Non-detects count as zero in the highest-result column.
Source: EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, finished water.
Farm chemicals and metals
EPA's file holds results for all nine herbicides and metals it checked. Detected: atrazine in 19 of 39 samples, highest 8.7 µg/L (limit 3, 2 over); barium in 1 of 8 samples, highest 11 µg/L (limit 2,000). Not detected: alachlor in 39 samples, 2,4-D in 1 sample, chromium in 8 samples, cadmium in 8 samples, mercury in 8 samples, selenium in 8 samples, thallium in 8 samples.
| Substance | Kind | Limit | Samples | Detected in | Highest result | Samples over limit |
|---|---|---|---|---|---|---|
| Atrazine | Farm chemical | 3 µg/L | 39 | 19 of 39 | 8.7 µg/L | 2 |
| Alachlor | Farm chemical | 2 µg/L | 39 | 0 of 39 | not detected | 0 |
| 2,4-D | Farm chemical | 70 µg/L | 1 | 0 of 1 | not detected | 0 |
| Chromium | Metal | 100 µg/L | 8 | 0 of 8 | not detected | 0 |
| Cadmium | Metal | 5 µg/L | 8 | 0 of 8 | not detected | 0 |
| Barium | Metal | 2,000 µg/L | 8 | 1 of 8 | 11 µg/L | 0 |
| Mercury | Metal | 2 µg/L | 8 | 0 of 8 | not detected | 0 |
| Selenium | Metal | 50 µg/L | 8 | 0 of 8 | not detected | 0 |
| Thallium | Metal | 2 µg/L | 8 | 0 of 8 | not detected | 0 |
Non-detects count as zero in the highest-result column.
Source: EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, finished water.
Bacteria in the pipes
From 2012 to 2019, 0 of 4,906 routine total coliform samples taken in the distribution system at Aqua Ohio - Marion tested positive (0%); in 2019, the last year on file, 0 of 612 did.
A positive coliform test is a warning sign, not a violation by itself. E. coli is a sign that human or animal waste may have reached the water. Coliform counts are routine samples only; E. coli counts include repeat samples.
Source: EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, distribution-system presence/absence tests for total coliform and E. coli.
Fluoride
The Ohio Department of Health's report to the CDC (My Water's Fluoride) says Aqua Ohio - Marion adjusts the fluoride level to the recommended level for preventing tooth decay.
EPA's treatment table lists fluoridation among the steps at Aqua Ohio - Marion.
Measured fluoride: 0.91 mg/L on average at the plant's entry points in 2019 (in the range dentists aim for); samples ran from 0.88 to 1.21 mg/L across 8 samples in 2012 to 2019.
The recommended level for preventing tooth decay is 0.7 mg/L; the federal limit is 4 mg/L. The treatment list is what each system registered with EPA and can lag a plant upgrade.
Source: CDC My Water's Fluoride (fluoridation status as reported by the Ohio Department of Health, fetched September 2026); EPA Safe Drinking Water Information System (SDWIS) treatment table; EPA Six-Year Review 4 compliance monitoring data, 2012 to 2019, entry-point fluoride samples.
Lithium
Lithium was found in 4 of 4 UCMR 5 samples at Aqua Ohio - Marion, highest 19.4 µg/L; detections averaged 18.2, last sampled in 2024.
Lithium is not regulated. EPA's draft health reference level is 10 µg/L, and it occurs naturally in deep groundwater, so well systems in the northwest run highest.
Source: EPA UCMR 5 occurrence data (final release, August 2026), samples from 2023 to 2025.
Algal toxins
Ohio EPA tests for microcystin, a toxin that harmful algal blooms can release, in raw water at the intake and in treated water.
At the intake, microcystin was detected 1 time in 226 raw-water samples, across 1 bloom season (2018); the highest raw-water result was 0.643 µg/L on August 21, 2018. There has been no raw-water detection since 2024.
Microcystin was never detected in treated water (83 samples).
In all, 309 samples from 2016 to 2026, the latest on August 24, 2026.
| Water | Samples | Detections | Highest result |
|---|---|---|---|
| Raw water, at the intake | 226 | 1 | 0.643 µg/L |
| Treated water | 83 | 0 | not detected |
The ten-day advisory levels for treated water are 0.3 µg/L for children under six and 1.6 µg/L for everyone else. Any detection at the intake triggers more frequent testing until two clean weeks.
Source: Ohio EPA public water system harmful algal bloom monitoring, 2016 to present (HAB data, fetched September 2026).
How well the service area is mapped
The service area drawn on the map for Aqua Ohio - Marion comes from the utility's own map.
Counting the people who live in the ZIP codes it overlaps, this atlas estimates 36,795 residents are inside the boundary, 78% of the 47,102 people Aqua Ohio - Marion reports serving.
The resident count is an estimate from 2020 Census ZIP-code populations, not a count of customers.
Source: EPA Service Area Boundaries; resident estimate by this atlas from ZIP-code overlap.
Photograph
On the map
Show this system's territory on the map — 3 ZIP codes in all.
Sources
U.S. EPA SDWIS and Community Water System Service Area Boundaries (v3, 2026), Ohio EPA primacy data, 2020 census blocks: the system serving most residents, traced through purchases to the treating utility; Ohio EPA 2023 Sewer and Water Rate Survey (Ohio State, May 2025) for household bills; Ohio EPA DEFA loan awards since 2016 for the loans paragraph · EPA SDWIS · EPA service area boundaries · Ohio EPA drinking water · Ohio EPA rate survey
EPA's own record for this system: Enforcement and Compliance History report for OH5100414 (EPA ECHO).
Aqua Ohio - Marion's own pages: news.marionwatch.com, aquawater.com
